How to drill a mortise

[Brian Kent]

How do I drill a mortise in white oak?

7/8" wide, 2" long, 3" deep through-mortise.

No, I'm not buying a mortiser or drill press mortise attachment.
Yes, I have done this before, but am not satisfied with results.
Yes, I have used a mortise chisel. But my widest one is 3/8".
Yes, I have a big steady drill press.
Yes, I have googled this question and I get movies of "drilling my first mortise".

Questions:
What size drill bit would get best results?
Forstner bit, brad point bit, or spade?
Drill through both sides, with a fence?

In what ways am I ignorant without knowing it?

Thanks in advance.

Brian

[Carl Beckett]

When I did my workbench, I made a template with a cutout the size of the desired mortise, that guided a router bit with a pattern guide bearing. You could use a 1/2" bit and take the first pass with the bearing on the guide, then you just chase it down the next level letting the bearing ride against the previous cut. Can go as deep as your plunge router will allow. (3" deep sounds pretty deep, you might go 1.5" from each side this way)

A thought - not sure its your best bet but something different.

[Brian Kent]

That's a good idea. I just found out my pattern bit is messed up, but I could use template guides and a straight bit.

[phil harold]

Layout the mortice on both sides with a knife
I would use the drill press with a 3/4 forstner bit
use a fence first hole will be the slowest drilling back it out often
than make over lapping holes untill you are long enough (2")
take a very sharp WIDE (1" +) chisel and pare the 3/4 holes till you are at 7/8 (on layout marks) wide
take a 5/8 chisel and clear out the corners

you dont need a "mortise chisel" because the drill did most of the work and all you need is the chisel to clean up the mortise

[Brian Kent]

Thank you Phil. That's 'zakly what I needed to know. I have a 3/4" forstner that hasn't been used often (still sharp) and I am on better speaking terms with the drill press than with the hand-held router right now. Chisels are my friends, too.

Brian

Never mind. I'm wrong. My Rockler 3/4" is all burned up. I have the Fine Woodworking review so I can see if there is a good replacement I can get tomorrow.

[johnny means]

I use a forstner on the DP. I would actually use a 7/8 bit. Using a fence, I drill out separate holes, then go back and drill out the material between the holes. I use the forstner to cut out the ridges it leaves behind, until the sides of the mortise are almost straight. If I do a good job, I can just chisel out the corners and be done with it. The slight ripples left behind actually help create a tight joint, sort of a wedging affect.

Of course, this only works with a a really sharp forstner and a good DP.

[Brian Kent]

I have a good 20" Jet drill press. I am looking for Forstners I can buy locally: Diablo, Porter Cable, Rockler, Irwin.

The Fine Woodworking review is 3-1/2 years old so I imagine some of the products tested have changed (like the Porter Cable bits).

I just found Freuds at ToolMart in Escondido, but I am not sure if they sell through their brick and mortar location.

[phil harold]

You could use a 7/8 but, if something is out of whack your mortise may be wider than planned
easier to chisel wider than than chisel it narrow

I have a mostly Taiwanese forstner bits and a few higher end bits too, they all dull and burn, so I touch them up with some slips and back in business
Now my carbide ones last a long time if you dont chip them

[Brian Kent]

I assume "touch them up with some slips" means sharpen or hone them with slipstones? (which I don't have, but I'm just wonderin')

[phil harold]

slips or a dremel

[Jim Matthews]

+1 on the 3/4" Forstner to hog out the hole.

I've yet to cut one this large. I have done this with smaller mortises.
I like to start at either end of the mortise, to establish the ends just shy of the mark. I use a chisel to square the corners in any case.

The first mortise I made this way was out of square, so the relation between the drill press table and the bit is now the first thing I check.

FYI - I purchased the cheapo set from Rockler and it cuts white oak well but clogs in cherry.
Chip ejection is a real concern with a hole this deep.

[Jerome Hanby]

You said no to buying a mortiser, what about a mortise pal? I've heard great things about them. I actually bought one from a 'creeker and it looks like a quality jig, haven't used it yet.

[Prashun Patel]

I have a mortisepal. It's great, but the prob with the router solutions is the depth.

If it were me, I'd use a 7/8" forstner to hog. Overlap the holes. Once the nibs are small enough, you can use yr drill press like a router, by plunging the bit in 1/8" then sliding it back and forth along the fence between 2 stops. Then plunge a little deeper and repeat until the walls are smooth. Any ridges left are very easy to clean up with a paring chisel.

I'd cut the tenon AFTER the mortise is made, and I'd sneak up on the fit. This way, any runout from the quill becomes a non issue.

[Erik France]

An oversized brad point will remove the waste pretty quickly too. I picked up a 5 pc set of Jumbo brad points from MLCS a while back for ~$25. I'll use them for deep mortices. The set includes sizes: 9/16", 5/8", 3/4", 7/8", and 1".

You might want to mark and score both sides of your mortice. Scoring the back will lessen the likelyhood of tearout. I'll usually use a wide chisel a give the line a wack or two. Like others have said, I'd use a 3/4" bit on the press then clean up the sides and corners with a chisel.

[Brian Kent]

Jerome, if I had $199 to spend on a mortise pal I would go ahead and spend $238 on a mortiser.

By the way, I exaggerated. it's only 2.5" thick.