Kant Twist alternative?

[bernard towersParticipant @bernardtowers37738]

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.

[VicParticipant @vic]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Very tidy, Vic

MichaelG.

[Neil WyattModerator @neilwyatt]

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

Neil

[VicParticipant @vic]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 24/12/2021 21:10:37:

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

Neil

.

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.

[Mike PooleParticipant @mikepoole82104]

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

[Neil LickfoldParticipant @neillickfold44316]

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.

[Clive FosterParticipant @clivefoster55965]

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

[VicParticipant @vic]

Another view in case it helps others contemplating making one.

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 24/12/2021 21:10:37:

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

Neil

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

[VicParticipant @vic]

Nice job Jason. I think I prefer Bernard’s design though as it looks likely to be more rigid. I only lost some of the angles on mine to make it easier to cut out.

If anyone can get the arms water or laser cut at a good price I’d be interested in a couple. Probably 2” or 3”.

[EdHParticipant @edh]

The site for Bengs in Germany has them for sale, not sure what they would cost by the time the import, vat and postage was added

https://www.bengs-modellbau.de/werkzeug/werkzeuge/parallelzwinge-spannhand?number=3431

[VicParticipant @vic]

Once you have a suitable search term – Parallelzwinge, it opens up all possibilities!

**LINK**

[JasonBModerator @jasonb]

Having had a bit of a play it seems that the angled larger plate allows the clamp to poen further than just a basic "L" shape would and the two legs can open until parallel like the drawing in Vics link that give sthe clamp sizes.

Those reading the current CAD thread will have seen my mention of how useful it is to be able to animate parts once assembled, this is a good example as I was able to see that the screw thread needed to be made 10mm longer to allow the clamp to fully close and that the spacer nearest the nut needed to be moved outwards from teh pivot so the smaller arms would not hit it. Even the jaws faces stay parallel, screws left out for clarity. I just need to fine tune that quick release thread

[VicParticipant @vic]

Due to the method of manufacture the original design required additional riveted spacers to ensure rigidity? This does not appear to be the case with my bolted version. As a result I’ve left two of these elements out of the design. After some little testing they don’t seem to be needed. I can, if required, fit two screws to the unbolted boss or add an additional spacer, but as said it doesn’t seem to be required. Time will tell so I’ve left my options open. Sometimes home machinists are not constrained in the way manufacturers seem to be. A big advantage for me as a home machinist is that using a bolted rather than riveted design is that I can make and exchange custom clamping pads as required. Whether I need to do this though remains to be seen but it is an option not afforded by commercial versions.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Vic on 25/12/2021 15:48:16:
.

Due to the method of manufacture the original design required additional riveted spacers to ensure rigidity? This does not appear to be the case with my bolted version. […]

.

It’s an ‘engineering balance’ really … Any additional spacers [adequately made and fixed] will increase the stiffness of the beam … up to the point where the beam becomes solid.

BUT, in reality, each spacer brings with it a hole in the plate [etc.]

This is where Finite Element Analysis comes to the fore.

MichaelG.

[pgk pgkParticipant @pgkpgk17461]

Posted by EdH on 25/12/2021 13:20:47:

The site for Bengs in Germany has them for sale, not sure what they would cost by the time the import, vat and postage was added

https://www.bengs-modellbau.de/werkzeug/werkzeuge/parallelzwinge-spannhand?number=3431

I stuck 4 small ones in a shopping cart to see what additional costs. Postage was quoted as 4.20 euro inc vat at 19% and the original prices shown were also vat included: presumably we buy vat free and pay 20% this end +.- any extra customs handling?
..not that I bought any.

The link Vic produced was a more complicated shopping cart I didn't want to fill details into so not sure what delivery and vat may apply.

pgk

[JasonBModerator @jasonb]

I'll leave the FE to someone else.

However if the holes are kept on the mid line of the plates their effect will be minimal, much like drilling joists within the neutral zone is acceptable upto a certain diameter or why a castellated bean can be riddled with holes.

It's only when the postie squashes it sideways that the holes will have a greater detrimental effect on strength !

[VicParticipant @vic]

Posted by pgk pgk on 25/12/2021 16:23:18:

I stuck 4 small ones in a shopping cart to see what additional costs. Postage was quoted as 4.20 euro inc vat at 19% and the original prices shown were also vat included: presumably we buy vat free and pay 20% this end +.- any extra customs handling?
..not that I bought any.

pgk

If you change the shipping destination from Germany to UK the shipping cost goes up to €15.

[Michael GilliganParticipant @michaelgilligan61133]

Jason,

My inclusion of [ etc. ] was pertinent … the behaviour of such an ‘assembly’ is much more complicated than that of a homogenous beam with holes in the web.

MichaelG.

[VicParticipant @vic]

Have any of you bought this “plates” only kit?

**LINK**

I’m just wondering how much the postage is and whether you got hit with import duty, tax and courier charge etc.

[John BaronParticipant @johnbaron31275]

Hi Guys,

The design details for the "Kant Style" clamp are here ! Using this information any size clamp can be produced simply by drawing two circles.

NOTE: that this this drawing is provided for personal use only. Not for any commercial use.

Copyright remains with me and MEM magazine.

[Tony Pratt 1Participant @tonypratt1]

Posted by Vic on 15/01/2022 15:50:47:

Have any of you bought this “plates” only kit?

**LINK**

I’m just wondering how much the postage is and whether you got hit with import duty, tax and courier charge etc.

I bought the complete kit & no extra duty, tax or courier charge was added, took a long long time to arrive but to be fair the project has not been started yet. Just fill in the order form to find out postage cost.

Tony

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