Best way to make a square mortise?

[fjdog]

My current method of cutting mortises is to use a plunge router with a jig. For the most part, I am pretty happy with this method and can use it with loose tenons that are fit with a planer and rounded over on the router table.

But for some projects I prefer or need a square mortise. I have been toying with the idea of a hollow-chisel mortiser, but shop space is very limited in my one-car garage. So until now I have been cutting/paring these square with bevel-edge chisels. This works ok, but takes a bit of time. I was thinking of trying a mortising chisel or corner chisel so I could pound these out quickly. Has anyone on the forum used either of these tools for this purpose? I heard that corner chisels are very hard to sharpen properly. Mortise chisels would only really work on the exact width of the router-generated slot.

Or, should I just bite the bullet and get a HCM and find some way to shoe-horn it into the shop? Used ones seem to be getting pretty cheap due to the Domino.

Thanks in advance!

 

[creasman]

I frequently use a mortise chisel to cut these. I'm not sure it takes any longer than it does to drill first and then clean out the hole, square the ends, etc. It does require some practice with the proper technique to become efficient. The only time I really care about how the mortise looks is if it's a through mortise that is seen from one side.

I also use a drill press and then a paring chisel to clean out the hole, particularly if it's a large mortise (say 5/8" or wider). I have a 3/8" corner chisel that I use for the ends, though it's almost as fast just to use a mortising chisel. Most likely on these I leave the ends of the hole round and use the paring chisel to round the tenon, instead.

Unless you do a lot of mortises, I don't see the justification for a dedicated tool like an HCM. As you point out it will take up space and sit unused much of the time. Everybody is different. This is just my two cents. For the cost of an HCM you can buy a nice set of chisels.

 

[pop-pop]

A corner chisel will get stuck if you try to take a large bite. About 3/32” at a time is about right. Other chisels are about as fast.

 

[fjdog]

Thanks for the input. Are the Narex low-end mortise chisels from Lee Valley decent enough or should I save up for something better? For sharpening, I assume these should be sharpened to a higher angle than a normal bench chisel. I don't think they will fit in my veritas side-sharpening jig. So maybe I can use the worksharp 3000 to sharpen.

 

[HITCH-]

Do you have a drill press?
Mortising attachments can be had for about $100 and it would not take up any more space.

 

[McRabbet]

I would avoid buying a mortising attachment for a drill press -- in my experience, they do not perform very well.

In place of a Hollow Chisel Mortiser, I recommend the method that Jim Creasman uses in his post. I have done this with both standard bevel edge (bench) chisels or mortising chisels (stronger, aka "pig stickers"). For multiple mortises, my go-to method is a Hollow Chisel Mortiser (I have a Powermatic Benchtop unit) and it works very well and is very accurate. Just be sure to use sharp (here is a good pair of sharpening hones) and top quality hollow mortising chisels.

 

[Melinapex]

Thanks for the input. Are the Narex low-end mortise chisels from Lee Valley decent enough or should I save up for something better? For sharpening, I assume these should be sharpened to a higher angle than a normal bench chisel. I don't think they will fit in my veritas side-sharpening jig. So maybe I can use the worksharp 3000 to sharpen.

I bought the narex set after I got rid of my HCM (very fiddly - did not work well for me) and decided to learn to do them by hand. Since I am not in a hurry I don't mind that it takes me a while. While I am not very good at it I do really enjoy it.. plus have learned how to fix them when I mess up! I find them fairly easy to sharpen (diamond stones) as there is a lot of surface area to place them on the stone and hold the correct angle. Still, When I use them, I pick a slightly smaller mortise chisel and finish up the sides with a paring chisel.... so far I am happy with them.....

 

[creasman]

Are the Narex low-end mortise chisels from Lee Valley decent enough

Those are the ones I have (6mm, 8mm & 10mm). They've been good chisels. I sharpen at 25 degrees. Anything less and you risk breaking the edge. Cutting a mortise in hardwood can take a toll.

 

[mdbuntyn]

I have Narex mortise chisels as well. They're a great value

 

[bob vaughan]

A hollow chisel mortiser speeds up the operation but not all hollow chisel mortisers are the same. The current crop of Asian-made mortisers are pretty flimsy and the bench top ones are worse. The only drill press mortiser rig that I thought worked ok was the old USA-made Powermatic 1150 press with the heavy Powermatic mortising yoke. I've had other drill press mortising rigs and they all came up lacking. A mortising yoke on an Asian-made drill press is very likely to disappoint.
My mortising machine is a pipsqueak compared to the good ones, but small size makes it perfect for the home workshop. The bigger ones are simply too big for me. This little Oliver 194-D weighs right at 500 lbs so its rigid enough for most of my work. Wysong and Miles made some great mortisers but those were simply too much. Back in the day most machinery makers offered a mortiser.

My point is that a cheap mortising machine is usually better than nothing. It is a good starting point and a lousy stopping point.

my 194-D

when a lot of mortises need to be made, a good mortising machine is your friend.

This type of work is where a mortising machine really speeds things up.

 

[KurtB]

I have the Narex set as well. Quality seems just fine so far.

 

[fjdog]

Sounds like the Narex chisels are the right answer. Since I am a hobbyist who makes a few pieces of furniture a year, I certainly won't get the use out of a floor-standing HCM. If I used a drill press model, I question whether the bearings would hold up on my old craftsman drill press, which was passed down from my grandfather (probably 1960s era). Plus, it sounds like those typically are not very good. I appreciate all of the suggestions! This forum is super helpful.

 

[KurtB]

I'm a hobbyist as well and just worked with chopping the mortises for the first time using the chisels. Paul Sellers, Rob Cosman and Chris Shwarz all have good videos on how to do it. I just took my time, watched the chisel alignment and didn't take any huge bites. It turned out to be far easier than I thought.

 

[Gofor]

Hand chisels will work fine. The trick is to work up to the end gradually (as Kurt said, don't take huge bites). If you take too big a bite, the bevel on the chisel tends to push the flat side into the wood, crushing it. Not a problem if you take small bites with a sharp chisel. For the final couple of cuts, you should be able to push it down without using a mallet, and not have to "lever" out the waste. Levering out the last cut will also tend to crush the fibers. For hand chopping, my mortising chisels have bevels closer to 35 degrees than to 25 degees.

 

[Hmerkle]

@fjdog did you see this?

https://ncwoodworker.net/forums/index.php?threads/powermatic-benchtop-mortiser-for-sale.77200/#post-718584

 

[joec]

@fjdog did you see this?

https://ncwoodworker.net/forums/index.php?threads/powermatic-benchtop-mortiser-for-sale.77200/#post-718584

I have this machine for sale and it is now on hold through Friday. It is great for square mortises and especially thru-mortises if that comes up in your projects. Check in on Saturday and I will update my post.

 

[Rwe2156]

May I ask why it needs to be square?

 

[Gofor]

May I ask why it needs to be square?

I am assuming (maybe in error) that the OP is talking about mortises that are squared off on the ends, as opposed to leaving the ends rounded when drilling out the waste. Actually they are oblong in most cases.

One reason to square them is is aesthetics, where an exposed part of the mortise looks finely finished. Examples would be a through mortise or a half bridle joint.

Another reason for this is to eliminate any voids in the surface for those same joints.

Mortise tenon joints provide a large glue surface on the long side of the tenon, as well as the broad area helps prevent coming out of alignment. An example would be a face frame on a cabinet. The M&T joint prevents it racking front to back. A squared mortise also is better at preventing racking top to bottom, rather than just relying on the shoulders of the tenoned piece.

The downside of squared of ends in a blind mortise is that they can cause a hydraulic lock when trying to put them together with glue. If fitted snug, there is no relief channel for any excess glue to escape when the joint is pushed together, preventing the shoulders to fit tight against the mortised piece. (The same can happen with a domino-type joint)

Although I usually square off my mortises, for blind mortises I bevel the corners of the tenons with a rasp to prevent the hydraulic lock.

Probably TMI for you, DrBob. If so, my apologies. I hoped to better explain things for the more novice readers.

 

[fjdog]

I have this machine for sale and it is now on hold through Friday. It is great for square mortises and especially thru-mortises if that comes up in your projects. Check in on Saturday and I will update my post.

Thanks. Looks like a fine machine, but maybe more than I want to spend for the occasional use.

May I ask why it needs to be square?

Usually it does not and for my last project I left them rounded on the ends with a loose tenon (like a huge domino). But I think @Gofor summed it up pretty well why square are sometimes preferred.

 

[Jim Wallace]

Like Mark, I was taught to chamfer all the edges of all tenons. This makes the glue escape channel automatically and also makes the tenons easy to start in a tight mortise. I usually make the mortises first by drilling out the waste with a Forster bit and cleaning the sides with a bench chisel as Jim Creasman suggests. The sides of the drilled holes show you exactly where and how much to cut. However, in stead of leaving the ends round from the drill bit I finish them with the mortise chisel. I usually drill the holes at both ends a little shy of the mark so that when I use the Mortise chisel to pry out the waste I don’t damage the surface at the end of the mortise. Then I work back to the line with a series of light cuts (no mallet here). I rough out the tenons by cross cutting on the table saw and final fitting with a rabbet plane. The table saw gives a very good shoulder to work from and the rabbet plane flattens the cheeks very fast and accurately.
I agree with Jim that many mortises can be cut about as well and quickly by chopping with the mortise chisel (pig sticker). I find that a goose neck chisel helps clean out the bottoms of the mortise here depending on the depth of the mortise and the wood.