Thread: How much use is an out-of-square mortise chisel?

Hi

Very useful for cutting non square mortices.

cheers

dazzler

That's all well and good, but then how do you cut the non-square tenons?

Originally Posted by gregoryq

That's all well and good, but then how do you cut the non-square tenons?

Just down half a dozen of your favourite alcoholic beverage first and you will be almost gauranteed a non square tenon.

Mick

the profile of the chisel is actually not square....It's a couple of degrees out, so it's more of a rhomboid profile than a square.

GW

I don't know how to break this to you ...

There is nothing wrong with your mortice chisel!! It is meant to be that shape. Truely. This is to enable chips to be cleared more easily, that is, so the chisel does not bind on the walls or the mortice.

Some mortice chisels have parallel sides, but they tend to be the cheaper ones.

Regards from Perth

Derek

I hesitate to venture into Dark-side territory, where I am pretty much a fish out of water, but I do know my geometry. Presumably Derek means that good-quality morticing chisels have a trapezoidal cross section, that is, that the sides converge slightly. If Green Woodchips was using the term rhomboid in its strict sense, it is a quadrilateral in which the opposite sides and angles are equal, so that the sides would be parallel to one another, but skew-whiff. Hopefully, his chisel's profile is trapezoidal rather than rhomboid.

Rocker

Originally Posted by Rocker

Presumably Derek means that good-quality morticing chisels have a trapezoidal cross section, that is, that the sides converge slightly. If Green Woodchips was using the term rhomboid in its strict sense, it is a quadrilateral in which the opposite sides and angles are equal, so that the sides would be parallel to one another, but skew-whiff. Hopefully, his chisel's profile is trapezoidal rather than rhomboid.

Rocker

Ooowwwww...my head hurts

Squizzy,
trapezoid = triangle with top cut off
rhombus = square pushed out of square (racked)

mick

Hey guys.

It's rhomboid.

GW

Originally Posted by gregoryq

That's all well and good, but then how do you cut the non-square tenons?

I never cut any other kind.

Its my understanding their are three different types of morticing chisels.

Standard - Straight.

Registered - Thats rectangular in cross section but tapers from the shoulder to the bevel. Sounds like what Green W has.

Swan Neck - Which has a large curve in the botton third that looks similar to the handel on a coffee mug. They are designed for deep morticing and easy clean up of the bottom edges by alowing the chiseld waste to be levered away easy

My reply is like the others but there seems to be some confusion about which cross-section we are talking about.

If you stand the chisel vertically with the handle at the top and take a horizontal cross-section then it should be square/rectangular. The sides should be parallel and at right angles to the cutting edge.

The front and back of the blade are tapered getting gradually thicker near the handle for the reason Derek mentioned so you can easily work it out if you cut too deep and the chisel is stuck.

If your problem is the horizontal cross-section is not square/rectangular then you will need to grind and polish it back or throw the chisel away.

If the cutting edge bevel has been ground incorrectly by you or the previous owner then a bit of work on a stone or a wheel should correct your problem.

It seems unlikely someone like Triton would sell a chisel that was not square/rectangular in the horizontal cross-section. It's almost impossible for it to creep after manufacture.

I suggest the bevel has not been ground properly or you have aquired a reject that was destined for the scrap bin at the factory but somehow came into your possesion.

Let's know the outcome or take a photo in case we have misunderstood.

Wood Borer --

It appears to me to be a manufacturing fault. A cross-section of the chisel is rhomboid in shape. It is only slightly out (a couple of degrees) but it is out nonetheless. A photo would not show it up adequately.

This is an old wooden-handled Titan. Who knows, it might be 50-60 years old. Sharpening will not fix it. The two sides of the chisel would need to be remachined to be square to the bottom.

So am I wasting my time trying to use it?

Cheers,
GW

Are you sure that you have the bevel ground on the right side?!!!! These are thick, wide shafts - perhaps it is ground on the side, not the front?

I will post some pics of mine later today.

Regards from Perth

Derek

Hi Derek.

Wow. This is generating some intrigue.

I will try to get a pic today or tomorrow (day off) and post it up here on Wednesday when I come to work next.

From what I can see, I, and everyone else before me, have ground this chisel the right way. But I guess an error is possible. In any case, the profile is still a rhombus and not a square, and so I doubt that would make any difference.

Cheers,
GW