Having A Melt Down! ( Face Milling )

[blaser.306]

I have a 2 1/2" face mill that has been working very well for me. I felt it was finally time to freshen up the inserts ( SPG422 ) As soon as I did , like clockwork. My surface finish went away? No smooth with crosshatch appearance. I have now tried 2 different types of inserts, One a off shore TIN coated the other is an uncoated Kennemetal. Both give decidedly poor results. I checked for "foreign bodies" stuck up in the mill spindle to no avail and completely disassembled the face mill to be sure there were no chips where they weren't supposed to be. One glaring difference is the original carbides are .188" And the new are .125" thick. Any suggestions where to look to remedy the problem?

 

[JimDawson]

Can you post a picture of the new and old inserts, the face mill, and the finish you're getting. I can't think of why the thickness of the insert would cause a problem.

 

[hman]

Maybe a silly idea ... but could you try putting .032" or so spacers behind the inserts? There may be something magical about the inserts being exactly on diameter lines, rather than .032" behind. That would be the only thing I could think of that differed between the old and the new, and did not differ between the two types of inserts that are giving you problems.

Well. maybe something else ... are the new inserts being held securely by the mounting screws (meant for thicker inserts)??? I guess the same remedy as above would test this theory.

 

[brino]

1) as human suggests, have you run out of thread on the insert clamp mounting screws?
2) any washers used on the clamping screws, did it all get re-assembled correctly?
3) inserts use the body of the insert against a shoulder or registration feature for alignment and support, is the thinner insert not aligned/supported correctly?
4) matching inserts is difficult, many threads here attest to that. There are so many similar types with completely different numbering conventions it easy to get one that looks similar, but is not the same. Are new and old truly identical (except for thickness)?

Oh and adding a spacer may be reasonable, but if placed behind the insert it may make things worse if it produces a gap between the insert and the supporting shoulder, maybe you can try a spacer on top the insert, but under the clamp.

-brino

 

[blaser.306]

The counter person at the machine supply house checked the insert marking #'s and claim it to be the same? I re-installed my old inserts just for giggles and my old surface Finish came back? The TIN coated "less expensive" inserts almost seemed to have 1 that was of a different lot and just slightly different dimensions ( one tip slightly lower than the other 3 ) so as the face mill would run ' the cutter would leave not a terrible finish going one direction But as soon as the trailing half started onto the work ' the first pass was completely wiped off the surface and ridges were left behind in the reverse pattern. I am going to go back and get the thicker inserts today and give them a try.

 

[chevydyl]

Sometimes you need to break in carbide inserts, they will actually produce a better finish with a little bit of miles on em. Keep working one edge on some scrap and see if it starts to improve