What Happened to My Part?

[ddickey]

Starting a project and had to cut a 1.5" round to 3/8" and bore to .801".
Bore is spot on but when I measure the Ø I get .375 and .372 on the opposite side.
I wonder if when I parted it and returned it to the 4J if it did not go in square. I did bump it with a bearing on a holder and felt true.
Any other reasons?
I'm going to take a face cut on a large piece before I redo the part.

 

[Bill Gruby]

What am I missing in your first sentence? You said you turned 1.5 inches to .375 inches. Then you bored to .801?

"Billy G"

 

[ddickey]

.375 was the length of the part. Came from a 2" long bar.
1.5" is the OD.

 

[markba633csi]

Ok so this part looks like a ring or washer and the faces are not parallel; instead they are off by 3 thou. Could be that the steps on your 4 jaw are not the same height.
Could be a burr from parting off. Did you face again after parting? Or did you part to size?
Mark S.

 

[ddickey]

I faced slightly after parting. Maybe five though.
Almost set up and ready to do it again.
I took a test cut on a 6" diameter round stock. It cut basically flat.

 

[RJSakowski]

Squaring "pancake" type parts can be difficult. I usually square to a spacer. The are three threaded holes for offset studs to square the spacer to the spindle axis. Commerciaql versions are also available.

 

[ddickey]

I would like to try and make something similar to what RobRenz did. Definitely would eliminate the problem.

 

[woodchucker]

Squaring "pancake" type parts can be difficult. I usually square to a spacer. The are three threaded holes for offset studs to square the spacer to the spindle axis. Commerciaql versions are also available.

I have something similar, no jack screws. one is thinner than the other.

 

[pdentrem]

You can use a dial indicator and write on the face of the part the high spot. Set the part in the chuck with the marked spot aligned with one of the jaws. Now the tricky part is to get the part set up with the dial indicator showing the correct readings of what you have. I have done this many a time with thin parts that are next to impossible to clamp against a stop.
Pierre

 

[ddickey]

I'm rethinking now and believe it may have been my parting tool.
I use one of these,
http://www.eccentricengineering.com...mart&page=shop.browse&category_id=19&Itemid=3
This time, and maybe I should do this all the time, I indicated the blade. Normally I would use a square on the holder or post and square that to the chuck. Anyway, not sure why cause the clamping system is really proper but under the clamp the blade is straight but the part that is doing the cutting curves away from the center line. I only ever have just enough blade stick out to make the cut.
This time I parted to size and all is well.