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magnetic transfer parallels for surface grinding

cuttergrinder

Hot Rolled
Joined
Mar 16, 2007
Location
Salem,Ohio
We have a job at work that we do every once in a while that requires surface grinding 1/4" steel bars that are 52 1/2" long. The problem is that our surface grinder magnet is only 48" long. The grinder will travel about 54" but the bars spring down on each end where they hang over the magnet causing the ends to grind thicker than the rest of the bars.

Would it work to take maybe 10 pieces of 1/4" x 1" x 53" flat steel and make a laminated parallel with these bars sitting up on their edge with a gap between each one. Then fill the space between each one with fiberglass resin. After it cures then you could grind both sides on the surface grinder. Would this then transfer the magnetism up through the bars and also out to the ends even where it is hanging over the magnet? I have been a machinist for 30 years but I have never used a magnetic transfer parallel. I know they are usually laminated with brass.
 
Will it transfer "magnetism" though the laminated block? Yes but not very well. Will it transfer out to the ends? No, it will fade the further from the mag-chuck you go. I've made my own blocks, they are not to be fully trusted and require blocking/clamping so there's a solid mechanical hold on. For just about everything that gets a grind the test is: "With the piece on the chuck and the magnet on can I move it?" If the answer is yes then the piece needs blocking or should be put in a grinding vise. Your 1/4" bars are thick on the ends for a different reason, 2" of overhang does not droop it's a wear in the grinder (provided you've ground the chuck accurately) What sort of accuracy are you seeking? Seems like the perfect job to farm out to an outside shop for blanchard grinding instead of fussing with machines and a process that isn't working for you. Have you ground the chuck? Have you determined IF the machine is capable of grinding to your tolerances? Are you grinding wet? Do both sides need to be ground or just one side?
 
I have ground the chuck but the problem definitely that the bars are springing down where they overhang the chuck. The way I do them now is on plate that has tapped holes to match the countersunk bolt pattern on the bars. They grind straight with this plate but I was just trying to find a faster way so I don't have to bolt each one down. Blanchard grinding would definitely be the way to go but the boss don't like to send work out.
 
I have done over length parts just by putting steel blocks under the end ,no magnetism but it is something for the wheel to act against .
 
That would definitely help. I thought about drilling and tapping the ends of the chuck and bolting some blocks on but am not how deep I could drill without hitting the wires
 
The magnetism will be very much less using the magnetic parallels on the outboard 2” but the part should hold down and having under support should stop the deflection (to wheel pressure) causing the part to increase in size. We made such with 1/8” strips steel and brass being soft doweled and hammer swaged to be tight. Some use SS and steel plates and then weld along the sides. Some send out to have copper brazing to fill and stick assembly together. An end stop in go direction should be employed. * The fiberglass spacer and fill will reduce magnetism so not a good idea.
Sable's suggestion of a bar under would be my first try. The part it self should hold flat with wheel pressure pushing down. A bolt to keep from sliding (but the bolt may stress the part) or the end stop in the go direction. End stop should be used. Sucking up will be a problem if any burning should occurs so *coolant, feed and wheel choice is important. Often climb grinding can increase chance of burning and sucking up so might try into grinding (down feed on one side only)

I have used double back tape for grinding non magnetics with much success. Yes tape with the longer bar in this case only if needed.

Oh that brings up another point... How do you grind? Incremental stepping across..Or feeding down into part?
1/4" by what width? How tight are size limits?

Setting a job and then pushing with two fingers to see movement under a tenth indicator often tells the deflection amount... often just a one finger push will tell.
 
You can find out about the 'magnetic' parallels by placing a few of your part long wise on the chuck with an eighth of an inch separation, energizing the chuck, and see if your part will stick to the top of the 'parallel'. I do not think it will work, but it's easy to try. The problem is that the parallel bars need to align with the chucks magnetic serrations which usually go from front to back, not left to right.

All of the chucks I have seen have tapped holes in the ends for mounting rails . . . can you use these to mount a support plate?
 
Withing reasonable range of thickness the parts should not deflect with a little overhang, if they are then the wheel is glazed and pushing too hard, and its not accurate grinding if you aren't using coolant and dressing the wheel as required, you should be able to spark out to get rid of deflection. 1/4" is pretty thin for 2" overhang I think.
you should be able to drill and tap 1/4" into the end of an electro magnet chuck and be well away from entering the reactor core! The only one I've pulled apart had about 25mm thick walls! But don't hold me to it! It won't need much to just hold up the ends even an inch away from the chuck so you have an inch overhang. Problem solved maybe?! :-)
 
Can you scab a support on each end of the magnet, either with Red's idea from the end screws or as part of the hold down clamp? Put tap holes in the extensions to match the part spacing you are already using. Then grind the extensions to match the rest of the magnet. Now you can mag your part down, and just use a screw on each end. It should make things faster.
 
Sounds like you only need a 2-1/2" block added to the chuck at each end. Make it thick, bolt through the rail holes as other note. Leave them a fraction high, and grind with the chuck.

Per some suggestions, another it to just take a regular magnetic transfer block and place it on the chuck. Observe how much force is transfered with the laminations parallel to chuck laminations as opposed to crosswise to them? IOW, if your chuck has lengthwise laminations, your idea though cumbersome might work with and end stop (to keep the part sliding). If your chuck laminations are crosswise, it probably won't work very well at all.

There are a lot of old large chucks without controllers at the back of equipment dealers sometimes. You might check HGR listings or some others. I know a PM'er posted me to an old 60" chuck last week for my planer.

Try the blocks on the ends, and then just keep an eye out for a while for a longer magnet. Or maybe the blocks will be all you need.

smt
 
I had these bar all packaged for shipment but I got a few out and put them on the magnet but there was no magnetism out on the ends at all. So I guess the blocks are the only answer. The chuck has tapped holes on left side but none on the right. I think I can incorporate a block into the clamp on the right side.
 
I had these bar all packaged for shipment but I got a few out and put them on the magnet but there was no magnetism out on the ends at all. So I guess the blocks are the only answer. The chuck has tapped holes on left side but none on the right. I think I can incorporate a block into the clamp on the right side.


Someone said you might bolt the support blocks to the table (not the chuck) out board the chuck, grind to chuck height. That seems good, you could just leave them there. End block might be also good for off chuck mounting a diamond at times.
 
The reason there is no (significant) magnetism at the ends of the chuck is that the ends are just solid blocks of steel, no laminations. I've drilled and tapped into mine.

(Wanted to hold a Hitachi pemanent magnet on an electromagnet chuck. This was a few years ago. Somewhere I got the idea that putting a permanent magnet on an electromagnet might cause problems or demagnetize it. I still don't know if that is a possibility.)
Also did not want to "suck" down the center of the swivel chuck though that is probably less concern Anyway, I drilled and tapped the end blocks right into the face about 5/8" deep & tapped 3/8-16 for bolt holes to grab the tilting magnet swivel brackets. This is a 1024 Hanchett Magnaloc chuck, with a 618 swivel chuck on top. You could no doubt go deeper than 5/8" in from the ends so long as the bolt holes were well in the top plate and not in the body of the chuck.

smt_F-Ecutterhead8.jpg


smt
 








 
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