Not milling flat

R

rzw0wr

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I have a Smithy mill.
Not the best mill out there but it is the one I have.

I trammed in the table and head yesterday to within .001".

I have a vice I made soft jaws for.

I cut a lip in top of both jaws.

I put a piece of CRS 1"x2"x4" in the vice and milled the top.

When I checked the block it was 0" on one corner, across the 2" end it was .001" and the other end measured .003" on both corners.

I checked the lip in the vice and got about the same measurements.

When I cut the jaws I tightened up the jaws together and ran a 1/2" four flute across them.

Any idea why they ate not parallel with the table?

Thanks,
Dale
 
Sometimes parts are not firmly seated in the vise, and is the vise perfectly parallel between the bottom and the seating surface, and is the back jaw perfectly square with the seating surface? To assure seating, a couple of pieces of shim stock under the ends of the part can be tried for slippage when the part is thought to be seated.
 
I checked the piece seat with a .0015" feeler.

I get the same results with parallels under the part.

I have tightened all the gibs up.

X and Y axis movements appear to be ok. Just the Z is out.
 
CRS is part of the problem. Retained stress from cold rolling causes the work to deform when a cut is taken off one side. Milling CRS is a great way to make banana shaped parts.
 
Correct me if I misunderstand. I have never seen a .0015 feeler?
 
rzw0wr said:
When I cut the jaws I tightened up the jaws together and ran a 1/2" four flute across them.

Any idea why they ate not parallel with the table?
Click to expand...

1st check the tram of the mill again, make sure it didn't shift

If good, take another light pass on the jaws, it's possible the end mill moved in the collet when you cut them the first time
 
On a lot of vises the movable jaw will lift when tightening a part. Try running the movable jaw to where it's just a couple of thousandths from touching the part. Put your dial indicator on top of the jaw and then tighten it. If it changes position this could mean that when you machined the lip they aren't the same depth on both jaws.

Ted
 
Yep, we call it 1 and 1/2 thousandth.

we had .001" fellers also


I just tried a piece tied down to the table.
I got 0,0,0,-2 on the four corners.
Same block.

I have never had a problem with CRS when I cut both sides. Sometimes you need to recut the first side or even both. This block has been cut several times. I can not find that is not flat, just not parallel.
 
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