# Round Magnetic Chuck for Lathe



## darkzero (Jun 9, 2017)

I know they're not very common for use on a lathe as they have lots of limitations. Just wondering if anyone here uses one? I've only used mag chucks on a surface grinder a few times, never on a lathe though & spinning. Don't know what to expect.

I'm going to use it for making thin washers or spacers. Unfortunately it'll only work for ferrous metals of course. In the past I would use epoxy or double sided adhesive which I will still have to do for non-ferrous metals.

I just bought a NOS 6" fine pole Yuasa mag chuck. Can't wait to get it.


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## petertha (Jun 9, 2017)

Some info here & I think he discusses in some of his YouTube videos
http://gtwr.de/rant/magneticchuck.html


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## darkzero (Jun 9, 2017)

petertha said:


> Some info here & I think he discusses in some of his YouTube videos
> http://gtwr.de/rant/magneticchuck.html



Thanks, yeah Stefan's web page & his videos is where I first got the idea from.


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## mikey (Jun 9, 2017)

I have one of those Yuasa mag chucks, too, Will. I have to mount it still but it should come in handy. I cannot begin to count the number of times I needed to make a spacer of a specific thickness or face both sides of a thin piece.


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## darkzero (Jun 9, 2017)

mikey said:


> I have one of those Yuasa mag chucks, too, Will. I have to mount it still but it should come in handy. I cannot begin to count the number of times I needed to make a spacer of a specific thickness or face both sides of a thin piece.



Oh nice, which one do you have, fine or standard pole? Well that's what I'm calling it for the Yuasa ones that I was looking at. The first one pictured below I had saved in my ebay list but I wasn't sure about the pole spacing, looked very wide & nothing running down the center. I figured that would not work for me. Then I started looking at imports but they were standard pole as well. I've been reading that fine pole is not as strong for larger parts & finer pole is better for thin parts so I figured fine pole is what I should get.

Then today another Yuasa popped up on ebay from the same seller as the other one. Finer pole & $55 less than the other one but oddly it has the same exact p/n. Seeing how much the Eclipse & Suburban units cost I jumped on the Yuasa. The second one below is the one I purchased. Should clean up nice, listed as NOS.

I hope I made the right choice about the pole spacing. Anything I should be aware of?


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## mikey (Jun 9, 2017)

Yeah, I read that fine pole is not as strong as the standard pole, too, so I got the first one you pictured above. I don't know that it will make a big difference because you aren't taking heavy cuts on these things. I think either one will work fine. Another reason I didn't go for the second type is because of the brass - I thought it might be more susceptible to damage and would need facing more often. Probably not a major concern given how little use it will see but it gave me pause. 

I bought the wrong backing plate from Grizzly. I need to return it and get one that has no holes in it so I can drill it the way I want. Too much going on right now to attend to this so I'm sure you'll beat me to it but I know for sure this tool will come in handy.


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## darkzero (Jun 9, 2017)

I see, thanks Mike. I'm thinking I'll only use it for thin parts so I was just going based off what Stefan mentioned in his videos for fine pole. I didn't even think about the brass but it should be fine. He's the only one I could find info about lathe mag chucks. Well I guess I'll find out when I get to finally use it.

Awe man, another backplate I have to get, I hate machining CI!


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## mikey (Jun 9, 2017)

darkzero said:


> I see, thanks Mike. I'm thinking I'll only use it for thin parts so I was just going based off what Stefan mentioned in his videos for fine pole. I didn't even think about the brass but it should be fine. He's the only one I could find info about lathe mag chucks. Well I guess I'll find out when I get to finally use it.
> 
> Awe man, another backplate I have to get, I hate machining CI!



To be honest, I don't think it will make a big difference with either type. 

Yeah, cleaning up CI chips is not my favorite thing to do, either. I was thinking of facing the back plate and then sticking the chuck face onto it and then lightly facing the rear of the chuck to get it flatter. I don't own a surface grinder so I thought it might make it slightly more accurate. What do you think?


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## darkzero (Jun 9, 2017)

mikey said:


> To be honest, I don't think it will make a big difference with either type.
> 
> Yeah, cleaning up CI chips is not my favorite thing to do, either. I was thinking of facing the back plate and then sticking the chuck face onto it and then lightly facing the rear of the chuck to get it flatter. I don't own a surface grinder so I thought it might make it slightly more accurate. What do you think?



Yeah, I agree, not going to be taking heavy cuts with these things anyway.

I think that's a great idea. I've had times where I wanted to face the back of a cheap chuck just for good measure but those times I didn't have a way of holding the chuck to do so.

But in this case, simple cause it's a mag chuck. Good thinking! As long as the rear face is flat & perpendicular with the chuck body, that's good enough for me. Not like it really matters but hey why not.

I will check though once I get the adapter faced, I'll stick the chuck on & see how it measures. If it's good, I'll leave it & just skim the front face.

What size is yours? Is the back flat or does it have a register? I'm going to wait until I get it in hand before ordering the backplate. I can't find a product page, specs, or a manual for it online. With 6" chucks it varies & I don't want to go through with getting the wrong back plate. 6" chucks are all over the place, they come in 5.9"/150mm, 6.0", 6.3"/160mm, & 6.5/165mm".


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## mikey (Jun 9, 2017)

Mine is a "6". The back has a 50mm register, about 1.5 mm deep. Otherwise, back is flat. It has threaded holes at 90 degree intervals for mounting. 

I think its a good idea to wait, measure the chuck and then decide on the back plate. I got mine from Grizzly and it will actually work fine for what I want. I wasn't going to machine a nose to fit the register, since the chuck will see very little force but we'll see. 

Let me know how yours turns out. I won't use this thing often but when I need it, I know I'll be happy to have it. Nice thing is that it isn't all that expensive, either.


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## darkzero (Jun 9, 2017)

Ok, will do. I'll probably start another thread when I get working on it.


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## Bob Korves (Jun 9, 2017)

Coarse pole mag chucks are best for THICKER and larger parts.  Fine pole mag chucks are best for THINNER and smaller parts.  The heights of the magnetic fields above the chuck are proportional to their spacing.  The holding power will be minimal for much lathe work, compared to a regular chuck, and light cuts will be be necessary.  I think I would prefer the brass spacers over the white metal ones.  The white metal ones are made out of something similar to Babbitt metal.  Both are soft, as are the chucks themselves, which are made from mild steel for better magnetic properties and less residual magnetism.  A fine India stone will be your friend with these mag chucks, get used to feeling for burs with one before mounting anything to the chuck.  I would prefer to grind the chuck in while mounted and turning on the lathe, perhaps with a tool post grinder, but it would sure be messy!  Still, all in all a very nice score, and a useful tool in the arsenal...


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## mikey (Jun 9, 2017)

I was messing with the chuck last night and put a thin washer on the face. I cannot move it with my girlie-man hands when the magnet is engaged, although I can knock it out of position. I think it will hold well enough for my purposes. The last time I needed a thin washer, I was taking a 0.002" deep facing cut on a piece with only 0.003" sticking out of the chuck and maybe 0.007" being held by the jaws - too close for comfort. With all the tension I felt you would think I was trying to hold that part with sphincter power alone! It took a long time to get that washer aligned in the chuck as well so yeah, I think this new toy will come in handy.


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## darkzero (Jun 10, 2017)

Got the chuck today, man that was quick. My heart sank when I saw the box though. Completely smashed, I thought for sure the chuck would have been damaged. Luckily it wasn't & even the tiny chuck key didn't fall out, that's cause it was stuck to the face of the chuck. 

It feels like it's got some sort of clear coat on the face but that will come off when I face it. Kind of cool, it has a 7mm square for the switch. Most of these either have a hex or D shaped key.

At first I thought it was defective. I put a razor blade on it, turned the key, I was able to slide it right off! Then I stuck my 6" hook scale on it, couldn't pull it off. Threw a M12 washer on it, same thing, couldn't move it. Then I put a 3" dia spacer that's about 1.5" thick, I tried my hardest to pull off by hand & I couldn't. So I'm happy!

It's 6.3". Time to order the back plate now.


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## mikey (Jun 10, 2017)

Looks good, Will. I bet a facing cut on that chuck will sure make it look purty.


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## darkzero (Jun 10, 2017)

Thanks Mike, I think so too. It's odd though, it really seems the mag surfaces of the chuck has a clear paint on it. I can scratch it & it turns white, just like clear coat. But the cast iron body doesn't seem to have it.

It was listed as NOS so I'm wondering if it some kind of protective coating on it. If it is, it's something I've never encountered before. Doesn't matter though, I just thought it was weird.

Another thing that is interesting is the switch is not an instant on off. The pinion turns more than I expected from end to end with no feeling of an indent or overcoming a cam or whatever. It's like it gradually applies the magnetism. When fully switched off, there is no residual magnetism like Stefan shows in his videos with his chuck. Not complaining though as I suppose I can adjust the strength of magnetism to hold different size parts for indicating & then fully switch on.

Does yours behave this way too? I'm just trying to learn more about how these things work.


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## mikey (Jun 11, 2017)

Mine has a small amount of residual magnetic attraction when disengaged, then pours it on when fully engaged. You're right though; you can gradually increase the attraction with the key. Mine is a hex, by the way, and I'm wondering why the difference. Maybe you got the deluxe model?


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## darkzero (Jun 11, 2017)

mikey said:


> Mine has a small amount of residual magnetic attraction when disengaged, then pours it on when fully engaged. You're right though; you can gradually increase the attraction with the key. Mine is a hex, by the way, and I'm wondering why the difference. Maybe you got the deluxe model?



Thanks Mike. That is weird, I too wonder about the differences. I wish there was some sort of documentation on these. I even searched Yuasa's catalog, they show mag chucks in the table of contents but the pages they're on is not available for download.

Of the 2 models I posted on, they even have the same exact p/n which is more confusing. Mine says made in Japan & the other one says made in France.

Mine, deluxe model, I don't know about that. I got the cheaper one. Mine was listed at $190 + $15 shipping & the other one like yours is listed at $259 free shipping by the same seller. I know that doesn't mean anything but it seems the seller thought the other one is worth more.


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## mikey (Jun 11, 2017)

Hey, you're right - mine is made in France! I searched but could not find who made it - LFA, you think?

I suspect performance will be very similar because the ability to hold the work depends more on the thickness of the work piece. For small or thin work, not much force is transferred so I doubt we'll see much difference. What I want is to be able to machine both faces of a thin part without distorting it and this tool has that potential - we'll see.


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## darkzero (Jun 11, 2017)

Yup, I believe both of our chucks will work fine for whatbwe want to do.

Funny, I was just searching on who possibly made these, well yours anyway. On pics of the 8" model made in France is the name Braillon on the name plate which is Brallion Magnetics located in France. They don't list models in the same size or appearance as the Yuasa models though. I'm thinking Yuasa had them specifically made for them or these are older discontinued models. 

Braillon does say that one of their features is adjustable power from 0-100% so it looks like our chucks are working as they should be.

Well that explains yours, mine is still a mystery!


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## mikey (Jun 11, 2017)

Thanks, Will. Personally, I would have preferred if Yuasa made it themselves but as long as it works, I'm good.


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## ddickey (Jun 11, 2017)

How are you guys going to mount these?
I see on the Braillon site some are mounted on what looks like a MT flange. Looks very interesting.


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## mikey (Jun 11, 2017)

Just screw it onto a D1-4 backing plate. Even if the mount isn't dead on, you indicate the part before fully engaging the magnet so the part will run concentric with the spindle. I cannot even count the number of times I needed a thin part faced accurately on both sides and of a precise thickness; this should do the trick.


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## darkzero (Jun 11, 2017)

Yup, like Mike said, exactly like how you would mount any other plain back chuck.

I got my backplate today, gotta love Amazon same day shipping! Unfortunately I'll have to wait a couple of weeks until I recover before I can start working on it (had surgery this past Fri)

Mike, another odd difference with mine. Mine has a 125mm register with a 4 hole mounting bolt circle of 140mm.


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## mikey (Jun 12, 2017)

I plan to leave a bit of room between the registration boss on the back plate and the hole in the chuck so I can knock the chuck into close alignment. This chuck will not see much, if any, side force so I do not think it important to machine it too close. I would rather have it accurately aligned so it runs without vibration but I won't obsess about it ... well, not much more than I normally obsess about such things.


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## darkzero (Jun 12, 2017)

Yup, good idea. Will be perfectly fine with this chuck. That's what I did with the original China 3-jaw that came with my lathe. I call it Tap-Tru. 

I decided to keep it & use it for "dirty" work, sanding, polishing, CI, etc. I haven't done any heavier machining on steel with it but it hasn't slipped on me yet. It actually holds pretty good.

I think I'll start out machining mine with a close fit to see how the runout is. If it runs out considerably I'll go with the Tap-Tru method too.


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## mikey (Jun 12, 2017)

darkzero said:


> Yup, good idea. Will be perfectly fine with this chuck. That's what I did with the original China 3-jaw that came with my lathe. I call it Tap-Tru.
> 
> I decided to keep it & use it for "dirty" work, sanding, polishing, CI, etc. I haven't done any heavier machining on steel with it but it hasn't slipped on me yet. It actually holds pretty good.
> 
> I think I'll start out machining mine with a close fit to see how the runout is. If it runs out considerably I'll go with the Tap-Tru method too.



I like that - Tap-Tru!

My Samchully chuck manual recommends that the user make the boss 0.01 mm (~0.0004") smaller than the hole in the chuck. This is contrary to common practice but the supposition is that you will indicate the chuck in with an accurate pin so Samchully agrees with the Tap-Tru technique. I do, too.


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## darkzero (Jun 12, 2017)

Oh wow, you have a Samchully chuck!?! Those are nice! 

I don't think I'll ever get to replace my Bison chucks with nicer ones but that's ok. At least I can drool! I love a good looking quality chuck, aka chuck porn.


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## mikey (Jun 12, 2017)

Yeah, Samchully makes really nice chucks. I only have one of their 3 jaw chucks but it is smooth as silk with no discernible play. I have two Rohm/Emco 3 jaw chucks and two Rohm/Emco 4 jaw chucks. Gotta' have back ups, right? I've sworn off buying any more chucks because I'm pretty sure I have enough of them. 

Unlike someone I know, I don't have a Bison 6 jaw Adjust-tru.


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## darkzero (Feb 13, 2019)

Finally got back to this & finished making the back plates. I didn't end up facing it. It cleaned up pretty nice, a bit too nice, wasn't expecting this much shine. I hit the face with scotchbrite & the OD with some sandpaper. Got really lucky, the body only had just under 1 thou run out & for the face basically none. DI really didn't show any runout, just slight movement from the surface finish. I'll check it later with a tenths indicator.

Here's what it looked like before clean up.







And after.







Then put the name plate back on.







Also made a backplate to mount on the rotary table.







Unfortunately I wasn't so lucky with this one. Getting about 1 thou variance. I'll figure out what's going on with that some other time. Edit: Fixed that here.
	

		
			
		

		
	








Needed to make a spacer faced & parallel on both sides with the bore square to the faces. Came out pretty good & I'm happy.







Here's what it started out as, a slug from an annular cutter.


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## mikey (Feb 14, 2019)

Pretty cool there, Will. That thing cleaned up really nice!

Glad you're getting back into the shop.


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## darkzero (Feb 14, 2019)

mikey said:


> Pretty cool there, Will. That thing cleaned up really nice!
> 
> Glad you're getting back into the shop.



Thanks Mike! Yes it feels good to play in the shop again. Been a while. Spent last week changing the oil on the lathe, mill, bandsaw, & air compressor as well as fully cleaning the lathe & mill. Haven't done any of that in almost 3 yrs. I'm so sick of oil changes now! Also changed the leaky spindle seals on the mill. Ready to start making chips again & finish long overdue projects.


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## mikey (Feb 14, 2019)

You've been missed, Will, I assure you. Happy to see you back and I enjoyed your usual high quality work and photos. 

My mag chuck is still sitting in the box, waiting for me to actually find time to get into the shop. Life is hectic right now but I'll get back to it eventually.


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## john.k (Feb 14, 2019)

I am interested to see some actual results.............I have a round mag chuck that came with a Landis grinder...........it works great on the grinder...........but on a lathe ,I found that its not so great.......the main issue being if the tool picks up the cut,the work moves ,tool jags in ,and next thing the work is hanging off the chuck...(if you re lucky)............had a couple of narrow scrapes trying to deepen the O ring grooves in Cat transmission pump end plates,after facing them on the Landis.


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## macardoso (Feb 14, 2019)

Beautiful work. I've seen good success at an old job doing just what you are doing with the mag chuck. Very sharp tools and light cuts are key.  You're halfway between a lathe and a cylindrical grinder with this setup so think in terms of the care required for grinding.


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## darkzero (Feb 14, 2019)

macardoso said:


> Beautiful work. I've seen good success at an old job doing just what you are doing with the mag chuck. Very sharp tools and light cuts are key.  You're halfway between a lathe and a cylindrical grinder with this setup so think in terms of the care required for grinding.



Thanks! Yep, I quickly learned how deep of a cut I could take on such small part with not much surface area to hold. I thought about blocking the part in but after switching to a sharper tool (I actually used an alumn specific CCGT) & gave it more RPM it was fine.


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## darkzero (Feb 14, 2019)

Perfect timing, new chuck key showed up yesterday. I wanted a bit longer handle than the one it came with. 7mm square chuck keys aren't easy to find. I thought for sure I was going to have to make one. Got one all the way from the UK from Myford.

Good quality especially for the price. Handle was way too long so I shortened it a bit. I'm happy now.







Measured the runout on the lathe today. I get about .00015"-.00025" depending on the dia I measure on the face, well so my indicator says. Pretty good for not taking a skim cut.


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