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Unitron 128

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#26 sgorton99

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Posted 10 May 2013 - 05:37 PM

Lens, dusty - but should be fine.

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#27 sgorton99

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Posted 10 May 2013 - 05:37 PM

Lens again.

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#28 starman876

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Posted 10 May 2013 - 05:38 PM

Good catch

#29 sgorton99

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Posted 10 May 2013 - 05:39 PM

It for now. Should end up being a nice little 128. Although I hate to dive in to another project since my 155 is calling...
Steve

#30 sgorton99

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Posted 10 May 2013 - 05:40 PM

Thanks - I forgot to mention and probably would be fair, the seller gave me a partial refund because of the broken pieces in the first box.

#31 starman876

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Posted 10 May 2013 - 05:45 PM

Considering that shaft is most likely impossible to find I would suggest taking off the knob and having a machine shop make a new shaft. The knob is glued on so you will have to soften up the glue before you can take it off. I do not believe they molded the knob onto the shaft.

#32 Dave M

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Posted 10 May 2013 - 07:24 PM

Very Nice Steve, Congrats!

#33 terraclarke

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Posted 10 May 2013 - 08:12 PM

I agree. It would be an easy matter to machine a new threaded steel rod to the same specifications. It's a later model so should be a standard thread so a die will be available and threads won't have to be cut on the lathe. The "sticky" part (pun intended) will be transferring the knob from the original to the new rod. II am sure you are well up to it Steve considering your fine restoration work so far; it will be a simple task for you. The 128 drives are really nice. Before you know it you will have a lovely 128 next to your gorgeous 155.

#34 sgorton99

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Posted 10 May 2013 - 08:42 PM

Thanks! Like a Mini-Me for the 155. A fellow astronomy guy from the forums here offered to "fix" my control with a sleeve. He bought some EPs from me, so I will just ship it to him with those and he is going to take a crack at it.

#35 starman876

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Posted 10 May 2013 - 08:58 PM

I am not so sure Terra. Steve has a hard time finding screws :lol: :lol:

#36 starman876

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Posted 10 May 2013 - 09:12 PM

Steve

You could simply just put a thread on the part of the shaft that is left. That should work. If you put a sleeve on it you might run out of threads sooner than you want when using the scope. The mssing inch or so should not make that much difference.

#37 sgorton99

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Posted 10 May 2013 - 09:15 PM

And how would I do that? I don't "do" metal work...

#38 starman876

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Posted 10 May 2013 - 09:17 PM

all you need is a dye and then put new threads on the shaft.
Looks it up on google. Pretty simple. If you can sand and paint you can use a dye.

#39 starman876

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Posted 10 May 2013 - 09:19 PM

You take the broken threaded part to a auto parts store (not the large chains) and have them match a dye to the threads. Just buy the tool and put new threads on it. IF you ask them nice they will show you.

#40 terraclarke

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Posted 10 May 2013 - 09:29 PM

You need to put it on a thread gauge first to determine which die to purchase. You will also need the die wrench. Since its a later Unitron it should be a common thread standard. Once you determine which one you might just want to get a set of taps and dies that includes the wrenches too. Harbor Freight is a good place to shop for one.

Then just put the rod you need to re-work in the vise and the bent end, and cut the rod with a hack saw just above the bend. (Looking at your picture it looks like a clean break so you may be able to skip that step.) File the cut smooth. Put the rod vertically in the vise with the end you want to thread pointing up. Put a little oil on the tip of the rod, and balance the die on the tip in its wrench and slowly begin to rotate it with a tiny bit of downward pressure and you will feel the die bite into the metal. Keep it lubricated with a little oil and slowly rotate,the die until you have as much thread as you need, occasionally backing it off in the opposite direction to clear the filings. It's totally easy Steve. You can do metal.

#41 starman876

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Posted 10 May 2013 - 09:45 PM

Most important is to make sure the dye stayes square with the rod otherwise you will have a wigly rod when you turn it. There is special thread cutting oil. Ot maybe the local machine shop at the auto parts will be nice and do it for you.

#42 nightpilot

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Posted 11 May 2013 - 12:01 AM

Thats gotta be a tough part to find. Sleeve might work. As has been mentioned you may loose thread. Good advice on making the rod. You may have to do that or have someone make it. Boy other than that it should clean up good. Nice 128. I am a sucker for those black and white setting circles.

#43 terraclarke

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Posted 11 May 2013 - 07:14 AM

Most important is to make sure the dye stayes square with the rod otherwise you will have a wigly rod when you turn it. There is special thread cutting oil. Ot maybe the local machine shop at the auto parts will be nice and do it for you.


I've always just used plain old 10w30 and it worked fine with hand turned taps and dies.

#44 sgorton99

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Posted 11 May 2013 - 07:34 AM

Wow, a lot of great advice everyone! Having tried a bunch of screws in the hardware store that were not quite the right size, my biggest concern would be finding the correct die size for the sometimes funky Unitron threads. Losing a 1/4 or even 1/2 inch of threading is not critical, you would just have to loosen the lock a do a rough adjustment and not have as much travel with the slo-mo control.

#45 starman876

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Posted 11 May 2013 - 07:46 AM

IF you take the slow motion control to the store with the broken part they can see what trhead size it is and provide the proper dye. Or just find a machine shop in your area and bring some flowers with you. Now you need to know, around here they charge $100 an hour. The reason I bought a set of taps and dye and many other tools. Even a mini mill from harbor freight. I do not know if you live in an area that deserves a harbor freight. For years there was not one in the DC area. THe closest was in NJ. But if you like to tinker that is a great place. While you are there pick up some of those maple work tables. They are a joy for $120.

#46 sgorton99

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Posted 11 May 2013 - 08:02 AM

Here is a good example of the thread size issue. The complete control is from my 114, looks the same - right? Nope, does not work.

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#47 Mirzam

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Posted 11 May 2013 - 08:24 AM

To a trained eye that is obviously a coarser thread on the broken control. If you could find a coupler the right size for the rod diameter, you could make a flat spot on the two pieces and hold them together (after cutting off the bent section). Here is what I am talking about:

McMaster-Carr shaft couplers

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#48 starman876

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Posted 11 May 2013 - 08:44 AM

Just take it to the parts store and see if a dye matches up. Simple take the threaded part and see if it will screw into the dye easily. If it does you have the right dye.

#49 sgorton99

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Posted 11 May 2013 - 08:58 AM

Well, found another solution. I received a very rough 140 mount with the tripod I bought for this. Because of some damage to it, I decided not to sell it whole, but maybe for some parts that someone may need. Anyway, the part(?) the shaft screws in to fits on the 128 mount. Seems to be a good solution.

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#50 terraclarke

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Posted 11 May 2013 - 09:01 AM

That looks to be the perfect solution. Good for you Steve. :waytogo:






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