Bit slipping. Bad collet?

1

On Saturday I cut out a prototype sign from MDF. There was a pretty good amount of cutting as there were some through pockets.

Today I tried to cut a stacked text sign from maple. I started with a downcut 1/4” bit as I had masking on the top. I was using a .125” DOC but the router didn’t sound happy. About a minute or two in to the job I paused it to check and was certain at that point the bit had slipped so I stopped. It had definitely pulled down. I have a pretty religious habit of tightening the collet so I was surprised but assumed it was the down cut pulling into the hard maple.

So, at this point the piece was pretty much ruined anyway I decided to put the 201 in and restart the job. Similar situation and the router really started to struggle. I stopped again and could see that the bit had pulled loose.

I created a new job with just some rectangular pockets so I could do some testing and just used the same messed up piece.

This time I removed the nut and collet and blew everything out and then cleaned with a q tip and alcohol in the collet, but and shaft. I have to admit that I don’t clean inside the shaft as often as I should.

I put the 201 in and marked the bit at the collet with a sharpie and cut pocket 1. It looked like it still pulled down about 1/16” but I was not sure I marked it right at the nut so I marked on the other side of the bit and went again for pocket 2. Same thing. It slipped slightly for sure. Not nearly as bad as before I cleaned the shaft.

This is a fairly new precision collet. Is it bad? Time to replace the nut? I have extras of both I can try but wanted to hear the sage wisdoms of the group.

2

Standard Carbide Compact Router, ER-11, or VFD?

Note that we recommend only using the button to hand-tighten things so that they will stay in place while one fully tightens with a good quality pair of wrenches. The community has the following notes on Carbide Compact Router/Makita RT0700/0700 shaft and collet/nut wrench sizes:

If you could post photos showing your tool, nuts, and collet we might be better able to advise.

3

I am using the C3D router with the C3D precision collets.

I have never had this issue before. I do use both wrenches to tighten. I am only guessing that the excess MDF in the shaft acted as a lubricant somehow although the shaft inside the collet was clean (I think).

4

A few things more to check.

  1. Make sure you are NOT pushing the bit all the way into the collet and bottoming out in the shaft. It needs room to expand when heat builds up and to tighten up properly.

2.Take your calipers and check the actual diameter of the bit in several locations and make sure it is .250 diameter.

  1. If you have another collet or even the 1/8 inch collet the outside measurements will be the same compare the two and see if the 1/4 inch is sprung, bent, scored or damaged in any other way.

  2. Look at the shaft end and see if it is out of round or damaged any other way.

  3. look at the collet nut and see if there are any signs of stress cracking.

Hope this helps.

Anthony

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5

My Dewalt 611 router started slipping the bit in the collet. I cleaned it with brake cleaner but the problem persisted. I have the elair collets and swapped it out and problem solved. Collets do go bad and replacement is necessary.

These are good quality collets and they have metric as well as sae. You can buy bundles cheaper than the individual collets.

6

I am not pushing the bit too far up. I am careful about that. I will check out some of the other suggestions though.

I don’t understand the “sprung” collet concept. I guess the issue would be if the nut is unable to push the collet up far enough in the shaft to squeeze the bit properly.

7

I finally got back to this. Stupid day job gets in the way of real work.

I cleaned everything I could think of that could be related. I also made some measurements.

Both bits I was using are .2495.

I have 5 1/4” collets that range from .2475 to .25.

The bits do slide much easier through the ones that are .25, but I assume when tightened up they would both be ok.

I did notice that the nut I have now is .495 tall with threads about .2885 tall. I have an older nut that is .502 tall and threads of .168.

I did 2 test pockets about 1x8” with the 201 and they looked ok and the bit did not slip as evidenced by the sharpie mark.

Then I did a similar pocket with a downcut and it looked good and again did not slip. Again as shown by the marker.

So, I tried a more realistic test with the 201 in one of the collets that measured .25. This was a clearing path followed up by a 1/8” bit in a 1/4 collet. It was obvious that there was a problem pry way into the first toolpath but I let it go and then switch the bits to finish.

After the first path was done with the 201 I could see that the bit had slipped.

Before:

IMG_3800
IMG_38003024×4032 1.85 MB

After:

IMG_3801
IMG_38013024×4032 2.73 MB

After the first path I switched to one of the collets that measured less than .25. Of course I also switched bits and the toolpath had a lot less work to do. That one went ok and the but did not appear to slip.

The finished product is a disaster of course.

IMG_3804
IMG_38044030×2669 2.85 MB

So, what should the proper diameter of the bits be? And what should the diameter of the collet be? Not that I took the collet measurements on the business end of the collets, not the back. Also, my calipers are not the greatest.

Oh, and this was maple so pretty hard. I will say that the router was complaining more about the maple than the walnut I usually use.

The collets that measured .25 exactly are the flat bottom ones. The others have a slight almost chamfer at the opening.

8

Update:

Since the collets measuring less than .25 seemed ok I loaded up 201 and flattened out the pocket shown above. It looked good and the bit didn’t slip.

Then I ran the program using the 201 and 1/8 bit to cut the names and all is well.

IMG_3805
IMG_38054030×1641 1.68 MB

Those collets with .25 were the C3D precision collets and I have never noticed an issue until last weekend. One was potentially damaged when I accidentally left the router in the on position when I had a drag knife loaded but that was only one of three.

9

Collets in Makita/C3D routers are basically a spring. The collet is cut in to 4 even pieces. The inside of the router shaft is an inclined plane. So when you insert a bit into the collet and tighten up the collet nut you are forcing the bit, collet and nut up and the inclined plane squashes the 4 quadrants together to grip the bit. The Makita/C3D collet nut is not attached to the collet. That is why at times when loosening the collet nut the collet is still up the inclined plane and you have to tap the collet nut/collet to get the bit to release.

So C3D recommends using the button on the router and 1 wrench to get the initial tightening. Then when tightened enough to keep the bit from falling out you finish with two wrenches.

The CNC is a dusty environment. So periodic cleaning of the collet and collet nut and inside of the inclined router shaft is necessary. Small specs of dust can keep the collet from fully gripping the bit. I use brake cleaner but mineral spirits, acetone or denatured aclohol wold work. I like the brake cleaner because of the aerosol in the can helps flood away debris. You can spray a qtip with the cleaner and clean the inside of the router inclined shaft. Make sure there is no oil or lubricant inside the inclined plane, collet or collet nut. They should be clean and dry.

Over time the collets do wear out. That may be why some of your collets are different sizes or are just make improperly from the factory. No matter the size when the collet nut forces the bit and collet up the inclined plane they should tighten up barring any foreign objects like dust.

One way to make a visual help is to put a fine magic marker line on the bit where it meets the collet after tightening. Then you can pause periodically and when the router comes to a stop you can visually see if the line is still visible or had dropped down. Magic marker can be erased with acetone.

Bits can also become dirty and need to be cleaned periodically. Build up of tree sap or metal shavings can cause problems with the bits ability to be held firmly in the collet.

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10

I did use the marker method, pictures included above. That is how I knew it was the bit slipping rather than the Z lowering which many people assume.

I agree that tightening up should resolve the issue, but it is not in these cases so it feels like something has changed. The collets that work for me are the ones that are snug when I slide the bit through. The collets that fail are the ones that the bit slides through like butter.

So, if it isn’t a collet issue I still have something else to track down. My question to the group is what internal size should the collet be at the open end? Do your bits normally feel snug simply sliding in the collet while in your hand or are they loose?

I wouldn’t continue to beat this horse but these are fairly new collets without much use except for the one I may have damaged. I don’t want to order more and continue to have this issue if the root cause is something else. I will try swapping the collet nut and see if that changes the behavior.

11

You might want to take a quick look at the taper where the collet seats on the inside of the spindle shaft, it should be smooth and not scratched or burnt looking. Anything other than clean and smooth could prevent the collet from applying even pressure to the tool bit. Also, take a look at the inside of the collet nut. The one pictured below is pretty used up.

IMG_2303 Small

IMG_2302 Small

12

It’s hard to get a good view in there without pulling the router out but it looks Ok. Since the earlier posts I have gone back to using my older collets and have been very diligent about cleaning. It’s amazing how much dust gets in that shaft.

Things were going great until yesterday. I was cutting a couple of pieces out of maple. The first was perfect but I could tell about 25% of the way into the second that the bit had slipped so I stopped the job, fixed everything and then resent just the job for the second.

To be fair I was slot cutting in .75” maple with a .9” DOC on a #201. I know I shouldn’t have been, but very few of the folks on the internet seem to cut as a pocket instead is a slot.

The earlier cases where this happened were not slot cuts so it’s a combination of things I guess. Just kind of weird that I went a year without this and then it has happened several times.

Maybe I will pull the router out and l
Examine the shaft more closely. I have a spare C3D router that I could swap out if things done look right.

13

I have a small mirror I set on the spoil board to look up inside there.

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14

It is surprising how even just a small particle can upset things. The collets used in the trim router are not precision items and are very easily damaged. Remember that you are trying to keep the cutter perpendicular to the workpiece 100% of the time and anything else will affect the carve and the finish. It also has a deleterious effect on cutter life.

When using a Makita trim router, I was fastidious about cleaning the collet and the collet taper, along with the collet nut after every single job. That way you can eliminate the environmental reasons for a poor cut. I also spent money on the Elaire collets referenced by @gdon_2003 above. They cost more but they are made with more precision than off the shelf items and I can highly recomend them.

Tightening and loosening was tough with the Makita style thin spanners. I taped the handles with tennis racket tape to soften them in the hand. To tighten the cutter in the collet, I placed the collet nut spanner on the left and the spindle spanner on the right with an angle of roughly 30 degrees between them. Just squeezing together the handles will tighten the collet sufficiently while the unoccupied hand holds the cutter in the collet.

Loosening the collet nut required the reverse operation with the spindle spanner on the left and the collet nut spanner on the right. When spaced apart at an angle of say… 30 degrees and squeezed together, the collet will be loosened and the free hand will support the loosened cutter.