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Need Unitron 142 thumbscrew info

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#1 bluecoast

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Posted 09 June 2021 - 01:02 AM

Hi all,

 

I have a Unitron 142 and it's missing both thumbscrews that clamp the solar projection rod (actually they're broken off -- the screw parts are still seized in both rod mounts).

 

Anyway, can anyone tell me if they're the same as the thumbscrews for the finder, or are they a different size?

 

unitron

 

If they're a different size, would anyone want to measure one for me? I could probably make a decent copy if I knew the diameter.

 

Thanks!



#2 bluecoast

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Posted 11 June 2021 - 10:08 PM

Please help :) !



#3 ccwemyss

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Posted 11 June 2021 - 10:34 PM

On my 140, they are not the same. The threads for the rod rings are 10-24.

 

Chip W. 


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#4 apfever

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Posted 12 June 2021 - 12:50 AM

Chip, are the rod rings on yours the split type that squeeze the rod, or the solid ring type that the set screw holds the rod?

There may be a difference between the two. The OP is showing the solid ring type rod brackets. 

 

My 152 has the solid rings like the OP and they are also 10-24 SAE, not metric. I can not compare to my finder since my finder is much larger than the model 140. 


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#5 starman876

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Posted 12 June 2021 - 08:00 AM

PM me I can help you out.


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#6 ccwemyss

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Posted 12 June 2021 - 08:50 AM

Chip, are the rod rings on yours the split type that squeeze the rod, or the solid ring type that the set screw holds the rod?

There may be a difference between the two. The OP is showing the solid ring type rod brackets. 

 

My 152 has the solid rings like the OP and they are also 10-24 SAE, not metric. I can not compare to my finder since my finder is much larger than the model 140. 

The 140 from the loaner set has the thumb screws like the ones in the picture from the OP. My 142 has the split type. I didn’t have an answer earlier because the 140 hadn’t come back until yesterday. 
 

Chip W.


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#7 starman876

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Posted 12 June 2021 - 11:16 AM

The finder screws for the 140 and the screw that holds the sun projection rod are not the same size.   The finder screws are smaller.  However, the finder screws on the 152 finder are the same size as the projection rod screws.


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#8 bluecoast

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Posted 12 June 2021 - 03:23 PM

Hi all,

 

Thanks for the help. 10-24 is good info for a start.

I am also interested in the outside diameter of the knobs -- I'd like to try to make new ones, copied as close as possible.

 

The original photo is not my actual scope, but I do have the solid rod mounts same as the photo (where the thumbscrew bears directly on the rod). 

 

Thanks for the help so far!



#9 apfever

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Posted 12 June 2021 - 03:54 PM

The finder screws for the 140 and the screw that holds the sun projection rod are not the same size.   The finder screws are smaller.  However, the finder screws on the 152 finder are the same size as the projection rod screws.

I checked my 152. The finder and rod holder screws are the same thread (10X24) but different design head and length. These screws are plated brass. Stainless steel is a good match for color. I think a standard 10X24 hex bolt will have enough head material to machine a match. 

 

Mine are:

Head diameter 0.471"

Serrated edge 0.091" wide

working thread length 0.375"

There is some curved detail from the serrated edge down to the threads. I'm not attempting to blue print that. I suggest getting one to copy that you can send back to a lender. A stainless copy would be superior to the originals. Your nickel plated brass ones are broke, you'd probably break the bracket before a stainless screw. Stainless can be ground and sanded but is harder to machine with standard cutting tips. Stainless is 'chunky' to machine in a regular manner.


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#10 bluecoast

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Posted 12 June 2021 - 06:17 PM

Thanks all! apfever... those dimensions are awesome -- I think they would be good enough as-is (I would just copy the "dome" style button from the finder screws)

 

It sounds like I may be able to get spares and not have to make these, but if I do make them it'll be thanks to your measurements -- much appreciated.

 

I have been making some other parts and some 3D-printed tools to straighten the tube and dew shield (see pics below). I thought about using stainless, but since I had a few parts to make, decided to use brass and try to get them plated somewhere.

 

 

142 Tripod Stop Studs
Unitron 142 Tripod Nut
142 Dew Shield Dent Removal
142 Dew Shield Dent Removal 2

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#11 starman876

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Posted 12 June 2021 - 07:38 PM

Thanks all! apfever... those dimensions are awesome -- I think they would be good enough as-is (I would just copy the "dome" style button from the finder screws)

 

It sounds like I may be able to get spares and not have to make these, but if I do make them it'll be thanks to your measurements -- much appreciated.

 

I have been making some other parts and some 3D-printed tools to straighten the tube and dew shield (see pics below). I thought about using stainless, but since I had a few parts to make, decided to use brass and try to get them plated somewhere.

 

 

nice tube dent removal tool


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#12 starman876

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Posted 12 June 2021 - 07:39 PM

Thanks all! apfever... those dimensions are awesome -- I think they would be good enough as-is (I would just copy the "dome" style button from the finder screws)

 

It sounds like I may be able to get spares and not have to make these, but if I do make them it'll be thanks to your measurements -- much appreciated.

 

I have been making some other parts and some 3D-printed tools to straighten the tube and dew shield (see pics below). I thought about using stainless, but since I had a few parts to make, decided to use brass and try to get them plated somewhere.

 

 

those round nuts and double ended bolts to hold the tray to the tripod are not easy to find


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