Newbie to routers question.

[RmeDad]

Read this on another forum, is it legit?

"Remember to seat the bits, place an "o" ring in the collet between the bit and the bottom of the collet!"

Is this a safe practice?

Thanks.

[Thom2]

Read this on another forum, is it legit?

"Remember to seat the bits, place an "o" ring in the collet between the bit and the bottom of the collet!"

Is this a safe practice?

Thanks.

Very much so, if the bit is seated firmly in the base of the collet, it will expand slightly as it heats up during use. This can lock the bit in the collet and won't let it release until it cools. Using an o-ring keeps the bit suspended and the o-ring will collapse as the bit expands keeping it from locking itself in.

Since I work for a parts store, I have access to a pretty wide selection of o-rings I personally use the high temp green o-rings for automotive AC systems, the ones I use are much thinner than most that you'll find at a hardware store or such.

HTH

Thom

[drumpriest]

You don't NEED an O ring, you can also just seat it so that you leave a space at the bottom. You will transfer less heat between the bit and motor. Rockler does sell those O-rings, but I just never bottom out my collet.

[LCHIEN]

You don't NEED an O ring, you can also just seat it so that you leave a space at the bottom. You will transfer less heat between the bit and motor. Rockler does sell those O-rings, but I just never bottom out my collet.

that's what i do, too.

[RodKirby]

that's what i do, too.

Ditto

(Message has to be at least 10 chars )

[mater]

Like the the others I leave about a 1/16 space at the bottom and it works for me.

[onedash]

1/16 space where exactly? I never used an O ring and never had a problem getting bits out. Even after making a bunch of rails and stiles at the cyclic rate. My router smoked when I made some panels to fast in one pass. Still gotta take it in for the recall to get me a new motor but its working so im not in tow big of hurry.

[LarryG]

The 1/16" gap is left between the collet nut and the cutter head.

Router bits have a small fillet (curve) where the cutter head joins the shank, so there won't be a sharp 90deg corner. If you push the bit into the collet so that it is completely bottomed out, the collet will tighten down on the fillet rather than the shank itself. The collet will then be gripping the bit only at the fillet rather than along the full length of the shank. It's almost a sure bet that the bit will work loose while the cut is being made.

To prevent this problem, many people develop the habit discussed above: slide the bit into the collet until it hits bottom, then pull it back out slightly to make sure the fillet is clear of the collet. Alternatively, some people install rubber O-rings around their bits' shanks to keep the bit from bottoming out in the first place. Either method works.

[LCHIEN]

The 1/16" gap is left between the collet nut and the cutter head.

Router bits have a small fillet (curve) where the cutter head joins the shank, so there won't be a sharp 90deg corner. If you push the bit into the collet so that it is completely bottomed out, the collet will tighten down on the fillet rather than the shank itself. The collet will then be gripping the bit only at the fillet rather than along the full length of the shank. It's almost a sure bet that the bit will work loose while the cut is being made.

To prevent this problem, many people develop the habit discussed above: slide the bit into the collet until it hits bottom, then pull it back out slightly to make sure the fillet is clear of the collet. Alternatively, some people install rubber O-rings around their bits' shanks to keep the bit from bottoming out in the first place. Either method works.

I agree with Larry.
There's no magic in exactly 1/16th.
I insert a bit until
A) it bottoms out, then raise it a "bit"* so its not sitting on the end, or
B) the bit end of the shank approaches the outside end of the collet, by a "bit"*

*Now a "bit" some are saying is a 1/16th", I'm not that anal and don't measure it. The shank is generally 1 to 1-1/2" long so if its 1/16th, 1/8th, or 1/4" is not really that important, I would try not to go over 1/4", though.

The whole philosphy comes down to this:
1) you want to insert as much of the shank into the collet as you can for reasons of mechanical strength. This is most important for 1/4" but also applies to 1/2" shanks. It has the maximum engagement of the collet and shank, keeps the shank from wobbling and/or working loose. If it works loose it may shift cut depth or worse, actually be thrown from the collet.
2) you want to only engage the shank along the side and not engage the shank at the end or at the bit part because the collet can move in and out as the collet nut is tightened and prevent the nut from being properly tightened and allow the bit to become loose, or jam the bit and make it difficult to extract. Thus the rules above about 1/16th or an o-ring...


I hope that makes it more clear.

[LarryG]

There's no magic in exactly 1/16th.

That's a good point, and an important clarification.

I don't measure, either, but at a guess I'd say that for me, "a bit" equates to somewhere between 1/16" and 1/8".

[MBG]

Jocko - I recently went to using o-rings on my router table. You will find some manufactures make rail/stile bits in matched sets. Meaning if you mount them in the router at the same position you don't have to fool around with height adjustments - o-rings are just the trick....also check out this web site, I have spent hours looking at the info there:

http://www.woodshopdemos.com/cmt-jr6.htm

Mike

[jnesmith]

The 1/16" gap is left between the collet nut and the cutter head.

Router bits have a small fillet (curve) where the cutter head joins the shank, so there won't be a sharp 90deg corner. If you push the bit into the collet so that it is completely bottomed out, the collet will tighten down on the fillet rather than the shank itself. The collet will then be gripping the bit only at the fillet rather than along the full length of the shank. It's almost a sure bet that the bit will work loose while the cut is being made.

To prevent this problem, many people develop the habit discussed above: slide the bit into the collet until it hits bottom, then pull it back out slightly to make sure the fillet is clear of the collet. Alternatively, some people install rubber O-rings around their bits' shanks to keep the bit from bottoming out in the first place. Either method works.

I never knew that about the fillet. Good to know.

What about bits with shafts that are longer than the collet is deep? Those would not need to be "backed out" to avoid this problem. However, shouldn't they also be "backed out" for other reasons, like the bit getting jammed in the collet?

[RayintheUK]

What about bits with shafts that are longer than the collet is deep? Those would not need to be "backed out" to avoid this problem. However, shouldn't they also be "backed out" for other reasons, like the bit getting jammed in the collet?

Yes, they should also be backed up (or an "O" ring inserted) to prevent hammer action, particularly on plunge routers. Many good-quality cutters have a datum line on the shank to show the correct insertion depth.

Ray.

[Wood_workur]

I read a minum of 80% of the shank must be in the collet, so I measured, and drew a line at 85% of the way to the cutter, all the way around the bit. Now I just make sure the line is visible, and then drop the bit in just until I can't see the line anymore. Quick and easy.

[bigsteel15]

I read a minum of 80% of the shank must be in the collet, so I measured, and drew a line at 85% of the way to the cutter, all the way around the bit. Now I just make sure the line is visible, and then drop the bit in just until I can't see the line anymore. Quick and easy.

This is what an instructor at Lee Valley suggested.
He actually suggested taking the collet and sleeve right off the router and marking the bit with the sleeve fully engaged. Using nail polish works good.