stone to smooth mill table

calgator · Post by **calgator** » Thu Jan 21, 2010 2:48 am

While traming in the mill I found an area that was hit with a bit and some of the metal is displaced and protrudes above the surface. I know I need a stone to smooth this out but what kind of stone should I use?

Charles

Post by **Harold_V** » Thu Jan 21, 2010 3:59 am

Don't use a stone. They aren't selective, and will remove metal where you don't want it removed.

Use a somewhat dull single cut file, no handle. Place it on the mill table and draw it along sideways, with light palm pressure. It will remove anything that's above the surface of the table and not touch the desired surface. You'll be able to feel the hump, and will be able to tell when it's gone.

It's good practice to occasionally apply a file to a table surface as I've described. That keeps the little pips from becoming a problem. The surface of your mill table should have a silky smooth feel. If you feel anything, the table needs attention.

A good test for a mill table is to run a palm along the surface. The slightest blemish tends to stand out. Remove them as described. Don't be aggressive. The moment you feel no resistance when drawing the file across the surface, the job is done.

A new file can damage the table, so insure the one you choose isn't sharp.

Harold

Lodsb · Post by **Lodsb** » Thu Jan 21, 2010 8:59 am

I use the mill table to keep my stone flat...

A small hard Arkansas stone at that.

Jose Rivera · Post by **Jose Rivera** » Thu Jan 21, 2010 2:09 pm

I normally use a fine file and file just enough to remove the dimple.

Post by **JackF** » Thu Jan 21, 2010 4:21 pm

I have used a file to take dings out of my table but didn't know if I was doing the right thing. Thanks Harold for easing my mind

.

Jack.

Lodsb · Post by **Lodsb** » Thu Jan 21, 2010 8:29 pm

Harold_V wrote:Don't use a stone. They aren't selective, and will remove metal where you don't want it removed.

Try a smaller stone, about 1x3, and just fingertip pressure. New files scratch because they're not flat, and dull files don't cut well. I also like to use a stone on freshly flycut finishes.

Frank Ford · Post by **Frank Ford** » Thu Jan 21, 2010 9:06 pm

Now, I'd NEVER ding my mill table, but maybe if I did sometime, I'd try a solid 1-2-3 block with some nice 600 grit waterproof silicon carbide paper. It would show the slight high spots at the edges of the ding as it snicked them off neatly. . .

calgator · Post by **calgator** » Thu Jan 21, 2010 9:41 pm

Harond,

I've got a dull single cut file and will try it.

Charles

Post by **Harold_V** » Fri Jan 22, 2010 12:37 am

Lodsb wrote:
Harold_V wrote:Don't use a stone. They aren't selective, and will remove metal where you don't want it removed.

Try a smaller stone, about 1x3, and just fingertip pressure.

Nope. I don't care what the size, a stone is NOT selective, and will remove metal where it shouldn't. Makes no difference how much pressure you exert, it's a time and motion thing. By the time you've removed the damage, you've created more damage in the adjacent area.

New files scratch because they're not flat,

Perhaps you took note of my caution to NOT use a new file?

and dull files don't cut well.

Ya' think? Could it be that's the reason one is recommended?

Before you denounce this method, I strongly suggest you give it a go. If I'm wrong, then the seasoned machinists that passed on to me many of the things I promote must have been wrong, too. I have a hunch they were not.

A dull file is as you suggest. It cuts poorly. However, when it's applied as I suggested, it is not cutting a large area, just the raised portion. The edge of the file will readily remove the projection, even with light pressure, doing NO damage to the adjoining area.

Harold

Post by **Harold_V** » Fri Jan 22, 2010 12:42 am

Frank Ford wrote:Now, I'd NEVER ding my mill table, but maybe if I did sometime, I'd try a solid 1-2-3 block with some nice 600 grit waterproof silicon carbide paper. It would show the slight high spots at the edges of the ding as it snicked them off neatly. . .

I'm happy to hear you are exempt, Frank!

Personally, I'd not choose your method any more than I'd choose a stone. In either case, metal will be removed where not intended, although I confess that 600 grit paper and fine stones remove very little.

Harold

Post by **GlennW** » Fri Jan 22, 2010 7:29 am

A small very fine stone properly used would be far better than sandpaper.

600 grit Sandpaper would be by far the least selective.

It also depends on ones definition of a "stone".

My definition would be one of those 1/2" wide 3/16" thick, 3" long very fine Arkansas stones. (Like the one you should be using to finish the edge on your HSS tool bits)

calgator · Post by **calgator** » Fri Jan 22, 2010 11:18 am

Harold,
The file worked great removed the small ridge without putting and file marks on the rest of the table. I tried to take pictures but you can’t see it before and it looks the same after I filed it.

I will honestly admit that I was scared when I started and did just a couple of passes looked saw no file lines then did a couple more passes and noticed the ridge was almost gone. I’ve also taken a metal halide light with a metal scale on the edge to then run across the table and locate some more areas and now my table is clean all the way across.

Now I just need to adjust the jib on the knee