Quote:

---

Probably meehanite cast iron rather than steel. Yep - looks like a long-radius grinder for CX surfaces. Did you put a spherometer on it yet?

If you don't have a spherometer, an old trick Joe Appels showed me was to clean off your grinder, then spray WD-40 on it and get the sun's image in focus and measure the distance to focus. Not as accurate as a well-made and calibrated spherometer but better than trying to stack up valve shims under a straightedge.

Mike

---

I will clean it up and check its focal length..I had that idea earlier myself. I have everything to make a spherometer..just haven't gotten round to it..but I will.

Second...I finished my first tubes table..it is a cast iron 8.5" table and I put one of my students 8" mirrors on it and tried out the polisher...OH it's so sweet....Much easier then the Porter polisher.....

I'll post images tomorrow.

Thanks.

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

Post Extras:

Quote:

---

Probably meehanite cast iron rather than steel. Yep - looks like a long-radius grinder for CX surfaces. Did you put a spherometer on it yet?

If you don't have a spherometer, an old trick Joe Appels showed me was to clean off your grinder, then spray WD-40 on it and get the sun's image in focus and measure the distance to focus. Not as accurate as a well-made and calibrated spherometer but better than trying to stack up valve shims under a straightedge.

Mike

---

Hey Mike...It is made from cast iron..I also have another tool that is very similar but is flat and it has concentric rings cut into the surface. It to has the large taper pin on its bottom. What is this tool used for? Picture included.

Lastly my original question...if this concaved tool is just that..a tool used to grind in convexed surfaces on lenses/mirrors...how is it actually used on the machine?

My guess is it sits on the glass and is stroked by way of a poker pin with a ball tip in the recess in the tapered pin of the tool.

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

Post Extras:

Quote:

---

That's a cast iron tool, fellah! Welcome to the real optician's "lap"!
**************
A good exercise- machine it convex to a predetermined ROC with your handy flycutter, and recut the concentric grooves to do mirrors. It'll hold the ROC far better than any glass or tile tool. Or you could also machine and grind it in flat for doing such pieces. Nothing like a good cast iron tool.
Mark

---

All righty then....

So I have one cast iron tool that is concaved for making CX curves for lenses...and I have a cast iron tool used to grind flat surfaces? Or is pitch supose to be applied to this tool?

And since both have the same tapered pin on thier backs...how do I use them with this?

Expert!

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

Post Extras:

Quote:

---

With the concentric grooves, they are essentially grinding tools- though if you give them a good scrub to get rid of grit particles, you can pour pitch on them for polishing.
********
There are basically, only 2 ways to use them- TOT, or TOB.
I used to use a female tapered pin socket with a 1"-8 female thread adapter for use on Strassie polishers. Literally dozens of ways to adapt them for either spindle or quill use. The only limits would be skill or imagination.
Mark

---

Right..TOT or TOB..... I shoulda thought of that.. By Quill you mean the *Poker pins* that extend down to the tool from the over arm right?

Well..I think I'm going to enlarge the quill(Poker pin) ball recess on the taper pin of both of these tools so I can use them as a grinding and a polishing tool.

The original spindles on this machine were taper pins(I don't like those kind)...that is why they are threaded now with flanges.

I just finished building a 13" table for the second drum and now I can get Droids 12.5" mirror going too.

Fun fun fun.

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

Post Extras:

Quote:

---

The quills should be tapered, with a machined ball on the end, preferably hardened. If that ball is worn off, you will wind up with quill pecks or drops, when the quill jumps out of the socket on the back, slides off the back and hits the glass.
You don't want that to happen! It's a real pain in the butt, and will leave you with a ton of grinding to fix it!
M.

---

Right..quills are the same as *Poker pins*. Bob over at Mathews Optical* is an old school term guy...he calls his tools laps. He is a great sourse for professional info, and has been making lenses longer then most of us are old.

He even owns Porters first polishing machine..the one depicted in the first ATM book.

Bob is the professional opticians professional.

He owns one of the only two conical lens making/polishing machines on the West coast. He does awesome work.

My newest machine....has a stop and will not let the quill ever get to the mirror if such a disaster ever happened.

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

Post Extras:

Quote:

---

Jah Boss - I "pinned" a few parts when working at an optical shop back in the 70's to the boss's dismay until I figured out that the down stop bolt on the overarm was unscrewing during runs from vibration and letting the quill jump the socket and come down on the parts. I put a lockwasher and nut on the down stop and stopped that. You should check your overarms and set the down stops before starting a run to make sure the quill tip only comes down low enough to engage the driver socket and not low enough to pin your parts.

If you machine your cast iron grinder to a CX radius, you should make a matching CC grinder so you can grind them together with SiC to true them to each other and get them both truly spherical and on radius. They will grind each other a lot faster than trying to true them using glass; the wear rate is something like 100X faster on glass than on cast iron.

Also, the concentric channels are OK but you need to cut some radial channels as well so you don't get suction and sticking when you get to 9um or 5um. I prefer X,Y channels in a grid over concentric channels, but that's just personal preference.

Mike

---

I pinned my 18" when I was working it on the Porter.....I since then made a cable hoist that slings from the rafters...that i secure to the over arm....if the quill jumps from the holder it can't fall on the glass.

Like I mentioned earlier..this new machine has stop bolts to prevent that.

What application would I find myself needing to use these cast iron CX and CC cast iron tools? Making my 10"f/16 objective maybe?

I was under the impression we'd make the tools after we got the pregenerated blanks.

I'm not quite sure what Bob has in mind.

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

Post Extras: