Router Bit Shank Length

257 Views 8 Replies 5 Participants Last post by GNGRWW, 5 d ago

GNGRWW

Discussion Starter · 7 d ago

Hey guys,

First things first, I'm new here, so hello, hope you're all doing well!

Second, I have a question regarding my CMT7E router collet and router bit shank length. I recently bought this router, together with some 12mm CMT router bits.
Now, when I tried putting them in the collet, I noticed that both bits don't go all the way down to the recommended depth mark. (it bottoms out in the collet before getting to the mark)
My manual however says, that at least 20mm or 3/4 of the shank should be inserted (whichever is greater). I checked how much of the bit actually goes in until it bottoms out and it's about 28mm, so when lifting it and locking it in place it would leave about 27/26mm on the shank for the collet to grab hold off.

My question here is, how unsafe is this? Is the mark on the shank more of a guideline or is it a hard rule? Obviously I understand the closer it is to the mark the better/safer.
I seriously don't get why CMT bits don't go all the way down to the mark in a CMT router (which is basically a Triton TRA001 tbf).
Is there any solution to this, or am I fine as is?

I've added some pictures to show you what I mean and would like to have your opinions on it. If it's unsafe, I unfortunately have to return them.

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ger21

· #2 · 7 d ago

I don't think I've ever used a router that only allowed 26mm of insertion depth. That seems very shallow.
The more, the better, but if the bit is all the way in, it should be perfectly fine, if tightened properly.
We have one of those Triton's in our shop, and I'm sure it's handled far more dangerous situations just fine.
I'd keep the RPM down between 16,000-18,000 max, though.

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GNGRWW

Discussion Starter · #3 · 7 d ago

ger21 said:
I don't think I've ever used a router that only allowed 26mm of insertion depth. That seems very shallow.
The more, the better, but if the bit is all the way in, it should be perfectly fine, if tightened properly.
We have one of those Triton's in our shop, and I'm sure it's handled far more dangerous situations just fine.
I'd keep the RPM down between 16,000-18,000 max, though.

Yeah, it's weird right?! Should I worry much about deflection with shanks this thick? Yeah, I'm definitely keeping an eye on my RPMs too. Thank you for chiming in!

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old55

· #4 · 7 d ago

Welcome to the forum @GNGRWW

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GNGRWW

Discussion Starter · #5 · 6 d ago

old55 said:
Welcome to the forum @GNGRWW

Thank you!!

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jw2170

· #6 · 6 d ago

Welcome to the forum, @GNGRWW
I have just deleted a file I had on the forum, comparing the TRA and the Makita 3612C.
I will see if I can find a copy...

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GNGRWW

Discussion Starter · #7 · 6 d ago

old55 said:
Welcome to the forum @GNGRWW

jw2170 said:
Welcome to the forum, @GNGRWW
I have just deleted a file I had on the forum, comparing the TRA and the Makita 3612C.
I will see if I can find a copy...

Thank you! Not sure how that will help me with my question, but appreciate it!

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DesertRatTom

· #8 · 5 d ago

Welcome. It seems odd to me too. What I do is drop a grommet into the bottom of the collet. This lets me drop the bit in to an exact depth. Do you have something in the collet that is stopping the shank short? I'd remove the collet completely and check that. Or maybe there is a proud spot on the collet's interior. Collets are precision devices, Only a few thousandths between loose and tight, so a "bump" or minor warp would jam the bit as you describe. If you fit the shank into the collet when it's out, you can see where it gets stuck and if's this issue, then you replace the collet. I would never use a problem collet. Of course, you could order a spare collet and try the bit in that, in which case, there's something wrong on the shank.

If all other bits fit easily and this one doesn't, it's the bit. My take anyhow.

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GNGRWW

Discussion Starter · #9 · 5 d ago

DesertRatTom said:
Welcome. It seems odd to me too. What I do is drop a grommet into the bottom of the collet. This lets me drop the bit in to an exact depth. Do you have something in the collet that is stopping the shank short? I'd remove the collet completely and check that. Or maybe there is a proud spot on the collet's interior. Collets are precision devices, Only a few thousandths between loose and tight, so a "bump" or minor warp would jam the bit as you describe. If you fit the shank into the collet when it's out, you can see where it gets stuck and if's this issue, then you replace the collet. I would never use a problem collet. Of course, you could order a spare collet and try the bit in that, in which case, there's something wrong on the shank.

If all other bits fit easily and this one doesn't, it's the bit. My take anyhow.

Hey Tom! Thanks! Well, I did some Googling and apparantly there are some routers that have a very shallow bit recess, Triton and Hitachi were mentioned. So I think it's by design, unfortunately. I have checked the collet for flaws and there are none that I could see. When it bottoms out, it's definitely the machine I'm hitting and not something in the collet. I'm gonna check if it's the same depth with my 8mm collet to see if it's any different. If not, then it's definitely just how it's designed. I've never had an ''issue'' like this with any other router I've worked with and I find it very strange that they would design it like this. The pictures here show 2 separate bits btw! One big flush trim bit and a smaller one, both don't go all the way to the mark.

I greatly value my safety, so that's why I'm double-checking here with more experienced people. Thanks for your reaction!

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