Thoughts on Kerf Width

The current push in dovetail saws is for the narrowest kerf you can get away with. My dovetail saw has four thousandths of an inch of set, which is a hair less than the thickness of a sheet of copy paper. That's not a lot.
Reworking the Crappy Crown Gent's Saw got me thinking about kerf because when I finished filing it the first time the kerf was still far too wide, I thought.
I did the test cut and the cut was fast, effortless and straight, but it was wider than I wanted.
Now I'm wondering about the effect of kerf on joinery.
Where you have two cuts forming an angle of significantly less than 90 degrees, a wide kerf will give you a poor corner. Either you will have a groove in one kerf wall, or you will have a slightly rounded inside corner. The narrower the kerf the less effect there is.
However, when doing something like a dovetail, the wider the kerf the easier it is to release the waste when chopping it out. The waste won't wedge as easily - you have more room for the chisel.
When cutting in general, the less kerf you have the harder it is to steer the saw, however having too much kerf is a poor choice, as you need to expend too much energy keeping the saw cutting straight.
The minimum amount of kerf is dependant on the wood being sawed, the depth of the saw blade, and desired radius of cut, when cutting curves. Green softwood requires a great deal more kerf than dry hardwood, a panel saw requires more kerf than a bow saw, and a turning saw requires more kerf than a dovetail saw.
I don't know if there is a magical formula out there where you can punch in your requirements and it tells you the proper kerf to use. I suspect most manufacturers just use traditional values as a basis point and modify it as required.
More mulling on this matter is required, but I'm starting to wonder if striving for the narrowest kerf is the correct path.

New Life for an Old Saw

I have an old Crown Gent's Saw that I bought new a long time ago (15-20 years) and never liked. It's got far too much set, won't follow a line, and basically cuts terribly. When I got it I had no idea how to fix up a crappy saw, so I threw it into a box and forgot about it. I found it a while back, but now I have good saws that I love so I had no intention of putting any effort into this saw. It could stay in the box.
Recently a thread started on the Canadian Woodworking forum that included the notion of refurbishing a Crown Gent's Saw. A suggestion that I made was not taken gladly by some, so I've decided that I will refurbish my own elderly Crown Gent's Saw in the interest of proving the point that the method works.
First, the saw. Here it is in its crappy glory.
It will be refurbished into a dovetail saw, so for that it will need a rip-pattern tooth form, and it needs to have its set radically reduced. First, reduce the set. Take a pair of hardwood blocks and lay the saw between them. With raps of a hammer you can squeeze the teeth together to reduce the set. Depending on the size of your blocks, it can take a surprisingly hard hit. Below is the setup that I used for reducing the set. A chunk of red oak (would have preferred something harder) with another piece of red oak as a 'punch'.

Once the set was reduced it was time to file. I put the sad saw in the saw vise and got out my smallest saw file - brand-spanking-new. Only the best for the crappy old Crown Gent's Saw. :)


Now to file it to a rip cut. First I ran a mill file over the top to joint the saw. Not that I expected the jointing to be off... this saw had never been sharpened (or used, really) so the teeth should be in factory condition, but by taking a light jointing pass I can more easily see where I am in the filing process. After filing the saw I tried it out. I had done two test kerfs in a piece of white pine before starting on refurbishing the saw. The test board can be seen below. The two 'before' kerfs are each the result of 50 strokes of the saw. The 'after' kerf is the result of only 12 strokes of the saw, and I had to stop because the spine had hit the top of the board and I could go no deeper. The saw now cuts fast and straight, and all for about 20 minutes of effort. If I had it to do over again I would have done some more beating on the wooden blocks to reduce the set even more. The last kerf in the test board is from my Medallion dovetail saw. Only 8 strokes. Nice. Much longer saw, though, so it has a bit of an advantage, there.


Anyway, that was my refurbishing of a Crown Gent's Saw. It's not hard, so if you have one that you hate then have a go at fixing it up.