Slot cutting router bits

[Dave Novak]

I have a project that requires one of these, but I'm a little confused regarding how they work. I want a 1/2" slot, which is easy enough to find a bit for, but isn't that an awful lot to hog out all in one pass? It seems like they should have multiple bearings so you could get to the desired depth in 2-3 passes. Am I missing something?

[George Bokros]

Are you trying to do this with a handheld router? IMO it is not a safe thing to do. In a router table add some additional layers of subfence and remove them one at a time until you get to the depth you need. I do this all the time with panel raising bits in the table.

[Mark W Pugh]

Uh, bearing and slot, I don't get. If you "hog" it out a little at a time, not a problem. Hand held router and an attached fence, offset by the amount of the side of router from bit. Or, on a router table, piece of cake.

What exactly are you trying to do, and how big is project?

[Lee Schierer]

I want a 1/2" slot, which is easy enough to find a bit for, but isn't that an awful lot to hog out all in one pass? It seems like they should have multiple bearings so you could get to the desired depth in 2-3 passes. Am I missing something?

Some bit sets have multiple bearings so you can take small bites. With others you have to use a fence to control the depth of cut. The slot cutting bits are usually larger in diameter than regular edging bits so using them in a hand held router can leave a lot of cutting edge exposed behind the edge guide and some edge guides don't have enough opening to accommodate a larger diameter bit.

[Mike McGrath]

Dave, limit your passes to removing 1/4" of material each time for the best results. George's advice about using a shim works or you can adjust your fence. What project are you working on? Maybe a different way to go about making the cut?

[Dave Novak]

My wife's hobby is fused/slumped glass. She made a beautiful round piece of glass art about 12" in diameter. I need to make a display stand that holds it so we can donate it to a charity auction next week. The piece of the stand that will hold it is roughly 1/3 of a circle, kind of like a "C" with a grove on the inside of the "C" that will hold the glass, roughly 1/4" thick. I was planning on mounting the bit in my router table and running the inside of the "C" against the slot cutting bit. I'm concerned that hogging out !/2" in one pass will result in tear out or less than desirable results. Material is cherry. I'm not sure I'm smart enough to build a curved shim, so it seems using different sized bearings is my only hope. Any suggestions?

[Peter Quinn]

So you are making a 1/4" slot...1/2" deep..any suggestions? Get a bearing kit if you like bearings. Most slot cutters come with a single bearing, there are slot cutting kits with multiple cutter heights and multiple bearings that give complete control if you need that, or you can get bearing kits, mine is from amana, or just don't push it in so deep. Yup, run down the board with a free hand router, just skim it on the first pass, little deeper on the second pass, all in on the last pass. I do it all the time. You don't need a bearing to control the depth.

[Alan Schwabacher]

Just because the slot will be 1/4" wide does not mean you need to cut the entire width in one pass. Why not use a 1/8" slot cutter with a bearing, and raise or lower the bit as you take 2 or 3 passes?

[Steve Jenkins]

When using a slot cutter I make a first shallow pass climb cutting then a second pass full depth. This eliminates any tear out. Same thing when doing rabbits.

[Lee Schierer]

If the OP is cutting a partial circle, grain reversal is likely to be an issue. He may need to climb cut part of the groove and conventional cut the other portion depending upon the grain and type of wood being cut. Extremely light cuts (1/16" or less) should be the rule when cutting a curved piece like this and I would advise in using a holder of some type for the work piece. I've had pieces of red oak literally shatter when cutting into the grain when the bit caught the end grain.

[Jerry Miner]

I do these cuts as Peter Quinn describes above---freehand feeding in a router table. Use a piece that is large enough to keep your fingers well away from the bit, or rig a work-holder that does it. I also suggest you start with the piece over-sized so any tear-out on the end of the cut can be trimmed off after slotting.

[Ellen Benkin]

Don't over complicate this. Do several passes moving the fence each time. If the bearing is set correctly you can't cut too deep. Try a practice piece first.