I am milling 1.5" construction grade lumber. So I am using a upcut bit with a 2 inch cut depth. I have back my feed rate to 50 inches per minute and my pass depth is a quarter inch. There is really not much chatter at all by after a while the collet loses it’s grip on the bit shaft and it starts to slip out. Does anyone have an suggestions? On another forum someone recommended ER 11 collets. I am open to anyone else who has insight.
@kendallcaputo What router/spindle are you using? How far into the collet is the end mill?
Edit: Also, while you don’t want to overtighten, be sure to use two wrenches to tighten the collect nut, and not the red button/one wrench method.
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I like to clean the shank on the bits with rubbing alcohol before putting in the collet. Also clean the collet with alcohol, and like Grant said properly insert the bit to proper length.
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@kendallcaputo To elaborate on what @gwilki asked about how the far into the collet the bit is, I learned the hard way that you can’t put the bit into the collet as far as it can go. When you tighten the collet it squeezes the bit by pushing the collet up into the router and if the bit is already bottoming out it could damage parts or just not get a good grip on the bit causing it to be fine for awhile but then slip out at some point.
I ran into this when using a long bit on thick stock and with a 2" cut depth I’m assuming your bit is pretty long.
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Well, I came up with a solution that works. I superglued the a collet insert onto the shaft of the bit. It works great! Who would have thought?
How many times have you had a problem with bits moving in the router? I am wondering if you have actually squished the nut enough that you have misshapen it to the point that it won’t hold the bits? I would buy a new nut for it before relying on crazy glue to keep your bits in place. Actually buy a new nut and the insert for it to be safe. You shouldn’t have to wrench down real hard on them to secure them .
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Great suggestion. It is certainly easy enough to replace. But for the record. I am only having the problem with one project. I am cutting many parts out of 2x construction grade lumber for outdoor furniture. The wood is pretty wet, unstable and has a lot of tension in it and I am cutting some compound shapes that really pushes the limits of a bench top CNC. I have to use an upcut bit with a two inch cut capacity, the combination of the wood and bit results in a tremendous amount of vibration even with very conservative feed and depth of cut settings. I can cut hardwood for signs or trays etc., without any issues.
@kendallcaputo It’s good that you have fixed your problem. I will say, though, that you may want to keep an eye on things. A CA bond between metal is extremely brittle and prone to snapping/shattering. In your application, if that were to happen, the results could be dangerous.
Usual preface, I’m with PreciseBits. So while I try to only post general information take everything I say with the understanding that I have a bias.
You can’t use these. I have no idea where it come from to try and swap in “close” ER sizes in routers (not counting routers with ER chucks). The issue is that all these systems are based on compression of tapered section. This means that the taper angle in the router/spindle needs to match the collet. If it doesn’t, at best you will “pinch” the front or back of the taper and only get compressive force from that “pinched” area. For reference all ER collets are an 8° taper.
If you are having to do this to keep the bit from slipping then you almost certainly have a sprung collet and should replace it as it’s not only letting the bit slip but increasing runout. Using something like super glue will also almost certainly cause additional runout.
If you’re not aware runout is how much the tool will spin off the center axis of the router/spindle. Most people don’t give this as much weight as they should. I’ll give an example as to why.
We’re going to need a basic understanding of chipload for this. Quick, incomplete explanation of chipload is that it’s the width of the chip each flute is cutting per rotation. Or another way to think of it is that it’s the amount each flute is moving “forward” each rotation. It’s probably the most important cutting factor in CNC milling. It’s what all feeds and speeds are trying to get to and one of the primary factors in cut quality, tool life, and cutting force.
We need more data than you 50IPM. So let’s say that we are going 10KRPM and this is a 2 flute cutter. That works out to a chipload of 0.0025". Now let’s say that we have 0.002" of runout. In the worst case what will happen here is that the chipload will be added to one flute and substracted from the other. So now we are taking a 0.0045" chipload on one flute and 0.0005" chipload on the other. Or, we are functionally cutting 90IPM on one flute and 10IPM on the other. This is much less than ideal. Once the runout exceeds the chipload x (flutes -1) the worst case becomes putting all your chipload (feed) on a single flute.
Hope that’s useful. Let me know if there’s something I can help with.
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