Kant Twist alternative?

Way back when I started scratching out my DIY version of the Kant-Twist / Crab clamp on the backs of envelopes I reckoned the riveted pin and spacer construction was a major potential weak point if not precisely made. Seemed to me that it was one of those things that could only be done accurately and precisely on a production line with professionally set up tooling.

Getting things sufficiently precise with joint and gaps tight enough to ensure that things wouldn't try to twist whilst still being free moving looked to be a nightmare by one-at-a-time methods with simple pin and rivet construction.

Ended up with various combinations of welding, pressed in spacers having washers on the outer ends so the riveted over through pins wouldn't be hammered down against the arms and other associated exercises in misguided creativity to properly support the joints. None of which gave that nice warm feeling of working really well first time out.

After a week of lunchtime efforts I concluded that I didn't want some that badly and would be unlikly to seriously worried by not having any. 30 or so years on that turned out to be about right. Maybe half a dozen jobs where they would have been seriously better than what I had.

My then boss reckoned the reputation was mostly "American Hype" and flop-slop was inherent.

Clive

What appears to be the case in the ones I received is that the parts weren’t parallel when they were riveted. I would think that some sort of jig to keep them aligned would be required. It is often the case that I find myself wishing I could visit the factory so I could see for myself where things went wrong. I say this as MSC said all the clamps they have in stock of that size all looked like the ones they sent me. I can’t (Kant!) believe they all got damaged in transit?

I have seen designs that used milled out solid metal rather than riveted plates but thats quite a bit of work and tight tolerances/finish to ensure they work smoothly. I did think a while ago that a combination of solid and plates might work though.

This is CAD drawing of a posh one.

Guys you aren't likely to damage a steel clamp in 'transit', this issue has all the hallmarks of out sourcing to a lower cost facility

Tony

Hi Guys,

This picture contains all the data required to design what ever size Kant type clamp you may want to make.

Note that the size is based on two concentric circles, all the holes bar one fall on a circle. The symmetry makes designing your own easy. The dimensions on this drawing are the ones that I used to make 100 mm clamps.

I had my four pairs of frames laser cut from 3 mm plate for the sum of £10.00.

That’s neat, John

… and the laser-cutting sounds a bargain !

MichaelG.

I’ve seen some really nice looking components that were water jet cut but I don’t know anyone locally and I can’t supply a CAD drawing anyway. I’ll have to make do with my jigsaw. I’ve simplified the design to reduce the amount of work required.

Hi Michael,

I thought so too !

The chap that did the laser cutting said that they were in the process of cutting a load of 3 mm sheet and that there was quite large areas of that, that were scrap, and that he could put my bits onto the existing job and reduce the amount of material that they would only throw away. I actually ended up with a couple of pieces of 3 mm plate as well.

A quick sketch in OO.

I had my son laser cut my blanks and even then to make good clamps is a lot of work, you can see why they are so expensive to buy.

Finished. I won’t be making any more unless I find I really need them and I can get the plates water jet cut!

Mostly stainless with some brass and alloy. Using hex bar for the bosses proved to be a good call.

Very tidy, Vic

MichaelG.

Perhaps Vic or Bernard might consider a write up for MEW, and/or sharing a file people can send off for laser cutting?

Neil

Sadly the only drawing I’ve got is a sketch in Open Office so not much good for anything other than hand layout.

.

John Baron kindly provided an excellent ‘template’ when he wrote:

This picture contains all the data required to design what ever size Kant type clamp you may want to make.

MichaelG.

Despite the name the frame of a Kant twist will distort if tightened enthusiastically but maybe the name refers to the clamping action which does not apply any torque to the job being clamped as a classic “G” or “F” clamp will. Other types of clamp are available that will only apply a straight clamping force.

Mike

I bought my crab clamps back in 1984. The new sales rep had them priced per pair instead of each. I have since got a smaller pair of the Kant Twist ones, but are not the quality of the crab clamps from 1984. Some of the designs I have seen on here look to be better than anything I have bought.

By reason of its very design the frame of a Kant Twist clamp is torsionally weak. Probably intentionally as it allows the clamping blocks to self align against the parts being held even if they are not quite parallel so ensuring full contact.

Clearly there is a point where "slight flexibility" becomes "too easy to twist" so proper clamping action is not possible. My feeling has always been that the bobbins need to be a solid push fit in fairly substantial arms if the the design is to be stable under decent clamping loads. Maybe welded braces across the frame arms too.

As other posters of said its a lot of work to make a nice one. Vic and Bernard have shown just how nice the results can be if its considered worth the work.

Something that might go easier as a group effort making enough for semi-production line work. Five folk collaborating to do a pair each perhaps.

Clive

Edited By Clive Foster on 25/12/2021 09:36:51

Another view in case it helps others contemplating making one.

If nothing is forthcoming then I can do one or both.

Quick model based on John's circles.

Edited By JasonB on 25/12/2021 11:11:22