Tenon size in relation to thickness of stock.

[marksrob]

I am trying to determine Tenon size in relation to thickness of stock. Would 1/3 be about right.

1/4 in tenons on 3/4 stock.

Nark

[Tom]

Maybe a hair more than that, but it's close enough for me. Tom Work at your leisure!

[B Man]

I usually go with 1/3 of stock thickness - unless there a real good reason why it should be more (I woundn't go less).

That's a good "rule by thumb".

Brian

[Mike Hide]

I agree 1/3 the stock thickness.....mjh

[BobS]

Here's a good link for you.

S.

[Wes Stewart]

|I am trying to determine Tenon size in relation to thickness of stock. |Would 1/3 be about right. | |1/4 in tenons on 3/4 stock.

I use half the thickness of the thinner piece, i.e. 3/8" tenon on 3/4" stock.

[David]

I use either 5/16 or 3/8, depending on my mood. Seriously. 1/4 is a bit shy.

David

[e-mail] wrote:

[Upscale]

A question about mortising machines and bit usage. For cutting something like a 3/8 slot for a tenon, would it be acceptable to use a 1/4" bit and move it over 1/8" to cut the other side of the slot, or is it only recommended to use a 3/8" bit?

[patriarch]

"Upscale" wrote in news:0pRPc.15642$ [e-mail]:

There was a recent thread on this either here, or ABPW. The claim was that cutting the partial hole (?) caused a great deal of stress on the bit/chisel combo. Seems reasonable to me, but, then, my mortising machine is still in the factory box. I got impatient, waiting for it to ship, and cut the mortises in the then current project down at the Adult Ed shop.

Why would you not want to use a 3/8" bit?

Patriarch

[Upscale]

"patriarch [e-mail]" Why would you not want to use a 3/8" bit?

3/8" bit might be dull, might be broken, chipped or even missing. Just a question that occurred to me. I'd guess that the larger the bit, the more force it would take to cut the slot. Figured it might be easier to cut a smaller slot, with multiple cuts needed, but admittedly take more time.

[Leon]

"patriarch [e-mail]"

While that sorta sounds reasonable. Cutting the first hole produces the most stress. Cutting less wood on the next cut is less stress. Also, since most tennons are not square, the chisel is not cutting 4 sides after the first cut. Sharpening the new chisels is the key to a non stress cut.

[Leon]

Cut your mortise first, then match the tennon to the mortise. I prefer the tennoin to be as large as possible with out compromising the outer sides of the mating piece with the mortise in it.

[patriarch]

"Leon" wrote in news:VqTPc.1900$ [e-mail]:

OK, admitting as I have that MY machine is still in the box...

What I have read indicated that a proper procedure is to cut each end, and then work towards the middle. This was/is the method that seems to work best when mortising using the drill press and a forstner bit, prior to work wih a hand chisel.

Cutting a hole with less than full material seems to strain the bit in that case, as well.

Is my assumption correct that the bulk of the cutting comes from the bit, rather than the chisel?

Patriarch, willing to learn from the experience of others. It's cheaper.

[J.B. Bobbitt]

I've learned that it depends a lot on how you cut the mortise, and what size tool you have to cut the mortise. If you chop the mortise by hand, and you have a 3/8" mortise chisel, make the tenon 3/8" thick too.

-JBB

[Leon]

"patriarch [e-mail]"

Yeah. I remember, I was commenting more on the information that you had gathered rather than you person experience.

Yes, establishing a beginning and end is easier if done in the beginning.

Yes. The chisel simply squares up the round hole but the chisel provides the greatest resistance.

A little of advise if I may, If not immediately, very soon after you start using your mortiser, sharpen the chisels. LeeValley sells a cone shaped stone for your drill made to clean the burrs out of the inside end of the chisel and sharpen it. Just a little bit does a lot so go easy. Then polish the 4 sides of the chisel at the cutting end. I have a Tormek sharpener and used the leather buffing wheel to polish the outside of the chisel. While this may seem like over kill and especially on new chisels, it will make a great difference in how easily the chisel and bit will plunge into the work.

[loutent]

I've often wondered about this too. Generally I use 1/4 inch for 3/4 stock. But have always thought that 3/8 would be better but then I would only have 3/16 on either side - doesn't seem like a lot of material.

Ideally, probably a 'sloppy' 5/16 mortise with a tenon made to fit is probably just about right.

Lou

[loutent]

Have to agree with Patriarch. In another thread, I asked for help because I was cutting 1/4 mortises with my new Delta benchtop machine. After 6 mortises, the bit snapped.

On review/input etc, I discovered that I was taking TOO LITTLE material with each additional plunge of the bit. The auger may not grab enough material if you attempt only a half-plunge. This deflects the fragile 1/4 bit enough to snap it. Happened to me.

Larger bits may not be as fragile of course.

I found it better to take 'almost' full, overlapping cuts but proceed more slowly. See the Wood magazine article from May (I think).

I'm getting a better 1/4 chisel/bit set for sure.

Good luck.

Lou

[Andy Dingley]

Not really. Morticing machines are basically drills, with a chisel edge to clean the holes square. If you don't have the centre of the drill bit supported, cutting performance can suffer greatly. Cutting

2x chisel width is easy, but less than 1.5x is hard.

Some machines and chisels are more tolerant than others - particularly single spur augers, and those with augers that fit tightly into the chisel.

[Lazarus Long]

You'll want to take full cuts with the bit. Smaller cuts, like the one you propose will flex the bit resulting in a broken bit or a mortise wall not perpendicular to the bottom (or top)

Polishing the outside faces helps a lot with getting the chisel into the wood, as does sharpening the edges with a conical stone.

D>A question about mortising machines and bit usage. For cutting something

[Leon]

The smaller 1/4" bits tend to be fragile. I recall reading several counts in which the 1/4"ers did in deed fail more often in general. Seems many makers of small bits make them with only 1 fluke. The bit is basically destened to be fragile to begin with. The single fluke threw everything out of balance and were easily broken. Great care had to be taken regardless of the cut to prevent breaking the bit.