Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
Get a Cloudy Nights T-Shirt Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu uh, User

Equipment Discussions >> Classic Telescopes

Pages: 1 | 2 | 3 | (show all)
AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: fjs]
      #6148577 - 10/20/13 03:18 PM

vise vis--vis vice
versa


Post Extras: Print Post   Remind Me!   Notify Moderator  
dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: How to straighten a bended shaft (Unitron) new [Re: orion61]
      #6148614 - 10/20/13 03:43 PM

Another trick is to wrap aluminum foil and then lightly clamp vise grips on the shaft as a heat sink, I'd forgotten about that.

Good luck!!


Post Extras: Print Post   Remind Me!   Notify Moderator  
fjs
Pooh-Bah
*****

Reged: 03/25/13

Loc: Olympic Peninsula, USA
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148645 - 10/20/13 04:07 PM

Quote:

vise vis--vis vice
versa




truly hilarious, Allan.

I don't think you will go wrong with the 'vice' as long as the shaft is not bent too severely. If it is bent more than about 20 degrees or so; yes, I would want to heat it. If you choose to heat it(and I wouldn't blame you for doing that), there are many ways to deflect the heat away from the knobs. Any type of clamp affixed to the shaft between the heated area and the knobs SHOULD do the trick (WILL do the trick if adequate). What is required is the understanding that you are providing a large lump of metal that will soak up the excess heat before it reaches the plastic knobs. Aluminum(Aluminium) is well known for its heat transfer abilities.

As you can see from my post; we use the word 'bent' here. I don't know if Grendel would agree.


Post Extras: Print Post   Remind Me!   Notify Moderator  
terraclarke
Post Laureate
*****

Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: How to straighten a bended shaft (Unitron) new [Re: fjs]
      #6148707 - 10/20/13 04:48 PM

I would go with a vice and hard wood like oak in the jaws to not mar the threads. The vice will allow you to slowly and evenly apply compressive stress to the metal without as much chance of metal fatigue. Repeated blows with a hammer will possibly cause fatigue, metal crystallization and fracturing. Also, fast heating and uncontrolled cooling can result in metal crystallization and fracturing, aside from damage to the plastic knob. A heat sink is problematic. Use the vise and periodically, slowly release the pressure and examine then rotate the bolt as need be. That would be my first coarse of action. Heat or hammer as a last resort.

Post Extras: Print Post   Remind Me!   Notify Moderator  
dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6148967 - 10/20/13 07:31 PM

That sounds like sensible advice Terra

Post Extras: Print Post   Remind Me!   Notify Moderator  
AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149202 - 10/21/13 01:25 AM

Right Terra, this will be my 1. approach.

Thank you all, for all the good advice.
Truly a treasure chest of knowledge in this forum !

Allan

Edited by AllanDystrup (10/21/13 01:26 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149314 - 10/21/13 06:08 AM

Quote:

The vice will allow you to slowly and evenly apply compressive stress to the metal without as much chance of metal fatigue. Repeated blows with a hammer will possibly cause fatigue, metal crystallization and fracturing.




Terra:

Looking at it, it is steel and it is unlikely that it is very hard steel, it should be sufficiently ductile if one wanted to use a hammer. "Fatigue" seems unlikely to me unless it were already cracked/fractured and then it would probably grow the crack no matter what one did.

Heat could be good but would likely damage the finish. Heat sinking it would save the plastic, not sure about the finish.

I would use a vise initially, aluminum jaw covers are nice but there will likely be some residual deformation which would will need a final straightening.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
bremms
Carpal Tunnel
*****

Reged: 08/31/12

Loc: SC
Re: How to straighten a bended shaft (Unitron) new [Re: Jon Isaacs]
      #6149335 - 10/21/13 06:47 AM

Yes you will need to do some final tweaking after the vise. If you are good at delicate tasks, once it is close you can use a few nuts to hold it in position just shy of the bent area. cllamp those in the vise and use gentle pressure. Depending on the type of steel. The fix can be easy or it will crack and break. It's most likely a mild steel . The vise method can cause extra deformation if you are not careful. If I the unbent length is too long in the vise you will cause a bend in the opposite direction.
I would bend it back by inserting into a threaded fixture slowly and gently bending it back. Thread it in far as possible... Gently apply pressure... Little more maybe thread it in more .. You are bending it back the same way it was bent. It will work better than the vise method. If it fractures.. Well, it went well past the elastic limit and it wouldn't matter how it was fixed.


Post Extras: Print Post   Remind Me!   Notify Moderator  
terraclarke
Post Laureate
*****

Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: How to straighten a bended shaft (Unitron) new [Re: bremms]
      #6149342 - 10/21/13 07:10 AM

Hookes Law always applies.

Post Extras: Print Post   Remind Me!   Notify Moderator  
terraclarke
Post Laureate
*****

Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149420 - 10/21/13 08:41 AM

Be very careful. You can see in the following photo, posted by one of our CN Classics members, the point of weakness where the threaded portion meets the unthreaded portion. You can see in the photo that the shaft was bent prior to fracture. Don't know if the fracture occurred at the time of bending or during an attempt to straighten it.

http://www.cloudynights.com/classifieds/data/28/44420-1368137649DSC06295-larg...


Post Extras: Print Post   Remind Me!   Notify Moderator  
AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149530 - 10/21/13 09:53 AM

Dang, you've got me worried now Terra...

Well, I can't use the shaft as is, so I'll clamp softly
(and carry a [strike]big[/strike] tiny hammer...)

Allan

Edited by AllanDystrup (10/21/13 09:56 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
terraclarke
Post Laureate
*****

Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6149595 - 10/21/13 10:29 AM

Allan

Post Extras: Print Post   Remind Me!   Notify Moderator  
actionhac
Post Laureate
*****

Reged: 08/09/08

Loc: Seattle
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149623 - 10/21/13 10:45 AM

Wow Terra thats a good piece of detective work and may have saved Allan from a heart failure.
The item you found looks like it could be brass and if Allan's is the same material fracture is likely.
I would be very careful and possibly not even try straightening it if in fact it is brass. If its steel I'd say proceed with caution.

Robert


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149641 - 10/21/13 10:58 AM

Quote:

Be very careful. You can see in the following photo, posted by one of our CN Classics members, the point of weakness where the threaded portion meets the unthreaded portion. You can see in the photo that the shaft was bent prior to fracture. Don't know if the fracture occurred at the time of bending or during an attempt to straighten it.






When there are threads present, a stress riser exists and fracture is more far likely. Whether it occurred during the initial bending or the straightening, when it breaks, it breaks. Without actually seeing the threads on the photo, it does look to be in the threaded region.

If it were to break, good machinist could bore out the plastic and machine a new shaft but one would need a friend who is a machinist to make it worthwhile.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
terraclarke
Post Laureate
*****

Reged: 05/29/12

Loc: Just South of the Mason-Dixon ...
Re: How to straighten a bended shaft (Unitron) new [Re: actionhac]
      #6149739 - 10/21/13 12:01 PM

Thanks Robert. I knew I had seen a picture of a similar bent and broken Unitron mount shaft a few months ago so this morning I just set out to ferret it out by looking at posts and adds of several of our regular Unitron folks here and voila. It was Steve's.

Post Extras: Print Post   Remind Me!   Notify Moderator  
sgorton99
Post Laureate
*****

Reged: 04/30/08

Loc: Wisconsin, Madison
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6149785 - 10/21/13 12:22 PM

Yes, that is my broken shaft from my 128. Good detective work Terra! I have been watching this thread with great interest, as my long shafts on my 155 need some minor straightening as well.

Post Extras: Print Post   Remind Me!   Notify Moderator  
grendel
Pooh-Bah


Reged: 04/12/09

Loc: Canterbury, Kent, UK
Re: How to straighten a bended shaft (Unitron) new [Re: sgorton99]
      #6150169 - 10/21/13 04:25 PM

you can hold the handle end of the shaft in the vice (using the vice as a heat sink) then heat the shaft, you can then slacken the vice, move the shaft into the jaws to straighten.
all my metalworking vices have soft jaws used to cover the serrated jaws, usually made from sheet metal, folded over the jaws of the vice.
and we call stuff bent too (or kinked)
Grendel


Post Extras: Print Post   Remind Me!   Notify Moderator  
bremms
Carpal Tunnel
*****

Reged: 08/31/12

Loc: SC
Re: How to straighten a bended shaft (Unitron) new [Re: grendel]
      #6150294 - 10/21/13 05:41 PM

My feeling is, if its bent like that. It's useless try and bend it back very carefully. It break it breaks... You can trim it off and re thread a little more of the shaft. My Zeiss had a bent azimuth adjuster ( happened in packing) the seller sent me back some money to compensate. I knew it would not bend back without breaking.I was able to shorten it a little and it's hard to tell. It is about 8-9mm shorter.

Post Extras: Print Post   Remind Me!   Notify Moderator  
dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: How to straighten a bended shaft (Unitron) new [Re: bremms]
      #6150311 - 10/21/13 05:51 PM

I wonder if that shaft is also one of those odd ball non standard Japanese threads?

A magnet will show if its Steel or chrome plated brass or other non ferrous metal.


Post Extras: Print Post   Remind Me!   Notify Moderator  
actionhac
Post Laureate
*****

Reged: 08/09/08

Loc: Seattle
Re: How to straighten a bended shaft (Unitron) new [Re: dgreyson]
      #6150493 - 10/21/13 07:56 PM

Another idea is to not disturb that bend and add another bend in the opposite direction to bring the shaft back to straight?



Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | (show all)


Extra information
27 registered and 16 anonymous users are browsing this forum.

Moderator:  Rich (RLTYS), Brian Risley 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 1547

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics