# Slot cutter question from a Novice



## Spokaneman (Jul 20, 2007)

I need to cut a 1/4" slot (1/2" deep) into 10 feet of Ash and then 10 feet of MDF. The bit I just purchased has a 1/4" shank. My question is: should I cut the 1/2" slot in a single pass, or use multiple passes, say 1/8" at a time. I'm using a DeWalt 621 plunge router.


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## BigJimAK (Mar 13, 2009)

Spokaneman,

You should never make a cut that is larger than the diameter of the bit (or the diameter of the router shank, if it were smaller) to avoid the risk of breaking the bit. For a clean cut, make the first and last cuts very shallow.

In the ash, I'd make the first cut in the 1/16 to 1/8 range. The purpose is to shear the grain on the surface of the wood to minimize tearing on the top of the cut. Doing it on the bottom gives you a smooth end there. I recommend doing the ash first, as it will really benefit from the sharpest bit possible. MDF can contain bits of abrasive (sand, etc.) which can quickly dull bits. 

This is not to say "don't route MDF", I do it all the time. I just try to use my older bits to do it.


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## Bob N (Oct 12, 2004)

I would think the multiple passes is a better option for a 1/4" shank bit.


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## Spokaneman (Jul 20, 2007)

OK, multiple passes is the way to go. Now, I'm afraid I have to ask how. On the ash, I can use my router table with which I have the control (via the fence) I need to control the depth of cut. But how do I do it with a hand-held router?

My project is a workbench top consisting of 3 layers of 3/4" MDF and aproned by the ash. The ash is manageable enough to use the router table, but not the table top. I'ts easily 100 lbs and impractical for a router table.

So I'm looking for suggestions on how to make successive passes on the edge of the MDF such that each cut is slightly deeper than the previous. The slot cutter I have has a bearing that drives the cut to the full depth of the bit. How then do I cut less deeply than what is permitted by the bearing? An edge guide, a different bearing......? Just not sure.


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## Bob N (Oct 12, 2004)

You can clamp a board across your top to act like a fence and move it away from the edge a little with each pass until you reach the full depth. If you have an edge guide for your router, that would be an even better option.


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## jschaben (Jun 21, 2009)

Spokaneman said:


> OK, multiple passes is the way to go. Now, I'm afraid I have to ask how. On the ash, I can use my router table with which I have the control (via the fence) I need to control the depth of cut. But how do I do it with a hand-held router?
> 
> My project is a workbench top consisting of 3 layers of 3/4" MDF and aproned by the ash. The ash is manageable enough to use the router table, but not the table top. I'ts easily 100 lbs and impractical for a router table.
> 
> So I'm looking for suggestions on how to make successive passes on the edge of the MDF such that each cut is slightly deeper than the previous. The slot cutter I have has a bearing that drives the cut to the full depth of the bit. How then do I cut less deeply than what is permitted by the bearing? An edge guide, a different bearing......? Just not sure.


This is where the bearings come into play. Go from larger diameter bearings to smaller ones until you reach your depth of cut. You will need to change the bearing after each depth change. Figure depth by Diam of cutter - diam of bearing/2.
Don't know if you can use and edge guide or not, I've got one I have never used. If you haven't got enough of a selection of bearings you could clamp straight edges to the workpiece to use as a fence for your baseplate. Use that to get your first cut or two and use your bearing as a guide for the final cut.


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