Yesterday I had an “oops” when using a #201 bit in 1/4" MDF at CC recommended feeds and speeds (which usually works great). I do increase DOC to 0.1-0.125" depending on toolpathing optimization without issue.
When the cut started I thought it looked a little deeper than expected, but continued to observe. Red flag number one. The cut quality was pretty bad, so I noted to check the flutes and swap if necessary - but MDF cleans up nicely, so not a huge issue. Red flag number two.
The router started screaming loudly so I hit the pause button and noticed the path was getting progressively deeper throughout the pocket, when it should all be the same depth. Houston, we have a problem.
The only thing I can figure out is maybe I had too much tool sticking out of the collet, and it was getting pulled out further over time due to cutting forces. It was still tight in the collet when I brought it forward to inspect (couldn’t pull it out manually, and wrenches needed to loosen). I installed it deeper into the router, re-ran, and everything is peachy keen.
It’s a nice feature where tools have a minimum (or maximum?) insertion mark — for those that don’t, some folks usage one or more gauge blocks (made of a material which will be kind to delicate cutting edges) to ensure consistent stickout and to allow verification an endmill hasn’t shifted.
Usually tightening with a firm squeeze on a pair of good quality wrenches (low profile 13mm and stubby 22mm for a Carbide Compact Router or Makita RT0701/0700) works well.
Agree that is a nice feature. I feel like my routine for tightening is pretty good since I make many tool changes a day, what confused me is that I’ve had this same #201 bit extended this far before. Though I was machining foam in that case, so probably the machining forces were much lower and didn’t result in any walking.
I have been told that the collet in a Makita style router only grips the bit at the top. If this is so then if a bit is not quite at the top of the collet, it could possibly work it’s way down. With unfortunate results.
j
I thought the Makita style collets grip at the bottom — the conical shape is compressed as it’s tightened squeezing the bottom while the top is left uncompressed.
Yes, the precision collets from Elaire or Carbide 3D should be much better than the stock collet — better steel, more precise manufacture.
Another thing that can pull the bit out of the collet is the feed being too fast and the router speed too slow for the material. We had this issue the other day when testing my buddies Pro cutting some plywood. The bit kept walking out and I had tightened the bit. He checked the tightness and it did it 2 more times. We slow down the feed and upped the RPM and then it was all good. Cut another group with the new settings and no issue.
Had a similar incident while using an adaptive toolpath.
My problem was:
I used speed / feed parameters closer to the limits of my shapeoko (feed being too fast mainly)
Tool deflection- Stickout was too much using the #201 with it’s flute length, the deflection probably helped the endmill slip gradually from the collet.
The “step-down” from the slippage tells me that the deflection when the tool first engages the part is the main culprit, as it does look like it cuts straight at each “slip-down”
My solution:
Dial back on the feed or just the in-feed if the slippage is just when the tool first ingages.
With the limits of my stock collet, I would tighten the collet more frequently on lengthier cuts.
–Also want to note that the slippage occurred on 2 pieces, both when the toolpaths were traveling in -X direction.–
