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.

[Leo Graywacz]

You have two sides of the mortice. You have the side that will be covered by the tenon pc and the open visual side. What I might do is on the visual side use a router to make a nice neat clean sided hole, doesn't have to be all that deep, maybe 1/2". You can square up the corners with a chisel. On the other side youcan go the drill bit and chisel route. No need for it to be a clean looking cut as long as the mortise/tenon is pretty well fit it will work fine.

[Terry Beadle]

A brad point 3/4 bit would remove the waste a lot quicker than the forstner but would leave the sides a bit more ragged. Since you would be using a chisel to take the last little bit, squaring the cut, etc. It would be better to use the brad point IMO. Just buy a reasonably priced brad point 3/4" which a quick search shows it should cost less than $12.

I would definitely cut the mortise from both sides after careful knife layout. Take the time to make sure that nice DP is dead square in the cut.

[Brian Kent]

I just got the 3/4" Freud forstner. I have brad points up to 1/2". I'll try it on some scrap and see which I can personally do the cleanest job on for the exit side.

Thanks all.

[Alan Schwabacher]

The trickiest part is paring out the waste without making part of the mortise too wide, assuming you used a solid fence with nicely squared stock, and put the same face against the fence while drilling from both sides.

To keep the chisel square, use the bored holes as a guide. Check to see that the curved portion remaining after each cut does not change width from top to bottom. If it's even, you are paring parallel to the hole. If the hole was square, so is your mortise.

[Chris Parks]

To keep the chisel square get a nice piece of machined timber maybe three inches thick and clamp it to the marked line. Use the straight side of this to lay the back of the chisel against and the side of the mortise end up truly square.

Drilling, attach a fence to the DP so that the drill bit can't encroach beyond the layout lines and use anything you like to drill it with. Set the depth stop on the DP so you finish up at the same depth right across. I would drill the two ends first and the rest will take care of itself.

What you could do is take some scrap timber and practice chopping it by hand if time allows. I am no bleeding heart advocate for hand tools but the more you do it the better you get, DUH! With the amount of video techniques available nowadays you can largely self teach from the net and yes it is very satisfying to acquire skills.

[Jim Neeley]

I ran into a somewhat similar issue wanting to use my router to cut 3/4" dog holes through my 3" thick benchtop and found a solution.

In my case I made a template by drilling a 1-14" hole on a piece of 3/8" MDF and inserting a 1/2" bit in my router with a 1" guide. I started with a long freud bit (~1-1/2" long cutter) and took it as far as it would go.

Then I replaced it with a 1/2" bit with a 3" long cutter to complete the hole. The key with such a long bit us to use a large "tank" of a router and limit the depth of each pass to 1/4" or less to avoid too much side-stress on the cutter. Hey, I'm a chicken when it comes to a 3" long, double-bladed cutter spinning at about 12,000 rpms. :)

I found the bits for cheap for <$12 on ebay at a store called "super carbide tools". You can also find them by searching for "router bits" and looking for pictures similar to the ones I've attached. They have a distinctive placement of block-text on their pictures. Yes, they are cheap. Yes, they aren't domestically made (but I couldn't find any, let me know if you know of a domestic manufacturer). I did feel somewhat better since I could insert the bit about 1-1/2" into the benchtop before turning up the router. It also let me get around having less than a 3" plunge action.

Also FWIW, the shank of the ones I got were pretty long so I didn't have to really extend the bit but a small amount from bottomed in the collet to get the length. I don't have any connection with the store other than they get praise from a number of active members on another (router) forum.

YMMV.

Jim

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[Brian Kent]

The Freud 3/4" bit worked very well. The photos are on my thread on building an outdoor sunburst dining table:
http://www.sawmillcreek.org/showthread.php?170717-Building-an-Outdoor-Sunburst-Dining-Table/page3

Only the corners are left to clean out.

[Jerry Lawrence]

My first mortises I made with a forstner bit, but instead of chiseslling out the corners, I rounded over the tenons with a wood rasp. Of course, these were not through mortises, so appearance wasn't an issue.