Uneven cut

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

Moderators: Harold_V, GlennW

Post Reply
Fastadam
Posts: 15
Joined: Tue Oct 09, 2018 8:34 pm
Location: Tustin, Ca.

Uneven cut

Post by Fastadam » Sat Mar 28, 2020 7:24 pm

I have a new to me Taiwanese Husky knee mill. I noticed that I am getting an uneven cut but in a bit of a pattern. The picture is a bronze casting and I noticed it while cutting along the Y axis. I am not sure if I should be looking to make a gib adjustment on the table, or if I have a problem with the spindle. Has anyone had a similar problem? Does anyone have a fix?
Thanks
Adam
Attachments
20200328_163401.jpg

choprboy
Posts: 276
Joined: Sat Oct 29, 2011 11:23 pm

Re: Uneven cut

Post by choprboy » Sat Mar 28, 2020 8:38 pm

Are you climb milling or conventional milling? Also, are you maintaining a constant traverse speed or stopping/starting? Looks like climb milling with a stop/start and a bit of backlash in the X.

Fastadam
Posts: 15
Joined: Tue Oct 09, 2018 8:34 pm
Location: Tustin, Ca.

Re: Uneven cut

Post by Fastadam » Sat Mar 28, 2020 8:52 pm

I was conventional milling while feeding it as smoothly as possible with no stops along the way.

User avatar
Richard_W
Posts: 1942
Joined: Fri Jan 10, 2003 1:00 am
Location: Molalla, Oregon

Re: Uneven cut

Post by Richard_W » Sat Mar 28, 2020 10:33 pm

I would check to see if the pattern had the same spacing as the pitch of the screw in the Y axis. If it does? You may have a bent screw on the Y axis? Wouldn't hurt to check the gib either.

John Hasler
Posts: 1554
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Uneven cut

Post by John Hasler » Sat Mar 28, 2020 10:45 pm

Check all the gibs. A loose one can do that because of the cyclic force you apply to the table as you crank.

Did you have the x axis locked?

Fastadam
Posts: 15
Joined: Tue Oct 09, 2018 8:34 pm
Location: Tustin, Ca.

Re: Uneven cut

Post by Fastadam » Sat Mar 28, 2020 11:08 pm

Did you have the x axis locked?
I think I had the knobs locked but I honestly dont recall. At the time of cutting I did not notice the finish problem. Now I will be conscious of all setup parameters. I will also check the Gibs to see if they can be a bit tighter and do some test cuts.

LIALLEGHENY
Posts: 235
Joined: Sat Jan 11, 2014 12:36 am
Location: Bohemia, NY

Re: Uneven cut

Post by LIALLEGHENY » Mon Mar 30, 2020 5:14 pm

How heavy a cut were you making? What kind of cutter were you using? If you try the same setup and same end mill with a piece of aluminum do you get the same result?

Try taking a light finish pass, couple of thousands , climb milling, and try a higher helix mill .

Nyle

Fastadam
Posts: 15
Joined: Tue Oct 09, 2018 8:34 pm
Location: Tustin, Ca.

Re: Uneven cut

Post by Fastadam » Tue Mar 31, 2020 6:47 pm

After adjusting the gibs on the y axis, I feel like I have removed a lot of slop. I did a light test cut (.005) on a piece of aluminum and it shows much better results. I used the same 1/2" diameter 2 flute cutter that i had used previously. I locked the x axis as i moved along. The conventional cut direction still shows a bit of waviness, however I cant feel it with my finger. The climb cut does looks smoother than the conventional direction.
Attachments
20200331_163602.jpg

Harold_V
Posts: 18340
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Uneven cut

Post by Harold_V » Wed Apr 01, 2020 1:55 am

From the first picture, it wasn't obvious to me that the pattern generated was along the length of the piece shown. With the second image, it's now clear that the problem you see isn't related to the gib of the machine, but the cutter itself. If you examine the end mill cutting edges I'm quite sure you'll see the same pattern. Easy to fix. Use a different end mill, or sharpen the same one (requires a cutter grinder).

I should note that it's quite common for a pattern to display when using the side of an end mill. Modern grinding technology has improved them considerably, however.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

Post Reply