Thread: bit still not holding

What size the shanks are on the cutters you are using or what size the collet is in the router?
If your using a cutter with a 12" mm shank and a 1/2" collet I suspect the cutter will not tighten up properly .12.7 mm = 1/2". So a 12mm shank is too small for a 1/2" collet
I may be totally wrong here ,I don't know what the size collet is that comes with the GMC router ,
I'm just guessing .
It is the first thing I would check though.

Kev.

it cam with both the 1/2 and 1/4" colets and i am using th bits that came with it so they should be right.

Originally Posted by weisyboy

it cam with both the 1/2 and 1/4" colets and i am using th bits that came with it so they should be right.

Not necessarily Carl, The bits that GMC supply vary all over the place in diameter, and if they are all the same size in the one set, you can bet it's the wrong size.
Before you get really upset with the whole deal, just buy one good quality bit and see if the problem still occurs.
There's a reason you can get 75 GMC bits for the price of two Carbi-tool bits.

yes i will do that. i have a set of middle of the range ones ill try them.

Good Fella!
I hope it solves the problem.

Carl,

Any chance that those gmc supplied bits came with oil/wax/grease on them? One thing to try is to clean everthing up.. bit, collet etc and try again....

By the way, it doesn't only happen with GMC, I have had it happen wit aTriton at School....

Regards,

Chipman

Remove the nut and collet assembly. Holding it in your hand, slide a bit in. It should be slightly larger than the collet even when the nut is not tightened. The pressure on the bit is minimal but there. If the bit has play, something is wrong.

Special subject: the bloody obvious - but check the collet is properly seated in the nut. Wouldn't be the first time this has happened...

Damien

Flat out on GMC routers is around 32,000 rpm, waaay too fast for most bits.
The straight flute cutters going that fast on GMC routers get a wobble up and either shake the depth setting or the bit.

so how fast then?

Weisy what GMC router is it the 1050W I had/have that problem with mine rang GMC suggest you do the same.

Originally Posted by Chipman

By the way, it doesn't only happen with GMC, I have had it happen wit aTriton at School....

Not strictly on topic, but at the Sydney Wood Show I watched a Triton demo using the Gifkins Jig to make a box.

the guy didn't check the collet was tight and the bit came out - sorta wobbled around pretty ferociously, jumped up a bit and then fortunately dropped back down into the dust collector area in the router.

Coulda been real nasty.

Oh, if you're wondering how I saw it in such detail, it's was because I was in the front row, about 1 1/2 metres from the table...

Decided that the rest of the show defintely needed checking out at that point and beat a hasty exit!

Cheers,
Dave

Carl, just slow it down a bit a time until it becomes stable, although have found that GMC torque drops rapidly with reduction in speed.
The speed may not be the cause of your trouble, but it is a factor you should consider, if your collet has been damaged or forced out of shape by wrong sized shanks, or as suggested, a manufacturing defect, altering speed or trying to tighten will not help.
A point with tightening bits, you can over-tighten, if the bit moves when you use firm pressure, its no good trying to tighten further.

The Triton has a different problem with 1/4" router bits. Triton use a reducer which has to be aligned correctly or it does not work.
GMC use a whole new collet for 1/4" bits.

yer there are 2 collets.

i have both the 1200w? and 1050w models and same problem with both

Both routers doing it with same bits or all bits ?

The shanks should be clean, dry, oil free with no damage. If you wipe your bits with an oily cloth to help with storage, paper towels are great to remove oil from shank, a metho soaked rag also works.

Around 3/4 speed is good for straight flute bits up to 19mm or so, I go a bit slower for material removal with final pass at fastest speed that is stable. Taking too bigger bites at wrong speed will not help your case either.

Since you said you tightened up the collets as tight as you can, you may have damaged the threads and they may not hold anything anymore, feel the thread, if it is really sharp you have deformed the thread and nothing will help.

To be honest, I've never used GMC bits and never will, good bits are balanced, sharp and straight. Cheap bits are none of these.

I used the 1350W GMC in a table for a time, 2 big problems, the depth lock didn't, lower speeds for larger bits exposed the lack of torque and found power rating questionable.