How to mill a flat surface

I fixed an air compressor that blew gaskets by filing the warped block flat after pouring wax onto the pistons to catch the debris. It was too tall for my surface grinder. I ground the head flat and used it with bluing to see where to file the block. That problem is solved but it still has others...

I have a new coarse/fine stone that's only used to take the burrs off machine tool tables. The one I sharpen knives and plane blades on isn't flat enough any more. SiC paper on a flat block works quite well if you can find the flat block. I've used 1-2-3 blocks and a ground angle plate salvaged from an old rusty fixture. The area between the rust pits is still very flat.

In general you can work to whatever accuracy or flatness you can measure, because after measuring you know where to correct. I fitted loose scope bases to another shooter's rifle at the range by smoking the bases with a lighter and scraping the contact marks down with pieces of broken glass. He went from off the target frame to about a

4" group.

Jim Wilkins

Reply to
Jim Wilkins
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With the head meticulously aligned parallel.

Reply to
Jim Stewart

...

Didn't you buy a Clausing lathe from some old guy?

Reply to
Jim Wilkins

I sold it a long time ago, it was a very tiny old lathe.

Reply to
Ignoramus9931

End mill - solid carbide or inserts? It makes a difference. The solid carbide mills have a decent rake angle, and can be quite sharp. Usually, the inserts aren't.

Was the surface ground to begin with, or as-cast? If as-cast, you may have not been getting under the scale and hard surface.

Might also try upping the RPM.

John Martin

Reply to
John Martin

Far too hard to control, and will likely make such a small surface humped.

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Reply to
Joseph Gwinn

I have had to flatten a few 2"-5" pieces of mild steel recently.

FWIW, here is what works for me:

1) Sanding attachment in angle grinder - 40, 80, 120, 220 grit till I am happy it is flat 2) Clean up with *palm* sander 60 (sometimes skip), 120, 220, 320, 400 grit. 3) I love my 4x36" belt sander but for this job it did not work as well as the above.
Reply to
Michael Koblic

Here is what you do. Get ahold of a big ass hammer and wail the tar out of it for half an hour. It will look used, useful, and you will never know the difference. Shoot for a heart rate of 80 or so.

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Reply to
W. Stiefer

Take lots of little cuts instead of feeding the full width of the cutter

Reply to
Dan H

What kind of milling machine do you have? My experience with a smallish Clausing mill has been that a flycutter or shell mill taking a wide but very shallow cut gives the best finish, as long as the non-moving table and quill clamps are tight.

Reply to
Jim Wilkins

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