How to cut a deep mortise

[Prashun Patel]

I'm making a workbench with 3" thick legs. I'm attaching the rails to the legs with mortise and through tenons.

I was planning to make the mortises with a drill press/forstner bit and chisel. The problem is my drill press's spindle travel is not long enough to go all the way through to hog out the body of the leg mortise.

My plan is to hog out from both sides, and then use a chisel and hope the whole thing lines up square.

Is there a better way? (short of buying a bigger press / mortiser?)

[Rod Sheridan]

Hi Shawn, if your drill bit is long enough you can drill to maximum stroke on your drill press, raise the table and re-drill all the way through piece.

Or as you stated, drill from the other side......Regards, Rod.

[Mike Henderson]

If you drill all the way through, make sure the exit side is the side that will have the tenon shoulder. That way if you have any tearout it'll be hidden by the tenon shoulder.

But what I do is mark the mortise carefully on both sides and drill from both sides without trying to get too close to the lines. Then finish up with chisels.

Another way to do it is to make your tenon blind (the mortise doesn't go all the way through) and then put a faux piece on the exit side. Looks just like a completely through tenon.

Mike

[Floyd Mah]

There are extensions for Forstner bits which will give you some extra length on your existing bits. I think I got mine at an Ace Hardware, so they aren't too exotic or scarce. Also try Home Depot.

[Jerome Hanby]

I'm cheating on mine. I'm gluing up the legs and forming the mortises at that time...

[Matt Day]

There are extensions for Forstner bits which will give you some extra length on your existing bits. I think I got mine at an Ace Hardware, so they aren't too exotic or scarce. Also try Home Depot.


Extensions don't give you more quill travel. Even with an extension on your forstner bit which is now elongated by 6" or whatever, still only moves up and down the quill travel of your drill press.

[Prashun Patel]

Hmmm, not sure I understand, Jerome....

[Prashun Patel]

Hi Shawn, if your drill bit is long enough you can drill to maximum stroke on your drill press, raise the table and re-drill all the way through piece.

Or as you stated, drill from the other side......Regards, Rod.

Duh! I knew there was an easy way. Thanks. I didn't think about raising the table.

[Dan Gill]

Duh! I knew there was an easy way. Thanks. I didn't think about raising the table.

That's a lot easier than lowering the head. :D

[Joe Scharle]

Hmmm, not sure I understand, Jerome....

May be the technique whereby you leave gaps in the glue up where the mortises would be.

[Jerome Hanby]

Hmmm, not sure I understand, Jerome....

The legs/ends on my workbench are going to be a lamination of three pieces of wood. When I glue up the particular lamination, parts that need a tenon will have the middle piece longer than the two outside pieces. On pieces that need a mortise, the middle piece will have gaps leaving the space for the mortise. Planning to glue and draw bore the joints.

I will have to cut mortises for the stretchers , but they wont be all that deep, I'll be securing them with home made bench bolts.

[Floyd Mah]

Quill travel is an issue if you attempt to drill out the waste in one step. What you would do is drill as deeply as you can, remove the bit, attach the extension and then resume your excavation. Think of this as an oil drilling operation, where your quill travel is irrelevant since you are planning to dig several miles down and your actual bit is only a few feet high. If Exxon could not attach a few miles of extension to their bits, we would be driving Fred Flintstone cars.

Incidentally, you don't need a drill press to waste wood. You get the straight sides with your chisel. Put the drill bit on an electric drill and drill away. A Forstner bit is pretty easy to control in a free-hand way. Use the chisel afterwards to finalize your mortise. Your only restriction at the outset is to mark the boundaries of the mortise carefully and stay within the markings. I bet you could do a lot free-hand before you need to tackle the mortise with a chisel.

[Tom Schmidt]

Hmmm, not sure I understand, Jerome....

One way to make a through mortise is to take the leg and do it in two pieces, with a dado in each piece whose height is 1/2 the size of the dado, and then glue the two pieces up.

To see what I mean, go to the following link: http://www.eaglelakewoodworking.com/post/Arts-and-Crafts-Bed-Stickley-Panel-Bed.aspx#

Click on Watch The Video, and look at video #4. A great example of how to do it.

[Prashun Patel]

Yeah, thanks. Shopnotes had a recent article about that. Next time...