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10-23-2011, 11:21 PM #1
Grinding plates flat on a surface grinder
I'm curious how others grind plates flat after heat treating. I generally send out die blocks for heat treating, and of course, they are slightly warped afterwards. Normal sizes are anywhere from 6" x 6" x 1" up to 36" x 12" x 1 1/2". I usually put a sheet of newspaper on the chuck, and set the die block on it. Next, I turn the coolant on, so the paper absorbs it and expands, filling the voids between chuck and block. After the paper is soaked, I turn the magnet on to as low as possible, just to keep the part from launching off the chuck. I'll flatten the top face first. Next, I'll flip the part and use full magnet and grind normally after that. It usually works ok. One of my problems is that on large block, the paper in the center of the block is still dry, even after an hour of grinding. I guess the coolant just can't wick its way to the center. Does anyone wet the paper (sounds like my dog...) before they set the block on hte chuck? Not the way I learned, but was just wondering. Any other methods used out there? TIA, CH
10-24-2011, 12:11 AM #2
Why the paper?
Why put the paper in there in the firsst place. seems like a variable you don't need???
10-24-2011, 12:36 AM #3
The wet paper fills any minute voids between the part and the chuck allowing better holding of parts with slightly irregular surfaces.
10-24-2011, 09:20 AM #4
I use steel shims if the part is twisted a lot and block the part from sliding, or use a grinding vice if the part is small.
Croz liked this post
10-24-2011, 10:14 AM #5
x2 on what winger said. I usually put my blocks on three ground pads and then block all around and grind to clean up then flip and grind to size. The three points eliminate warpage and allow the part to "find itself". I wouldn't trust the wet paper trick.
10-24-2011, 06:04 PM #6
Use plastic color cosed shims from precision brand, or whoever.
I cut them to 2" x 4" pcs. If your parts are smaller go smaller.
For your parts that are 1' thick this is not so bad. Say you want to hold flat .005"-grinding 2 sides should do it. Anything less than .005 plan to flip the part 2x and grind 3 sides.
Always start the first side so that he middle is touching and the ends are up.
Laurentian liked this post
10-24-2011, 06:12 PM #7
have a set of magnetic parrallels? Put the part on that belly down and grind one side. Go easy - mag parrallels cut your magnets grip considerably. If you don't take the whole belly out on the mag parrallels, take enough to get a good bearing, flip the part, direct down on the chuck, grind to clean, flip again, grind to clean.
10-24-2011, 06:24 PM #8
When I grind plates as you are saying all I do is stone the first side real well thats going down and I also use a straight edge so I know the bow is up,then use filler gages to know how much shim to put under the plate were it is off the magnet,then grind till I get a good clean up,flip,grind to a few thou then flip again for finish.
Most every time 3 flips is enough to get to a few tenths in flatness.
If it must be dead nut flat,on the 2nd flip after I have ground to +.002-.004 of finish I turn magnet to residual,spray a light coat of bluing and LIGHTLY dust it till blue is all gone.Then flip 3rd time and go for finish.Keeping a nice dressed rock also.
05-04-2012, 09:06 PM #9
I use a blachard first with residual ( minimum magnet pull) magnet
well blocked and shimmed(warped areas)
2nd side full magnet if TIR is one thou
third side to size(plus .005)
take to surface grinder : can grind flat on table or magnet blocks if TIR over one thou
block well as tool steels A2, D2 don't have much magnet pull!
05-14-2012, 08:38 PM #10
You have to be careful about setting the magnetic pull. You'd be suprised how little it takes to hold a part on there (especially if just dusting to get flat). You also have the option of not using the magnet, and putting up the side stop. I never put shims nor paper under the part. Seems like a good way to get grit under it and not get a flat part. You can always see by using a magnetic base and indicator without the magnet on vs with magnet on if you are sucking bow out of the part.
06-05-2012, 07:04 PM #11
Laboratory Plaster,white fast set.