# Need advice on very small T-slot router bit



## gintosan (Feb 19, 2011)

Hi all,

New to this forum. Lots of good info. Need helpful advice.

I'm not a pro-woodworker - just trying to build something simple - but a lot of them hopefully.

I need to put a T-slot into a board that will accept and allow me to slide in a <1/4" (.206) thick piece of veneered plywood from the side edge. The T will hold the board so it can't be pulled out - except the way it went in...

Seems straight forward.

I bought a pretty standard Diablo DR70104 key hole router bit with 25/64" large diameter and 3/16" small diameter.

Works pretty well and I can slide the board in and out and it doesn't pull out.

BUT there is just too much play. Especially with the critical small diameter measurement - borderline.

Optimal size would be:
1/4" large diameter (by 1/4" deep) the top part of the "T"
5/32" small diameter (by at least 1/4"+ long) the shank I believe it is called

Unfortunately I am unable to find anything smaller than the std original ANYWHERE.

Plan B was to go to local sharpening and machining shop and ask them to take the diameter of both cutting surfaces down.

They suggested getting a few dual-fluted straight 1/4" router bits and they would cut it down to make the desired profile. They did but were skeptical that it would last. Made the dimensions perfect + some play.

Double unfortunately - bits didn't make it. Too brittle. One snapped in my hand and the other self-destructed when it touched wood. Oh well - worth a try. There were no guarantees - least they tried. 

Plan C is to route out or cut a straight slot vertically (no-T) to the desired depth and width. This is easy and I can be very exact on the vertical slot dimension. Then try to cut the horizontal top of T slot somehow - less wood - less pressure.

But the questions are:

1) Anyone know where to get a smaller key-hole router bit with 5/32 smaller dimension?

2) Is it worth this time machining or grinding a key-hole router bit small diameter down to 5/32" removing the smaller diameter cutting surface entirely. It would be going from 3/16" (6/32") to 5/32" - only a mere 1/32". Or will the operation still make the bit brittle and useless.

3) I can't really use a thicker piece of material - this stuff has all the right characteristics - stainable hardwood finish - cost$ - easy to get. I have considered building up the thickness at the end with epoxy or somehow - but that is another operation and adds to the complexity and steps involved.

Any ideas??

Thanks in advance for reading and hopefully guiding me in my quest.


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## Phil P (Jul 25, 2010)

Just an off the cuff idea or two, but maybe you're trying to be too complex here. I'd be asking myself why I need a T-slot in the first place, would it not be possible to simply glue in my strip into groove? And secondly is there no other off the shelf cutter which will do the job? The tools which spring to mind are the smallest dovetail cutters used with tools such as the Porter-Cable Omnijig and the Woodrat dovetailer. Their shape makes them less likely to break (although they are still fragile), but I'd still be tempted to groove out with the table saw or router first.


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## gintosan (Feb 19, 2011)

Phil P said:


> Just an off the cuff idea or two, but maybe you're trying to be too complex here. I'd be asking myself why I need a T-slot in the first place, would it not be possible to simply glue in my strip into groove? And secondly is there no other off the shelf cutter which will do the job? The tools which spring to mind are the smallest dovetail cutters used with tools such as the Porter-Cable Omnijig and the Woodrat dovetailer. Their shape makes them less likely to break (although they are still fragile), but I'd still be tempted to groove out with the table saw or router first.



Thanks for answering and ideas

_"possible to simply glue in my strip into groove?"_
Didn't make it clear in the original post - but this strip or panel needs to be slid in/out easily - so glue not an option. Also, the strip or panel actually has a mirror "T" cut into its edge that is suppose to give it enough edge to securely stay in the T-slot.

_"is there no other off the shelf cutter which will do the job?"_
I've considered other shapes - specifically a dovetail - but have run into same basic issue - the bottom of the "V" is still wider than the critical dimension 5/32". A "V" shape in the slot might also allow the panel to rock like a pendulum - not desirable.

You do give a good pointer to some small dovetail router bits. I'll investigate and get a couple of those to experiment with.

Question still out there is whether others have succesfully machined a router bit - especially down to smaller shank??

Much appreciated


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## TwoSkies57 (Feb 23, 2009)

MLCS offers a keyhole cutter that might suite your needs. The small dia. being 1/4" would require a 2nd pass to gain the extra 1/16th. 

Not sure how durable the bit would be or how well it would hold up for runs like this though.

MLCS Key Hole Cutting and T-Slot Cutter Router Bits


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## Ralph Barker (Dec 15, 2008)

See if the ones from Eagle America are a better fit to your dimensions:

Picture Framing - Picture Hanging / Keyhole Bits

If not, you might also try contacting them to see what they would charge to make a few to your specs.


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## gintosan (Feb 19, 2011)

The thickness of the panel before notching is < 1/4" (.250") actually more like (.206") - the 1/4" and 25/64" small dia. varieties are a bit too large.

I need to take the small dia. down to 5/32".

I think I'm starting to realize that router bits like this < 3/16" just aren't possible.

Pre-cutting a 5/32" straight slot (no "T") means I don't need the lower part of the "T" to be a cutting edge.

BUT there still doesn't seem to be any router bits out there with a 5/32" small dia. non-cutting shaft or anything < 1/4" (8/32"). 

I'm guessing that if I could find a one with a non-cutting > 5/32 shaft it might be more easily machined down and might survive. Maybe:sad:

Plan "D"

Maybe I abandon all hope of a single piece and one operation and just cut the hanger in 1/2 make a simple open slot on both sides and just glue it together....


I did not realize the larger router bit companies may be willing to custom make bits. I'll definately contact Eagle and investigate possibility - thanks.



Thanks all - keep the ideas coming - I would still prefer a simpler one step operation.


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## bobj3 (Jan 17, 2006)

Hi

You can always use two bits,that's to say one for the main tee slot and than turn it over and use a bigger OD and than glue a stick back in the that slot.

========


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## gintosan (Feb 19, 2011)

*Success cutting very small keyhole t-slot*

Success

Thought I'd share the ultimate result and end thread...

I was able to find a slightly simpler keyhole bit Bosch85608MC @ Lowes locally.

It was still the same size as basically all the others - 3/8" large dia. and 3/16" small dia.

The difference was that it has only one straight simple vertical cutting edge with a pronounced carbide cutting surface on large and small faces.

Got out my rotary tool with a diamond tapered cutter and was able to *quite easily *take the small dia. cutting surface and a slight bit of the shank down to the required 5/32".

Pre-cut a approx 1/8" wide slot with table saw for vertical "T" part then made the slot cut with modified keyhole bit riding in the pre-cut slot.

Interestingly the router now just eats through the wood like nothing - smooth easy fast. Not sure if that is because different kind of bit, it's cutting less lumber or maybe the single cutting surface clears out the wood better and prevents binding up.

Tried it on pine, MDF and oak - bit survived and didn't seem to be having any issues.

Very happy camper now - thanks all :sold:


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