VBit being pulled out of collet

[Ernie Martinez]

I first thought I was having an un-commanded -Z being sent to the machine. It turns out that while doing a profile cut with a 90 1.25" VBit, the bit is being sucked out of the collet. I'm cutting 1/2" acrylic .25" deep @ 25 IPM @ 15000 RPM. Is this too high a feed rate. Chip load calculations say I can go MUCH faster.

What else could cause the bit to be pulled out. I had it tightened pretty well.

Thanks

[Mel Fulks]

We had a CNC machine with some issues like that several years ago, since I had nothing to do with running it I was not consulted. When I did finally look at it discovered they were assembling collet the way the "technicians"had instructed and it was wrong! They had thrown some bits and had to replace some collets. A major supplier of the machines finally admitted their guys had been wrong. If there is anything about the way you were told to use it that seems counter intuitive I would have a serious conversation with the people who sold it.

[Ernie Martinez]

Theres not much to an ER11 collet, either it's in or it's not. The collet was tight enough as the bit shank has scrape marks from it being pulled out of the collet. I don't even understand how this could happen since the only 2 bits that this has occurred with was a V Bit and a 3/8" Round Over bit, both from Hartlauer Bits. These bits are straight flute which shouldn't have up or down forces like upcut/downcut type end mills.

I just changed the program to 2 passes of 1/8" deep per pass. First pass ok, second pass pulls the bit out. According to the Chip Load # from the manufacturer (.006) I should be able to go about 300 IPM @ 15000 RPM. I'm @ 25 IPM. I also changed from climb cut to conventional, same problem.

I'm baffled on this one.

[John McClanahan]

Does the spindle seem like its running as smooth with these bits as others? My thought is the problem bits are poorly balanced, and vibration at the bit is causing it to shake out of the collet.(OK, I know its a long shot!)

John

[Ernie Martinez]

Well it's a new machine, and I really haven't had much chance to run many bits. I really think I either have a defective collet or nut.

[Jim Underwood]

What amount of torque have you applied to the nut?

I normally torque our ER40 nuts to 120 ft/lbs. If you still have problems after ensuring proper torque, then I'd check to make sure that the shank is contacting the collet from front to back and not just halfway in.

Other than that, I'd figure it was the collet and replace it. You do have to replace them periodically. How old is it?

Are you sure the nut matches the collet?

How about the shank size and the collet size? If you use a metric shank with a standard sized collet, then you might have problems.

[Ernie Martinez]

I'm not using a torque wrench, but if I was to guess using my calibrated wrist, I'd say about 25 ft/lbs. I'm using ER11 collets. I don't quite follow on "front to back", do you mean shank all the up into the collet? I just got the machine and using the collets that came with it. I'm having the problem with a 1/4" ER11 collet with an ER11 collet nut, with 1/4" shank bits.

[George Carlson]

I've had this happen on my Bridgeport with R8 collets. Try replacing the collet. Sometimes they get cut with a bad taper, and no amount of tightening can fix it.

[Mel Fulks]

I looked up that collet and as you said ,it's pretty simple .The situation I described involved three pcs. Agree with new collet, but after bottoming out the bit , pull it back at least a 1/16 th before tightening. Saw a bit fly out on first time use of a new small router once and having it bottomed out was the cause. Compared to the silly warnings used today some of the necessary ones are buried in small print and not stressed enough.

[Jerome Stanek]

Are you sure the collet is snapped into the nut. I have seen people just place the collet in nut loose and try to tighten it up

[Ernie Martinez]

Yes, but it's really not snapping in very tight, if I hold the nut upside down, and shake it, the collet will fall out.

[Jim Underwood]

Those nuts and collets should snap together. Make sure that there is no space between the taper on the nut and the taper on the collet when you tighten down the nut. If it's falling out then it's probably not snapped in all the way- or it's defective. Have you talked to the manufacturer about this? What brand is it?

And yes, the shank of the bit should go all the way through the collet. In other words, the bit should be gripped by the fingers of the collet as much as possible.

[Ernie Martinez]

I don't know the manufacturer, it came with my Laguna IQ, but I'm sure it's Chinese. I've ordered a new collet and nut, since I think I may have gotten either a defective collet or nut.

I really appreciate your help, thanks.

[Jim Underwood]

Let us know what you find out. I don't know about the ER11 collets and nuts, but on my ER40 nuts and collets, you can hardly get the things together they're so tight. Then you got to get them back apart. The collet has to compress to fit into the nut.

They sure don't fall apart by themselves.

[Jerome Stanek]

My ER 25 are the same I had one collet that was loose and didn't want to stay together and I ended up pitching it. I tried it in the spindle and didn't like how it gripped the bit.

[Gary Campbell]

Ernie...
Many Chineese collets are made with a metric "range". i.e. 6-7mm, They usually dont work too well. Order a single size 1/4" collet, that should solve the problem. Torque to 25-30 ft lbs

[Ernie Martinez]

In the pic, the top collet is the original collet I received with the machine, the bottom one is a new collet I just purchased on Ebay. The original one has 1/4" stamped on it, but the new one has no stamp. They are both supposed to be 1/4". Here are the dimensions

New Collet Bad Collet
OD .459 .437
ID .250 .250
Length .705 .708

The original collet wouldn't snap properly into the collet nut, it would just fall out if I held it upside down. The new one snaps in firmly. In my research I've also noticed that not all ER11 collets and nuts are the same. There are ER11-A ER11-B and ER11-M. My collet nut is an ER11A. Turns out that the ER11-B collets are supposedly for the Chinese spindles, which is what I have. But the ER11-A nut fits just fine. You can get more info here. http://chinamarkt.de/html/advanced_search_result.php?keywords=er11&osCsid=sqjbuxetjl&x=7&y=8

I haven't tried using it yet, but just the mere fact that the new collet snaps snugly into the nut tells me that the original collet I received must have been an ER-11B and the cause of my problems. You can plainly see in the pic how the bottom (new collet) just looks more robust. Beware of Chinese collets. One key way to tell is that the ER11-B collets have more/thinner splines.

245925

[Jim Underwood]

Interesting. So you have no more problems with pullout?

[Ernie Martinez]

Don't know yet, haven't used the new collet and nut, will post as soon as I test run it again. But I did do a run with a 6mm collet and a 6mm Vbit and I had no problems.

[james mcgrew]

falling out is not good

[Mike Heidrick]

I do not snap mine. Grab the collet, hold at 45 degree angle in the nut, rotate clockwise. You will feel it seat into place. Remove the opposite way, angle and unscrew counterclockwise. I have ER20 on my spindle.

[Mike Heidrick]

A/B/C/M is the nut style not the type or source country of spindle. I have an ER20A on my Chinese 2.2kw and it works perfect.

[Ernie Martinez]

I ran several jobs last week and no more problems with the bit pulling out. It was the collet.