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Use of Allen Head Screws for Collimation Adjustment

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#1 Rustler46

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Posted 19 May 2019 - 10:29 PM

What would you say to me replacing the Bob's Knobs adjustment screws on my C-11 with Allen head screws? I have been wanting to do this because of the difficulty in turning the screw heads in small increments when very tight. Like Eddgie said in his collimation guide, these screws are not head bolts for a 454 CID Chevy V-8. So I'm aware how tight I should go with these screws in getting collimation adjusted. Given the extra torque available with the lever arm of the Allen wrench, I would need to be sensitive to the maximum force to be applied. The advantage would be in seeing small rotation angles as the screws are adjusted. 

 

What do you-all think? Has anyone done this? If so how has it turned out?

 

CS,

Russ


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#2 choward94002

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Posted 19 May 2019 - 10:43 PM

I've long ago replaced all of the adjustment screws on my scopes with Allen head bolts; they work very nicely PROVIDED you make sure you have the same length bolt and that the bolt shoulder (the part that the allen wrench goes into) is no longer than the original screw shoulder to ensure they don't make contact with the plate cover (can crack a corrector plate) or interfere with the rotation of a fastar cover (Bob's knobs will do that) for the reasons you cite; it's much easier to make adjustments with a lever than two fingers ... pan head bolts like this [https://www.google.c...558410078777402] work fine ...


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#3 Cychomartin

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Posted 19 May 2019 - 11:44 PM

I've got both on different scopes. I find the Allen bolts easier for the fine adjustments required for perfect collimation. 


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#4 Kunama

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Posted 20 May 2019 - 12:51 AM

I've got both on different scopes. I find the Allen bolts easier for the fine adjustments required for perfect collimation. 

Bob'sKnobs are just plastic caps pressed onto capscrews, I just pried them off to expose the Allen head underneath.... much better, especially for fine adjustments under tension....


Edited by Kunama, 20 May 2019 - 12:52 AM.

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#5 Rustler46

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Posted 20 May 2019 - 02:02 AM

Bob'sKnobs are just plastic caps pressed onto capscrews, I just pried them off to expose the Allen head underneath.... much better, especially for fine adjustments under tension....

Interesting discovery. One wonders why he just didn't supply the Allen head screws and a wrench. I suppose it would be hard to make a profit with off the shelf hardware store items. For now I will try removing the plastic knobs to expose the Allen heads. Eventually I will replace them with stainless steel screws. The Bob's Knobs screws are just black steel, not the best choice for a sometimes moist environment.



#6 Rustler46

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Posted 20 May 2019 - 02:04 AM

I've long ago replaced all of the adjustment screws on my scopes with Allen head bolts; they work very nicely PROVIDED you make sure you have the same length bolt and that the bolt shoulder (the part that the allen wrench goes into) is no longer than the original screw shoulder to ensure they don't make contact with the plate cover (can crack a corrector plate) or interfere with the rotation of a fastar cover (Bob's knobs will do that) for the reasons you cite; it's much easier to make adjustments with a lever than two fingers ... pan head bolts like this [https://www.google.c...558410078777402] work fine ...

Thanks for the reply and for hints on avoiding damage. Mine will soon be replaced with stainless steel substitutes.

 

Are you currently using all the SCTs listed in your signature. If so - amazing.


Edited by Rustler46, 20 May 2019 - 02:05 AM.


#7 bbqediguana

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Posted 20 May 2019 - 06:58 AM

I purchased Bob's Knobs for my Meade 2080 (which had Allen head screws as stock) and I used them for a season. I came to the same conclusion as you did - that I couldn't get the fine enough adjustments required to get precise collimation. I went back to the Allen head screws and the extra leverage from the Allen key gives me that precise control that I was looking for. 


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