chisel vs saw

[Alexis]

I know that every timber framer seems to have a love relationship with his chisel... but I find that I can make better joint by using my japanese pullsaw instead of my chisel.

I do the cross cut and the rip cut for the tenon to the line with my saw... the quality is better than with the chisel and the dimension are exact to the 1/16...

Is there others that do that or is it a sacrilege?

Alexis

[Brad_bb]

To the 1/16th?  1/16th is a huge noticeable gap in a visible joint.  A chisel is used to get that joint to 1/32 or less preferably, by shaving until it's on the money.  This is especially true with mill rule layout where joints are more exposed.  Housed joints will hide more of course, but even so, many timber framers are in the pursuit of "perfection and grace".  It's not about just getting it done, or getting it done quickly, it's about how well you do it, with perfection and grace, that gives us satisfaction and puts a smile on our face. (Words borrowed from my timberframe teacher who borrowed them from Olympic skier Jean Claude Killy).

[witterbound]

I really like to use my japanese pull saw to finish tenons that I've started with the circular saw.  I always finish with a chisel and plane, but the pull saw saves me a lot of time cutting tenons. 

[Alexis]

of course, I aim for perfection when cutting my joint
when i say 1/16, it's the worst difference i found when using the pullsaw but a lot of time, it's right on!
Like I said, I aim for perfection but the result isn't...

[moonhill]

Brad, I remember the Jean Claude story, even before that it was a practice of mine, preparation for the act. 

If I am going to be a 1/16" off it is going to be in the negative direction, the joint will fit.  I finish every thing with the slick, there is exceptions to every rule, though, shoulders are one of them, you won't see me paring the shoulder very often. 

Tim

[witterbound]

Just remembered, I also like to use the pull saw to cut the sides of a housing lies on the edge of a timber (as opposed to one that is centered).  I find that using the pull saw to cut the sides, and then make a few kerf cuts, really speeds things up for the chisel work that follows.

[Jim_Rogers]

Every timber framer has to develop a method to get it done correctly. However it is done as long as it is done "right" really doesn't matter.

Some methods are faster than others.

Some methods are less accurate then others.

You can do what works for you, but in most cases that I've seen here in my sawmill yard when someone used a saw, they cut off too much and then we had to redo the joint.....

Using a saw to cut away most of the wood is good as it gets rid of the bulk fast and easy. But I still pare to the line for accuracy. If the saw has done it's job right then there isn't much to pare and it shouldn't take long.

Also, paring to the line allows you to create the correct shape of the joint in order to compensate for future shrinkage and this can be important to someone when constructing a fine frame for a house.

If it's just a shed or outbuilding that's one thing, but if it's a show piece house that's something else....

Jim Rogers

[swampfox]

Can you explain this further please,

"Also, paring to the line allows you to create the correct shape of the joint in order to compensate for future shrinkage"

[Jim_Rogers]

I can but not today, I have to leave now for an afternoon meeting.

[routestep]

I generally saw out a tenon, mostly with a power saw, but sometimes with the handsaw if no electricity is available. I'm more accurate with the handsaw.

I find that when chiseling out a tenon the woods grain is very important to know. I end up putting in saw cuts to act as a stop in case of a diving tendency of the grain.

Also I have seen tenon twist on me over time and have had to plane them to fit their mortises. I guess I should just work faster on my projects.

[Alexis]

routestep,

do you mean the shoulder cut or you do both cuts with the saw, the crosscut and the rip-cut.

Alexis

[Raphael]

I love my japanese handsaw, I've even learned to make it cut some of those shrinkage contures that Jim mentioned.
I use it for both shoulders (crosscuts) and tennons provided the rip isn't excessively long or wide.

But one things for sure, it won't clean out a mortice or pare slopes for wedges or clean out the tight corners in lapped dovetails.  ;)


The advantage of a chisel is it's immense versatility.

[routestep]

Alexis, sorry it took so long to post a reply. I've been in the woods, mostly fighting ticks it seems.

I have cross cut and rip saws and use both types all the time for cutting tenons. I have them sharpened on a fairly regular basis. I use push saws only and they have to be sharp or I'll wear down.

I aim to split the line and then check both ends of the beam to make sure the tenons are in-plane. I'm currently working with oak timbers that have air dried for some time now. Most of them have a twist (I think that all nut woods are susceptible to twist), some have a significant twist and almost all have shrunk down in size. The shrinkage is not a problem but because of the twist in the wood I use chalk lines. If I didn't I would never get a tenon in plane and keep the tenon on or close to its required thickness (2inches or 1.5 inches).  It takes some more time, but my layout lines generally come out right on the money or very close to meeting as I go around the timber.

When I use green wood it always shrinks. I suspect that the mortise shrinks about the same amount as the tenon and keeps the tenon fairly well fitted, maybe the shoulder could open up a gap if not for the peg. As I said above the problem I find is when enough time has past for the wood to twist, then the tenon will need some persuasion to fit into its mortise, or the tenon gets planed down a little. If you can work fast, on a small frame or have some help the frame could be up and locked in place before a twist could happen.

[Piston]

Can you explain this further please,

"Also, paring to the line allows you to create the correct shape of the joint in order to compensate for future shrinkage"

I'm sure I can't explain this anywhere near as good as Jim can, and he can probably even show it in one of his fancy drawings he has.  But I believe he is probably referring to paring down slightly more in the center of the joint than towards the outside.  This is because as the joint dries tangentially the center will end up even with the edges, as opposed to if the joint was cut straight across and then dried tangentially, the outsides (corners) would show much more of a gap. 
Without a picture its hard to explain, but picture looking at a squared off timber from the end, as if your standing at one end of it looking down the length of the timber, if you were to allow the timber to dry, it would be slightly out of square because the 4 corners are shrinking more than the 4 centers (top, bottom, left, right)
Now I'll let Jim chime in and actually give a GOOD explanation of this.... :D

[Jim_Rogers]

You know I forgot to post something about that.

But Piston has explained it about as good as I could have.

As mentioned the timbers are going to dry out, and the joints will open up because of this.
Pre-planning for this helps to reduce the amount it will open up and show.

In Jack Sobon's book, "Build a Classic Timber-Framed House" on page 88 he shows the photo below:



And the caption reads: "The housing should be scooped out towards the middle to allow for shrinkage".

And he describes the process on page 87 in the right hand column, and I quote: "To create a surface that will be flat when the timber has seasoned, you must actually hollow the green timber, which is when the chisel or slick with a slightly curved back is necessary. On white pine, I hollow the shoulder between 1/16 and 1/8 inch, but use more for wood with higher shrinkage rates. Without this hollowing, there will be gaps when the timber dries."

There is also another picture on page 91 in the lower right hand corner, showing a hollowed out housing.

A lot is said in these few sentences and it takes a while to understand and see how it will effect the joints in a frame.

I hope that has helped you to understand shrinkage, but if not ask specific questions.

Jim Rogers

[swampfox]

thanks for coming back to that.

i guess i was a little confused because the thread talks about shaping the timber with tommy tenon and not about shaping the timber with molly mortise.  that makes good sense to scallop the housing.  i thought you all were talking about scalloping back the shoulder.  this doesn't help does it?

as far as the chisel vs. saw....  two different tools.  sorta like sugar ray vs. mike tyson.

[Jim_Rogers]

The shoulder at the tenon is sometimes not cut totally at 90°. I sometimes cut it a little more so that when the wood at the surface of the timber dries more then the wood in the middle of the timber the shoulder will be 90°.

You sort of under cut it.

I suppose I'll have to produce a drawing to show what I mean......

Jim Rogers