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Clamp and fixture projects

PeterT

Ultra Member
Premium Member
Good idea Dabbler. That solves the 'how to clamp a smaller diameter with a larger hole'. But I don't think it solves what I was referring to - clamping multiple pins of varying random diameter. This drawing is exaggerated to show what I mean. Green pin is smaller OD than pink pin. Now if tolerances don't vary much, the difference may get taken up in jaw distortion. But if they are perfectly rigid bodies & the front & rear of jigs are constrained by parallel main vise jaws closing, then the small pin wont get the same squeeze. Or, assuming the small pin is clamped on the tangent, then the big pin will not fit the hole the same way.
 

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Dabbler

ersatz engineer
@PeterT You are right! 100%...

This is where the 3 point contact thing comes in handy.

If Janger has centreless ground stock (like 01 drill rod) then they are close enough to clamp with elastic deformation.
 

Janger

(John)
Administrator
Vendor
here's my take on this: Make the holes .375 BUT there's a trick to it (there's always a trick)

View attachment 17974

You mill the holes with a .005 to .010 spacer, then after the boring is complete, relieve the holes (shown in red) an additional .020 - this relief amounts to about 15% of the diameter (if you include both sides) when complete. Now there is no way for the jaws to 'pinch' the pin when released, and when you tighten you get positive, repeatable clamping.

I don't quite get it. Sounds like to me I should bore it 0.375 diameter (with the spacer )and then bore it again to 0.375+0.020 = 0.395. Why is that any different than just boring it to 0.395 in the first place? I think I'm missing something.
 

Dabbler

ersatz engineer
it is just to relieve the centre of one jaw, not the complete hole. this form 3 points of contact like this: I'm sorry for not being clear, or illustrating poorly...

holes.PNG
 

PeterT

Ultra Member
Premium Member
Here is another idea to ponder. If you do enough of this gang style CNC machining, maybe it would warrant buying some cheapo drill chucks & mount them to a dedicated fixture plate. The advantage is you could grip a wide range of stock diameter & pop them in & out relatively quick with no special tools. Each chuck would be attached to plate at some fixed, known offset distance, so presumably once you indicate off one gripped reference pin, all the rest would immediately be in alignment. And each part would always be concentric to chuck axis regardless of diameter axis. On the downside, limited length range. I don't think stock can protrude through the backside even on the threaded ones? And runout will probably not be great at that price. OK.... how about v2.0, a gang of ER collet blocks perhaps?
 

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Janger

(John)
Administrator
Vendor
Some pics.
Milling parts (clamp standoffs) that could be lathe parts.

Then power tapping on the little manual mill. I bought a couple quality? Sowa taps after I broke my one #10-24 tap in the cnc. Somebody on here said to tap small parts with a drill chuck loosely tightened - then when Issues arise the Chuck just spins without breaking the tap. Kind of a red neck torque limiter. Doing it this way is also really fiddly and slow. It does work as I have not broken a tap so far. At $16 each I’d rather not break them.
 

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