Router Runout Gripe

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Forum topic by BigMP posted 01-30-2010 10:56 AM 4220 views 0 times favorited 14 replies Add to Favorites Watch
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24 posts in 4107 days

01-30-2010 10:56 AM

Topic tags/keywords: router runout

Ok so to make a long story short…
The other day, I started using a flush-trim bit for some template work. The bit I was using was a CMT 3/4od 2” overall length downward cut bit that was part of a cabinet set. I turned the router on and felt/heard horrible vibration so I turned the router off and noticed, as the bit slowed down that there was visible runout; in the neighborhood of 15thou. Thinking that it was the bit, I called CMT an the promptly sent me a new one (great customer service) free of charge. Well the new one arrived today and the same problem occurred. I knew that the 2 bits couldn’t be bent so I started thinking about other variables that could cause the problems. Turns out that, after lots of tests with a dial caliper, it seems to be the collet in the router.

With the dial caliper, I determined that the runout of the bit right above the collet is about 5thou and at the bearing it jumps to about 15thou. I tested it on other bits with the same result including a precision centering pin from Whiteside. Also the the part that the collet screws into is perfectly round and has no runout. So, by process of elimination, I’ve narrowed down to the collet causing problems. I tested both 1/2 and 1/4”, with the 1/4 being better, but not by much(3thou and collet and 10thou and bearing).

The router is a 690 series PC.

I guess my question is has anyone else had these problems?
And how should I go about fixing the problems?

I would say 4thou runout at the bearing is acceptable on such a long bit, but 15thou makes it unusable.

Any suggestions would be greatly appreciated, and thanks in advance!


14 replies so far

View Uncle_Salty's profile


183 posts in 3278 days

#1 posted 01-30-2010 02:39 PM

I have had students overtighten the collets on the PC (because it is a two wrench setup!) and break them. Have you tried new collets yet? I’d try that one first, as it is the most vulnerable link in the chain. I have purchased them at a local lumberyard (and not the big box home centers… take that HD and Lowe’s!). I would then try you spindle and a dial indicator to measure your runout. If you still have excessive runout, the next step are the bearings in both the top and bottom of the 690. Not sure what PC’s service dept. covers.

Best wishes on this one. .015 is a pretty substantial.

View Ger21's profile


1075 posts in 3336 days

#2 posted 01-30-2010 04:03 PM

I’ve got about a dozen PC collets and haven’t had a problem with any of them. If you want some really good collets, try these. I use them in my CNC for 1/16” bits.

-- Gerry,

View davidpettinger's profile


661 posts in 3406 days

#3 posted 01-30-2010 07:27 PM

Make sure there is no debris inside the collet holder. Another LJ here had the same problem back a while and he found some debris between the sleeve and the collet.

-- Methods are many,Principles are few.Methods change often,Principles never do.

View garberfc's profile


57 posts in 2460 days

#4 posted 01-22-2014 01:13 AM

On my first search I found this thread and noticed we’re using a very similar set up and share the problem problem. I didn’t hear the problem, but the first time I turned off the power I also noticed the run out with the naked eye.

I have a new PC 7518 motor and have mounted it in a table. I’m using a Whiteside flush trim bit that extends 3” out of the collet (RFTD5200).

After reading your posts I installed my Bosch centering pin and took some readings:
  1. Spindle (collet removed) – negligible.
  2. Base of centering pin (about 1/4” up from collet) – .0015”
  3. Centering pin (about 1” up from collet) – .002”
  4. Top of flush trim bit (about 3” up from collet) – .007”

All the numbers seem reasonable except the .007! I’m not sure I’d want to run and hard wood across a bit that’s wobbling that much!

It’s a brand new router and collet. There’s not dirt or dust in it. I wipe the bit shaft clean b/f sliding it into the collet.

Any thoughts??

Thanks in advance,

View bigblockyeti's profile


5290 posts in 1926 days

#5 posted 01-22-2014 01:26 AM

I don’t know what the specified procedure for testing is with PC, but working as a tech for an authorized Milwaukee repair center, they said to use a precision 1/2” dowel and measure the run out at I think 2” past the end of the collet. I do not remember what was considered to be within spec. but I do remember before installing the precision dowel, the collet had to be thoroughly cleaned, then cleaned again!

-- "Lack of effort will result in failure with amazing predictability" - Me

View garberfc's profile


57 posts in 2460 days

#6 posted 01-22-2014 01:55 PM

A couple more points that may contribute to the runout:

  1. The threads on the spindle seem clean while tightening the collet, but to the touch the tops of the grooves are rough. Like someone ran a file across them. Strange.
  2. The opening on the collet is very tight. At first I thought I may need to remove the locking ring that keeps the collet from slipping out of the nut. But I was able to push a bit in from the opposite side of the collet proving that it was wide enough. I put on some leather gloves and worked the bit into the collet.

I bought this router on sale from Woodcraft. I wonder if the router is some how defect or is a 2nd?

All thoughts on this matter are appreciated.

View bigblockyeti's profile


5290 posts in 1926 days

#7 posted 01-22-2014 02:08 PM

I wouldn’t think your router would be a second. I’ve noticed most of my PC collets are fairly tight, you can take off the snap ring, remove the nut and spring the collet open slightly to allow easier bit insertion, but you can also break the collet if your not very careful. The collet shouldn’t be so tight as to need gloves to safely install a bit, that sounds excessive to me. I checked my PC routers and the threads on the spindle feel smooth at the peaks, all of the nuts feel smooth going on as well. How old is the router?

-- "Lack of effort will result in failure with amazing predictability" - Me

View JAAune's profile


1853 posts in 2522 days

#8 posted 01-22-2014 05:44 PM

I’ve learned since building a CNC router that Porter Cable collets are notoriously poor quality and often have unacceptable amounts of runout. A lot of CNC users choose to replace them with aftermarket products for this reason.

Ger21 already linked to the same company I’m talking about but I’ll add the link again below.

Precision collets

-- See my work at and

View garberfc's profile


57 posts in 2460 days

#9 posted 01-22-2014 11:30 PM

Thanks JAAune. I saw the broken link and was going to post an updated one.

I think I will replace to collet. What a shame PC can’t get the collet part right. Seems like one of the more simple parts of the router…


View jumbojack's profile


1685 posts in 2829 days

#10 posted 01-22-2014 11:52 PM

Are you sure there is no debris in the collet?

-- Made in America, with American made tools....Shopsmith

View Dallas's profile


3599 posts in 2692 days

#11 posted 01-22-2014 11:56 PM

Wow! and I was wondering about the two HF 2HP routers I use.

-- Improvise.... Adapt...... Overcome!

View garberfc's profile


57 posts in 2460 days

#12 posted 01-23-2014 02:21 PM

@jumbojack – Yes, there’s no debris in the collet proper, the slots in the collet or on the shaft of the bit itself. I wipe them all with a cotton rag before use.

View garberfc's profile


57 posts in 2460 days

#13 posted 01-23-2014 02:35 PM

Just dropped some $$$ for a Precision 1/4 & 1/2 collets for the Porter Cable 8517. I’m hoping for some improvement!

View Jackietreehorn's profile


150 posts in 2144 days

#14 posted 10-29-2014 07:53 PM

Researching same problem. Any update on the upgraded collet?


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