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27th Jun 2022, 12:28 PM #1Diamond Member
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Threaded handles for machinist clamps
So, I have a pair of unfinished clamps without the threaded handles, and am trying to quickly finish them. Can't be bothered turning down stock, threading, knurning, and cross drilling.
(like a million apprentices have for centuries )
Threads are 3/8 Whitworth. Toolmaker suggested socket head screws, and weld/braze a rod as handle on to the top. Alas, I couldn't find cheap high tensile screws with decent thread length.
So, grabbed some cheap bolts from the "red hammer warehouse":
IMG_2806.jpg
The "expanding" thread handle is easy. I just machine the end to fit the pocket:
IMG_2994.jpgIMG_2996.jpgIMG_2997.jpg
The "tightening" handle requires some thought, though.
Needs a sleeve to clear the square lock under the bolt's dome head.
Or maybe bodgy some washers and weld the whole lot to a rod for the cranking handle?
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27th Jun 2022, 05:07 PM #2
Hi Nigel,
I would have turned off the square under the head first !Best Regards:
Baron J.
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29th Jun 2022, 09:39 PM #3Diamond Member
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Fair enough. I was thinking that might weaken the bolt head,
...but it saved time looking for washers, so:
IMG_3001.jpg IMG_3002.jpg
Then, ground some slots in the head, found some old 1/4" rod, bent a crank on one end:
IMG_3003.jpg IMG_3004.jpg
and did some welding:
IMG_3005.jpg IMG_3006.jpg
Sadly, on one of them I undercut the rod, and trying to build it up again failed.
Will have to find some more rod tomorrow
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30th Jun 2022, 02:26 PM #4Golden Member
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That type of handle will really restrict the usability of the clamp.
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30th Jun 2022, 06:34 PM #5Diamond Member
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Restrict? Yes, they will get in the way sometimes, but cheap and fast sometimes wins out.
(often, for me)
The other way they restrict is not clamping below about 30mm:
IMG_3007.jpg
because the thread on the expanding handle doesn't go far enough.
For now, I die cut its thread 10 or 15mm longer:
IMG_3009.jpg
Eventually, I might make some better handles from booker (all thread) rod,
with machined/knurled/cross-drilled heads.
I would have gone that way initially, except that all the threaded rod I found was rubbish.
Either soft mild steel which is soooo loose that it would strip at first clamping,
or stainless that was better, but I don't trust to not gall or fail under stress.
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1st Jul 2022, 12:20 AM #6Diamond Member
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- Oct 2008
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- N.W.Tasmania
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Stainless probably not too much of a problem if the clamp jaws are not stainless as well. I agree that hi tensile thread would be better though, as would a much finer thread. Some of the model Engineer threads - either 32 or 40 tpi would give lots of clamping power.
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1st Jul 2022, 12:56 PM #7Most Valued Member
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1st Jul 2022, 08:49 PM #8Diamond Member
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Indeed. I noticed that when cutting, so only did about half of the depth through the clamp blocks – to still provide some clamping strength.
Their steel is fairly nasty rubbish. Maybe from the bright galvanising?
I doubt they will last long, but I'm hoping soft thread in the handles will spare the threads in the clamp blocks.
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