The Giant Binocular

Flyinfool said:
Good excuse to make or buy a wobble broach setup.

Allen keys are case hardened, If they were hard all the way thru they would snap off all the time. That is why you can twist without breaking them in a very stuck fastener. Once you start grinding the case is gone.
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Ah ha, I didnt know that. I have some drill rod on the way to make one, I dont like that word "buy" :laughing:
 
There are a few threads here on HM for building a wobble broach.
 
savarin said:
Hi Bob, its not the screws I need to be hard, they will have very little pressure on them.
They are .5mm pitch for the tension adjustment on the mirror backs.
I just had the idea of broaching a hex hole in the stainless to make my own.
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Sorry Charles, I had the cart before the horse. However the same statement works for keys, A quality brand like "Unbrako" do have keys that are quite hard and tough. I have in fact done the very process you are trying to do, and it worked. Ok it was not into SS but worked in MS, I'd be checking the hardness of the SS. Good luck. I know you'll find a way, you always do.
 
At long last both plates are finished. I dont think I will ever try to do this again.
2-finished.jpg
Next drill and tap and countersink M10x0.5mm.
Before I can start polishing the mirrors I have to totally clean the machine. There is carborundum dust everywhere, it has to be spotless to ensure I dont scratch a mirror.
 
At last I am ready to polish the mirrors. First job is make the lap.
I used plaster that took over a week to thoroughly dry then soaked it in tile grout sealant to prevent it from adsorbing water from the polishing.
Used some firm plastic sheet to make a dam around the tool and poured a hot mix of pine resin and caster oil in.
p2-poured.jpg
Just before it was poured I tested the consistency with a 30 second thumbnail press to see it it raised a small lip, it did so it should be soft enough to conform to the mirror (He hopes)
p1-thumbnail.jpg

remove the dam wall
p3-dam-removed.jpg
bevel the edge
p4-beveled.jpg
cut the facets
p5-faceted.jpg
randomly score the lap and brush with a stainless wire brush to remove all particles.
p6-scored.jpg

coat the mirror in a very thick cerium oxide and water polishing compound layer
p7-thick-cerium.jpg
Lay the lap on top with a little weight and leave to cold press and hopefully conform to the mirror
p8-pressing.jpg
Panic stations arise when you cant separate the mirror and lap.
I will find out tomorrow.
 
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