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Magnetic chuck recomendations?

leeroy76

Plastic
Joined
Apr 19, 2015
G'day Guys

I'm after some advice on what magnetic chuck to by for my surface grinder.
I purchased my grinder used and it did come with a very coarse pole magnetic chuck. I've found however that it's in pretty bad shape with some very large and deep gouges etc (probably have to mill/grind off nearly a 1mm to get clean up) and the magnet barely turns off making parts very hard to remove so i need to replace it..

Most of the parts i grind a fairly small (Less than 50mm long and maybe 3-5mm thick.. I was considering a fine pitch chuck like one of these.

Rectagular Fine Pole Permanent Magnetic Chuck Dia.6"x12" | eBay

This one has a 1/16 pole with 1/32 brass spacers..
These are marketed as being ideal for small thin parts, however how well do they hold on large parts?

Also how well do these fine pitch chucks work with laminated transfer blocks or v blocks? Is there a rule of thumb if the blocks are different pitch? One would assume that the blocks would need an equal to or finer pitch than the chuck in order to transfer the flux lines?

Cheers
Lee
 
G'day Guys

I'm after some advice on what magnetic chuck to by for my surface grinder.
I purchased my grinder used and it did come with a very coarse pole magnetic chuck. I've found however that it's in pretty bad shape with some very large and deep gouges etc (probably have to mill/grind off nearly a 1mm to get clean up) and the magnet barely turns off making parts very hard to remove so i need to replace it..

Most of the parts i grind a fairly small (Less than 50mm long and maybe 3-5mm thick.. I was considering a fine pitch chuck like one of these.

Rectagular Fine Pole Permanent Magnetic Chuck Dia.6"x12" | eBay

This one has a 1/16 pole with 1/32 brass spacers..
These are marketed as being ideal for small thin parts, however how well do they hold on large parts?

Also how well do these fine pitch chucks work with laminated transfer blocks or v blocks? Is there a rule of thumb if the blocks are different pitch? One would assume that the blocks would need an equal to or finer pitch than the chuck in order to transfer the flux lines?

Cheers
Lee

You could open up your existing chuck and perhaps address the problem.. there are a number of threads on this site discussing that. Often the chucks have some linkage wear which results in the internal moving magnet assembly not aligning completely with the top.

Barring that, I would just warn that as you say, magnetic transfer blocks that are more coarse than your magchuck will indeed have some loss of holding power. I have a B&S micromesh fine pole mag chuck and some mag transfer blocks which are coarser than the chuck plate spacing, and the holding power isn't that great...

Ideally you would buy/make blocks well suited to whatever chuck you end up with.
 
my first thought is.. clean things up, get some time on the grinder and wait a bit and buy quality, that unit linked looks cheap and nasty.

BUT you didn't say what type of work/shop you have (hobby? fab with some machining on the side? I wouldn't think you were a pro machine operation from your post). 50 X 3-5 MM isn't small, a regular chuck will grab that fine. so it really depends on what your up to. you didn't even tell us what machine you got, and what condition its in.(!)

do you have a lot of really small parts to do NOW, and little money? go ahead and buy some crappy fine pole chuck, otherwise get some experience, shop around.
 
my first thought is.. clean things up, get some time on the grinder and wait a bit and buy quality, that unit linked looks cheap and nasty.

BUT you didn't say what type of work/shop you have (hobby? fab with some machining on the side? I wouldn't think you were a pro machine operation from your post). 50 X 3-5 MM isn't small, a regular chuck will grab that fine. so it really depends on what your up to. you didn't even tell us what machine you got, and what condition its in.(!)

do you have a lot of really small parts to do NOW, and little money? go ahead and buy some crappy fine pole chuck, otherwise get some experience, shop around.

G'day mate

Thanks for the reply (and you too Brandenberger).

I am some what of a rookie at surface grinding. I am a gunsmith with a fitting and machining trade. Most of my my trade was general machining with an emphasis on CNC. I now spend most of my days doing precision barrel fitting and custom rifle builds.
I have done a little grinding on a large chevalier 12"x36" grinder, mostly just refurbishing/sharpening punch and press tooling. It had a quality electromagnetic chuck which worked very well. I would have loved an electromagnetic chuck for my little machine but cost, and the fact it doesn't have a coolant system, ruled out an electromagnetic chuck.
My little 6"x12" grinder is so far an unknown brand (see my other thread in the section).. It has markings with with "TYT" on them but i have not been able to formally identify it. It's almost certainly a Taiwanese machine as there are a few tell-tale Chinese symbols, and it's a metric machine. Judging by the overall quality of the machine i doubt it's your typical Chinese import though as it had a quality "feel" to it. In any case it is in good condition and as best i can tell, will hold a few tenths over its work area.
I brought the machine mainly to do precision surface grinding of rifle recoil lugs, but also to do precision jigs and fixtures for my CNC machining center.
I plan to make a few custom sets of parallels etc, and would also like to do a little cylindrical grinding with an appropriate fixture.

I do agree with your sentiments on buying a quality chuck, however it's hard to justify AU$2000 for a top end chuck (Suburban tool) for the few jobs i'd do on it..
Out here in Australia we have very little in the way to engineering and tooling suppliers etc. You are truly lucky to have such good suppliers of these kinds of items in the US.

I'll take your advice and run the machine for a while until i can find a decent chuck..

Cheers
Lee
 
RE qt: {take your advice and run the machine for a while} Very good planing.

Dings and scalps don’t harm the chuck use very much if you flat hone to see the surface has no high spots. Not being flat diminishes the holding ability. A larger hone is best 6” or 8” that is never used for knife sharpening or any other use than chuck flat honing. It is used with thin oil on the chuck. Small hones make holes in your chuck. One can hone a chuck like scraping, by finding the +.0005 or .00002 and honing them back to dead flat.
Most grinder hands make due with the kind of chuck (fine or spaced) with use of block-in blocks alone. or with block-in and clamping.
A bargain set of 123 blocks can be handy along with home-made blocks for block-in or clamping to. A block-in that is almost as tall as a part, and it set at the part's go side makes a great holding aid.
For grinding work, it is good to have methods to check for dead square like a surface gauge or dead square blocks to eyeball with. Good to have a dead flat plate for checking and gauging parts.

A part set well off the chuck and double clamped to dead square something makes the part dead square, so giving two square sides to work from for the rest of grinding.

https://www.ebay.com.au/sch/i.html?...sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=MAGNET

parallel clamps photo - Bing

Simple light duty C clamps are great for clamping. (never tighten enough to bend the handles)
 
I agree with michiganbuck. You don't need to machine out the dings, just stone them flat. Like that old Joe Walsh song, "Turn To Stone". Hand stones are your friend when you're doing close work.

Magnetic parallels work best if they are the same pitch as your chuck. Also (duh!) be sure to align the magnetic parallels with your mag chuck when using them.

It makes financial sense to try to reuse the chuck you have because new ones are very expensive.

Clamp 4 blocks at the 4 corners and a 5th in the middle of the chuck, and take a cleanup cut until they are all fully ground, then measure them. Also, put a high-precision level on your chuck and slowly move your table fully left and then right while watching the bubble. Very good diagnostic tool for longitudinal way wear.

Finally, be sure you fully understand how to lubricate your machine, and never skip the way lube.

metalmagpie
 
QT:[barely turns off making parts very hard to remove so i need to replace it.]

Some types of material get magnetized and want to stay on the chuck. Some like to ring on the chuck so hold with surface tension. Sometimes there is a mechanical defect in the chuck.

Good to try another piece when the chuck is turned off to see if it wants to mag-hold when the mag is turned off.

Grinding .100-.200" x 2" parts on the flat or on the sides(edge) may be better ground with making some simple fixtures.
A flat block of 1/4" steel might be left on the chuck and the parts slid on top, sliding up to a bump stop that bumps the go direction and the feed direction.
Groves might be ground to the surface of this flat fixture to allow coolant to also go under the part.

Hold down needs little magnetism if there is a stop block in the go direction.

Thins like .100-.200 can bend into the chuck so to tale on any hole or wash out in a chuck..that may occur with setting a job in the same place to frequently.

A fixture part-set-on can be reground to true up that setting with not regrinding the whole chuck...And such a fixture can allow very fast loading and unloading of the parts. For a high production part one might make a row of fixtures and the time to return gives the parts time to cool.
some jobs prefer feed on the grind-side only.

Incremental cross-feeding can be time-consuming and the wheel lead edge can load and so cause the need for frequent dressing, or cause heat suck-up.

With finding the right wheel some times one might be able to full grind such a part faster than incremental crossing. A very open-wheel perhaps a white 46 h to 46 k might be good.
You might try a scrap part to test this method.
 
Others have mentioned blocking the part in; good advice- make your blocking from anything handy. At one shop they had an ancient power hacksaw; I made blocking from old blades.
Consider sticking parts to two sided tape, with blocking is quite effective.
Possibly consider an electromag chuck.
 
Another good material for blocking is washers, grind them flat first. I also have used ⅛" x 6" parallels from a milling machine on occasion.
 
One can use a long bar say 8" long (or whatever) will do with a 50* angle neat up sharp (.060 flat is good). Clamp this ber to a 123 block or angle plate with the but end-setting on the chuck and the out end pointing to the right to bump a tall part at near its top edge.

This makes a solid bump stop for the odd/tall pat that you don't have a block-in block just the right size.
 
I prefer an electromagnet chuck over a permanent type. With a good control you can vary the power to grind parts flat. No way would I waste any money on a cheap chi-com chuck.
 
It's worth noting that a "good" permanent magnet chuck can have it's power varied also - merely don't fully engage the lever. My PM chuck can be set to barely hold a part or to full power and anywhere in between. I switched out the original long lever for an insert with a female hex, and use a hex socket on a ratchet to turn it.
 








 
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