Broken router collet. Why?

[Simon Magennis]

I was trying to set up my Bosch GK600 (colt) the other day and the cutter went flying through the room. When I open the nut and looked at the collet, it was in four pieces. What is the likely cause? Overtightening? Or is this something that just happens to routers once in a while?

I ordered two replacement collets which will arrive in the next week but I hope I don't actually need more than one.

[Barry Daniels]

How much force did you use when tightening the collet nut?

[Daryl Kosinski]

In the 40 some years using routers, I have 3, I have never had a broken collet.

Your collet must have been defective.

[Simon Magennis]

Thanks both. I don't really know how tight I made it. I doubt if it was different from the few other occasions I have used it. I have just a short spanner for tightening it so it is not really possible to crank it a huge amount.

The only thing I have done with the router his cut binding ramps for 3 guitars using a jig based on the one in the Gore and Gillet book. If there was a decent selection of mid-lower range routers here I would pick up another in any case but the only ones I have seen here are professional level so I am waiting till the replacement collet comes by post before I try again.

I was fortunate where I was standing so that nothing happened me when the cutter went flying. That was a lesson in itself.

[Bob Orr]

Just a thought but do you clean out the collet regularly. I lost a cutter once because the collet was all gummed up with fine dust and although it felt tight it was not gripping the shank properly. If it was gummed up perhaps that caused the collet to split|? Bob

[Dan Smith]

Make sure the bit is not bottomed-out before tightening.
Stick it in and pull it out 1/8” or so.
I learnd this when I had a bit fly out.

[Mark Fogleman]

I've had bits creep out also during a rabbit/dado cut but have never had a collet chuck to break. That took a lot of force or your collet chuck had a defect or both. I saw a tip in one of the WW'ing magazines a while back where the author used a small rubber ball known as a Spaceball http://www.spaceballs.com dropped into the collet to allow space for the bit to expand yet maintain a repeatable depth. I've not had any creeping bit problems since I started using one. These balls are normally used to maintain pressure on floating panels in wooden cabinet doors during dry season when the wood shrinks and compress during the wet season when wood expands. They are sold at most cabinet supply stores in the US. I'm not sure where they're found in the EU. Rockler has a 100 each bag for ~$7. If you can't find them PM me your address and I'll send you one. You'll owe me a Neumarkter Lammsbräu Festbier the next time I visit my friends a little south of you near Künzelsau.

[Brian Evans]

I do know you can damage collets if you tighten them with an undersized shank, or no shank at all. But I too have never damaged a collet or had one break. I've killed my share of bits, mind you.

Brian

[Simon Magennis]

I doubt if the photos really tell any story except how small the collet is (1/4"). I would need a fancier camera to get a more useful image. Anyway, just for completeness sake, this is what it looks like now. My new collet should arrive sometime next week and then I can continue with my current builds which are waiting for the binding.

Insides

External

Edit:

Since I posted the images I searched online and found the user manual. This might be the root cause:

Do not tighten the tightening nut of the collet without a router bit inserted. Otherwise the collet can be damaged.

While I don't recall tightening the nut very much when there was no bit inserted, obviously I had it at least tight enough enough to prevent the not and collet falling off - perhaps I over tightened it then.

[Clay Schaeffer]

That is a really delicate collet design for a trim router. The PC and Rockwell routers have a single cut through . As others have said leave a little space at the bottom of the chuck because the bit gets pulled down some as the collet is tightened and if it bottoms out it will not tighten properly and even if it holds the bit you will get more vibration with it in contact with the spindle. I have used broken (in halves) collets in larger routers which still worked o.k.

[Simon Magennis]

That is a really delicate collet design for a trim router….

Tacky is the word you are looking for.

When I bought the thing, the Bosch Colt routers were getting great reviews. This is the Euro version or to be more specifically the UK version. The Euro version takes 6mm and 8mm bits. The UK version only takes 1/4". That is not at all obvious from the product name and the box set I bought with accessories included the 8mm collet which won't work due to the way the shank is routed out. I got it from the UK as I though I was getting a bargain - about 30%-40% cheaper than in Germany at the time.

Hidden away on the small print in the specs for the GFK600 is another number: 3601 FOA 171. This is the key. 3601 FOA 1xx takes 6mm and 8mm (and I assume 1/4" as well). Whereas 3601 FOA 16x and 3601 FOA 17x take only 1/4" due to a conical routing of the shaft. All of them come from mexico like the colt.

I am not very lucky with my router choices. I also bought a trend T4 based on some forum recommendations. Again there is an issue that might be nothing for an experience person but makes it next to useless for me. The height adjustment on the base is shoddy beyond belief. There locking mechanism consists of a nut covered by a plastic lever. The nut wears the plastic out in no time flat with the result that the only way to lock off the height is to use a spanner of some kind, as opposed to just using your thumb to press a lever, and even then it gets loose. I suppose with a third party base or locked into a jig it would be alright.

[Clay Schaeffer]

"When I bought the thing, the Bosch Colt routers were getting great reviews"

Unfortunately ideas and recommendations on forums are kind of like viruses. You have to let them run their course for awhile before seeing if they are worth adopting. I have at least a dozen trimmers. Most of them are the old green Rockwell's and Porter Cable brand, but also an older Bosch, and a Virutex. I've used Ryobi, Makita, deWalt, Freud,and Ridgid trimmers. They all seem to have good and bad points.
The current favorite on forums seems to be the Ridgid trimmer. I haven't used the new model, but the old model didn't hold up to daily use. It had a plastic base that fell apart and the motors burned out fairly quickly.
If the trend has a decent motor and is otherwise O.K. you might want to try to fix it's short comings or figure out a work around. The older 1608 and 1609 Bosch trimmers (and others) used a 43 mm mounting ring for it's fixed base - the same diameter as the trend t4 uses. So if you wanted to go to a fixed base or the various other Bosch bases (tilt, off set, etc) you can find them on ebay:
http://www.ebay.com/itm/BOSCH-ROUTER-TR ... SwmudZ9hjJ
http://www.ebay.com/itm/Bosch-360570261 ... SwAaJZ9hfY

[Daryl Kosinski]

Are you sure it is a 1/4 inch collet? If it was a 8mm then that would do it.

I needed to buy a 8mm collet for my Porter Cable so I could use Leigh Jig bits.

[Clay Schaeffer]

Porter Cable makes 8 mm collets for the 690 and larger routers, but probably not for the trimmers. An 8 mm bit is too large for the spindle shaft hole of the P.C. trimmers

[Bob Hammond]

It's fortunate that you weren't injured. This is the first time that I've heard of a collet breaking, but come to think of it, I've never tightened a collet without a bit in it.

On router bits that I use frequently, I put a rubber O-ring on the shank at the proper insertion depth. It also acts as a 'third hand' for tightening the collet if the arbor lock has a springloaded lever.

[Mark Fogleman]

On router bits that I use frequently, I put a rubber O-ring on the shank at the proper insertion depth. It also acts as a 'third hand' for tightening the collet if the arbor lock has a springloaded lever.

Great idea Bob!

[Simon Magennis]

Just to complete the story.

My replacement collets came along with a 1/4" flush trim cutter which I haven't used yet. Once I opened up the fresh packet, I realized that the collet was much tighter in its not that what I remember the broken one to be. So it could very well be that I damaged the original one. They are pretty delicate. I had a go at doing the binding ledges on the three in progress instruments and the router and the collet are working fine. I will bring the ledges to their final depth in the next day or so.

I haven't quite figured out the dust collection on the jig I am using but have the vacuum attached even in provisional way sure kept the place much cleaner than using nothing at all. However, I will put two ideas into action before I sue the set-up again.