I'd be concered about the setup time for using the guide. I suggest you practice it freehand for a little while, and you'll soon be accurate enough, and faster. CB.

I second Clark's advice.
Before I had a mortiser I used a drill... with a simple square as a guide (or one of Clark's mirrors) - you get good at it.

Liam,

We've used the protool guide with 1 1/2" milwaukee self feed bits to hog out mortises before. These bits are like forstners with lead screws. Milwaukee makes a nice bit extension for these in 3 lengths and the one we already had happened to be the perfect length. I think it was 12", but can't remember for sure. They make 2" self feed bits as well.

As far as using the guide, we just took the center ring out like you said and had no problems. With SF bits, there's no point in making a different sized guide ring, as the bit is built basically like a forstner. It didn't seem to torque the frame overmuch. The depth stop alone makes it an improvement over free hand.

I consider it a viable way to produce mortises in a low to medium production environment. And the guide is still usable for peg holes and other tasks with a simple bit change and replacing the center ring.

I'd forget about forstner bits for mortises -- no lead screw makes it way too much work to drill 4 or 5 inches deep.

And it used to be that those lead screws were replaceable - or at least could be taken out to sharpen.

Back in the good old days we drilled a few thousand this way with a Milwaukee HoleHawg - too much torque, really, to be safe.

Adding a mortise centerline to the layout was very helpful.

We have 2 Protool 460 Guides in our shop and we use them all the time with 1 1/2" WoodOwl bits. It works great and we have never had a problem.


Colton

Good to know that the manufacturers OK the use of larger bits. Thanks for the info.

One way I guide my drilling is with a bullseye (round) bubble level glued on the back end of the hole-hawg or other drill. Gets my body position, hand grip, and 'eyeball' plumb before starting, and helps check plumb-ness while drilling.

The longer the bit (and extension?) the easier it is to be accurate.

A hard knot will try to deflect any bit or boring machine in my experience, at least somewhat. I even built a custom drilling tower as Timbeal suggests, clamped it to the timbers etc, but there is so much torque involved that it would twist and distort in bad knots no matter what.

If perfect mortise walls are an issue, one can drill a little undersize then pare with a chisel.


Pete

Even if the bore holes are "off" you can pare only what needs removing, leaving a section of the bore hole on one side of the mortice.

I was asked a while back what I used for bit sizes, if they were under the mortice size, I found my measuring device and the 1-1/2" bit is right on, not undersized. I like it that way.

I like the idea of the bulls eye level, its nice and low tech. I have tried using the mirror idea (actually a cd upside down) but found it difficult.

I suppose the bulls eye level should work, as long as the timber is true and level.

I use a combo square set to 0, registered in two directions and let it rip. this works as long as the timber is not out of square. I also bore peg holes from the side orientation, not down from the top. I wonder if boring mortice holes from the side would add any benefit? The chips would fall away. Maybe better control of the Hole Hawg?

I tried the mirror, at one time, the last time, the bit got sucked out the exit side and the chuck was pulled into the circle hole in the center of the mirror and it broke into two pieces. Now, I have a mirror in the shop to look into as an aid in extraction of the occasional wood chip.