# Safe router bit shaft depth



## Rhaugle (May 12, 2017)

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?


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## woodnthings (Jan 24, 2009)

*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/inde...how-to;topic=router-bit-shank-install-depth.0


I don't understand the reply just above ^.........:sad2:


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## DrRobert (Apr 27, 2015)

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.


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## FrankC (Aug 24, 2012)

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.


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## woodnthings (Jan 24, 2009)

*This is not clear to me .....?*



DrRobert said:


> 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-to-install-router-bits-properly-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.


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## epicfail48 (Mar 27, 2014)

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


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## FrankC (Aug 24, 2012)

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.


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## Larry42 (Jan 10, 2014)

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.


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## sunnybob (Sep 3, 2016)

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.


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## Larry42 (Jan 10, 2014)

*Safe collet use*



sunnybob said:


> 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?


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## sunnybob (Sep 3, 2016)

I havent heard of that make. this link shows the depth mark clearly
https://www.amazon.com/Amana-Tool-C...BGAWZZTBESA&psc=1&refRID=FRW1DHADVBGAWZZTBESA


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## _Ogre (Feb 1, 2013)

DrRobert said:


> 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.





woodnthings said:


> 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


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## Larry42 (Jan 10, 2014)

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.


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## DrRobert (Apr 27, 2015)

woodnthings said:


> 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.


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## GeorgeC (Jul 30, 2008)

sunnybob said:


> 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


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## GeorgeC (Jul 30, 2008)

Larry Schweitzer said:


> 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


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## epicfail48 (Mar 27, 2014)

GeorgeC said:


> 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.


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## woodnthings (Jan 24, 2009)

*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/ref=psdc_552574_t2_B0009H5MPM


:vs_cool:


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## NoThankyou (Mar 21, 2018)

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 ¼ 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 ½ inch of bit depth. I don't think that you'll get much more safely than that.


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## epicfail48 (Mar 27, 2014)

woodnthings said:


> 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/ref=psdc_552574_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


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## woodnthings (Jan 24, 2009)

*Well of course....*

If you only gonna stick 1/4" into the collet, and then tighten it, of course it will deform. Who's gonna do that, not me. Common sense has to play some role here, doncha think? :|


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## John Smith_inFL (Jul 4, 2018)

like a lot of people, I have a coffee can full of router bits.
I don't think I have seen a mark or line on any of them as a depth gauge.
my common sense has always told me to make sure the bit is all the way
inside the collet for the proper grip.
this subject was also discussed in depth on another forum and a member
posted this drawing - it may help - or help to confuse.


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## epicfail48 (Mar 27, 2014)

woodnthings said:


> It would be impossible to tighten it at the bottom before it's tightened at the top and in the center. :





woodnthings said:


> If you only gonna stick 1/4" into the collet, and then tighten it, of course it will deform. Who's gonna do that, not me. Common sense has to play some role here, doncha think? :|


You claimed that it's not possible to distort a collet and have it grip at the top before the bottom, then dismissed that exact same thing happening when a bit isn't inserted far enough. You're right, common sense has as much a role to play as humility


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## woodnthings (Jan 24, 2009)

*A straw man's arguement .....*



epicfail48 said:


> You claimed that it's not possible to distort a collet and have it grip at the top before the bottom, then dismissed that exact same thing happening when a bit isn't inserted far enough. You're right, common sense has as much a role to play as humility



Now, I have no common sense or sense of humility? You pick a situation where no one would perform which is ridiculous as it is and then it's my fault? Come on. :|


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## Larry42 (Jan 10, 2014)

To illustrate a point it is often reasonable to move the parameters further than would normally be true. 

J Smith, that illustration looks like it is saying the bit should never be totally inserted into the collet but should have 3mm of collet unfilled. Totally untrue. The bit should not touch the bottom of the socket by the 3mm so it has a bit of room to be pulled down. 
I've got machines with HSK63, ISO30 (ER32), R8, 5C and the typical woodworking routers. The later is the crudest by far. Woodworking routers can probably get away with it because they don't have to transmit nearly as much power/torque as the others.


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## John Smith_inFL (Jul 4, 2018)

Larry - that drawing was produced by Tork Craft, the manufacturer
of the router bits. it is their suggestion that the bit should not "bottom out"
in the cavity, but raised the 3mm and still be fully supported within the collet, 
of which I agree.
(their bit does look a little short compared to the long collet).
the drawing also says not to tighten the nut on the round shoulder of the cutter.
it is my personal opinion that a router bit should never be even slightly
out of the collet and only partially gripped in place. it's just not safe.

when you have a bit flung out of the router while in use because it was not
properly inserted into the collet or the nut was not properly tightened,
you will get that proverbial "wake up call" and pay more attention to what you are doing.

.

.


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## Rick Christopherson (Jun 27, 2016)

I know this thread is a few weeks old, but it has a lot of responses, and my name was mentioned as a source. For those reasons, I would like to expand on some of the information presented here, and hopefully clear up a few misconceptions.

*First off, some terminology.*
The router spindle (orange/brown) is part of the motor shaft, and is hollowed out to contain the internal taper to mate with the collet. It is threaded on the end to secure the collet nut. The spindle depth is the limiting factor as to how deep a router bit can be inserted, especially a straight fluted bit, as shown.

The collet (green) has an external taper matching the internal taper of the router spindle. As the collet gets pressed deeper into the spindle, the mating tapers cause the collet to become compressed--the internal diameter of the collet gets smaller, and this grips the side of the router bit.

The collet nut (light blue) presses the collet into the spindle. Most modern routers have a captive collet nut, such that the nut and collet are locked together. The benefit of this, is that as the nut is unscrewed, it actively "pulls" the collet out of the spindle. Prior to the development of captive collet nuts several decades ago, the collet nut could be completely unscrewed, and the collet would still be stuck inside the taper due to friction.

*History:*
Years ago, Hitachi came out with the M12V router. It had a very shallow spindle bore, and the collet itself was threaded (no collet nut). The spindle bore was so shallow that many/most router bits could touch the bottom of the spindle bore. This prevented the collet from being properly tightened.

The Hitachi M12V router was one of the most popular routers of its time. Because so many M12V owners were talking about this problem of bits bottoming out, many other woodworkers assumed it was a common problem for all routers. In reality, most routers had deep enough spindles that it was nearly impossible to bottom out a bit in the spindle.

*Misinformation Side Effect:*
Because the topic of router bit insertion was coming up so frequently, the topic ended up morphing into the idea that all router bits needed to be inserted to the point of bottoming out, and then retracted slightly...even for routers without this shallow bore. 

This led to a new version of the topic where woodworkers believed that router bits needed to be inserted almost all the way until the head of the bit reached the face of the collet. Not only did this result in a lot of carbide getting chipped during removal, but also ended up with router bits not getting tight sue to the fillet between the shank and head of the router bit.

*Proper Bit Insertion:*
Ignoring any reasons to do otherwise, the proper insertion of a router bit for maximum gripping of the bit by the collet, is to insert the bit to the same depth as the "Gripping Surface" (dark blue) of the collet. This is shown in the right-hand image. 
Inserting the bit deeper than this will not increase the grip.
Inserting the bit less than this will decrease the grip.

*Exceptions to Bit Insertion:*
As I prefaced above, "Ignoring any reasons to do otherwise"; here are some of those reasons.

If you have a router bit with a very large diameter head, especially if it has a small shank (1/4 inch), then you may wish to insert the bit deeper so less of the router bit's shank is exposed. The same is true if you have a router bit with an unusually long shank.You are not doing this for greater grip on the bit, but instead, to reduce vibration and chatter in the head of the bit.

Exceptions for inserting a router bit shallow should be taken with care. Too shallow, and the grip can be dangerously unstable. However, it should be noted that every router manufacturer uses their own collet designs, which have different lengths of gripping surface. The graphics shown below are exact representations of the Festool OF1400/OF2200 collets and nuts. These collets have approximately 1-inch of gripping surface. If the need arose, and the router bit was small, you could reduce the insertion depth slightly, simply because this collet has such a long gripping surface.


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## Rick Christopherson (Jun 27, 2016)

Larry Schweitzer said:


> 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.


Several people discussed this portion of the topic, but the popular opinion is not quite the correct one. Without going back to re-read everything for a third time, I believe it was WoodnThings that was correct. 

The taper of the spindle and collet are specifically designed such that the collet always presents a cylindrical surface toward the router bit. In more simple words, the interior bore of the collet will always have parallel sides. Only in the extreme example that one of the posters brought up with only 1/4" insertion will you have appreciable deformation of the collet, but that is simply because the force from the collet on the router bit is so concentrated that the resulting pressure is also extreme.



Larry Schweitzer said:


> Always fully remove the collet when changing bits. Clean the socket & collet.


Yes, I have been telling woodworkers for decades that they should periodically remove their collets and clean the tapered surfaces on both the collet and the router spindle. My recommendation has always been to use a Scotch pad to clean the surfaces (as opposed to something like steel wool), to eliminate the risk of leaving steel fibers behind that can corrode and seize the tapered surfaces.



Larry Schweitzer said:


> You can get just enough lube there to wipe on the shank of the bit to keep it from sticking.


This quotation is the main reason why I am responding to this post. *NEVER *apply lubricant to the router bit shank, nor the internal bore of the collet. You can (and should) apply lubricant to the tapers, however. This will permit the collet to seat into the spindle easier, and therefore, with greater gripping force on the bit.



Larry Schweitzer said:


> 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.


While I cannot completely disagree with this, it does get emphasized far too much for home routers. Unless you have router bits spin in the collet, the collet itself is not likely to wear out. 

In my experience, the reason why some people (not referring to anyone here) claim to have encountered worn collets is simply because they fail to clean the tapers. As the mating tapers get pitted and corrode, they no longer slide against each other. This results in loose router bits. Cleaning the collet is typically sufficient, unless the pitting is extreme.


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## NoThankyou (Mar 21, 2018)

OK Guys,

You got a router. You're going to do some edge finishing work.

Stop for 30 seconds. With the router on the surface of the work, LOOK at where the router is in relation to your various body parts. 

Now, put the router bit into the router as far as it will go. Back it out about an eighth of an inch or so and tighten. Look at the router bit. Is it being held by the collet on the fillet? No, you're fine to go. Yes, loosen the collet and back the router bit out a bit more and retighten.

Look! You have a chunk of steel, high speed steel and or carbide spinning at some gaud awful number of RPM. The last thing that you want is for the router bit to walk out of the collet. In addition to doing an ugly vasectomy, the bit flying could kill someone. Anything less than the maximum amount of router bit shank being held in the collet is insanity.


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## Tool Agnostic (Aug 13, 2017)

I have been reading this thread with interest. My experience with routers is limited. 

I recently added a picture hanging slot to the back of a prototype sign, using a Rockler keyhole bit in a Makita compact router. I used a plastic template and a matching template guide bushing to guide the router. You plunge the bit in to cut the large hole, and then move it sideways while plunged to cut a rimmed slot. The rimmed slot is used to hang the sign on a screw or nail. 
https://www.rockler.com/hanging-slot-router-bits-router-bits

Here is my problem: 
In order to get a decent slot, I had to extend the bit farther than suggested above. If I had simply bottomed out the bit and then pulled it out 1/8 inch, it would have cut a dado, not an internal slot with a rim. I had to pull the keyhole bit out a lot more before it would plunge in and cut a rimmed slot. In test cuts, I got slots with different thickness rims (including too thick), but had to pull the router bit out more than I wanted, more than I am used to. 

I looked at the router and bit configuration, and the problem is universal to any router with that particular keyhole bit. Even if the collect almost touches the wood, the bit sticks out farther than suggested above to make a proper slot. 

Is that normal with keyhole bits? Am I missing something obvious?


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## John Smith_inFL (Jul 4, 2018)

T/A: I agree with the 1/4" shaft key hole bits that are a bit short.
I would ask you - how thick is your router base plate ?
anyone that does a lot of hand-held router work, has quite
an assortment of shop-made base plates for different applications.
with your router, you may need a 1/8" thick plexi base plate.
I have had projects in the past that required a hefty key hole cut.
what I did was use a 3/4"" plunge bit to the depth I needed.
then come with with a 3/8" bit to make the 4" long slot.
yes, it is a little inconvenient to change and adjust bits if you have
only one router - (this is why you eventually wind up with half a dozen routers).
MLCS makes a more robust bit but I don't know how long the 1/2" shaft is.

















.


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## FrankC (Aug 24, 2012)

Food for thought.

I have had no personal experience with a router bit coming out of the collet in use, I have read theories on what would happen and also of instances where the bit just basically, harmlessly dropped out of the router. If I recall correctly there was a post about that here a few years ago.

I can understand the danger of part of the bit breaking off spinning at 20,000 RPM, just not sure exactly what would happen with a loose bit.


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## epicfail48 (Mar 27, 2014)

FrankC said:


> Food for thought.
> 
> I have had no personal experience with a router bit coming out of the collet in use, I have read theories on what would happen and also of instances where the bit just basically, harmlessly dropped out of the router. If I recall correctly there was a post about that here a few years ago.
> 
> I can understand the danger of part of the bit breaking off spinning at 20,000 RPM, just not sure exactly what would happen with a loose bit.


If youre lucky it either harmlessly falls straight down or works its way deeper into whatever cut youre making, scrapping the part. If your unlucky it catches on the way out and is flung sideways at considerable speed


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## Tool Agnostic (Aug 13, 2017)

John Smith_inFL said:


> T/A: I agree with the 1/4" shaft key hole bits that are a bit short.
> I would ask you - how thick is your router base plate ?
> anyone that does a lot of hand-held router work, has quite
> an assortment of shop-made base plates for different applications.
> ...


Great point! I had not thought about the fact that I used a 1/4 inch guide template, effectively tripling the "base plate" thickness between the router and the hole. That is the reason I needed to extend the keyhole bit more than I expected - I needed an extra 1/4 inch for the guide template. Duh!

Additional Details:

Router: https://www.makitatools.com/products/details/RT0701CX7
Router template adapter for guide bushings: https://www.makitatools.com/products/details/321492-3
Keyhole bit, same as above: https://www.rockler.com/hanging-slot-router-bits-router-bits
Guide Bushing: https://www.rockler.com/short-shank-guide-bushing-and-nut-5-8
Picture Hanging Template: https://www.rockler.com/rockler-picture-hanging-keyhole-template

The base plate is the stock black plastic base plate that came attached to the plunge base. The black plastic base plate is 1/8 inch thick. In addition, I installed a Makita template adapter in the plunge base plate so it could take a guide bushing. I used a 1/4 inch thick plastic template to guide the cut. Thus the template plus base plate is 3/8 inch thick. 

The way I set it up, the plunge depth was determined by making sure the collet did not bump into the guide bushing. After that, I made test cuts with the bit extended different lengths, until I found the depth that yielded the right "rim" thickness. I was nervous about extending the bit, but figured that whoever designed the products knew how far it could go safely. My concern about it is why I posted above.

I read your suggestion about using a plunge bit and a straight bit with interest. With a straight bit, you would get a slot, but it would be missing the overlapping lips on each side, unless you followed it with a T shaped bit. I have seen T-slot cutting bits that required a drill hole and a straight bit, because the T-slot cutting bits did not have plunge or straight cutting features, only the wider keyhole "slot" part below. The bit I used had all three features in one bit: plunge, straight bit narrow gap for the screw threads, and wider T-slot below to hold the screw head.

The next time I use the bit, I will measure how far it sticks out, and determine how much is left in the collet. If it is too little, I may give Rockler tech support a call to ask about it. If I don't like the answer, I can always ditch the guide bushing and picture hanging guide template and use an edge guide instead.


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## John Smith_inFL (Jul 4, 2018)

oh no - I forgot the third step.
after cutting the slot, go back with the key hole cutter to make
the groove that the screw head hangs on. DOOHHHHHHH sorry.
anyway, it makes a bigger slot for heftier screw or bolt heads to slide into.
sorry - I forgot that "key" element.

if you spend some time cutting the key slots freehand,
eventually you can just draw a pencil line and never
use the bushing guide or template.

.

.


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