Hand saw double taper

[Christian Castillo]

Hi, may someone please make clear to me why a double taper ground saw plate was used by the old saw manufacturers? I can understand the benefit of a saw being tapered from top of the saw plate down to the teeth, but I don't see why it would have been beneficial from heel to toe. Wouldn't this make set of the saw also follow the geometry of the taper? Would one have to compensate for this by introducing more set as the saw approaches the toe? I've decided to try my hand at filing a saw and many of now I find myself pondering over these questions.

Thanks for your time, any response will be greatly appreciated.

[David Weaver]

No need to ponder how accurate the saw is with a taper front to back, you're never going to cut accurately enough for it to make a difference. We're talking thousandths of an inch over a saw plate front to back, which creates a minute "error" in perfect sawing, I'm sure more than offset by the flexing of the plate even if you could saw perfectly.

I don't know the reason they're tapered front to back, but I'd bet it helps with balance and I'd bet it reduces the chance of a kink, too, or at least friction.

[Andrew Pitonyak]

Consider a double taper, as you mentioned.

There should be no taper along the cutting edge (teeth). This makes the cutting edge the thickest portion of the blade. Also, the back of the saw (by the handle) is also the thickest portion.

This should prevent the blade from binding in the cut. It makes sense that you may want the blade near the handle to be stiff (rather than blindly tapering from the teeth to the handle), so that you can then have good strength into the handle.

I cannot comment on how well this works in practice.

[David Weaver]

I'm not sure who the first person to race with calipers or a mic will be, but the saw should have thinner plate on the front teeth, and if it doesn't when it's new, it will once it's been resharpened several times or had new teeth cut.

But again, it's such a small amount over the length of the saw that it's really trivial.

I'd really like to see how those saws were ground back when they were mass produced, just out of curiosity - if it was done with stones or what.

I remember seeing something between Jeff at Sharp Tools and Mike W about how Mike W was one of the few people who actually wore a tormek out, but it was because he was using it to grind blades - could that have meant grind a taper on them?

At any rate, the impact of the taper on the amount of saw in the cut would be a fraction of a thousandth of an inch. I don't too often get a fresh sawn edge off a panel saw that doesn't need shot or trimmed, let alone within those kinds of tolerances.

Just know double taper grind is nice in a saw, and appreciate how nice those old saws feel, especially for how cheap they can be gotten. One of the few antique bargains left, and it's changing fast.

[Pedro Reyes]

The only reason I can think of is that binding at the very front excerts the most moment on the saw, making it prone to bending. Any small twist in the stroke would cause the saw to bind, binding closer to the toe matters less since there is less moment.

/p

[george wilson]

Disston had,if I recall correctly,a big,wooden frame machine with a horizontal,large sandstone wheel. A carriage ran the blades back and forth under the grinding wheel. If the saws were ground AFTER being sheared to their tapered shape,there would have been much less metal at the front end of the saw. The wheel would have naturally ground deeper where the less wide blade was. It would have taken a much more precision machine to avoid that happening.

It has been many years since I saw a picture of the old saw grinding machine. Correct me if I'm wrong.

[Christian Castillo]

Consider a double taper, as you mentioned.

There should be no taper along the cutting edge (teeth). This makes the cutting edge the thickest portion of the blade. Also, the back of the saw (by the handle) is also the thickest portion.

This should prevent the blade from binding in the cut. It makes sense that you may want the blade near the handle to be stiff (rather than blindly tapering from the teeth to the handle), so that you can then have good strength into the handle.

I cannot comment on how well this works in practice.

Alright, I just googled a bit more and found some information regarding the amount of taper in a saw plate. Andrew your explanation makes sense and is in line with what the picture I looked at. I wrongly assumed that the taper from heel to toe was also present in the geometry of the tooth line and it isn't. So my worry about a "variable" set from heel to toe is not even an issue. About just enjoying double tapering in my antique saws, I certainly will.

Knowing more about the thought that was placed into my old tools design ,however, help me enjoy them even more. I am amazed into the design, thought, and refinement present in these old wonders.

[Tri Hoang]

I learned somewhere that the taper was added to certain saws to reduce bindings due to them having little set. Those saws use a certain type of steel that is harden & would break if too much set was added on.

Either that or my memory is fading...

[Christian Castillo]

Your memory serves you correctly, while searching for information on the double taper, I came across a study written on saws, specifically the Disston Acme line. I believe that is the saw that you are referring to.

[Jeff Burks]

This article (http://books.google.com/books?id=8dwOAAAAYAAJ&dq=taper%20ground%20saw&lr&as_drrb_is=b&as_minm_is=0&as_miny_is=1700&as_maxm_is=0&as_maxy_is=1930&as_brr=1&pg=PA730#v=onepage&q&f=false) on saws explains what was expected of a properly taper ground handsaw circa 1897.

Disston (http://books.google.com/books?id=bvHNAAAAMAAJ&dq=taper%20ground%20saw&lr&as_drrb_is=b&as_minm_is=0&as_miny_is=1700&as_maxm_is=0&as_maxy_is=1930&as_brr=1&pg=RA1-PA316#v=onepage&q&f=false) Advertisement explaining what to look for when purchasing a quality saw.

The Disston Acme (http://www.disstonianinstitute.com/acmepage.html) saws had a more extreme hollow grinding to allow the saws to cut dry wood with no set to the teeth. Saws were taper ground long before this line was introduced.

[Jonathan McCullough]

My feeling about the second taper grinding is that sawyers at the time the saws were manufactured may have been sawing a greater variety of wood, not the kiln-dried stuff we get today. They may also have been thriftier, and not using table saws or circular saws, they would probably be less afraid of using reaction type wood. But wet wood can heat up, expand, heat up the saw, cause more binding. Reaction wood can close up the kerf on a saw like a big vise. If you're going to kink a saw, it'll always be at the front third. If the last portion of a saw stroke, made by the thicker rear portion of the saw, gives a slightly larger kerf than the beginning of the next stroke, there's more room to maneuver, or if the kerf is starting to bind, more of a margin to prevent binding, and kinking. Yes, the amount is miniscule, but like many things about old saws, a combination of subtle things can make a huge difference. And if .0015" were insignificant, you wouldn't be able to feel something that thin. Makes a pretty big difference fitting pistons to cylinders. Why not saws in kerfs?

[David Weaver]

George - thanks for that bit of information, i suspected it was wheels and a contraption, just didn't know how precise.

I would bet you're right about the slope of the taper increasing as it nears the end of the saw. Might be worth checking on a couple of saws for curiosity.

[Bob Smalser]

Here's a rather frank, old conversation I can no longer find in the archives that I felt portions of were important enough to save. The thread was originally several pages long:



I also don't believe (taper) is necessary….(it was mostly) Disston marketing…wasn't until about 1927 (taper) appears and not until about 1929 was it widely introduced.

Most English saws never were, btw. Aside from why I think it began, a tapered blade on a saw with proper set is unnecessary.

The saw plate is stronger without it, as is fitting a saw that may be called upon for ripping a deeper tenon. In a cross cutting situation, again, with proper set it is unnecessary.

(Nonsense.)

Once Erik von Sneidern accomplished the final testing on Disston blades and found (surprise) they all came out of the same crucible of molten steel, then the primary factor that determined quality was width of the kerf.

Kerf width depends on blade thickness, taper, and polish. The thinner, more tapered and more polished the better. Thinner required more tensioning on the trip hammer, or the saws would kink easily, and kinked saws wouldn't have survived in the numbers #16's do.

As I continue to collect, borrow, measure and use hand saws, the thinnest Disstons made were the #12's and #16's, not the ones Disston advertised as their " very best". In blade thickness and attendant potential ease of use, the #15-#115 Victory and #120 Acme series are merely D-8's with better polish, and in the case of the #120, harder steel.

As fine as the research is by collectors like Erik, none of them except Pete Taran mike blades, and many are prone to repeating Disston's advertising claims about which were the "best" saws.

There is no real difference in thickness and taper between #12's and #16's, Disston's thinnest. Next in blade thickness come the #115's and Atkins #400's and #93's, next come the #120's and D-8's followed closely by the D-23's and D-7's.

I don't have good sample sizes on the Atkins, PAX or Roberts and Lee, but the modern saws equal the D-8 in thickness but with inferior polish.

Ain't done yet by a long shot, but this is the direction I'm heading.

And the other primary saw manufacturers also had equal quality saws, they just aren't as available to examine.

http://www.vintagesaws.com/library/ftj/winter97/w97_4.gif

I'm not alone in contending that taper-ground sawblades are hardly the Disston marketing gimmickry some say they are these days....and that taper plus its attendant requirement for less set makes for cleaner, faster cutting.

http://pic3.picturetrail.com/VOL12/1104763/4007700/124794835.jpg

Before this revelation goes much further, let's measure your best-cutting saws and see how many have taper ground in. Perhaps taper isn't just the providence of either Disston or "best-quality" saws in general.

Saws aren't the easiest critters to mike...especially with vernier mikes....so I used an average of three readings for each measurement.

Here's my three representative saws:

A Disston 7 26" 7pt rip ...a medium or "fourth" grade saw.

Back to Front Taper at Back: .0070
Back to Edge Taper at Heel: .0074
Blade Thickness at Edge, Heel to Toe: .0434-.0392

Disston #16 26" 5pt rip: One of Disston's "second-quality" saws.

Back to Front Taper at Back: .0150
Back to Edge Taper at Heel: .0031
Blade Thickness at Edge, Heel to Toe: .0369-.0282

Disston #12 26" 9pt xct: A "first-quality" saw, according to Disston.

Back to Front Taper at Back: .0137
Back to Edge Taper at Heel: .0030
Blade Thickness at Edge, Heel to Toe: .0363-.0325

The #7 is an exceptionally tough, stiff saw that can muscle its way thru wet, gnarly oak with the best of them, but I find it takes more effort to use.

The #16 and the #12 are similar, although the larger heel-to-toe taper of the #16 surprised me a bit. What makes them cut easier than the #7, however, isn't the taper, as the #7 has even greater taper...it's significantly thinner blades that average around .0345 instead of .0413.

http://www.toolsforworkingwood.com/prodimg/pz/reg/PZ-HS303XX.gif

If anyone has a modern PAX, made of fileable, tapered steel, I'd like to see how it compares with my old Disstons....fancy tenon saws alone aren't impressive....but perhaps there is a modern successor to what I consider to be the best handsaws ever made.

Replies:

1) I bought a new Roberts & Lee rip saw last week. Length 650 mm, handmade, Dorchester model 570, walnut handle, and as the toolshop told: "fully taper ground skew-back steel blade with breasted toothline and bevel sharpened teeth to ensure the finest possible cut without binding".

Here the thickness measures:
Back thickness near handle: .0386
Edge thickness near handle: .0402
Back thickness at toe: .0197
Edge thickness at toe: .0374

Testing after diminishing set and a little filing on a dry oak board 4 cm thick, gave me a 25 cm long cut in one minute without much effort.

2) Bob, here we go:

It is a brandnew Pax from Thomas Flinn in England.
660 mm (25,98 inch)

Handle (heel) = 1,48 mm (0,058 inch)
middle = 1 mm (0,039 inch)
toe = 0,9 mm (0,035 inch)

hope my calculation from mm to inch is correct. I mesured with a Micrometer. Althoug I do not have that much experiance with this saw I can confirm that the setting might be too much and the cut is quite rough. Do you recommend to reduce the setting?

Answer:

I just went and measured, and all my western saws are about .040 -.042. My thinnest Japanese saw is .016 thick, and it needs a stiffener or it'll flop around. I'm preparing an article this year on selecting handsaws and advanced sharpening, to include retensioning, sloped gullets, and other long-lost techniques. Lotsa old saw filers out here in sawmill country I'm collecting skills from before they die.

http://www.vintagesaws.com/library/ftj/winter97/w97_4.gif

The best saws....Disston 12, 16, 43, and others...Atkins 400...were taper ground to around 35 thousandths at the edge near the heel, tapering to as thin as 28 thousandths at the toe.

These saws require little to no set because of all that taper, and as a consequence are the easiest to push. Less set means a cleaner cut and less handwork to clean up, at the expense of a more fragile blade. This differentiates Disston's "cabinetmaker's saws" from those designed for 1920's-era carpenters doing primarily house framing and ship-boat building..

Second-line saws like the Disston 8's and 7's were also taper ground, but not as severely, and were of the next thicker gage steel at around 40+ thousandths at the edge. The #120 Acme was a specialty saw and is much ballyhoo'd today....but is really only a D-8 made from harder steel. That's far better than anything made today however, as manufacturing with a pre-1927 level of taper and polish is very expensive.

The difference between a 12 and an 8 wasn't the steel, it was the tensioning applied to stiffen the thinner blade. This was done by hand using hammers and anvils, just like the better makes of Japanese saws are done today.

When thin tool steel is hit with a hammer, a dimple occurs, and pulls steel from the edge to the center of the dimple. Pulling the steel inward causes successive rings of tension to eminate from the center...the further from the center, the more tension. Try hammering a successive line down one side of an old hand saw blade, and you'll see it bend into a fair curve until you hammer equally on the opposite side.

Cheapo saws like Warranted Superior's and Penna Saw's worst, had straight gage blades around 45+ thousandths at the edge with no taper, and little tension. These saws require gobs of set to cut without binding and kinking, with a net effect of pushing 55+ thousandths thru a cut rather than the 38 thousandths of the best saws.

The best handsaws made today are by Roberts and Lee in the UK and hard to find...about the quality of a Disston 8 for 200 bucks or so. Sadly, the more reasonably-priced, modern PAX saws newbies are buying in numbers because they don't know how to sharpen don't even come close to that.

Backed saws like dovetail and the smaller tenon saws generally run as thin as 28 thousandths. Japanese saws can run thinner, but many of those achieve that with Rockwell hardness alone, and such saws can't be refiled. Those untensioned saws are generally "floppy".

[David Weaver]

Bob - thanks for that back-and-forth.

I agree with the commenter who noted the 12 is an entirely different experience from the 8, which isn't bad itself, especially compared to anything new.

I didn't really get a desire to use western saws much until about 6 months ago, purchased a few (including 2 12s), a couple of 8s, a 7, some atkins saws that I already had and a couple of D8s that I got cheap over the years even though I didn't use them.

I've seen the comment before that the steel is the same in all the saws, be it a 12 or a keystone saw, and I see the mention of tension. Having sharpened all of those saws over a short period of time, it seems that the hardness of the 12s is also a little higher. Not enough to make them hard to file with a new file, but enough to notice they are harder on the files.

I've noticed them to be much harder than 3 newer saws that I've come across (and didn't keep). Did disston do anything to harden them to a higher level, or is it just in my head, or is it part of the tensioning?

The recent talk about saws has made the old ones more expensive in the last couple of years, but they are still dirt cheap compared to new saws. Too much more talk, and they'll be expensive all the way around, though, at least for one with a straight plate and no pitting.