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I was looking at the directions that came with my 1/2" shank 3/4" tongue and groove router bit, and noticed that it recommended it be mounted on a router table for improved safety.

Which got me thinking, is there a general cutoff for when a router bit is too big to use in a handheld router? I figure bit diameter and profile both figure in, with the diameter playing the largest part.

6

I would guess it is more profile and how much wood you both expect to remove and how much surface area you have in contact with the wood.

The shank size is only the first indication. I haven't seen any 1/4" bits that 'Need' to be mounted in a router table. However that doesn't mean that you can't benefit from doing so.

The larger shank bits allow for a larger torque to be placed on them and to be used in larger machines. They also will tend to have less vibration movement for a cleaner cut (At least that is what I have read).

When it is easy to use my Shaper (like a mounted table router but slower and more powerful) I will. Bits that cut the 'tongue' in tongue and groove, raised panel bits, shapers for moldings and such should really be mounted in a table for best results and safest practices.

But just because it's a 1/2" shank doesn't mean you have to use it that way. If it is a 3/4" straight bit on a 1/2" shank it will be just as safe as a 1/4" shank, and will likely have a cleaner cut. I would like to replace all my bits with 1/2" shank bits (at least the ones that I can)

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Use the router table if the piece is too small to have the router base firm against the work piece.

Use the router freehand if the piece is too large to safely move across the router table.

If using the router freehand, plan on using some sort of jig or fixture to direct the router. A guide bearing on the bit works as a sort of jig.

In general, if you don't feel you can completely control the router, build a jig or a fixture to contain it.

6

Larger bits will generally recommend that they be used in a router table or with a speed control or both.

That bit is spinning very fast. Even with a small-radius bit it's moving past the wood at a pretty good clip. Increase the radius, and the linear speed at which the bit hits the wood also increases by the same ratio. If a large bit takes too deep a cut and kicks, it will kick hard. In that situation you want the wood to go flying, not the router with its still-spinning bit... so it's safer to anchor the router in place and bring the wood to it than the reverse.

There are other advantages go working with a router table that make it a worthwhile investment; it makes some tasks much easier than freehand routing. Think of it as a basic adjustable jig for the tool. Like an edge guide but more so.

(Reminds me that I need to put an edge guide on my want list.)

  • ... right. Asleep. Will fix. – keshlam May 6 '15 at 2:26

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