Saw Pitch (with Maths)

[Jonathan Board]

Hi All

I'm a little confused by the advice to select saw pitch to match stock thickness by keeping between 5 and 7 teeth in the cut.

A little mathematics and excel magic lead me to the following:

Stock Thickness	Length of Cut	5 Teeth in Cut	6 Teeth in Cut	7 Teeth in Cut
1/4	1/3	14 1/2	17	20
1/2	5/7	7 1/2	8 1/2	10
3/4	1	5	6	7
1	1 2/5	4	4 1/2	5
1 1/4	1 3/4	3	3 1/2	4
1 1/2	2 1/8	2 1/2	3	3 1/2
1 3/4	2 1/2	2 1/2	2 1/2	3
2	2 5/6	2	2 1/2	2 1/2
2 1/4	3 1/6	2	2	2 1/2
2 1/2	3 1/2	1 1/2	2	2
2 3/4	3 8/9	1 1/2	2	2
3	4 1/4	1 1/2	1 1/2	2
3 1/4	4 3/5	1 1/2	1 1/2	2
3 1/2	5	1 1/2	1 1/2	1 1/2
3 3/4	5 1/3	1	1 1/2	1 1/2
4	5 2/3	1	1 1/2	1 1/2

Looking at the Disstonian Institute webpage for the D-8, it seems that the coarsest rip saw Disston made was 2 1/2 TPI (suitable for 9/4 stock) and the finest saw was 6 TPI (suitable for 3/4 stock). Personally, I've never found a 28" rip saw this coarse or with anything other than 4 to 5 TPI, so what did people use to resaw thicker stock?

Also, most modern woodwork bloggers suggest that a range of 5 to 8 TPI is ideal for fine woodworking needs which suggest working material in the 4/4 and 2/4 range. Have I misunderstood the logic of this, is the rule wrong, do people not re-saw any thickish stock or do people just accept that sawing thicker stock will be slower and take more effort?

Lastly, the recommendations for cross-cut saws tend to be finer still, in the 7 to 10 TPI range; why do we break the #teeth rule for cross-cuts? I understand that the cut will be finer but it will also be slower and harder, isn't adjusting the rake and fleam (and set?) sufficient to change from separating the wood fibers (Rip) to dividing the wood fibers (CC)?

Thanks in advance for your comments...

[Patrick Chase]

Hi All

I'm a little confused by the advice to select saw pitch to match stock thickness by keeping between 5 and 7 teeth in the cut.

A little mathematics and excel magic lead me to the following:

Stock Thickness	Length of Cut	5 Teeth in Cut	6 Teeth in Cut	7 Teeth in Cut
1/4	1/3	14 1/2	17	20
1/2	5/7	7 1/2	8 1/2	10
3/4	1	5	6	7
1	1 2/5	4	4 1/2	5
1 1/4	1 3/4	3	3 1/2	4
1 1/2	2 1/8	2 1/2	3	3 1/2
1 3/4	2 1/2	2 1/2	2 1/2	3
2	2 5/6	2	2 1/2	2 1/2
2 1/4	3 1/6	2	2	2 1/2
2 1/2	3 1/2	1 1/2	2	2
2 3/4	3 8/9	1 1/2	2	2
3	4 1/4	1 1/2	1 1/2	2
3 1/4	4 3/5	1 1/2	1 1/2	2
3 1/2	5	1 1/2	1 1/2	1 1/2
3 3/4	5 1/3	1	1 1/2	1 1/2
4	5 2/3	1	1 1/2	1 1/2

Looking at the Disstonian Institute webpage for the D-8, it seems that the coarsest rip saw Disston made was 2 1/2 TPI (suitable for 9/4 stock) and the finest saw was 6 TPI (suitable for 3/4 stock). Personally, I've never found a 28" rip saw this coarse or with anything other than 4 to 5 TPI, so what did people use to resaw thicker stock?

Also, most modern woodwork bloggers suggest that a range of 5 to 8 TPI is ideal for fine woodworking needs which suggest working material in the 4/4 and 2/4 range. Have I misunderstood the logic of this, is the rule wrong, do people not re-saw any thickish stock or do people just accept that sawing thicker stock will be slower and take more effort?

Lastly, the recommendations for cross-cut saws tend to be finer still, in the 7 to 10 TPI range; why do we break the #teeth rule for cross-cuts? I understand that the cut will be finer but it will also be slower and harder, isn't adjusting the rake and fleam (and set?) sufficient to change from separating the wood fibers (Rip) to dividing the wood fibers (CC)?

Thanks in advance for your comments...

The 5-7 thing is more of a lower bound, by which I mean that you don't want fewer teeth than that engaged because doing so will lead to rough cutting and binding. It isn't really an upper bound - when you use a finer-toothed saw all you really leave on the table is some potential speed.

[Jonathan Board]

The 5-7 thing is more of a lower bound, by which I mean that you don't want fewer teeth than that engaged because doing so will lead to rough cutting and binding. It isn't really an upper bound - when you use a finer-toothed saw all you really leave on the table is some potential speed.

Ah! I see. How far can you push this? That is to say, what is the thickest stock that can be efficiently cut with a 5TPI rip saw and how much slower do things go as stock thickness increases?

[Brian Holcombe]

I can cut up to 3-4" stock fairly well with a 4-5tpi saw. It's starts to get very slow over that range.

[Jonathan Board]

I can cut up to 3-4" stock fairly well with a 4-5tpi saw. It's starts to get very slow over that range.

Thanks for the feedback Brian.

So, if a 4 TPI saw can rip up to 3-4" stock, what's the reasoning behind upp-ing the tooth count when cross cutting wouldn't that slow things down even further? Is it because the cross-cuts are generally pretty short and you don't want to mess up the end grain?

[Brian Holcombe]

It's totally different. Crosscutting is shearing the fibers, where rip cutting is more like many micro planes making a groove. The reason why you only want so many teeth in the cut is that the gullet will fill with sawdust, the long it's in the cut the more dust will fill the gullet eventually stopping it from cutting. Few TPI means larger teeth and larger gullets which can carry away more wood.

[Jim Koepke]

Howdy Jonathan and welcome to the Creek. Your location isn't indicated in you profile. You may be near another member who has a lot of saws they would be willing to let you test drive to see what all this is about.

For my own situation I have cut railroad ties with a 6pt saw. It was slow, but there is a technique of lifting the saw to clear the gullets.

The longer lumberman saws with the deep teeth and raker teeth would be better for such a thing.

When it comes to normal crosscut work consideration toward the quality of the finished cut is the guiding factor. The more teeth on the saw, the smoother the finished cut tends to be. For my average work a saw with anywhere from 7 to 10 ppi is used. When I want a smooth finish a 15 ppi saw is used.

For ripping I like my 6 ppi saw. I did have a 4 ppi rip saw that bound in a cut and now I have a much shorter saw and a piece of saw blade to use for making scrapers.

jtk

[Jonathan Board]

So, to sum up - when rip cutting:
- 6 teeth in the cut prevents the saw from binding and is the coarsest you want your saw
- There is an upper limit (is there a rule?) which allows the saw to cut without the gullets clogging and is the finest you want to go.

[Jim Koepke]

So, to sum up - when rip cutting:
- 6 teeth in the cut prevents the saw from binding and is the coarsest you want your saw
- There is an upper limit (is there a rule?) which allows the saw to cut without the gullets clogging and is the finest you want to go.

For me, a 6 point rip saw is fine. For others it may be more or less ppi.

The rule is each person has to find what works best for them.

Take a look at http://www.vintagesaws.com and check the library. The page on sharpening will explain some of the finer points of saws and tooth counts.

I have not seen the 'maths' you listed or the idea of how many teeth should be in the cut.

Makes me think of the phrase, "ignorance is bliss." Not knowing about these 'rules' may be why things that shouldn't work seem to work fine for me.

jtk

[Jonathan Board]

Thanks Jim

I agree, ideally I'd experiment with a range of saws over a period of time and work out what's right for me but I'm ploughing my own furrough down at the bottom of the world (New Zealand) and when I start talking rip saws people tell me to get a table saw.
I've scoured the flea markets for old Disston saws and I've got four 26" saws that I'm in the process of rehabbing into "rough" and "fine", rip and cross-cut saws; currently they mock me from the box under my sharpening station because I can't commit to toothing pattern.
I will admit to over-analysing subjects like this but I think it's good to understand where these rules of thumb come from so that you can make a more informed first guess.
If you'd asked me last week, I'd have told you that I would be filing the saws 5 TPI Rip, 7 TPI CC, 8 TPI Rip and 10 TPI CC but now I'm not so sure.
I have an idea to use progressive pitch and let the saw file guide my range of TPI but of course no two woodworkers can agree on which range of teeth a particular saw file files.
Adam Cherubini makes a 24-28" Saw with 3-5 TPI progressive pitch and handily Mike Wenzloff recommends a 7 Slim for exactly this range of teeth so I might start out with that.

[Patrick Chase]

I have an idea to use progressive pitch and let the saw file guide my range of TPI but of course no two woodworkers can agree on which range of teeth a particular saw file files.
Adam Cherubini makes a 24-28" Saw with 3-5 TPI progressive pitch and handily Mike Wenzloff recommends a 7 Slim for exactly this range of teeth so I might start out with that.

I wouldn't recommend progressive pitch to somebody just starting out with saw-filing. If you go down that route you'll be messing with so many variables at once that it will be harder to diagnose any issues that may crop up with basic stuff like rake and set.

I'd pick a "beater saw" or two (if you're not willing to sacrifice any of your 4 Disstons then get another), pick a toothing for each, and go with that. It won't take that many tries to get a rough idea of what you like, and then you can start getting fancy.

[Jim Koepke]

I haven't done this myself, but I have thought of experimenting with making a saw at 5 ppi. If it was to aggressive it should be easy to joint the teeth and refile it to 10 ppi.

BTW, my recollection is that TPI (Teeth Per Inch) is measured from valley to valley and ppi (points per inch) is measured point to point.

The other consideration is to just buy every cheap saw that comes your way to see what you like.

I did have a coarse 4 ppi saw. It was a little faster than my 6 ppi saw, but a lot more effort was required. A bit of hard work can tire a person. A lot of steady easier work can keep one going longer and getting more done. Of course this doesn't mean as much go the young folks among us as the old, out of shape folks like me.

jtk

[Patrick Chase]

BTW, my recollection is that TPI (Teeth Per Inch) is measured from valley to valley and ppi (points per inch) is measured point to point.

jtk

Valley-to-valley and point-to-point will return exactly the same result. Think about it - the valleys are spaced at exactly the same distance as the points by definition.

Both TPI and PPI are measured point-to-point (or valley-to-valley if you prefer, it doesn't matter). The distinction is whether you count the last point or not. Consider a saw with 7 teeth per inch. This means that if you put a ruler to it with the first point at 0, then the 8th point will line up with the first inch mark. If you don't count that 8th point you get 7 TPI. If you do count that 8th point you get 8 PPI. PPI is always TPI+1. It's that simple.

I personally find PPI utterly pointless (pun intended). TPI is the only true measure of pitch, in the sense that taking the reciprocal gets you the point-to-point spacing, which is what really matters.

[Chuck Nickerson]

Hi All


Lastly, the recommendations for cross-cut saws tend to be finer still, in the 7 to 10 TPI range; why do we break the #teeth rule for cross-cuts? I understand that the cut will be finer but it will also be slower and harder, isn't adjusting the rake and fleam (and set?) sufficient to change from separating the wood fibers (Rip) to dividing the wood fibers (CC)?

Thanks in advance for your comments...

An additional point I didn't see covered above (skimmed some of it): a crosscut saw actually cut two parallel kerfs which end up joining together and becoming one. That's why you'd want more teeth in the cut: for a while it's two kerfs.

[Luke Dupont]

Whilst I haven't all that much experience yet:

I actually find my rip saws (okay, all bow saws) that are 9-12 tpi rip 3/4" (4/4 that has been planed/surfaced) stock much quicker than the 6tpi rip saw I have. I've found teeth on the slightly finer side to be faster.

I have a slight suspicion that sawdust clogging up the kerf is more of an issue with crosscuts than rip saws. Whilst I haven't ripped stock much more than 3" before, I've never found that I had much if any issue with sawdust clogging up the kerf.