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
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
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.
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.
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.
The dust can collect inside the arbor - it can get very deep.
The old Sears routers fall apart pretty fast
The old Sears routers fall apart pretty fast
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.
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.
Thanks to all of you for taking the time to help with your advice. The router in question is mounted upside down in a homemade router table with downdraft dust control. The setup is working great for dust control, but it also pummels the collet with mdf dust. Besides tightening the collet more, I've not yet tried to remedy the situation, as I wanted to get some advice first.
I will implement the suggestions above. Thank you for your help. I may be back for more help depending on what I encounter.
David
I will implement the suggestions above. Thank you for your help. I may be back for more help depending on what I encounter.
David
There were some Craftsman routers made where the collet is machined into the end of the motor shaft and not replaceable. Unfortunately that doesn't work so well compared to a collet that's slit from both ends. What works okay for large machine tools doesn't work so well when the slits are only a half inch long. When you tighten the nut force is applied to the bit from the end of the collet over a comparatively small area. Particularly when using solid carbide bits with very high shaft hardness there just isn't enough grip. Cleaning the collet well can help. If you have one of these routers and decide to lube anything (after good cleaning, otherwise forget it) it's probably best to use very light oil, soon subject to complete evaporation might not be too bad (like WD 40), and put it, lightly, on the nut only. That might get you by for loading one cutter, and unless you load a carbon shafted cutter next, you'll probably have to do it all over again. These were not good routers.
The dust can collect inside the arbor - it can get very deep.
The old Sears routers fall apart pretty fast
Mine is about 30 years old and works as well as new. Of course, that's why I bought the Rigid.
Three votes for lube on the threads. I had a problem with the Sears router where it would slip the adjustment in the base. A bit of lube on the bolt of the clamp and wa-la. Now I it gets correct clamping force with just thumb supplied torque.
Anti seize is a good choice for lube in this use. It is non-galling and handles force well. A TINY amount will do. TINY. Did I mention you need only a tiny bit?
Hate to be a grump, but routing 3/4" mdf with a 1/4" bit is, well, scary (or really slow). I know people do it, but years ago I had a bit snap off when edge routing and was fortunate it didn't hit me. I truly believe that for efficiency, and safety, a 1/2" router is really the only way to go.
I have a old Sears, the lever for the lock broke (I might had one before this also). I never could find a way to lock up the Arbor to tighten.
Sears is really goods about small parts, maybe go spend a few $$ on a new collet, couldn't hurt.
WD is good for a few things:
Starting 2 stoke engines (weed wackes, etc.)
Bike chains
Cleaning parts
Shooting potatoes (propane gas for propellent)
Sears is really goods about small parts, maybe go spend a few $$ on a new collet, couldn't hurt.
WD is good for a few things:
Starting 2 stoke engines (weed wackes, etc.)
Bike chains
Cleaning parts
Shooting potatoes (propane gas for propellent)
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I'd put aside some cash for a 1/2" collet router too if I were the OP ... especially for table duty. Bearings on that 1/4" Sears will be going next.
btw, found a spanner wrench that fit the collet (?????) it fits perfectly, but since it fits over the collet - 7/8" is biggest cutter that I could use.
Always good to have 1/2" router and a smaller 1/4" on hand, for trimming, 45 and round overs bits.
Always good to have 1/2" router and a smaller 1/4" on hand, for trimming, 45 and round overs bits.
Okay, so...tonight before I began working I cleaned the inside of the collet well with some emery cloth and mineral spirits, being sure any residue was wiped clean afterwards. I also cleaned the threads, both on the collet and the collet nut. Per one poster who said that his Craftsman router like mine required that he make sure the bit was seated all the way in the collet otherwise it would slip (contrary to general practice), I tried this, tightening the collet nut as much as was possible (remember, my router does not have a double nut tightening setup). I also made sure the bit shaft was clean. Proceeding only 1/8" at a time, I completed all driver cutout holes with no problems with the bit slipping.
Previously the bit slipped mostly with oak veneered plywood and with cuts in excess of 1/8". Maybe it still would under those conditions, but that's neither here nor there, as I won't do that again. The good news is I am making progress now without problems.
Thanks for all your help, guys.
David
Previously the bit slipped mostly with oak veneered plywood and with cuts in excess of 1/8". Maybe it still would under those conditions, but that's neither here nor there, as I won't do that again. The good news is I am making progress now without problems.
Thanks for all your help, guys.
David
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