Variation on cuts from top to bottom

[MogulTx]

I am experiencing something that I may have the answer to- but I want you folks opinion.

I am cutting peripheral cuts on some materials that are about .8" thick. The material is pretty "hard". It is a resin that is hard.The cut is a final pass to define and make the edge smooth.


I am running a cut file at 14,500RPM and 2.5/.7" ips, and am using spiral ramps throughout the cut ( .25" cut depth per revolution around the part), on a 4HP HSD spindle.

Now down to the issue: I am seeing variations in the cut from the top of the material to the bottom of the material. It is much smoother when the bit is absolutely fresh and new- but 4-5 parts into the bit , and you can identify the spiral ramps. I know the bits dull and fail, but this is a bit excessive, I think.

I am wondering if the bit, as it starts to lose its edge, is getting side-loaded and gets pushed out of the way. I am wondering if a different speed needs to be used (I have used as low as 9.5K and as high as 16K. The edge finish goes to **** with divots and what not from the bit at anything above 15. It is only really good quality between about 12.5 and 14.5).

Alternately, I am wondering if the pinions for the X are getting sloppy, and when the bit loses its pristine edge, that the side loading on the bit tends to divert it a hundredth of an inch ( +/-) and causes it to have this characteristic...

Opinions? I will try to get a photo and post it for all to look at.

[MogulTx]

If you go to my profile and look for the album "routing resin" you will see the edge issues I am concerned with. The deviations are probably only .007-.010 ( way big enough to grab and follow with a fingernail) and can be sanded down easily. I just want to get the edges back to what they were a few months ago...

Any ideas on the cause?

Bit is a 1/4" DS w 1.5"CEL Carbide. This bit had cut maybe 1000-1500" of material.

[jerry_stanek]

when I was routing fiberglass shower bases I was seeing this I decided it was wear on the bit and as I stepped down the first .25 of the bit would get just a little smaller and each step after that would be stepped like a step drill. What I ended up doing is on the final cut I would put a new bit in and run a clean up cut the would go back to the dull bit for the next batch

[garyc]

MGM...
If there is glass or carbon fiber in the material all of the above may be true. You may have to switch to diamond bits especially made for these materials. If not, this doc may help you diagnose your problem: https://docs.google.com/open?id=0B-M73Wl_urKBTlI0WElheERfc28

[Brady Watson]

Check your PM.

-B

[MogulTx]

Gary,

Thanks. I have a couple dial indicators. I will get a magnetic base and check the play. I failed to mention that I switched to a 60 x 120 machine a few months back, and this probably gives a bit more propensity to deflect IF I am sideloading ( probably going a little fast for the bit and material) like I think I am.

Brady, I got your PM and will follow up on your suggestion.

Thanks VERY much to all you guys ( and ladies) on FB.

MGM