Tips for centering Mortis and Tenons?

[Michael Drew]

Most of my projects are mission and arts and crafts stile furniture, cabinets, etc. I have progressed from a drill press and chisels to a Delta Mortis cutter and from my not so great dado set to a Delta Tenoning Jig. Getting the tenons perfectly centered is a no-brainer, but I still struggle centering the mortis on the work piece. I typically just cut a few until I get the fence set and then cut the rest. I can’t help but think there’s some nifty tricks to make this simpler and reduce my pile of rejects. How do you guys do this?

[Joe Scharle]

First things first, is to use a double marking gage to define the cut. After the first perfect mortise the rest should be automatic if all other things are the same. However, it takes just a quick stroke, so I mark them all.

[Michael Drew]

This is probably a really dumb question, but what's a double marking gage?

[Ray Newman]

"Double" marking gauge for mortises--here are a few

http://www.woodcraft.com/Product/2007282/2063/CROWN-Marking-And-Mortising-Gauge.aspx

http://www.leevalley.com/wood/page.a...21&cat=1,42936

Wheel gauge & double heads:
http://www.leevalley.com/wood/page.a...55&cat=1,42936

http://www.leevalley.com/wood/page.a...88&cat=1,42936

[Kevin Groenke]

I often use a self-centering mortising jig and a plunge router:

I think I made this jig from plans in AmericanWW, but it was probably 10 years ago.

Crazy, it's in the Sketchup 3D warehouse:
http://sketchup.google.com/3dwarehou...de2d307cd2d09a

This jig centers and clamps your stock in a single action. The plunge router attaches to the clear plate. The height of the router/clearance for stock is variable by using different slots. When using this jig you need only mark the beginning and end of the mortise. To make an offset mortise, you can just add a shim. To use: with a upcut spiral bit, make full-depth plunges spaced about 2/3's of the bit's diameter apart, go back and remove the 2/3's waste, then make a cleaning pass the length of the mortise.

Much faster and cleaner than a square chisel mortiser.


Here's a simpler one that works on the same principle:

http://www.woodstore.net/semojigpl.html

g'luck
-kg

[Michael Drew]

Thanks guys.. That jig looks interesting. I attempted to use a router once and my work piece met a horific death of chips and cussing. I gave up the use of a router after that incident. But, your jig idea gives me reason to try to use a router again.

[Walt Pater]

In the past, I've done two passes on my mortiser....1st pass with the long of the board to the left, then a second pass with the long of the board to the right. If you roughly center the bit before the first pass, you won't be taking that much off on the second pass. Since you're referencing off both the front and the back of the board, your mortise will be centered.
If you do this, you'll need to cut the mortises first, then fit the tenon to the mortise...easy to do if you're cutting your tenons with a dado blade.

[Peter Quinn]

Michael, I have found few situations where centering the mortise is of particular value. That is what reveals are for. Does the A&C furniture you are making have rails that are thinner than the legs or other receiving end? If so than you only need to get to relative center and make sure to reference corresponding pieces off of the same plane. Don't frustrate yourself getting exactly centered if it is not necessary.

For instances where true center is necessary or at least very convenient (like doors for example) I simply drop the mortising chisel into a test piece to make marks, spin the test piece 180 degrees, drop the chisel again and note any overlap. Adjust the fence by half this amount in the appropriate direction, and test again. It usually only takes two or three tests on a single small scrap of the same thickness as your work to get it done. I do this with the drill bit raised up or taken out and the machine off.

Another option is to use the center point of the drill bit to meet a center line scratched on the test piece, but this will not give you any indication of how square your chisel is to your work.

[Frank Drew]

Peter,

You've got a slot mortiser, don't you? So why are you still using a hollow chisel mortiser?

[Or is this at work, and the slot mortiser is at your home shop?]

Michael,

A plunge router with spiral end mills and a jig like the slick one Kevin shows make quick (and slick) work of mortises; give it another try.

[Greg Hines, MD]

I use a plunge router and a base with a pair of rails on it to plow out the mortises. You can adjust the fences to position the workpiece centered, offset, or at a edge, based on your needs. I have tried to attach a photo from Woodsmith, but you cannot put the same photo on two different posts on Sawmill Creek, so here it the page:

http://sawmillcreek.org/showthread.php?t=79953

[Gary Muto]

In the past, I've done two passes on my mortiser....1st pass with the long of the board to the left, then a second pass with the long of the board to the right. If you roughly center the bit before the first pass, you won't be taking that much off on the second pass. Since you're referencing off both the front and the back of the board, your mortise will be centered.
If you do this, you'll need to cut the mortises first, then fit the tenon to the mortise...easy to do if you're cutting your tenons with a dado blade.

That's my method too. One of the first rules I learned (from Norm) was Mortise first then tenon.

[Rick Fisher]

I have the roller marking gauge from Lee Valley.. its great..

Make the mortise first.. for sure.. I usually cut the tennon without removing the shoulders, then mark the shoulders on the actual mortise.. I cut them a bit big.. then snug them up with a chisel..

I really like making mortise and tennon joints.. I am really slow .. and not saying that I am that good at it .. but I love the process.. If you take your time, and make the joint a project within itself.. its very rewarding to do a really good job ..

I bought a domino, and have been thinking for some time that I need to go back to making M&T joints.. I actually miss doing it ..

[Philip Rodriquez]

Step 1: place your stock against the fence
Step 2: lower the chisel to where it just touches the material and leaves small indentations (I actually use the drill bit)
Step 3: turn your stock around, keeping the face with the indentations up
Step 4: repeat step 2. Be sure to make the indentations as close as possible to the first set
Step 5: adjust your fence, as necessary
Step 6: cut your tennon to fit the mortise
Step 7: buy a good shoulder plane, you’ll thank yourself
Step 8: realize that there will always be some handwork to get perfectly flush joints. Even with the same setup, some will require more than others. I use a #4 or a block plane to flush the joints. It should only take a pass or two

[Michael Drew]

I glad I found this forum. Thanks for taking the time to assist without making me feel like a dolt. Everything I know, albeit isn’t much, has been self taught through some head scratching and coming up with whatever I can. You all have been very helpful and I have a lot of new things to try.

I would prefer to continue working with my square chisel cutter, seeing how I did just buy it and it still stinks of shipping grease. But, I’m also going to look into build some jigs for using a plunge router as I am certain there will be times when I just can’t chuck up the work piece in the cutter and will need to use the router. Routers, in general – make me nervous. I tend to not use them if I can find another way to do what I’m trying to achieve. I suppose I should buy a book on router use…….

I have NO planes, but was wishing I had one yesterday. I need to buy a couple…. Anyone have a recommendation for a shoulder plane and another general purpose one?

[Philip Rodriquez]

I love the LV Medium shoulder. However, since you do not have any planes, I would suggest this one:

http://www.lie-nielsen.com/catalog.php?sku=60_5R