Centrotec Square Drive Bit

[Tom Hummel]

I love my Festool cordless drills and I really appreciate the engineering of the unique Festool chucks.  Like others I use square drive Robertson screws along with all the various other types.  I have grown to appreciate the accuracy and the speed of the Centrotec chuck.  It is so much better than all the other quick change chucks/adapters out there.  So this square drive Centrotec void has kept me searching for a better way. 

I always assumed that standard 1/4" bits are a little too big to fit in the Centrotec chuck.  Not so... the Festool bits simply have the corners knocked off, the flats are  the same size as any standard bit.  I believe this was posted in an email on the old Festool Yahoo site by Jerry.  Aside from that the only significant difference is that the detent is in a different location to allow the shaft of the bit to go all the way inside of the drill. 

Experimenting with a 6" squared drive bit and the grinding wheel I was able to produce a crude working version that slipped right into the Centrotec chuck.  Once I knew it would work I created the following bits with my Mill/drill.  The metal lathe is the perfect tool for this, however I was able to produce nice working versions on my mill with a ball endmill and a straight endmill with my rotary table.

One added benefit with these bits is that the factory detent does not seem to be a problem and as a result my homemade bits fit the offset chuck as well.

 

[Dan Clermont]

Nice Job!!!

I'll take 4!!! of each Robertson size

Do you ship to Canada?

Dan Clermont

 

[Mirko]

Nice job Tom, or shall we call you "Mr Robertson"
I have thought about this before but never got around to trying it, glad to see it works!

Your version is also stronger than the Festool bits because they lack the small green "O" ring (besides looking nice what is its purpose??) this dam thing is a fracture point, you will find this out very quickly when you drop your drill! they break like glass, o ring marks the spot.

Great work!

Mirko

 

[Corwin]

Honey hush!  That is one slick bit.  I'll take several also.

 

[Tom Hummel]

Nice Job!!!

I'll take 4!!! of each Robertson size

Do you ship to Canada?

Dan Clermont

Dan,
Sorry I am not set up to make these for others, I'll be happy to provide detailed instructions.  I don't think the bits that I made with the Mill/drill work any better than the ones I made with the grinder, they just look better.

Nice job Tom, or shall we call you "Mr Robertson"
I have thought about this before but never got around to trying it, glad to see it works!

Your version is also stronger than the Festool bits because they lack the small green "O" ring (besides looking nice what is its purpose??) this dam thing is a fracture point, you will find this out very quickly when you drop your drill! they break like glass, o ring marks the spot.

Great work!

Mirko

Thanks Mirko
I believe the green O ring keeps the Festool bit from going in too far, this is only an issue if the Centrotec chuck is off the drill.  On my bit the milling stops where the O ring would normally start. 

I have modified several brands of bits, I picked up the bit in the photo at McMaster Carr.  My favorite bit is the Senco #2, they are sold locally in a 2 pack that can be seen here:

 

[Tom Ryan]

Would the following work (for someone that doesn't have milling equipment)?

Put the drill in a vice (or otherwise hold it secure), with a non-Centrotec chuck.  Put in the bit to be modified.  Turn on the drill.  Hold a small round file against the bit where you want the new detent.  Are drill bits soft enough to file?  Is the spacing between detent large enough to provide enough clearance?

Tom (who almost exclusively uses square drive screws).

 

[Tom Hummel]

Would the following work (for someone that doesn't have milling equipment)?

Put the drill in a vice (or otherwise hold it secure), with a non-Centrotec chuck.  Put in the bit to be modified.  Turn on the drill.  Hold a small round file against the bit where you want the new detent.  Are drill bits soft enough to file?  Is the spacing between detent large enough to provide enough clearance?

Tom (who almost exclusively uses square drive screws).

Tom,
That could possibly work depends on the hardness of the bit and the hardness of the file, the best way to find out is to try it.  The detent does not have to be absolutely perfect so you could just put it in a vice and file your way around.  You would need to use a flat file to take part of the points off.  I don't understand your question "is the spacing large enought to provide enough clearence?"

 

[Jim Becker]

I had the pleasure of trying out Tom's bits tonight and they are awesome. They run absolutely true and eliminate the runout that I've been living with using the BH-65 to hold "commonly available" square drive bits.

As a note to Festool...I really can no longer accept that Robertson/square drive bits cannot be had in acceptable quality to have in the Festool line when Tom presents a clear example of what one guy can do in his home shop using a relatively common type of mill/drill to machine the corners and the correct detent location. (and this after a test run with a grinder) I brought this up several years ago when I first bought my Festool drill/driver with all the bells and whistles. North America is more in love with square drive fasteners every day...it would be nice for folks investing in what is arguably the best portable tool system to have that option "natively".

 

[Dan Clermont]

Not to jump on the bandwagon here but in Canada we use Robertson head screws almost exclusively EH!!! I have one stored in my toque all the time.  ;D

I'd really like to see Festool make the effort to produce Robertson bits.

Thanks for Listening
Dan Clermont

 

[Dave Ronyak]

Would the following work (for someone that doesn't have milling equipment)?

Put the drill in a vice (or otherwise hold it secure), with a non-Centrotec chuck.  Put in the bit to be modified.  Turn on the drill.  Hold a small round file against the bit where you want the new detent.  Are drill bits soft enough to file?  Is the spacing between detent large enough to provide enough clearance?

Tom (who almost exclusively uses square drive screws).

Tom,
That could possibly work depends on the hardness of the bit and the hardness of the file, the best way to find out is to try it.  The detent does not have to be absolutely perfect so you could just put it in a vice and file your way around.  You would need to use a flat file to take part of the points off.  I don't understand your question "is the spacing large enought to provide enough clearence?"

Files are generally very hard, and probably harder than the driver bit shank.  If the steel of the driver bit is too hard to to file, grind the needed detent profile om the shank of the driver bit.  Grinding is standard machine shop practice for shaping materials that are too hard for use of cutting tools.  The rim of a narrow vitrified grinding wheel or fiber-reinforced cut-off disk could be dressed to a rounded profile approximating shape to be ground into the hexagonal shank of the driver bit you are modifying.  Drill bits are likely to require grinding to shape; they have to be hard to do their intended job at cutting metals that are softer than the bit.

Dave R.

 

[Richka]

I did the same thing a while back. I used a metal lathe with carbide insert tooling. The driver bits turn fine with carbide. I turned 1/4" hex which is approximately 7.15 mm to 7.0 mm and added the detent location. Modifying standard tooling (read cheap) appeals to my Yankee sense of thrift... (repost: Photo didn't go the first time)

 

[Bob D.]

I know this is a very old thread but I will add that I just did the same after seeing a YT
video by Paul (Half-Inch Shy) about how he modified his square drive bit in his drill press.

I did mine on the wood lathe mounting a drill chuck in the headstock of my Nova DVR XP.
Files really didn't do much so I got out the Dremel tool and using a 1.5" dia. cutting wheel
held at an angle and the lathe turning at about 220 rpm I cut a nice cove in the bit at the
right distance from the end. The wheel was held at about a 30 degree angle from perpendicular
to the shaft in much the same way as if you were making a piece of cove molding on your table
saw and running the board across the blade at an angle. After cutting the ball detent groove I
rounded over the corners of the hex with a piece of emery cloth and the lathe speed up to 600
rpm. It took less than five minutes to make the mod.

When cutting the groove I found it easier to run the lathe in reverse so that the wheel was spinning
in the opposite direction and cut better with better control.

I thought this worked out pretty good and while I was set up I might modify a couple other hex bits
to fit the Centrotec chuck but none of the hex bits I had enough length to add the second ball detent
groove plus the additional shaft length past there to fit in the Centrotec chuck. The shaft diameters
increased so the bit could not be inserted deep enough for the hex to engage the drive shaft on my
T15+3.

But I got a #2 square drive bit I can keep in the box with my drill now and that's what I was after.

 

[Cheese]

Here's some previous discussions.
http://festoolownersgroup.com/festo...ec-compatible-drill-bits/msg489333/#msg489333

 

[Bob D.]

Thanks, that's where I saw the video from Paul.
You turned yours down on your metal lathe. I don't
have that option. I was thinking about making a tool
holder but it's not worth it for this small operation and
I really don't want to use my DVR for metal work.

I noticed you cut a square shoulder. Do you worry that
creates a stress point?