Centering T-Slots

D_Harris

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I'm curious as to how most here go about centering the slots in their cabinets for T-Molding.

Do you lock the base or blade with the blade situated inside an already slotted edge. Do you lock the blade using something of known thickness in between the base and blade. Or do you measure and lock another way.

I use a Colt palm router, and the only way for me to get accurately centered slots is through trial and error on a scrap piece. I try to use the micro adjustment until the center ply is cut leaving the four plies plus veneer on each side.

Darren Harris
Staten Island, New York.
 
If there is already a slot then I use that to set the depth.
If not then I use a scrap piece and the trial and error method.
I will mark the center of a piece and line up the bit to get close and then adjust from there.
Either way I test on a scrap piece first to be sure.
 
I've found that even on a quality router, when you flip the lever to lock it, it likely shifts a tiny bit. Trial and error - you got it. Never go right at the cabinet, but test on same thickness scraps of plywood or something and dial it in. Same thing I went through getting the bit height dialed in for a dovetail jig. Test it on a scrap piece, then measure.
 
Cut it from both sides before assembly if possible. Set your grove a smidge narrower than needed then make two passes, one from each side. Guaranteed to be centered!
 
"Set your grove a smidge narrower"? Thanks, but that not the way the router works.

The issue with old particle board is that the thickness and the slots are no longer consistent and of the same width as when new from the factory. I've had to use wood filler in a lot of it just so I can start from scratch on the slots so that the slots will hold the new T-Molding.

Darren Harris
Staten Island, New York.
 
I ended up doing a bunch of test-slots on scrap. Once I got the slot just right, I kept that portion of scrap. When I'm doing my tests, I'll do the routing from one side, then dry fit the slot cutter from the other side to see if I'm perfectly centered.

When I need to cut a new slot I dry-fit the router on that piece of "perfect slot" scrap and then tighten things down with the slot-bit in the scrap; this way it helps the "shifting" issue when you're tightening your router base.

You'll have to make a new "scrap" template for each type of wood you are making things out of - for example, I have one for the MDF I typically use and one for the plywood I typically use.
 
"Set your grove a smidge narrower"? Thanks, but that not the way the router works.

The issue with old particle board is that the thickness and the slots are no longer consistent and of the same width as when new from the factory. I've had to use wood filler in a lot of it just so I can start from scratch on the slots so that the slots will hold the new T-Molding.

Darren Harris
Staten Island, New York.

That method is correct, IF you're using a bit narrower than the actual cut you need. Let's say you needed a slot/cut, centered, 1/16" wide, but could use a bit with a kerf of 3/64". To get an end result cut of 1/16", the cut would be done in two passes, cutting from each side. This is a fairly common 'trick' used in woodworking.

I scratch built cabinet doors with this method. Needed a slot cut along the rails and stiles to hold the plywood panel. You'd think I could just make a 1/4" dado, but no, as the plywood panel was undersized and not 1/4". Therefore, I used my usual blade, cutting offset of the center, in two passes, which nailed the proper width I needed.

Here, the rail and stile joints are cut so that the tenons/slot/plywood are slightly under 1/4":

21089B71-2B05-41C9-B5ED-8D924D883E9F-253-000000401FA13C2F.jpg


Knowing the way a router works, I wouldn't think you'd have issues centering a cut.
 
I don't waste time measuring after cutting a slot on a test piece.
I just test a small piece of the T-Molding I am going to use.
Once I get it right I then cut the new one on the cab.
On older cabs there is most likely going to be some variance in the thickness of the plywood though,so it might not be perfect along the entire edge.
 
On older cabs there is most likely going to be some variance in the thickness of the plywood though,so it might not be perfect along the entire edge.

Yes. This applies especially to particle board. I've been putting wood filler in the original slots and re-cutting them because they have become way too wide over the years and no longer grab the T-Molding.

Also, it is not recommended to cut from both sides in two passes with a smaller clot cutter because it is too difficult not to end up with a groove that is either too tight or too narrow. A single pass with the .062 slot cutter is the best bet.

Darren Harris
Staten Island, New York.
 
Yes. This applies especially to particle board. I've been putting wood filler in the original slots and re-cutting them because they have become way too wide over the years and no longer grab the T-Molding.

Also, it is not recommended to cut from both sides in two passes with a smaller clot cutter because it is too difficult not to end up with a groove that is either too tight or too narrow. A single pass with the .062 slot cutter is the best bet.

Darren Harris
Staten Island, New York.

I had to basically do this on my Robotron cabinet - the slots were oversized from splintering wood coming out with the old t-molding. PITA..

Agreed, one pass is best. You can usually test on an inconspicuous place, like a bottom edge.
 
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