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Equipment Discussions >> Classic Telescopes

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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
How to straighten a bent shaft (Unitron)
      #6148124 - 10/20/13 10:06 AM Attachment (24 downloads)

Today I bought a heap of Unitron/Polarex stuff from the estate of a Danish amateur astronomer.

Apparenly this Fellow had been very active in visual astronomy, had a pair of Celestron Cat's plus some Polarex scopes, and had liked to mix/match and ATM with his gear.

After having sold off the Cat's, the family allowed me to fill my rear seat with what was left of Unitron/Polarex stuff (for the very fair price they asked), among other things a D60/f700 guide scope and a 128C mount (the guide will fit nicely on my Zeiss Telemator, and I can use the mount for my 114 ) :

Now, the stuff obviously has beeen out of use for a long time, it's dirty and needs cleaning & restoring. among other issuses, the slow motion shaft of the declination on the 128C mount is bended :


Any suggestions for straightening out a bended shaft (without risking to break it) ?

Thanks,
Allan

Edited by AllanDystrup (10/21/13 06:03 AM)


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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148139 - 10/20/13 10:15 AM Attachment (23 downloads)

Here's a pic of the bended Unitron 128C slo-mo shaft...

Allan


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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]
      #6148203 - 10/20/13 10:59 AM

Wow Allan, what a great haul. You are going to love that eq. mount! They are wonderful. Looks like you got a duatron too. How cool.

Terra


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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: terraclarke]
      #6148258 - 10/20/13 11:33 AM

Yep, a lot of good stuff there...
The 128 EQ came with the drive for 60mm too ,
working ,-- but all needs a good cleaning & lubrication.

Allan


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dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148296 - 10/20/13 11:58 AM

Spot heat it with a propane torch until its close to red hot and then it will be mallible enough to straighten out. Could be hard on the knob. Someone made a jig here in a different thread that would pull it straight but dunno how universal that is aa a fix. Cold bending wont work.

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hottr6
Carpal Tunnel
*****

Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148317 - 10/20/13 12:14 PM

Put it on an anvil and tap the bend with an engineer's hammer. As the bend straightens out, roll the shaft on the anvil, tapping the shaft to get the bend (presumably straight) you want. Don't use heat as it will melt the plastic handle.


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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: hottr6]
      #6148342 - 10/20/13 12:30 PM

Hmmmm, to heat or not ...
seems to be the

Allan


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tag1260
scholastic sledgehammer
*****

Reged: 10/07/12

Loc: Ohio, USA
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148362 - 10/20/13 12:44 PM

Not being familiar with it but will the knob come off?
You may also be able to get some of it out by clamping it in a large vise and using that as sort of a press. It may be less stress on it to get some out that way rather than beating it all out with a hammer.


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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: tag1260]
      #6148382 - 10/20/13 12:57 PM

Quote:

clamping it in a large vise




No, the knob doesn't come off.
But clamping the shaft in a vise sounds like an idea worth trying.

Allan


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roscoe
curmudgeon
*****

Reged: 02/04/09

Loc: NW Mass, inches from VT
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148424 - 10/20/13 01:17 PM

You'll get most of it out in a vise, (you may want to pad the jaws with scraps of hard wood) but the last part will have to be done with a hammer - find one with a flat, smooth face, and also a flat, smooth piece if sturdy steel for an anvil. Many light taps, rather than a big boom, is the way to go, rotating it regularly as you tap on it so the high point is up.
good luck!
R


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actionhac
Post Laureate
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Reged: 08/09/08

Loc: Seattle
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148425 - 10/20/13 01:20 PM Attachment (11 downloads)

I like using a vise also. With wood supporting the shaft the knob will not interfere. Squeeze out the bend and roll it on a flat surface to check progress.

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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: actionhac]
      #6148452 - 10/20/13 01:36 PM

Thank you Guys !
I've decided to go ahead with the vice as a first approach.
Seems like the most gentle, incremental and yet controlled way of straightening out the bend.

ps @Shane :
The problem with tapping the bend with a hammer is, that the end of the shaft is threaded (doesn't show well on my photo), so the tapping risks destroying the threads.

Allan

Edited by AllanDystrup (10/20/13 01:43 PM)


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Ron500E
member


Reged: 06/01/12

Loc: Illinois, near the River Styx
Re: How to straighten a bended shaft (Unitron) new [Re: actionhac]
      #6148458 - 10/20/13 01:38 PM

I'd bring it to a small machine shop and have them use a hydraulic press to slowly get it to its original position.
Not sure how much it would cost in Denmark but in the States, if they even bother to charge you, it would around $20 USD.
Kind Regards,

Ron


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AllanDystrup
sage
*****

Reged: 09/27/12

Loc: Denmark
Re: How to straighten a bended shaft (Unitron) new [Re: Ron500E]
      #6148469 - 10/20/13 01:47 PM

Good idea Ron -- i'll check what's available in the neighbourhood.

Allan

Edited by AllanDystrup (10/20/13 01:47 PM)


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fjs
Pooh-Bah
*****

Reged: 03/25/13

Loc: Olympic Peninsula, USA
Re: How to straighten a bended shaft (Unitron) new [Re: AllanDystrup]
      #6148475 - 10/20/13 01:50 PM

Quote:

I've decided to go ahead with the vice as a first approach.
Seems like the most gentle, incremental and yet controlled way of straightening out the bend.




NO! definitely not a vice! Drinking while performing delicate tasks is NOT recommended! (use a vise)


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grendel
Pooh-Bah


Reged: 04/12/09

Loc: Canterbury, Kent, UK
Re: How to straighten a bended shaft (Unitron) new [Re: fjs]
      #6148535 - 10/20/13 02:48 PM

its a vice in the uk, but dont ask the Americans what colour!
Grendel :-)


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fjs
Pooh-Bah
*****

Reged: 03/25/13

Loc: Olympic Peninsula, USA
Re: How to straighten a bended shaft (Unitron) new [Re: grendel]
      #6148548 - 10/20/13 02:58 PM

Oops! I knew about 'colour', et al, but not 'vice'; sorry. Thank you for setting me straight!

P.S. Why can't you spell 'defense' correctly? We are not removing fences here.

Edited by fjs (10/20/13 03:17 PM)


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greju
Carpal Tunnel
*****

Reged: 10/13/05

Re: How to straighten a bended shaft (Unitron) new [Re: hottr6]
      #6148559 - 10/20/13 03:03 PM

Quote:

Put it on an anvil and tap the bend with an engineer's hammer. As the bend straightens out, roll the shaft on the anvil, tapping the shaft to get the bend (presumably straight) you want. Don't use heat as it will melt the plastic handle.





This works well with a piece of soft wood on two sides.


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roscoe
curmudgeon
*****

Reged: 02/04/09

Loc: NW Mass, inches from VT
Re: How to straighten a bended shaft (Unitron) new [Re: fjs]
      #6148560 - 10/20/13 03:05 PM

To preserve the threads, you could use a block of hard wood instead of metal for your anvil.

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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: How to straighten a bended shaft (Unitron) new [Re: greju]
      #6148563 - 10/20/13 03:08 PM

If you heat it, wrap the knob and part of the shaft in Modeling Clay or Play Doh it will absorb the heat and not allow the heat to transfer up the shaft and melt the plastic knob.

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