Using surface grinder chuck for milling

converterking · Dec 16, 2016

I have a 12x24 electromagnet chuck for a surface grinder. Has anyone ever used one for milling? I just need to take a facing cut on a 12x24 A36 plate. How aggressive could you cut this? thanks, Terry

sable · Dec 16, 2016

It works ,the only problem is that chips stick to the magnet and workpiece ,obviously you have to be careful not to be too aggressive with your cuts else the part will fly.

manualmachinist · Dec 16, 2016

I have seen it done before with a high density 18" x 48" chuck on a large Cincinnati vertical. Lots of holding area. Never saw them take very heavy DOC but they were running a 12" carbide face mill. Maybe .03" to knock the mill scale off of plates.

michiganbuck · Dec 16, 2016

Had a fried who did that. He said the the high accuracy let him be a little less mill cutter aggressive and set ups were quicker. good to consider the cutting force direction to force part to the bump rails.
Hogging with the mill table stressing the locks likely to move a part.
A flat part with forces to the bump rails likely go as fast as you want.

DavidScott · Dec 17, 2016

Best case you get around 70 psi of hold. Magnetism drops off drastically with small gaps so be somewhat gentle if the bottom of your steel plate is rough. Keep this in mind as you learn how well it works.

Forgot to say that you need a demagnetizing cycle before you remove the part. All per a tech at Walker Magnet.

IronReb · Dec 17, 2016

Have used a mag chuck to hold odd shaped parts many times. Used to do a repeat job making horse shoe shaped shims from 1/4 stock. They stepped down in .020" increments, to avoid massive amount of time surface grinding of excess material, I used the mag chuck to machine them to +.010 of finish size then went to surface grinder. On the thicker parts were I had good hold I didn't have to go to surface grinder at all, was able to hold the +-.001 and finish right on the mill.
Beware the thinner the part the less hold you have on it. Thinner than 1/8 starts to get tricky.

Trick is to block your parts in with thinner scraps of material and be aware of which way the force of the cutter is going to push the part, keep the force going toward the "blocks".
Use of kool mist or flood coolant is a very good idea to on thinner parts so you can avoid heat warp from the milling up.

onecut · Dec 17, 2016

Iv used them to machine castings with weird shaped profiles.As has been said light cuts with cutter posistioned so the force is pushing the job back towards the rail.If your doing smaller type work depending on thickness think of getting a swan necked clamp on to act as a stop.If not possible use thinner stock up against job to help job not to push away

michiganbuck · Dec 17, 2016

QT Iron Reb:
[Trick is to block your parts in with thinner scraps of material and be aware of which way the force of the cutter is going to push the part, keep the force going toward the "blocks".]

Agree 100% to that, my friend would even have block-in blocks that were bolted to the mill table to bump-in a part on the go direction. With a high solid block the part may wish to slide but can not..It is rare that a part will lift straight up.

adama · Dec 17, 2016

Nother quirk, if regular mild steel it works well, even mild alloys and differing states of heat treat really effect grip, hardoz grips nothing like as well as mild steel, yet has very little additional alloying elements, lots of the tool steels can vary so much depending on heat treat, annealing and age.

Part lifting off is not likely, part slippage then comming off is, hence you need to use the rails.

Spyderedge · Dec 17, 2016

michiganbuck said:
Had a fried who did that. He said the the high accuracy let him be a little less mill cutter aggressive and set ups were quicker. good to consider the cutting force direction to force part to the bump rails.
Hogging with the mill table stressing the locks likely to move a part.
A flat part with forces to the bump rails likely go as fast as you want.

Make sure the bump rails are over 1/2 the height of the part, or else it might tip up and into the cutter and causing a crash if it's a narrow part.

PegroProX440 · Dec 17, 2016

I do it all the time. We do not have a hard milling chuck or an electro permanent chuck yet so I just use the Hermann Shmidt grinding chuck and sometimes an old walker chuck from a scrapped surface grinder to hold things. I am the only one who uses these techniques in the shop but they are fast to set up and accurate as long as you stay on the conservative side.

michiganbuck · Dec 18, 2016

Had another friend who had a fine pole magnetic chuck on a tapered arbor for ID grinding out of his work head spindle. After grinding in, if put in on the line up mark it would run very true... Yes if out of spec he would tickle grind it. Yes we both worked at the big shop and had a shop on the side. His was space rented in a shop that had a leaking roof, so he called his shop the swamp.

I had a box of surplus centered stubs so he would often bring a part to me so I would make him a special between centers stub mandrel from that box of stubs. Some times I would grind a size on each end of a stub so being good for two parts. I had a good Landis, a Norton and a brand new Parker OD grinder at my use but would most often use the 13 grinder for one-ups(Brown & sharpe 13.. I should have brought the box of stubs home because when they close the big shop it went into the dumpster. They call the 13 grinder a Tool and Cutter grinder but I think it is one of the best one-up OD grinders ever made.

GScot · Dec 19, 2016

One more for it can work. If the starting condition is flat enough for strong attraction by the magnet and you can brace against bump rails it is a fairly stable set up. It doesn't take much in the way of surface roughness to really drop the magnetic adhesion.

Hazzert · Dec 20, 2016

I pull the mag chuck for the guys when sales ends up sticking us with thin (like 1/8") simple plate profiling work that should have been water jet cut. Beats using tape for the ability to use coolant and no time wasted making vacuum fixtures or heating parts to remove wax or other adhesives. I take it easy on the feed since we're already saving time on the handling w/o using tape, you just wipe it off, stick it down and hit go.

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