Breaking Bits

[nat_wheatley]

I've had 2 bits break unexpectedly this week, both in the middle of cutting sheets of 3/4" melamine. Having cut well over 1000 sheets of this same material, I can't remember this happening before. As far as I can tell, haven't changed anything. Same sheet good supplier, same bits (1/4" MC), from the same bit supplier, same parts cut with the same setting in the SB Link. Same feedrate, RPM's etc. 8ips 14.5K RPM's) Cutting at full depth less skin thickness.

I did notice one of the bits was extremely hot, which I'm guessing is what's causing them to break. It's entirely possible that the bits have always gotten this hot and that I've never noticed, but I've always gotten decent life out of the bits w/o issue. What I'm not clear on is, why it's only now that they're breaking.

Any thoughts?

[supertigre]

Take the collet off of your router and pitch it into the nearest garbage receptacle. Do not hesitate, do not second guess, do it now!

[myxpykalix]

of the two bits that broke, were they bought at the same time? Possibly they came out of a bad batch?:confused:

[gerryv]

I'm with Guy on this one. I'd swab out the chuck recess as well if you've not already. I recently had to replace the 4HP spindle on a PRS I'd just bought, all because dirt and metal filings in the collet and chuck put it out of balance so badly that even the face of the collet had become burred. That was $2000 lost for no good reason.

[garyc]

Nat...
Check with your sheetgoods supplier to see if the current materials come from a "new" batch. Sometimes they experiment with the mix or overcook the melamine which tempers it. Sometimes its the chip core from a different supplier that is more dense.

You may have to drop your feeds (and or speed) to get thru it. How does the chipload look?

[nat_wheatley]

Thanks Guys.

Guy:

I'll replace the collet, for starters. I do have a new spare one here.

Jack:

The 2 bits were from the same order, my first thought was that this may be the issue.

Gary:

The rep for my sheetgood supplier is pretty hapless, and I would almost guarantee that he wouldn't know of an issue if there were one. I have had just the issue you mentioned, inconsistent core, with another brand of melamine, but I noted the brand to be markedly consistant. Not to say that's not the issue though. It did happen with 2 different colors, which may be irrelevant.

I'm wary of turning down my RPM's. With the 14.5K they're down to the point that my first cut (climb) is pretty rough, but clears up well with the finishing (conventional) pass. If I go any lower with the RPM's I think this first pass may be too rough to be cleaned up...

FWIW, I did cut 10 more sheets after this, yesterday, w/o incident. It was a new bit from a new order. I'm not sure what to expect, but we'll see how it progresses.

Thanks again for the help.