Routering help needed: collet grip / bit slip

[dstmbgh]

I have a twenty year old Sears Craftsman router with a 1/4" collet, and I'm using a new spiral downward solid carbide bit to cut recesses and holes in a 3/4" mdf baffle. When I make test cuts in 3/4" oak veneer plywood the bit slips, extending outward, making the cuts deeper than intended. I have not yet had this happen with the mdf, but I'm worried that it will, and ruin my work. I understand what's happening: the new, sharp downward spiral bit is gripping like a drill and pulling into the hole, causing the bit to slip in the collet. I understand that a narrower 1/4" collet/shank is more susceptible to slipping. I also understand that shallower cuts and a slower speed will lessen the tendency to slip. The router is not variable speed.

Besides the above, any suggestions on how to "treat" (clean, sand, adjust, etc.) the collet and/or bit to lessen the slipping?

Thanks for all help.

David

[Melo theory]

Is the inside of the collet clean and free of mdf dust, or any debris?
Soak the collet and bit in ammonia for a a minute.

[DUG]

Tighten the collet more...been there done that.

[bear]

buy new collet.

if that fails buy a real router.

[tvrgeek]

Yea, my old Sears router I have to snug pretty darn tight. Not a problem with my RIgid.

[Kindhornman]

dstmbgh,
If all else fails and you can not tighten the collet enough to hold the bit you can always try and wrap without overlapping a piece of very fine wet/dry sand paper around the bit so you have more compression on the bit. I thought about saying put a small piece of paper clip in the collet but at the speed we are talking that may cause an out of balance condition and make the bit vibrate. Many times the collet insert is just worn and a new holder will do the trick. I have an even older router than that from Sears, at least 40 years old and it still works fine. However for heavy cutting I use my Bosch for that with a larger collet diameter.

[Einric]

Or, you could use an Up-Cutting bit or Compound/Compression bit.
I would agree though, if you clean it out with some mineral spirits or denatured alcohol and it still slips then you may need a new collet and collet nut.

[DrNick]

Originally Posted by dstmbgh

I have a twenty year old Sears Craftsman router with a 1/4" collet, and I'm using a new spiral downward solid carbide bit to cut recesses and holes in a 3/4" mdf baffle. When I make test cuts in 3/4" oak veneer plywood the bit slips, extending outward, making the cuts deeper than intended. I have not yet had this happen with the mdf, but I'm worried that it will, and ruin my work. I understand what's happening: the new, sharp downward spiral bit is gripping like a drill and pulling into the hole, causing the bit to slip in the collet. I understand that a narrower 1/4" collet/shank is more susceptible to slipping. I also understand that shallower cuts and a slower speed will lessen the tendency to slip. The router is not variable speed.

Besides the above, any suggestions on how to "treat" (clean, sand, adjust, etc.) the collet and/or bit to lessen the slipping?

Thanks for all help.

David

Glad it's not just me then! This happened to me with mdf when I was making the hole for a driver in mdf. I found nd this happened most when plunging a new hole, and when the sawdust builds up around the bit. If you can use a vacuum attachment to keep the bit free of dust, that helps stop this happening with mine. If you are making a deep cut wider than the bit try going down in steps, changing the radius so there is free space on one side of the bit, which helps keep it free of dust.

[ODougbo]

The dust can collect inside the arbor - it can get very deep.

The old Sears routers fall apart pretty fast

Originally Posted by Melo theory

Is the inside of the collet clean and free of mdf dust, or any debris?
Soak the collet and bit in ammonia for a a minute.

[1audiohack]

Something not yet mentioned. This may seem counterintuitive but dry or damaged threads can friction lock before the required force to hold the bit is transmitted to the collet.

Check the condition of the collets threads. What locks threads and keeps them from loosening is actually thread deformation. In our CNC mills when loading tools we clean the collet, nut and the tool holder bore, then lube the taper of the collet and holder with light oil on a paper towel and the threads with moly grease/paste, all the while being carefull to keep the grip of the collet and the cutter absolutely dry. At the very least, lube the threads with something that won't migrate into the collet bore. With the same input of tightening force you will transmit much more clamping force on the tool.

Yeah, I do this with my routers and have never pulled a bit nor stuck a collet.