Questions answered - Recutting saw teeth

Q:

Paul,

I just bought a Disston 14"tenon saw on ebay the teeth are in bad shape i will have to cut new teeth. I was wondering if 12 ppi would work as well as the original 14 ppi. Thanks Paul, I always enjoy your blog, great information.   Also building a new bench per your book. Thanks again,

Dennis

A:

There are some issues here, Dennis. We should be entering the realms of fleam cut and ripcut here.  When teeth get larger we obviously have less teeth per inch run of saw. The larger the teeth the nearer we come to shaping the teeth to a fleam cut. 12 ppi can go either way and a ripcut pattern will work fine for tenon cheeks and other with-the-grain cutting, but not always so for many if not most crosscutting aspects of the same joints and so this will automatically necessitate a second, smaller-toothed saw for crosscutting shoulders. Not really a big deal as generally we tend to keep a small saw to hand too. The problem lies more with large tenon cutting in coarse-grained woods such as oak, where the large teeth tend to tug and rip at fibres when used on any crosscutting work; rather than severing. As most tenon saws are sharpened to a ripcut pattern, you will definitely need a second saw and especially is this so for large work. On the other hand, restoring a 14-16ppi pattern size will enable you to do what most people do and that is sharpen with a progressive ripcut pattern that cuts both with and across the grain using only a single saw. Alternatively you can put a passive rake on the teeth, but then that compromises the power of the ripcut, which is not what you want for tenon cutting at all.