Router Bit walks out?

[Jim Foster]

I have an older (25yrs) PC690 and when I use straight shank bits, they tend to walk out... not fun. I don't have this problem with other bits. This happens with straight cutter bits or spiral bits, and it's happened with the 1/4" collet and 1/2" collet.

The router works fine, but not sure if it's me or I need to replace anything besides the collets.

For example today I was taking a 1/8 inch deep groove with a 1/4" diameter straight bit and it walked out to 3/8" after about 40 seconds (about 45" down the board. I was not pushing hard or in a rush. It came down over a 3-6" section, I noticed something was up and shut things down. I retightened it and did two more passes down to 3/8 without mishap... but this has happened several times now.

Any advice? I'm going to replace both collets (they are pretty old anyhow) and toss any bit that has slipped. (not a big investment, just 3 straight bits)

[Ray Newman]

Since you say it is only three straight bits that “walk out” of the collect(s), my SWAG (Scientific Wild Arsed Guess) is that the problem lies with the bits, not the collects.

Seems if the collets were at fault, any bit in the collects also walk out??

Who made the bits and do you have a way to measure the shank diameter? Wonder if there is a film/coating on the shanks that prevent the collect from gripping the shank. Might want to de-grease the shanks.

Or, just maybe you are not tightening the collects enough to hold the bits??

[Steve Jenkins]

make sure there is no rust on the outsides of the collets and also inside the area that the collets engage the router. If there is a bit of rust on these areas it can make the collet stop tightening before it is really tight enough.

[Bill Huber]

Make sure you are not putting the bit all the way down. I had some bits that walked out and that is when I learned not to put them all the way in.

[Thomas Hotchkin]

Jim
Had the same problem with your PC690's big brother. As others has said make sure that all is clean. Take your collet apart remove all saw dust. As dust builds up in collet you can not full tighten on bits shaft. I placed a very small amount of graphite based thread lube on collet threads, and collet contact points, do not get it on the router bit shaft. Works like a champ. I have read that once router bits start to slips it will continue to slip. I cleaned shank of all problem router bits with 3M scotch bright pad. Tom

[Neil Brooks]

I always think threads like these are good places to add .....

Whenever I put a different bit in my router, I use a rag, barely moist with some WD-40, and give the shank a good cleaning.

I also have 1/2" O-rings on the shanks of most of my bits (the ones that will hold an O-ring, meaning ... most besides straight bits, and ... occasionally, those, too !), to keep them from bottoming out in the collet.

I also make it a practice to use my compressor, and blow out the collet, periodically.

Probably won't fix ya' up, this time, but may help you, down the road

[Lee Schierer]

I have to agree with the idea that the shanks are undersized compared to your other bits. I had a similar issue with my craftsman router until I took the collet apart and cleaned up a couple of burrs that would prevent the collet from tightening completely. See of you can lay your hands on a micrometer and measure some of your other shanks and then those on the problem bits. Any machinist should have one and know how to use it. If they measur undersize, I would toss them and get new brand name replacements.

Another solution is to tighten the bits completely then run a 3-4" cut in scrap, stop and re-tighten the bit.

[Edward A Miller]

As some have already mentioned, (1) make certain the bit is not bottomed out in the collet before tightened because when tightening, the bit moves toward the collets bottom (because it travels with the action of the threads). Also (2) make sure the bit is inserted into the collet far enough to allow the clamping action to function.

(3) Check the router base with a straight edge. It could be that if it was ever dropped, the aluminum housing could have bent just enough to cause some issues. There is also an outside chance (4) that one of the three screws securing the base plate has become loose and crud has worked its way under part of that plate. Maybe (5) the plate itself has a burr on an edge that might allow a wobble during the feed (as the router moves along while cutting).

What are you using to guide your cut? Routing 45" in length! (6) If you are using a clamped-on straight-edge it could be flexing some. Also, (7) if using a bearing, it could be worn which could allow the cutter to wander and cut wide. Haven't ever seen this, but if you are using a cheap bit, (8) it could be that the flutes are off center (one out wider than the other) which could cause some wild cutting action. Regrinding by an inexperienced cutter-grinder is a crap-shoot!

Although the 690 is not the most precise piece of machinery, it can provide years of faithful service. I have 17 of these still in service in my shop, most with a dedicated bit/function, all with Whiteside bits and never had this problem (9) as long as I was feeding in the direction that kept the guiding surfaces (bearing against a straight edge, etc) drawn together.

Cleaning the parts has been mentioned several times as well it should have been........................., (10) clean the parts! Be safe and have fun.

[Ole Anderson]

To keep the bits from bottoming out, just drop one of those round rubber "space balls" in the collet, or slide a small o-ring the inside diameter of the collet to its bottom.

[Larry Edgerton]

Like Edward I have over a dozen of these routers. I routinely blow the collet/cup out with every bit change, and every once in a while I spray collet/cup with TopCote. I know some will say you can not do that, but I have never had a bit walk since I started doing it.

You can't get them too tight. I have a method I use where I get the wrenches in such a position that I can get my hand on both of them and give them a very hard squeize. You can get them tighter this way as you don't have to worry about wrenches slipping.

I have in the past seen bits from the far east that were undersized. I learned that money spent on better bits comes back to you.

I just noticed that you have an old 690. About 25 years ago, maybe a little less, they switched to a 4 split collet from a two split. If you have a two split they did not hold all that well. You definately want the newer style.

Larry

[Jerome Hanby]

I don't buy metric bits, so I'm not familiar with the "standard" shank sizes, but are there metric shank sizes that are close enough to 1/2" and 1/4" to be confused with the imperial sizes? Seems like metric "equivalent" sizes always run a little smaller. If all these straight bits came from a single set or maybe just the same vendor, maybe they are metric...

[pat warner]

Indeed if the collet is not tight, (15 pounds on 10" wrenches min.) cutters will change depth under power.
A ding on the cutter or a scored collet (inside or out) will frustrate a good grip.
In that case a new cutter or collet is warranted. And, of course, 100's of hours of ordinary routing will kill a collet too.
The design of the cutter in the collet is important too.
Some cutters pull themselves from the collet.
Those tools that are engaged/stuck in the work are the easiest to pull from the collet.
A slotter e.g., if the router tilts, can pull itself from the collet. Glue joints, bead tools and others whose radial design sticks them in the stock, can all pull themselves from the collet if the router tips.
Upcut spirals are about the worst offenders. They pull the chip out of the excavation, alright, but the equal & opposite vector/force is pulling the cutter from the collet. Straight fluted bits do not have this force component.
Bottomline, in your case, change collets. A tight grip on a uniformly round shank is your best defence after that.

[Bob Wingard]

Pick up a few brass brushes for gun cleaning at the sporting goods store, and thoroughly scrub the collets with acetone. Clean the bit shanks as well. NO LUBE ... bone dry ... if the bits still slip, it is very likely that at some time you've over tightened the collet nut without having the collet itself fully supported internally by the shank of a bit, and you might have "sprung" it. If so, replacement is the ONLY option that will be safe.

[Edward A Miller]

Jim, I have an unused NOS 4-segment PC 690 1/2" collet, no rust; will send ya one if you're using 1/2" shank bits. Just let me know where to send it. Same goes for anyone else having a bonafide (1/2") collet issue. (3 oz ea)

Also have (13) extra NOS instruction manuals (w/parts list) still in the plastic bag along with the 2 original wrenches, no rust (specify print year): (1) 1997, (4) 1998, (4) 2006 and (4) 2007. (1 lb ea)

Free and with your optional to reimburse for the ship cost after ya get em. Contact on or off thread with a ship-to.

I'm not taking these with me, so it would make me happy to see these go to a good shop.