Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Types of grinding/polishing machines
I would like this thread to help educate me and other newbies about the types of grinding/polishing machines.
The types: Porter. Hindle. Elgin. Draper. Let’s get more names, guys, and details about what makes one type different from the others.
Characteristics: How large does this type of machine typically get? What size mirror can it take? What speed does the mirror turn?
Can it figure? How many arms, how many eccentrics? What are the Advantages/Disadvantages? 
Personal preferences: Which type do YOU like and why?
Lastly, how to build it. 
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Richard Caldwell
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danmdak
member
Reged: 10/03/07
Posts: 37
Loc: NE Ohio
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Good luck. I have wanted plans/advice on this for YEARS! Finally, years ago, Amateur telescope Making Journal (undated, issue #13)ran an article on one. Unfortunately, they took the easy way out: they referred you to a website that had all the plans and dimensions. okay, no problem. I turned on the computer, typed in the web address....and it was not to be found  ! That is the one trouble with these computer webistes..here today, gone tomorrow. Meanwhile, had they actually printed the plans, I could have access to them always.
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Main instrument: homemade 16" f/4.5
secondary instruments: Homemade 8" f/8 & Meade 2045 4"
Garrett 15X70 binos
In the works: Homemade 8" f/4
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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I made a Hindle type machine from scrap machinery with a 48 inch capacity, I made two 48", one 42", and a 32" mirror and a 30" inch objective lens. plus many smaller mirrors and doublets up to 8". I cast the massive concrete table in situ, the machine was sited in a tiny workshop only half as big again as the machine. The table rotated at about 2rpm, the driver at 28 rpm, but the offset spindle was static, and fixed to a cross slide so that the degree of offset was managed by accasionally shifting it manually.power source, a half horsepower squirrel cage motor from the first world war era.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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For every ones information, some illustrations culled from a paper to the BAA,by J,Wall and R,Nichol. Journal of the British Astronomical Association, 1992 August. vol 102, No4.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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And
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Also.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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And.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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And for my last trick.
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Beri
sage
Reged: 06/29/05
Posts: 294
Loc: Croatia
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Thanks!
Any chance for a larger size of these images ?
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15x70 Binoculars
10" truss Dob
http://www.scopemaking.net
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Thanks for responding, guys. Crayfordjon, about that first picture. It shows 2 types of machines. The top one is labeled a Hindle machine, the bottom one is labeled a modified Hindle machine. Am I right in saying that the bottom one is also called a Draper? I would very much like to know the relative merits of these designs.
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Richard Caldwell
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Here is a better pic of the first one.
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Richard Caldwell
Edited by Glig (08/28/09 08:55 AM)
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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2nd one.
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Richard Caldwell
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Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
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http://www.astrosurf.com/gap47/T400/Machine/3-machines-type-eng.htm
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Stefan Van de Rostijne
4.5" F4.5 newt 5°widefield/finderscope
8" f/5.6 travel dob
old 12.5" F5 dob (used to look better...)
30 cm f/30 Classic Cassegrain (polishing primary)
23" f/4 dob project
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Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
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Here are some vids of our own draper style machine.
Recently we finished polishing a 18" f/4 mirror.
http://www.youtube.com/watch?v=3VGmGk2eIEw
Currently we are figuring out how to parabolise. There is very little information on the internet about figuring with a machine. I also would like to know more about that.
Edited by Stefan Rostyne (08/28/09 10:58 AM)
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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That's a great link, Stefan. Couldn't find the link for the videos, though.
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Richard Caldwell
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Post deleted by Crayfordjon
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Hi glig. both are Hindle type machines, the top one is the standard as laid down in scriptures; ATM book 1. pg 235. The bottom one is a modified version by yours truly, I have replaced the alligatior by a double beam, and the offset spindle is not driven but static and mounted on a cross slide, so that the spindle can be moved occasionally, this makes for a simpler design machinery wise. I cannot send any picture that is larger due to the 10kb restriction on the web site.
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Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
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Sorry Richard, I forgot. I added the link, now.
EDIT I'm the one that steps into view in vid #7
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Stefan Van de Rostijne
4.5" F4.5 newt 5°widefield/finderscope
8" f/5.6 travel dob
old 12.5" F5 dob (used to look better...)
30 cm f/30 Classic Cassegrain (polishing primary)
23" f/4 dob project
Edited by Stefan Rostyne (08/28/09 11:19 AM)
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Beri, try printing out the pics, the definition is much better
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Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
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http://articles.adsabs.harvard.edu/full/1992JBAA..102..198N/0000198.000.html
This is the same as in Crayfordjon's posts, but in better resolution.
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Stefan Van de Rostijne
4.5" F4.5 newt 5°widefield/finderscope
8" f/5.6 travel dob
old 12.5" F5 dob (used to look better...)
30 cm f/30 Classic Cassegrain (polishing primary)
23" f/4 dob project
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Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
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Our machine is a welded frame from 2" square steel bars.
We use two 1/2 HP electrical motors and 2 Siemens frequency controllers. Pulleys are from old washing machines. Further some waterproof plywood.
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Stefan Van de Rostijne
4.5" F4.5 newt 5°widefield/finderscope
8" f/5.6 travel dob
old 12.5" F5 dob (used to look better...)
30 cm f/30 Classic Cassegrain (polishing primary)
23" f/4 dob project
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Stefan,
Thanks for the excellent links.
Gary
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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In my sig line is a link to videos of my 3 machines.
Check out the bottom link.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
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There are several machines in the Allan Mackintosh books from Willmann-Bell. Also, study the Strasbaugh, Loh, Coburn etc. catalogs, and, if possible remove the cover from the rear to see the Reeves variable speed cone and belt drives, DC variable speed drives, etc.
I have a small Strasbaugh planetary lapper for flats, which I am not using. Ditto Gaertner 1.5 meter optical bench, autocollimators, etc.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Do you guys have access to the old ATM books, published by Scientific American, these are the ATM's bible, well, if so, go to book two pg 141, there is a chapter on building and using small lens spindle grinders. I have one of these and produce small lenses up to 4 inches diameter, I once made two six inch mirrors on one.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Here is a pic of my spindle grinder on which I am currently rough gring a 90mm objective lens, the spindle rotates at 50rpm.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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I now use a much smaller three spindle grinder that will take up to 12 inches. Note the manually adjustable offset spindle on the cross slide.
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2156
Loc: salem, OR
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Here's the main menu for the first site Stephen linked:
http://astrosurf.com/gap47/T400/Machine/accueil-machines_eng.htm
The sections that haven't been anglicized yet are inactive. If you notice any errors in the translation the group that's doing this would appreciate knowing!
Best,
Mark
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
Do you guys have access to the old ATM books, published by Scientific American, these are the ATM's bible, well, if so, go to book two pg 141, there is a chapter on building and using small lens spindle grinders. I have one of these and produce small lenses up to 4 inches diameter, I once made two six inch mirrors on one.
I have these books in my library...and refer to them often.
Great books!
I'm fortunate to have my machines.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
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So; how do you figure to get a parabola -by machine?
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Stefan Van de Rostijne
4.5" F4.5 newt 5°widefield/finderscope
8" f/5.6 travel dob
old 12.5" F5 dob (used to look better...)
30 cm f/30 Classic Cassegrain (polishing primary)
23" f/4 dob project
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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I grind and polish the optic by machine and then hand figure on the rotating table. For big mirrors up to 32 inch I used sub diameter tools to grind and polish and figure. Single element plano convex objective lenses for retro focal dialytes, the lens has to have an elliptical figure, this requires a ring lap in the initial stages of figuring to work the zone to be polished away, by machine action, then final hand figuring, all on the machine turnable. I figure lenses using null test at infinity by an oil flat. Oil is very stable and self dampening, and vibration will not register.
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Guys please list the books that are most helpful (lots of pics or diagrams) in understanding grinding/polishing machines.
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Richard Caldwell
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Here is my twin table modified Draper machine.
I polished an 18" on this machine.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Here is my porter polishing machine. I use for hogging out mirrors and for making larger then 15" mirrors.
This machine is very versatile with to ecentric tables dor control of stroke in both X, Y axis. Also I can control the rotation of the tool and make it run in reverse to the table.
Sweet table.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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And finally my new machine....a four spindle multi speed control over arm machine. This machine is my workhorse.
I have an 8" a 12" and a 13" on it right now.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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All my machines lines up.....
Mirror making is fun now....... 
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Lastly....grinding my 17" on the Porter....an 8" and 13" on the new machine.
This is a lot of activity...and generally I'm not working on more then 2 mirrors at a time.
I figure by hand on the porter table while it rotates..without the over arms.
I plan on attempting to figure using the new machine my buiding a sub diameter star polisher and simply setting the machine to work the necessary zones.
It's all good.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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gatorengineer
scholastic sledgehammer
Reged: 02/28/05
Posts: 880
Loc: Hellertown, PA
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Newbie to figuring question - For say a mirror like a 16" Say F4, how long does it take a machine to get it ready to parabolize?
Thanks
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20" F5 Dob
16" Dob in pieces
Comet Catcher
MN71
12" Doc Clay Sky Patrol MEADE SCT
12.5" F4 Newt under construction
Siebert 45mm Binoviewers
Lots of binos---
Optics Past - 8" Stf Mak, 4" B&W triplet, 6"Schmidt newt, 12"LX200, C8, Meade LX10-10", 10" MEADE ACF, SN8, TAL150K, Orion 150MC, Jason 60mm refractor, ATM 6" F8, WO 110FLT, 92mm Off Axis Newt, Televue Genesis, Nikon 20x120 bino's, 15x110 Boarderguards, Kuhne Flaks
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
Newbie to figuring question - For say a mirror like a 16" Say F4, how long does it take a machine to get it ready to parabolize?
Thanks
F/4......Well that is a lot of glass to remove. On my Porter with a diamond blade cutter on my tool...took about 6 hours to cut the sagitta for a 13"f/5. Couple that with grinding...fine grinding..oh another...12~16 hours.
Polishing.......another 6~12 dependant on how finicky you want to be.
If you were diligant...probably 34~42 hours of total machine time. but this number is probably not vary reasonable...since I removed every problem that may arise...and there are plenty.
Rob
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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gatorengineer
scholastic sledgehammer
Reged: 02/28/05
Posts: 880
Loc: Hellertown, PA
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Rob,
thanks for the response, let me flip the question around a bit, how long for a F8 at 16 inches?
Thanks
Mark
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20" F5 Dob
16" Dob in pieces
Comet Catcher
MN71
12" Doc Clay Sky Patrol MEADE SCT
12.5" F4 Newt under construction
Siebert 45mm Binoviewers
Lots of binos---
Optics Past - 8" Stf Mak, 4" B&W triplet, 6"Schmidt newt, 12"LX200, C8, Meade LX10-10", 10" MEADE ACF, SN8, TAL150K, Orion 150MC, Jason 60mm refractor, ATM 6" F8, WO 110FLT, 92mm Off Axis Newt, Televue Genesis, Nikon 20x120 bino's, 15x110 Boarderguards, Kuhne Flaks
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Grinding machines save you work - but do they save you time as well? John Dobson says it takes one hour per inch of aperture to finish a mirror by hand from rough grinding to polished out. Now, he's talking about shallow F/7 mirrors and relatively soft plate glass. But there are ways to grind and polish even faster then John Dobson does it. You can grind faster by using rougher grit and heavy cast iron tools. Polishing faster has been raised to an art form -try this link.
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Board/atm/Number/2151093/page/2/view/collapsed/sb/5/o/o/fpart/all
So are grinding machines faster than by hand?
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
Rob,
thanks for the response, let me flip the question around a bit, how long for a F8 at 16 inches?
Thanks
Mark
The number you can fudge with is the 6 hrs at the *HOGGIN* table. Pretty much the same..cept when you get to figuring.
I'm just telling you my numbers...I'm sure some of the professionals here have completely different ones.
They're probably faster at polishing.
All in all...if you were racing and had a week... were you did nothing all day(8~12hrs)..but grind/polish your mirror...you could probably polish up a mirror pretty quick.
I'm sure the professional home boys...have awesome answers.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Maybe John Dobson can make a mirror in one hour, but can the rest of us? It takes me a long time to figure a mirror to the standard that I desire, I dont think that JD should be taken as bench mark, no disrespect intended, anyway, are JD's mirrors light buckets that will not stand high magnification, but are super for looking at the universe at X40, I have made plenty of these fun mirrors. The advantage of a machine is that it takes away the sheer tedium of grinding and polishing by hand, and the hard physical labor, you can sit down along side the machine and catch up on the reading, or get on with something else. Hand work comes in when the final figuring starts, then it is either fun or heartbreak.
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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"maybe John Dobson can do a mirror in one hour..." No he means one hour per inch of aperture. A 10 inch mirror takes 10 hours and a 20 inch in 20 hours, etc.
Anywho, Rob what would you say the advantages/disadvantages of a porter machine? Is it a "stroke dependent" machine? In other words, do the eccentrics spin faster than the mirror?
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Richard Caldwell
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
"maybe John Dobson can do a mirror in one hour..." No he means one hour per inch of aperture. A 10 inch mirror takes 10 hours and a 20 inch in 20 hours, etc.
Anywho, Rob what would you say the advantages/disadvantages of a porter machine? Is it a "stroke dependent" machine? In other words, do the eccentrics spin faster than the mirror?
Yes the eccentrics spin faster...well the large one that drives the over arm does. The smaller one turns at the table rate.
So you can set your stroke with the main eccentric table...and then set your cross stroke with the smaller.
This permits you great flexability in keeping the tool from any pattern and from creating any kind of zone.
Plus my machine allows you to turn the tool in the opposite direction of the table...where as a free spinning tool follows the tables rotation.
A Porter machine permits you the freedom of control and stroke......nearly infinite strokes. You can work a specific area if you want.
I luv it. Right now I'm using it to hog out my smaller mirrors. But I do grind and polish all mirrors Bigger then 13" on it.
Rob
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Lalith
member
Reged: 06/09/06
Posts: 49
Loc: IL
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Hi Rob,
I like to know more details of your Poter machine. I have been collecting parts to build a mirror grinding machine. I was thinking of an Elgin type, after reading your posts now I am inclined to upgrade to one like your Porter. Looks like yours frame is made of wood, what type of motors, turn tables do you use. So far I have two 1/4 hp DC gear motors (42, 125 rpm), with speed controlers and some pulleys. First like to try a 16" thin mirror, and larger sizes later. Like to see more details and photos of your machine. Thanks.
Lalith
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
Hi Rob,
I like to know more details of your Poter machine. I have been collecting parts to build a mirror grinding machine. I was thinking of an Elgin type, after reading your posts now I am inclined to upgrade to one like your Porter. Looks like yours frame is made of wood, what type of motors, turn tables do you use. So far I have two 1/4 hp DC gear motors (42, 125 rpm), with speed controlers and some pulleys. First like to try a 16" thin mirror, and larger sizes later. Like to see more details and photos of your machine. Thanks.
Lalith
Right....here is an image of the over arm. It sits on the eccentric table and the counter arm sits on another eccentric at right angles.
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Here are some pics of the workings of the Porter.
The large eccentric table that drives the over arm.
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Here is the smaller counter eccentric table.
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Here is the drive. A single 1.5hp motor does all the work.
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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To the left is the gear drive for the large eccentric table.
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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To the right is the gear drive for the main table..which has a leather belt drive that activates the small eccentric table.
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Finally the leather belt drive that leaves the main table to the smaller eccentric table.
Very simple...but effective drive for this Porter.
Rob
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Lalith
member
Reged: 06/09/06
Posts: 49
Loc: IL
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Thanks a lot Rob, wow, that is an elegant machine!
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
Thanks a lot Rob, wow, that is an elegant machine!
Yes..it is very well built and waterproof.
The table comes off and it can be completely disassembled for cleaning.
I luv it.
Rob(good luck)
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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I hope no grade 80 grit gets into that beautiful worm gear drive. Lovely job.
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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I'm very interested in the draper machine. But I what I can't figure out, though, is whether or not the drive arm rests it weight on the fixed guide or on the polisher. Some diagrams show weight on top of the drive arm, meaning the polisher gets the weight from the drive arm. But some show just the polisher with the weight - the pin apparently contacting just the sides of the pin hole. 
Thanks guys
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Richard Caldwell
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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The weigjht of the drive arm should rest on the drive crank and not on the mirror, the mirror can be weighted separately to suit requirements, yes the drive pin contacts the side of the hole, and should not contact the bottem.
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Thanks John. Do you mean rest on the fixed guide? A draper has only one drive crank and the other side is a fixed guide.
So the fixed guide has a roller that supports the weight of the overarm? Perhaps teflon is used for support?
Hmmm. If the lap passes from the edge to the center, the lap dips a bit, right? So the hole has to be as tall as the sagitta, plus some for clearance.
Now the Utube video
"Draper mirrorgrinding machine #2" shows weight on top of the drive arm. Is that for stabilizing? 
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Richard Caldwell
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Yes on the fixed guide, in essence no part of the working motion should press on the mirror, as I said you can load this separately. Also the hole in the driving button that takes the pin should be deep enough so that the pin does not slip out when the mirror is at the edge of the tool. As for support for the slide, it can be teflon, but metal to metal contact is ok, just oil it occasionally.
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Mark Harry what is your opinion of the draper machine? I would have thought the oval pattern it makes would be a very good match for your style - But you use an Elgin right?
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Richard Caldwell
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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I am looking into using a variable speed setup for my mirror grinding machine. This seems to be a very nice variation of grinding machines so that's why I bumped the thread. What I want is a control knob that allows me to adjust the speed of the turntable and/or the eccentric without the whine, hum or other irritating noise many variable speed setups have. I repeat, WITHOUT the whine, hum or other irritating noise most variable speed setups have. 
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Richard Caldwell
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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My old Draper used to make a noise like a very ancient steam loco, you get used to it eventually.
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3120
Loc: Northeast
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"Mark Harry what is your opinion of the draper machine?"
**************
Never laid eyes on a real one. In the shop where I worked, we had CNC polishers, and Elgins exclusively. Oh, and one other, a pair of hands!
M.
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So many projects, so little time!
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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The problem with the Draper machine is that it does not lend itself well to off centre (sorry I'm English) work, this can be a limitation when it comes to figuring.
John
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GlenM
Vendor
Reged: 05/20/07
Posts: 1734
Loc: Lancashire UK
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Just logged in after a few days with health problems. It's good to see that you have joined CN John.
Could I just say that the mirrors I have purchased from you in the past have been excellent.
Good to see you here.
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Glen
www.lyraoptic.co.uk
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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Been around for a while Glen, just a little shy when it comes to posting!! Thanks for your comments about my mirrors.
John
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GlenM
Vendor
Reged: 05/20/07
Posts: 1734
Loc: Lancashire UK
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Sorry John,didn't realise.
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Glen
www.lyraoptic.co.uk
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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O. K. back to the Thread.
Anyone know a hot setup for a variable speed grinding machine? I need to adjust the speed of the turntable and/or the eccentric without the whine, hum or other irritating noise many variable speed setups have.
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Richard Caldwell
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8306
Loc: Bremerton Washington
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Quote:
O. K. back to the Thread.
Anyone know a hot setup for a variable speed grinding machine? I need to adjust the speed of the turntable and/or the eccentric without the whine, hum or other irritating noise many variable speed setups have.
Well..My 60+ year old machine utalized large bronz wheels that run against each other. The smaller which afixed to the drive shaft drives the much larger one that drives the vertical stroke arms and table. When the smaller wheel runs against the larger closer to its central the larger one turns faster. If you slide the smaller out to the larger ones edge the control arm/table rotates slower.
Of course..I'm the luckiest person alive..since I was given my pre WW2 4 table/tub machine.
Honestly I don't know of any machine that isn't noisy to some degree. My 4 table machine is very quiet...short of its motor and chain drive noise.
Grinding mirrors makes more noise....... 
Good luck in your search.....
All my machines have their noises...the Double table Draper..clunks back-n-forth...the Porter's leather belt drive and gears makes a repetative burring clink...and then the 4 table machine whirs and makes chain clinking noises...
Rob(I just play the shop radio a bit louder)
(Now the blank cutting machine makes the worst noise)
--------------------
www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
|
john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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Richard,
Let me explain the system I use with my machines here in the UK, it involves using the single phase mains electricty supply to run a 3 phase motor. By using a phase inverter it is possible to run a 3 phase motor from mains and have the facility to maintain torque whilst being able to vary the speed. The system works very well and there are no noise problems. I recommend it as a great method of producing a variable speed machine with all the advantages that this will give you.
John
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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This only works with 3 phase motors? And what is a "single phase mains electricity supply" Is it a self contained unit or a kind of installation from the power company?
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Richard Caldwell
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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Hi Richard,
The single phase supply is what is 'piped' into every home as standard, I am sure it will be that same in the US. 3 phase is used by companies running heavy duty elctrical machinery with higher power demands. You could look on ebay for phase inverters (single to three phase), or google it, might prove helpful.
John
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3120
Loc: Northeast
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I'm wondering if John is referring to frequency control, possibly? That readily changes speed with induction AC motors.
I use DC drives, for they maintain mega-torque at low speed. It offers extremely wide range, and are also very efficient with today's controllers. If you want to get rid of the hum, there is a way to install a filtering capacitor somehow to get rid of the 'spikes' on the DC side. You won't hardly note that it's running. The capacitor has to be matched to the particular setup. Don't ask me how, though. I prefer to hear them run anyways.
M.
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So many projects, so little time!
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Redstone2
journeyman
Reged: 02/28/09
Posts: 5
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Hello,
I have a MOM that I am converting to a three speed turn table with a VFD eccentric. The turn table will be driven by a three speed PSC motor (removed from a HVAC air handler). The eccentric will be driven by a 1/3 HP, 3 phase motor (I found it on Ebay for $0.99 + 20.00 s/h). The VFD also came from Ebay for $45.00.
To prevent "humming" proper attention must be paid to shielding and grounding. If you are looking into an AC VDF, I would recommend finding the install manual for a Minarik VFD02-D230AC or an Altvar 11 VDF. Both manuals will give you points and tips on installing a VFD.
I am building a series of pulleys for the VFD motor in order to give a wider range of eccentric speeds without motor cogging (and resonance) being a problem. DC is a good option also; I just found some good deals on an AC VFD.
Tom
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