What have we lost?

With the yard sale and flea market season now in full swing, old rusty tools shake off their dusty winter coats and wander out into the warm sunlight once more in hopes of finding a new home. Each Saturday morning in New England dawns with the promise of finding one of these long-lost treasures.

Last week, on one such morning, I stumbled across this apparently common table saw blade from a nest of saws in the bottom of an old tool chest…

I was first struck by it as the etch was very bold and it looked little used. As I picked it up to get a closer look at the etch, I then noticed what I first thought was a terrible sharpening job, but soon revealed itself to be a strange hybrid tooth geometry.

As soon as I got a chance to look more closely, I realized that this was no hack-sharpening job…this was a very deliberate filing…

It seems that the teeth are filed in groups of 2 + 5, meaning that there are two stout teeth followed by 5 finer teeth. The only difference I can see from the 2 teeth to the 5 is the degree of rake…the 2 teeth are more aggressively raked than the 5 teeth. This pattern repeats itself for the whole length of the saw…2 stout, 5 fine, 2 stout, 5 fine, etc, etc. You can see this very clearly in the picture above.

So what the heck is this all about?

The filing does appear to be factory original…meaning that this was the way the saw was filed by the Disston factory. The teeth are perfectly jointed and the fleam is very consistent on all of the teeth. Further, the saw has seen very little use…I know this because the blade is arrow straight (table, keyhole, compass and all narrow bladed saws are invariably found bent and kinked) and the etch is as bold as the day it was made.

If in fact the filing is not original and was filed by the owner, it was executed with such fine precision that it must have been done by a master filer, so that further suggests it was most deliberate. Either way, factory or custom, this tells us that someone very learned in the art of saw filing intended this tooth pattern….so there must be an advantage to it.

As I further inspected the saw, I tried to understand how this filing would benefit a table saw…

Table saws are intended to cut gentle curves in table tops and similar patterns, hence the narrow blade to follow a curved line. This means that in the wood, the teeth encounter grain parallel to the line and across it and thus make ripping and cross cuts. So does this strange tooth pattern help make both types of cut? Perhaps the aggressively raked teeth are intended to rip more effectively? But then why not file them straight across like true rip teeth?

I’ve never seen teeth like this before on a hand saw, and I’ve never read about them either. Disston and other saw makers patented many hybrid tooth patterns to improve the function of their saws…perhaps this is one more?

As I wonder about these odd teeth, it makes me think of what other knowledge of saw filing we’ve lost to history, perhaps never to find again.

In a way, we are starting over in this hand tool renaisance…we are reading Moxon and Roubo and Nicholson….all long dead. What secrets of working wood by hand died with them? Will we ever discover these secrets again?

What else have we lost to time and technology?

-Matt

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Published in: on June 11, 2011 at 9:08 pm  Comments (16)  

Rake and Rip saws…

The first time I got my hands on a proper rip saw was, unfortunately,  a bitter-sweet experience.

It was sweet because it was the first moment of the rest of my woodworking life….like a door had been opened to a place that was fun, fulfilling, and free from the threat of lung cancer and systematic dismemberment. But it was bitter because I was frustrated with the performance of the saw….and just so you know, the saw wasn’t from Home Depot or Ace Hardware. The saw was a vintage Disston D-8 with a thumbhole from the classic 1896 to 1917 era…we’re talking about the greatest rip saw ever made by human hands. And it was professionally sharpened by a well-respected saw guru. So what was the problem?

Well, the saw was gorgeous, perfectly tuned, sharp as English wit, but to my inexperienced hands, every time I stroked the saw through wood, it was not a pleasant experience. The teeth felt like they were sticking in the wood…and like I had to push really hard to get them to cut. I could feel the moment each tooth sheared a chunk of fibers from the board, and that feeling reverberated from the teeth, to the saw plate, to the tote, to my palm, and up my arm to my shoulder. It was jittery and rough and un-nerving. And I was pissed.

What the hell?!?!? This was not the zen like experience I had read about in the pages of books and magazines…this was a hands on demonstration of why people started the asinine folk art craze of painting on hand saws instead of using them!!!

Well, like most things in life, it turns out knowledge really is power. And in this case, the knowledge I didn’t have about rip saws was disempowering me to use them. What I quickly learned was that hand saws, much UNLIKE powered saws, require an intimate knowledge of their form and function to use properly.

Any toothless caveman can go to Home Despot, buy a $99 table saw, plug it in, and be ripping white oak all day long like he was Norm Abrams. But to do so with a hand rip saw requires knowledge of the physiology of wood, body mechanics, and saw tooth geometry.

So which one was I missing?…..the one about saw tooth geometry, and in this case, that was the most critical absence. You see, what I did not yet understand about rip saw teeth was the fundamentals of tooth rake. And the rake was what was making this saw cut like a jack hammer.

Rake, or “pitch” as it also is traditionally called, (not to be confused with the common, modern designation of pitch meaning tooth spacing) is the measure in degrees that the face of each cutting tooth is rotated back from 90 degrees relative to the tooth line. The illustration below (from Disston and Sons “Lumberman Handbook”, 1907) demonstrates two different rakes….

In the first image is shown a saw with 0 (zero) degrees of rake. The face of each tooth is 90 degrees to the tooth line, and in effect not raked forward (like Japanese saws) and not raked backward.

In the second image is shown a saw with 12 (twelve) degrees of rake, meaning that the face of each tooth is rotated back 12 degrees from vertical (90 degrees from the tooth line).

So, what’s this have to do with how a saw cuts? Lots. And lots. And….well, you get the idea. Which is this: the greater the teeth are raked back from vertical, the less resistance the teeth encounter as they cut the wood. So teeth with zero rake–meaning the cutting faces of each tooth are 90 degrees from the tooth line–will cut more aggressively and meet with more resistance than teeth that are raked 5 degrees back from vertical (relative to the toothline). Make sense? Good.

I should also point out that the more teeth are raked back, the less aggressively they cut. So before you go and file 25 degrees of rake into all your rip saws, you should know that by doing so, you’re effectively turning them into giant bread knives. Not good for wood!

So, can you guess how much rake was on the teeth on that fortuitous first D-8?

Zero degrees. And if you’re paying attention at home, you now know that means that the face of each cutting tooth was 90 degrees from the tooth line…just like in the first illustration above.

And that’s why my first nice rip saw–though perfectly tuned and filed with a precision that would make even ole Henry Disston proud–made me want to call the guy I sold my table saw to and beg him to sell it back to me!!!!! But I didn’t give up. In stead, I started filing my own saws and here’s what I figured out…

The reality that I discovered about rip saws, is that there’s a sweet spot relating to the rake of the teeth. And by that, I mean you have to strike a balance between relaxing the rake to cut smoothly, and still have it be aggressive enough to actually do some work. For me, that sweet spot is about 5 degrees of negative rake for most saws with 6 or 7 points per inch, and about 5 to 10 degrees for more course toothed saws. You can play with the range of rakes, but anything much past 10 and you start to lose a lot of performance from your saw.

The other important point to mention here is that I work mostly with hard woods, and hard woods are the ones that respond nicely to a little relaxing in the rake department. If all I was ripping was white pine and even a little poplar, I’d probably be okay with zero rake rip saws. But the truth is, I work a lot with white oak, maple, cherry, locust, walnut, etc….some very hard woods. And believe me….a little relaxed rake goes a looooooonnngggg way. Those 5 little degrees that each tooth is swept back turn them into sweet little stanley #80 scraper blades….very nice! As opposed to zero rake teeth, which act more like a dull scrub plane iron on end grain. Ch-ch-ch-ch-chattering teeth anyone???

And just in case you’re curious, here’s some pics to illustrate…

First, is a 5 and 1/2 point saw with zero rake…given the tooth spacing and rake of this saw, I can comfortable rip pine, fir and poplar…

And here’s one of my favorite rip saws….a Wenzloff 5 point with 10 degrees of negative rake….and she is a sweet ripper! This is the saw that I used to make TheBigRip. Mike Wenzloff, smart guy that he is, recommended this rake and damn if he wasn’t right as rain. 🙂 I use this saw to do all of my heavy ripping…anything 8/4 and up in white oak and the like….

So, that’s the skinny on rip saws and rake. I encourage you to pick up a few and check out the rake, start filing and never stop trying new things.

I have to remind myself every day that this slippery slope of hand tool work is littered with unsolved mysteries and long-lost skills begging to be rediscovered.

Here’s to the next revelation!

-Matt 🙂

Published in: on March 10, 2011 at 9:05 pm  Comments (17)  

T.P.I. vs P.P.I.

If you’re like me and you find yourself falling further and further down the rabbit hole we call hand tool woodworking, then you no doubt have a laundry list of questions that are waiting to be answered by the long deceased hand tool deities. So, it can only be expected in my quest to revive the once grand love and labor of hand sawing that my list includes everything from how much set should a hand table saw have to what the heck did they do in the “jimping room” at the Disston factory?!?

One such question that was on my list for a while was the difference between the traditional English pitch measurement, and the American measurement. Pitch, in case you are wondering, is the number of teeth that a hand saw has per inch and is given in two different standards: teeth per inch (TPI) is the traditional/British measure and points per inch (PPI) is the American gauge.

It’s fairly simple to determine the difference between the two (we’ll get to that in a minute) but it is entirely another animal to know what gauge a person, sawyer, or even saw smith is using with certainty, because I found many people using the two gauges interchangeably. And even more annoying, I found that very well versed people would do so. Just because someone said 6 ppi didn’t matter because they could in fact be measuring full teeth and not in fact the points as ppi would indicate. And just so you know I’m not harping on insignificant details, I’m referring to major hand tool retailers, makers and users….and in situations where they were describing goods and services (and no, I’m not talking about the Home Depot website…I’m talking our people here!)

So, in case you’re like me, and you long for accurate language, then here’s a quick tutorial of what I’ve learned and how to gauge the pitch of a saw:

Teeth per inch (TPI) is the traditional method that Englishmen brought over from the old country. When measuring the teeth, you measure from gullet to gullet, and count only the number of full teeth in one inch. I like to imagine the teeth as little mountains…only count the mountains that have a full left face, peak, and a full right face. I use little brass calipers to make it easier.

Now, points per inch (PPI) on the other hand, is a measure of only the peaks, or points, of the teeth and NOT the full tooth including the left and right face. Because PPI only measures the points and not the full teeth, there will always be one less tooth than points. So a 6 PPI saw and 5 TPI saw are one in the same. American makers like Disston, Atkins, etc., actually stamped the pitch of their saws on the heel…that’s what that number under the handle is…a measurment of the saws pitch, or PPI.

How about some pics to demonstrate…

Here’s a pic of a 4 TPI rip saw…

See how the calipers measure from gullet to gullet and show 4 full teeth?  That’s the 4 “T” in 4 TPI.

Now here’s the exact same saw, but measured in “points”…

See how the calipers measure from the point of one tooth to the point of another tooth in one inch? When you measure this way, you pay no regard to gullets, the faces of the teeth, or anything…just the points. That’s how to gauge PPI. That means this saw is 5 PPI. And if you’re following along at home, you now know that 4 TPI = 5 PPI.

So you see how things can get confusing, right? Here we’ve got the same saw measured two different ways and having two different pitches. The problem in converting from one to another…as you often have to do when buying an English saw…is that you don’t actually know for sure if the measurer used one method over another based solely on the number. What I mean is, its not like converting yards into meters, where the number changes by some small fraction and gives the conversion away (like 1 yard = 0.9144 meters). This is what I was running into in catalogs, websites and blogs….companies or dealers or craftsman would say PPI, but mean TPI and I had no way of knowing what they actually meant without measuring the darn thing myself!!!!!

Like i said…annoyance. But, then again, it was really a matter of just sitting down and first understanding the real difference myself.

Here’s a couple more examples…

Measured in TPI, this saw has 4 and 1/2. Measured by PPI, it equals 5 and 1/2 PPI.

But (and here’s where it gets a little more tricky) because this saw has no negative rake to the teeth, that means the gullet and the top of each tooth are at the same linear point along the tooth line, meaning that you don’t even need to move the calipers to change gauges. Get it?

 As stated above, 4 and 1/2 TPI = 5 and 1/2 PPI….one less tooth than points.

Here’s one more…

Here’s 2 and 1/2 TPI…

And measured in PPI…

…it’s 3 and 1/2 PPI.

So, figuring out the two methods was an important step forward for me. Its important to be able to refer accurately to a saw’s pitch for learning its function, selecting the best saw for the job, and conversing via internet about a perspective purchase.

Confussed? No worries, apparently, half of the hand tool world is too! 🙂

Happy sawing!

-Matt

Published in: on December 16, 2010 at 8:34 pm  Comments (11)  

The Saw Blog is HERE!!!!

Greetings!!! And welcome to the saw blog! This is the first of many posts dedicated to my love of hand saws….hand saws of all kinds….back saws, rip saws, panel saws…you get the idea! Anyway, without any more to do, lets jump into my first post…

This past weekend I decided to make a HUGE change in my woodworking routine…I decided to sell my table saw…..YIKES!!!!! Now, I know what you’re thinking….”How can you make anything without a table saw?!?!? Won’t your productivity grind to a halt?!??! What about the quality of your work?!??!” I’ve heard it all before, and to the nay sayers, I simply say, “NAY!” The whole purpose of my woodworking hobby is to ENJOY my work, and the reality is that I have always HATED my table saw…..its noisy, dusty, and DANGEROUS!!! So, since I now am able to sharpen and use rip saws to a satisfactory level, I no langer need my table saw.

Have you ever ripped a piece of 4/4 cherry in half with a hand saw? How about 8/4 mahogany? Will I have, and it is pure pleasure….smooth, quiet, meditative even….its just you, your muscle power, the soft munching of wood fibers and the warm apple handle of a gorgeous and supremely functional antique Disston rip saw. Aaaaahhhhhhh! Pure Zen!

Now, have you ever ripped a board on the table saw??!?! Its a pain in the @$$!!! You wrestle the beast onto the table, flip the switch with your knee (a lot of fun in itself, and safe too!!!), and while you;re desperately trying to not cut your fingers off, you get to choke on mounds of sawdust flying into your nose and mouth while the whine and squeel of the blade tears at the wood!!! Hey kids, who wants to get lung cancer AND be an amputee???? Oh, meeeee, meeee!!!!! I do, I do, I do!!!!

So there you have it….from now on, armed with a stable of antique rip saws, back saws, panel saws, miter box saws (the kind that run on YOU, not electrons!!!) I’ll be pleasantly, quietly, and peacefully cutting and working away in my uncluttered, safe, and wonderful wood shop.

Jealous? ;o)

Published in: on October 21, 2010 at 1:38 am  Comments (5)