Build of a permanent magnetic chuck / base / vise. Part I: prototyping

[@Bakafish]

Small permanent magnet chucks are quite cheap on the used market here in Japan, and I've picked up a number of them. The main reason they don't typically allow magnetic flux through the bottom is that you are essentially halving the flux available and toe clamps or other mechanical fixturing is always going to be more secure. Having said that, one of my chucks (Kanetec RMWH-2F) has separate switchable magnets for the top and bottom, so you can just slap it down on a bed. The reason they don't use cylindrical magnets is that rectangular profiles perfectly align to the magnetic and paramagnetic laminations. So when the chuck is off as the magnets are fully covered by the shorting plates instead of just partially off (due to the round profile) like you are seeing with your design. The weak force you are getting when off may be acceptable to your usage though, just explaining the standard design. The force you are seeing is due to you using stronger magnets, chucks typically do not use neodymium, instead choosing higher temperature tolerant and shock resistant ceramic blended magnets that are tuned for the task. They give up some strength (by volume) for other beneficial properties. Lastly, in the units I disassembled for cleaning, the sliding interface between the magnet and the surface is just a thin layer of molybdenum grease and the other side is air gapped from the base (I recommend you do this and use mechanical fixturing on the bottom.)

[@Michel-Uphoff]

Thank you for your detailed response, I really appreciate it! >> that you are essentially halving the flux available

[@Bakafish]

@@Michel-Uphoff Yes, I understand some of the issues I brought up will likely not apply in your situation, just wanted to explain some of the design decisions you are seeing with the commercial products. The likely reason you don't see a lessening of the power is you are not testing it with the rear side of the magnets properly isolated. The field shape of your magnets being so wide relative to the commercial type may make rear isolation harder to do, I think it is just un-shunted and open air but they may be doing something more complex. There really is likely many other reasons why they don't use cylindrical magnets. But try testing with the magnet plate isolated on the bottom with a thick wood spacer and test that. Another thing I didn't properly mention is that the pole spacing has a big influence on the thickness and size of the materials you are fixing. I have chucks with wide spacing for large thick items, and ones with smaller and even micro spaced poles (lots of laminations) for thin and small items. Look at the Kanetec offerings for a better idea what I mean. You will likely find that your design isn't great for thinner materials, again maybe not a consideration, but try to test with different shapes and thicknesses of work during your prototype phase.

[@Michel-Uphoff]

@@Bakafish Thanks again. I will do some more tests, with and without bottom plate and with different spacing between the magnets, and show the results in an upcoming video.

[@Michel-Uphoff]

@@Bakafish I gave it some more thought, and I am now convinced that it can't be true that a steel bottom touching magnet would lose any pull force at the top. That would be a violation of the laws of conservation of energy. It should be the other way around: A set of magnets touching a steel bottom should pull slightly harder at the top. Of course I will test this and report it in a upcoming video of this project. I will also try to measure and quantify the impact of narrow and wider poles on thicker and thinner steel objects.

[@Bakafish]

@@Michel-Uphoff I'm just relaying what I read, I've been trying to find the exact quote, but the closest I've been able to find is from a footnote in the Kanetec catalogue, "Note that when workpieces are held on two or more faces simultaneously, the holding power of each face drops." This is not the 1/2 that I recall, that may have been my misremembering, but clearly there is an impact and they isolate the backside of most chucks/blocks for a reason.

[@jamesb.9732]

Drilling all those holes is really something to look forward to!!😂. Thanks for the informative video. I’m looking forward to the next!

[@bearsrodshop7067]

55 yrs ago Science class were boring, but now at 70+, I find those creators as your self regaining my interest in the world of magnets and there uses. I am a late bloomer into the machining world, and also attempting to build my own mag plate for thin parts that clamping becomes an issue. I look foreword into following your content on this. Bear in Tx.

[@Michel-Uphoff]

There are two follow up videos now published.

[@dougl892]

Fantastic explanation of building a very simple version of this very practical fastening system ! I will certainly make one sooner than later. Well done - and yes I have subscribed as well and will be back regularly.

[@heinrichhemker8123]

Absolutely excellent video! Waiting for the next episode!

[@LordOfTamarac]

Really cool, excited for a full size mag base

[@homemadetools]

This is going to be another nice project. We shared this video on our homemade tools forum this week 😎

[@tek9102]

Cannot wait for the next episode This is just what I have been searching for - thanhs

[@jeroen-surf]

Great video! Can’t wait to see the next episode.

[@wibblywobblyidiotvision]

That's fabulous. Just fabulous.

[@reprapmlp]

For the materials used to make your test jigs, rather than the word "rubbish" (waste, litter) you could use the more-appropriate word "scrap" (small piece left over after the greater part has been used).

[@Michel-Uphoff]

Ok, thanks. As you noticed, English is not my native tongue.

[@reprapmlp]

You are welcome. Your English is much better than *any* of my not-English.

[@laszlohentes61]

érdekes ötlet,köszönöm

[@Michel-Uphoff]

Szívesen

[@shadowcard6923]

I think you’d probably see best results if you found some way to basically flatten the magnet plate such as a surface grinder or a non ferrous spacer plate such as a copper or nickel strip on the base of the sliding plates and then introduced an eccentric cam to shift the poles.

[@Michel-Uphoff]

See next video

[@alpha-hv9ck]

Just wow 😮 … ❤🥰

[@lucianovasco4654]

I think I know. You used neodimiun magnets, and in that other vídeo they used ceramic magnets. Neodimiun is stronger than ceramic.

[@tek9102]

Are you flipping the poles on every other magnet?

[@Michel-Uphoff]

Yes, see the drawing in the video.

[@zachaliles]

12:20 is that a bowling ball on your bench?

[@nerddub]

most likely a calibrated weight

[@bobweiram6321]

No it's a salvaged demon core!

[@Michel-Uphoff]

Two calibrated lead spheres (2 kg and 10 kg)