End mills never walk out of collets when in use, that's just an old superstition

[J Tiers]

Or so many "experts" will tell you.

No I don't believe it and I just had a nice little demonstration of the phenomenon. And, was I milling some tough material, some sort of gummy or hard steel?

No, I was actually using the mill to rout some "melamine covered" particle board for a drawer front. I was routing slots for the sides and bottom to be glued into.

Had I just put the end mill in, and then forgotten to tighten it? Nope, it was untouched since a day or so ago when I was milling a slot in some steel. It had shown no tendency to come out then, and that involved a number of passes.

And, beside that, when I readjusted the cutter after spotting the issue, the nut was tight on the drawbar, and I had to beat the top of the bar with a copper hammer to pop the collet loose.

OK, by definition, if the cutter moved, it was not tight enough, because being tight enough is when the cutter does not move. That is, however, circular reasoning.

I don't know exactly why I bent down to look at it, I mean, who expects particle board, which cuts like butter, to pull out an end mill? Regardless, it was sure trying to cut right through and out the front side, which would really have annoyed me. It didn't get that deep, and there is enough of a correct depth cut all around to allow assembly to work OK. Major annoyance avoided.

The only Weldon end mill holder I have for this mill takes a larger cutter shank than what I was using. I have to use collets for most at the moment. That dang head on the Benchmaster is so large that I have to squat down to see much of the cutter in the work. I'll have to keep a better eye on it.

Anyhow, some pics, because no pics it did not happen. First is the "deep end", when I spotted the issue. Next are a couple showing the gradual "ramp" downward from the initial setting. You can also see the correct depth of the pass that cleared the slot to proper width.

[PStechPaul]

All I can think of is that particle board is a non-homogeneous material, which may cause chatter and variable radial forces, while being soft does not provide much upward axial force to keep the tool from extending out of the collet.

[J Tiers]

I could see that, but the odd thing is that there was essentially no vibration or noise, not even any "feel" of resistance in the cut. Spinning about 1800 rpm, cut like a hot knife in butter, no obvious reason for an issue.

[eKretz]

Maybe the higher speed had something to do with it. Vibration perhaps or centrifugal force opening the collet a smidge.

And Weldon shanks aren't bulletproof against pullout either... When I was an apprentice I used to work with an older Mexican fella who was a journeyman and he worked afternoons while I worked midnights. I followed him up on a 5" spindle G&L every day for over a year. One day I came in and as I walked up to the machine to get my lineup he was shaking his head, looking rueful. He was unclamping the part from the setup on the machine table. He didn't speak very good English, but he knew enough to get by. I said "Eddie, what's wrong?" (His name was Eduardo, but he went by Eddie). He looked up at me and says, "I f**k it up!" Heh. I'll spare you the rest of his broken English, but to make a long story short, he had not pulled the endmill out when mounting it in the endmill holder so that the bevel of the flat was hitting/seated against the set screw. He had tightened it up, but it still pulled out. Ended up cutting a keyway too deep, and the part was headed to the weld bay. Oopsie-daisy.

[BCRider]

I've milled wood on various mills over the years and didn't have any issue. But I don't think I'd ever milled melamine. Still, I find it odd.

Were you by any chance using a very heavy chip load without enough speed? I'm thinking that if the flute filled up so the chips jammed then that might produce a strong axial force to pull the end mill out like that. I've always wound the mills up when doing wood. I wonder if I could duplicate your result if I tried it with an RPM that was used on steel?

[ikdor]

That's some impressive pull out force from the wood. Guess it's trying to screw itself into the wood at such low rpm. Would be interesting to stick an endmill into a 30k rpm router and see if it also pulls out at those speeds. Was it a high helix endmill or standard?

[JoeLee]

That's some impressive pull out force from the wood. Guess it's trying to screw itself into the wood at such low rpm. Would be interesting to stick an endmill into a 30k rpm router and see if it also pulls out at those speeds. Was it a high helix endmill or standard?

I have to agree. I've had a couple end mills pull out slightly when milling steel but I later found that the reason was the cheap import end mill that I was using for roughing had a shank was slightly undersized. The same thing can happen with a cheap low quality collet and a good end mill.

But cutting through wood is like cutting through air. I've slotted / routed a lot of melamine board and never had that issue.

JL..................

[Ian B]

Maybe it depends on what design of collet holder you're using. I use Clarkson Autolock holders, collets and endmills. I've never had one spin, come out or come loose yet. Not sure if they're still being manufactured, but there's more than enough on Ebay to last my lifetime.

https://www.denfordata.com/bb/viewtopic.php?t=1057

Ian

[Doozer]

Maybe I missed it,
but what type of collet were you using ? ?

--D

[lynnl]

... (snip)...
Had I just put the end mill in, and then forgotten to tighten it? Nope, it was untouched since a day or so ago when I was milling a slot in some steel. It had shown no tendency to come out then, and that involved a number of passes.

....(snip)....

Well this is just a grope in the dark, but had there been a substantial temperature change in the intervening time since the collet was tightened on the endmill? Enough maybe to loosen it JUST enough?

I try to resist the temptation to be too heavy handed. But I've had router bits slip repeatedly until I tightened to the point I thought either my hand or the wrench would fail.

[strokersix]

I always anticipate an end mill will walk out of a collet and act accordingly. I had an early experience with this 40 yrs ago and remember vividly to this day. I was doing some fairly heavy milling with a 3/4 inch diameter end mill. Well, heavy for a typical BP machine. Was making some nice chips with it. Thankfully I didn't spoil the work or damage the machine or myself. A lesson for sure.

Solid holder with weldon flat for me is always first choice. I've never had one come loose. My experience anyway.

Worn or crappy collet, poor spindle taper, off size cutter shank would certainly cause problems.

[J Tiers]

I've milled wood on various mills over the years and didn't have any issue. But I don't think I'd ever milled melamine. Still, I find it odd.

Were you by any chance using a very heavy chip load without enough speed? I'm thinking that if the flute filled up so the chips jammed then that might produce a strong axial force to pull the end mill out like that. I've always wound the mills up when doing wood. I wonder if I could duplicate your result if I tried it with an RPM that was used on steel?

That's some impressive pull out force from the wood. Guess it's trying to screw itself into the wood at such low rpm. Would be interesting to stick an endmill into a 30k rpm router and see if it also pulls out at those speeds. Was it a high helix endmill or standard?

US made MT2 collet, 3/8". No wear or "springing" visible. The end mill seemed well held, and had to be loosened up with a hammer on the drawbar before readjustment.

US made 2 flute end mill, 3/16" (to cut 1/4" and 13/32" slots). The RPM 1800 rpm or so (maybe a little faster toward 2000), approximate 1:1 pulley ratio with 4 pole motor, so the "such low rpm" is an odd comment. "Low" with respect to a router, but hardly low for a mill.

Different cutters anyway, as a router usually is not using a spiral fluted cutter. Speed is also different effectively, as the 2 flute cutter compared to a one flute which would likely be used with a router in this size cutter. The 2 flute would act as if it were spinning at double the rpm compared to a 1 flute at same rpm, so chipload is half.

The wood was coming out as fine chips, almost powder, fluffy, light, with no tendency to stick in the cutter flutes, just flowing easily out of the slot. Particle board, so not much stringy fiber holding it together as with "solid" natural wood.

The cutter was cutting very freely, no particular force required to advance the cutter. Not surprising, as a cutter for steel is not likely to have much trouble with a much softer material. The "melamine" exterior covering is really quite thin, the makers do not waste any material beyond what it takes to get the appearance they want, so the melamine was not a factor as a material.

As you can see, the pull-out was a classic slow ramp, taking perhaps 150mm travel to pull out by another 6 or so mm. Odd that the previously cut steel did not pull out the cutter, despite some full depth passes to clean up the sides of the cut.

I have no explanation other than that the cutter was obviously not tight enough for cutting wood, even though it was tight enough for steel. I tightened it after readjusting, and it did not pull out any more, despite taking full depth cuts (6.5mm deep) slotting, i.e. the first cut through solid material. as far as I can see, it never moved a bit after the readjustment.

Anyhow, a cautionary tale..... If it can happen with WOOD, using very low cutting force, it can happen with almost any material.

[A.K. Boomer]

Don't forget particle board is made from a substantial amount of glue. and when heated when being cut can definitely have more "grab effect" have seen this just with skill saws and not so new of blades....

[skunkworks]

Playing devils advocate.. Are you sure the tool was pulling out or were you losing Z position...

[A.K. Boomer]

I had the rare incident just happen when building my wheel spacers --- I knew I was taking off a fair amount of material with my 1/2" 4 flute carbide endmill so I cinched it up accordingly --- or so I thought,,, It walked, I did catch it in time, im attributing it to a very oily shank - do not know if it was vactra or cutting fluid but it was oily, I cranked down about another 1/8 to 1/4 turn on the drawbar and it stayed put for the duration of heavy cuts....

Edit; in the past there has been allot of guys complaining about the R-8 holding system and I do get it - but still I think for hobbiest machine work it's just fine - it's when you go and CNC and expect immense production out of them that yeah i believe your going to run into trouble....

I don't cut with anything bigger than 1/2" for endmill - I would if someone gave me larger endmills but half inch gets it done for what I do,,, I do use the heck out of my other larger collets but not for endmills just flycutter and other tooling that does not have the "spiral effect"