Mortising Hardwoods with Mortiser !

[Brian Holcombe]

Elmer, I know a lot of folks use diamond hones but personally I much prefer a tapered reamer. After reaming, I touch up lightly with a diamond hone. The outside of the chisel I make flat and polished.

I go back and forth between the honing plate (ceramic stones) and the cone until the burr is gone.

After which I put a microbevel on the inside of the chisel tips, this helps change the cutting angle and makes the chisel more durable.

The auger I sharpen with an auger file, and grind the ramp to allow the chips to exit easily. I grind them to mimick the shape present in older high quality augers.

[Thomas McCurnin]

I still doubt they are truly sharp inside and out. Sharpening a hollow chisel mortising bit is more than a couple swipes on the outside with a diamond stone.

I do two sharpening sessions on the outside of the chisel with the two highest diamond stones I have then strop all four sides with a leather strop and sharpening compound.

Then I use the two dedicated cone sharpeners from Lee Valley on the inside. You can't strop the inside, but using a dowel and tiny kerf, and a small piece of 2000g wet dry paper, you can make a shop made flap sander to polish the inside.

Don't forget to sharpen the drill bit with a couple swipes of a file on the leading edge and the drill bit can be polished with a felt pad in a drill or grinder charged with sharpening compound.

Then adjust the drill bit on the mortiser. The chisel depth is more or less fixed with a set screw. Loosen the drill chuck with a chuck key and let the drill bit drop slightly. That is a little fussy, so what I do is lock the mortiser depth in place about an 1/8th inch from the table, then loosen the drill chuck which allows the drill bit to drop to the table, so the drill bit protrudes about an eighth from the chisel. Then tighten the chuck. Test the mortiser with scrap. Still difficult to cut? Then repeat with the locking depth 3/16, let the drill bit drop then tighten and test as before. If necessary repeat at 1/4, let the bit drop, re-tighten and re-test.

[Tom M King]

Any burr on the outside of the chisel makes both in and out aggravating. The gap is important. Set up correctly, it should be no problem. If I'm doing a long run, I keep an extra fine diamond paddle at hand to flatten the outside of the chisel if friction increases, without taking anything apart.

[Edward Weber]

Not trying to argue but the OP said the chisels and bits were sharp in two different posts.
Some of you don't seem to believe him.
This has now become a sharpening thread

[mike stenson]

Not trying to argue but the OP said the chisels and bits were sharp in two different posts.
Some of you don't seem to believe him.
This has now become a sharpening thread

I just did about 40 mortises, most of them 3/4" wide through mortises... some as long as 11.5" in 4" cherry (and the OP mentioned walnut, which is about the same in terms of hardness here).. It was not difficult, unless the chisel was dull and/or the bit wasn't protruding enough.

[Jared Sankovich]

Not trying to argue but the OP said the chisels and bits were sharp in two different posts.
Some of you don't seem to believe him.
This has now become a sharpening thread

Experience using similar machinery with no issues in similar or harder woods tends to narrow the focus to the one varible (sharpness)

[Edward Weber]

Don't tell me, tell the OP, he said they were sharp.

[Brian Holcombe]

Not trying to argue but the OP said the chisels and bits were sharp in two different posts.
Some of you don't seem to believe him.
This has now become a sharpening thread

Correct, however, it’s not that I don’t believe that he thinks they’re sharp, it’s that I don’t believe they are sharp relative to what I know cuts well.

[Larry Edgerton]

My guess is that he needs to throw away the chisels that came with the morticer and buy a Clico, Fische, or other high quality set. The chinese imitations are just not up to heavy use no matter how much you massage them. One big difference is the arch between points on the chisel. On the chinese it is a shallow partial arch, on the better brands the arch is deeper, the points are a steeper angle so giving the cut more of a shearing action rather than a blunt cut. You can massage a china chisel all day and it will still not be a Fische.

Before I bought a larger machine I had a Delta similar to the ops, and switching chisels/bits was like night and day.

Couple more thoughts: Is your chip ejection slot oriented in the direction of the mortices? And, inspect the chisel for a split on the side of the chip ejection slot. That causes the chisel to split in the cut and become hard to plunge. Solution is, wait for it, throw out the chinese chisel and buy a good one.

PS: I want a Maka!

[Richard Coers]

Here is an experiment for you. Take the chisel out of the machine, drill a hole in your wood, then try and pare the hole square by hand. You are removing a ton of material, both end grain and long grain. It takes lot of machine rigidity and leverage. Neither do you get with a bench top mortiser. The drill spins too fast and builds up tremendous heat that doesn't help one bit. And when you say sharp, have you tried shaving with the mortising chisel? When you get it that sharp, it really is sharp! I have also seen a lot of mortise chisels that have faces that curve in at the cutting end from being dressed on a sanding belt at the factory. There can almost be no greater harm done to the chisel. It makes it a wedge. And finally, I find walnut to be one of the most easily machined hardwood there is. Hard maple and white oak I can understand. Walnut and red oak? Those machine easily by comparison.

[Cameron Wood]

My experience as well- walnut and oak are regular woods. It takes some muscle, but if the bits are sharp, even cheap ones, it goes OK.

[William Hodge]

I mortise a lot of Sapele. It can be pretty oily. I find that the 5/16" hollow chisels work a lot better than the 1/4" hollow chisels. Th 1/4" chisels approach the design limits of a hollow chisel. There's more room for chip clearance in a 5/16" chisel. Given sharp augers and chisels, Sapele mortises fine with a hollow chisel. If I do get jams from dull tooling, I will pre-bore with a 3/16" drill bit to avoid taking down a set up.

Here's another vote for the Maka mortisers. The first one I ran was for structural timbers. It would cut (5) 1" x 3" x 3" mortises all at once, in seconds. The SM6P is more user friendly.

[Lee Schierer]

I have never had any problem with a similar (Delta) mortiser. I suspect your bits are not sharp. Often, they are simply not honed fine enough out of the box.

For the outer bit, the chisel, the outsides need to be sharpened flat and polished to about 600g+ and the inner portion sharpened with a cone type sharpener in a hand drill, usually the finest grit you can fine--Lee Valley has a good one. Of course, the inner drill bit needs to be sharp as well. The mortiser also has to be set up so the drill bit hogs out the first 1/8th of an inch or so, not the chisel. Finally, some wax or glide coat on the outside of the chisel will help things move along nicely.

Here is a good video on how to do all of this: https://www.finewoodworking.com/2014...mortising-bits

Tom is correct. I used to struggle with my mortising attachment for my drill press until I polished the out side surfaces so they are slick. I also learned that the drill bit should be about 1/16" spaced ahead of the inside of the chisel cutting edges. The tips of the chisels should just be clearing the corners while the drill bit removes the majority of the waste.

[roger wiegand]

I, at least, am in the camp of "been there, done that" with respect to mortise chisels. I spent several years hanging all my (not insubstantial) weight on the end of the lever arm on my General floor mortiser. Then I bought better chisels, the sharpening cones from LV, polished the outsides on a 10000 grit water stone and now it takes some effort but a fraction of what it used to to cut mortises in hard maple. A real night and day difference. I also would have told you my chisels were sharp before going through all that.

[Tom M King]

I really like the Star M Japanese mortising bit and chisel sets. Not only are they very good quality, and hold edges good, but the drill bit comes long. It takes some careful fiddling to cut the bit just the right length, but it saves time setting up once you have it cut correctly and you can seat the bit all the way home in the chuck with zero chance of it pushing up into, and ruining the chisel. You just seat the chisel and push the bit all the way up with no adjusting gap with a dime or whatever once you cut the bit the correct length.