Safe router bit shaft depth - Woodworking Talk - Woodworkers Forum
 13Likes
Reply
 
Thread Tools Display Modes
post #1 of 35 Old 11-09-2019, 01:21 AM Thread Starter
Senior Member
 
Join Date: May 2017
Location: North Houston, TX
Posts: 248
View Rhaugle's Photo Album My Photos
Safe router bit shaft depth

Hi all,
Curious what a minimum safe depth would be for the shaft of a bit to be in the router collet. I need to get about a half inch more depth and not sure how far I want to push it.. a half inch? 3/8 inch? 3/4 inch?
Rhaugle is offline  
Sponsored Links
Advertisement
 
post #2 of 35 Old 11-09-2019, 05:38 AM
where's my table saw?
 
woodnthings's Avatar
 
Join Date: Jan 2009
Location: SE, Michigan
Posts: 25,936
View woodnthings's Photo Album My Photos
How much shank depth is "enough" ....?

That depends on the diameter of the shank, but in any case a 1" depth will allow the collect to properly hold the shank on most routers. Yes, they are different. This question was raised on the Festool Owners Group page and Rick Christopherson, a favorite source of mine for technical info has a great response:
https://festoolownersgroup.com/index...nstall-depth.0


I don't understand the reply just above ^.........

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
woodnthings is online now  
post #3 of 35 Old 11-09-2019, 11:00 AM
Senior Member
 
Join Date: Apr 2015
Location: NE FL
Posts: 239
View DrRobert's Photo Album My Photos
If you remove the collet and insert the bit so it is flush with the bottom, this is the minimum depth. Mark the shaft with sharpie and use it as a guide.


Not having the collet fully engaged on the shaft increase the danger of the bit coming loose.
DrRobert is offline  
Sponsored Links
Advertisement
 
post #4 of 35 Old 11-09-2019, 02:35 PM
Senior Member
 
Join Date: Aug 2012
Location: British Columbia, Canada
Posts: 5,283
View FrankC's Photo Album My Photos
I am not going to comment on how much shank you need to grip in the collect because I don't know diameter of bit, etc, but will say if it is for the holes you are drilling with only downward pressure you should be able to safely grip less length in the collet.

Wise men speak because they have something to say; fools because they have to say something -Plato

FrankC
http://sawdustmaking.com
http://woodworkerglossary.com

Last edited by FrankC; 11-09-2019 at 02:38 PM.
FrankC is offline  
post #5 of 35 Old 11-09-2019, 03:44 PM
where's my table saw?
 
woodnthings's Avatar
 
Join Date: Jan 2009
Location: SE, Michigan
Posts: 25,936
View woodnthings's Photo Album My Photos
This is not clear to me .....?

Quote:
Originally Posted by DrRobert View Post
If you remove the collet and insert the bit so it is flush with the bottom, this is the minimum depth. Mark the shaft with sharpie and use it as a guide.


Not having the collet fully engaged on the shaft increase the danger of the bit coming loose.

With the collet installed and the bit fully inserted, this is the maximum inserted depth ...... which should be avoided to prevent the bit from sticking in the collet. Typically, 1/16" up from the full depth is enough to prevent a seizure when the collet is installed. Some router bits have a rounded shoulder at the intersection of the shank and if fully inserted, will bind in the collet. So, that's why you pull it back out a 1/6" or so.....



The OP's question was about the minimum amount of shaft length inserted which will hold the bit securely. There is very little info online about this question. Some sites say 80% , others say 75%, other say no less than 1" ... except this:
https://www.thesprucecrafts.com/how-...operly-3536395



Try to find the shank dimension of a router bit ...... I couldn't, not On Freud's site or MCLS's site. I gave up. I may just go to the shop and measure a bunch of my bits ...... now I'm curious.


OK, my 1/2" bits standard length, measure about 1 3/8" of shank. The 1/4" bits measure about 1 1/8" of shank. So, given the 1" recommendation, there's not much extra length, maybe 1/4". Given the 3/4" dimension, about 1/2" extra length.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 11-09-2019 at 05:32 PM.
woodnthings is online now  
post #6 of 35 Old 11-09-2019, 04:51 PM
Village Idiot
 
epicfail48's Avatar
 
Join Date: Mar 2014
Location: Springfield MO
Posts: 4,707
View epicfail48's Photo Album My Photos
On a bit where the actual bitnis larger than the shank, there should be a radius between the actual bit and the shank. You want about 1/16" of gap between the tip of the collet and the start of that radius, like wood things mentioned. For a straight bit, bottom it out in the collet, then pull it out of the collet a bit, bout 1/8"-1/4". You want as much shank in the collet as possible, the last thing anybody wants is a 3/8" roundover slipping out at 20k rpm

I need cheaper hobby
etsy.com/shop/projectepicfail
epicfail48 is offline  
post #7 of 35 Old 11-09-2019, 07:43 PM
Senior Member
 
Join Date: Aug 2012
Location: British Columbia, Canada
Posts: 5,283
View FrankC's Photo Album My Photos
It was once explained to me that the reason you raise a bit up from the bottom of the collet chuck is so the collet will grip properly, as the nut is tightened the collet is squeezed in and also pushed down somewhat, therefore the shank has to have room to move down as it is gripped.

This may or may not be the case with certain router collet chucks.
woodnthings and NoThankyou like this.

Wise men speak because they have something to say; fools because they have to say something -Plato

FrankC
http://sawdustmaking.com
http://woodworkerglossary.com

Last edited by FrankC; 11-09-2019 at 07:48 PM.
FrankC is offline  
post #8 of 35 Old 11-09-2019, 09:46 PM
Senior Member
 
Join Date: Dec 2016
Location: Nebraska
Posts: 413
View Larry Schweitzer's Photo Album My Photos
A simple way to look at the grip of a collet is to picture the bit only part way into the collet. If there is force on the collet in an area where there is no bit to grip the collet will try to squeeze into that void area. The result will be the inside of the collet will deform causing the top of the collet to open or grip less. Taking this a bit further and you can see that you have a taper trying to hold the bit. Pinching the bottom of the bit harder than the top, trying to squeeze the bit out of the collet. Really bad things can happen when a bit comes out at 20,000rpm! Your as safe as it gets with the bit inserted the full depth of the collet. Any further doesn't gain you anything. Any less and get really fast at ducking.
Always fully remove the collet when changing bits. Clean the socket & collet. This may sound strange but you have oil glands on the side of your nose. You can get just enough lube there to wipe on the shank of the bit to keep it from sticking. Always there, handy. If a bit has any rust, clean it with some Scotch bright pads. If you get any vibration, Stop!, check the setup, check the collet nut. Collets wear out over time and should be replaced. That may take years on a home shop router but less than a year on a CNC production machine. You can test the fit/wear on a collet by using some machinist Prussian blue. Just wipe it on one surface to a very thin film. Assemble, slightly twist and pull straight out. Where the blue transferred is where the collet is holding. It will show if the collet or socket has become bell mouthed.
gmercer_48083 likes this.
Larry Schweitzer is offline  
post #9 of 35 Old 11-10-2019, 01:31 PM
Senior Member
 
Join Date: Sep 2016
Location: Cyprus
Posts: 286
View sunnybob's Photo Album My Photos
Any decent quality bit will have a depth mark on the shank. An arrow with a cross line across the point. The cross line should be flush with the collet / nut.

SunnyBob
my projects can be viewed here
http://www.pbase.com/john_cooper/bob...dwork_projects
sunnybob is offline  
post #10 of 35 Old 11-11-2019, 07:53 PM
Senior Member
 
Join Date: Dec 2016
Location: Nebraska
Posts: 413
View Larry Schweitzer's Photo Album My Photos
Safe collet use

Quote:
Originally Posted by sunnybob View Post
Any decent quality bit will have a depth mark on the shank. An arrow with a cross line across the point. The cross line should be flush with the collet / nut.
That's interesting. I've never seen that. We primarily use Leuco bits & saw blades, so you must consider them less than decent quality. How far down the quality ladder do you consider them?
NoThankyou likes this.
Larry Schweitzer is offline  
post #11 of 35 Old 11-12-2019, 01:47 AM
Senior Member
 
Join Date: Sep 2016
Location: Cyprus
Posts: 286
View sunnybob's Photo Album My Photos
I havent heard of that make. this link shows the depth mark clearly
https://www.amazon.com/Amana-Tool-Ca...ADVBGAWZZTBESA

SunnyBob
my projects can be viewed here
http://www.pbase.com/john_cooper/bob...dwork_projects
sunnybob is offline  
post #12 of 35 Old 11-12-2019, 03:46 PM
Senior Member
 
_Ogre's Avatar
 
Join Date: Feb 2013
Location: Motown
Posts: 437
View _Ogre's Photo Album My Photos
Quote:
Originally Posted by DrRobert View Post
If you remove the collet and insert the bit so it is flush with the bottom, this is the minimum depth. Mark the shaft with sharpie and use it as a guide.
Quote:
Originally Posted by woodnthings View Post
With the collet installed and the bit fully inserted, this is the maximum inserted depth ...... which should be avoided to prevent the bit from sticking in the collet. Typically, 1/16" up from the full depth is enough to prevent a seizure when the collet is installed.
i agree with drrobert, max out the collet, more won't grip better, less would be unsafe

typically i do like woodnthings does, max insertion with a little pulled back. his not clear comment- drrobert suggested max collet with the collet out of the router. the collet does not go full depth of the hole in the spindle

i dropped a router bit one time. it was a little terrifying to say the least. it was like a top with knife edges spinning at 29,000 rpm, bouncing off the walls, ceiling and shop equipment. now i tend to over tighten the router chuck
_Ogre is online now  
post #13 of 35 Old 11-13-2019, 01:58 PM
Senior Member
 
Join Date: Dec 2016
Location: Nebraska
Posts: 413
View Larry Schweitzer's Photo Album My Photos
Ogre, Careful with that "over tightening" It can damage the threads or deform the socket.
Our CNC router tool holders always have the collet nut tightened with a torque wrench. Tight enough to hold but still not damage the tool holder or collet.
Larry Schweitzer is offline  
post #14 of 35 Old 11-13-2019, 05:22 PM
Senior Member
 
Join Date: Apr 2015
Location: NE FL
Posts: 239
View DrRobert's Photo Album My Photos
Quote:
Originally Posted by woodnthings View Post
With the collet installed and the bit fully inserted, this is the maximum inserted depth ...... which should be avoided to prevent the bit from sticking in the collet. Typically, 1/16" up from the full depth is enough to prevent a seizure when the collet is installed. Some router bits have a rounded shoulder at the intersection of the shank and if fully inserted, will bind in the collet. So, that's why you pull it back out a 1/6" or so.....
I'm referring to the bottom of the collet insert, not bottoming out the bit. Sorry if that wasn't clear.
DrRobert is offline  
post #15 of 35 Old 11-13-2019, 06:56 PM
Senior Member
 
Join Date: Jul 2008
Location: Florida Panhandle
Posts: 11,843
View GeorgeC's Photo Album My Photos
Quote:
Originally Posted by sunnybob View Post
Any decent quality bit will have a depth mark on the shank. An arrow with a cross line across the point. The cross line should be flush with the collet / nut.

I must not have any decent quality bits. Or, it is possible that I have just overlooked this line/arrow.


George
GeorgeC is offline  
post #16 of 35 Old 11-13-2019, 06:59 PM
Senior Member
 
Join Date: Jul 2008
Location: Florida Panhandle
Posts: 11,843
View GeorgeC's Photo Album My Photos
Quote:
Originally Posted by Larry Schweitzer View Post
A simple way to look at the grip of a collet is to picture the bit only part way into the collet. If there is force on the collet in an area where there is no bit to grip the collet will try to squeeze into that void area. The result will be the inside of the collet will deform causing the top of the collet to open or grip less. Taking this a bit further and you can see that you have a taper trying to hold the bit. Pinching the bottom of the bit harder than the top, trying to squeeze the bit out of the collet. Really bad things can happen when a bit comes out at 20,000rpm! Your as safe as it gets with the bit inserted the full depth of the collet. Any further doesn't gain you anything. Any less and get really fast at ducking.
Always fully remove the collet when changing bits. Clean the socket & collet. This may sound strange but you have oil glands on the side of your nose. You can get just enough lube there to wipe on the shank of the bit to keep it from sticking. Always there, handy. If a bit has any rust, clean it with some Scotch bright pads. If you get any vibration, Stop!, check the setup, check the collet nut. Collets wear out over time and should be replaced. That may take years on a home shop router but less than a year on a CNC production machine. You can test the fit/wear on a collet by using some machinist Prussian blue. Just wipe it on one surface to a very thin film. Assemble, slightly twist and pull straight out. Where the blue transferred is where the collet is holding. It will show if the collet or socket has become bell mouthed.

Which version of Hulk Hogan is required to do this?


George
GeorgeC is offline  
post #17 of 35 Old 11-13-2019, 09:41 PM
Village Idiot
 
epicfail48's Avatar
 
Join Date: Mar 2014
Location: Springfield MO
Posts: 4,707
View epicfail48's Photo Album My Photos
Quote:
Originally Posted by GeorgeC View Post
Which version of Hulk Hogan is required to do this?


George
None of them. It doesnt take much to deform a collet, if it did wed never be able to tighten them. The taper in the collet is going to be tiny the way that Larry describes it, but it is enough to interfere with grip on the bit. What Larry said is accurate, you want something being in the collet the full length of its grip, and empty space at the front or the back will cause the collet to deform more in the empty space and not grip where its needed.

I need cheaper hobby
etsy.com/shop/projectepicfail
epicfail48 is offline  
post #18 of 35 Old 11-13-2019, 10:05 PM
where's my table saw?
 
woodnthings's Avatar
 
Join Date: Jan 2009
Location: SE, Michigan
Posts: 25,936
View woodnthings's Photo Album My Photos
The collet is tapered outside .......

The collet is tightened by compressing the slotted taper from the end towards to middle. It would be impossible to tighten it at the bottom before it's tightened at the top and in the center.

https://www.amazon.com/dp/B01GJ84P5W..._t2_B0009H5MPM



The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
woodnthings is online now  
post #19 of 35 Old 11-14-2019, 01:41 AM
Ancient Termite
 
Join Date: Mar 2018
Location: Huntington Beach, California
Posts: 532
View NoThankyou's Photo Album My Photos
Put a small rubber band around the shank of the bit.

Push the bit and rubber band into the collet until the bit bottoms out or the collet rests against the bit fillet. Measure from the rubber band to the end of the shank of the bit. This tells you how deep the collet is relative to the bit. Record this depth measurement.

Remove the collet nut and measure the area of the collet that actually grips the bit. This is usually the length of the splits in the collet. Record this grip measurement.

Add to the grip measurement and record the sum. Subtract this sum from the depth measurement. Save this measurement. Set the rubber band this distance from the end of the shank of the bit.

Reinstall the collet nut and bit with the collet barely touching the rubber band. Tighten as normal and route away. Just be careful and feel for vibrations which would indicate that the bit is moving.

It would probably be a good idea to reduce the RPM of the router. I would avoid a bit extender at all costs. Just the thought of the bit spinning in an extender at something North of 15,000 RPM terrifies me.

BTW - This is a lot of work to gain as little as inch of bit depth. I don't think that you'll get much more safely than that.

Rich
In furniture 1/32" is a Grand Canyon
NoThankyou is offline  
post #20 of 35 Old 11-14-2019, 07:08 AM
Village Idiot
 
epicfail48's Avatar
 
Join Date: Mar 2014
Location: Springfield MO
Posts: 4,707
View epicfail48's Photo Album My Photos
Quote:
Originally Posted by woodnthings View Post
The collet is tightened by compressing the slotted taper from the end towards to middle. It would be impossible to tighten it at the bottom before it's tightened at the top and in the center.

https://www.amazon.com/dp/B01GJ84P5W..._t2_B0009H5MPM


Thats just flat out not true, a collet can compress more at one end if theres nothing for it to grip. If you dont believe me, go out to your shop, grab your router, and only insert a bit 1/4" into it and tighten it down. If the collet was making a perfect cylinder with parallel walls, i.e no taper like you said, the end of the bit wont wiggle. Itll wiggle though, because youll only be grabbing the very end of the bit.

Alternately you could talk to and machinist whos ever used collets for work or toolholding and they can tell you the exact same thing. If you dont have a collet gripping something over the majority of the collets length, itll deform and tighten at the empty end without grabbing what you want properly

I need cheaper hobby
etsy.com/shop/projectepicfail
epicfail48 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Woodworking Talk - Woodworkers Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome