Drawing temper from a saw

[Mark Baldwin III]

I think that one of my saws a little too hard. It is a Penn State saw, and is my only rip cut hand saw. Filing the teeth is a bear. After the last sharpening session (which lasted a couple nights) I set the teeth. While trying to add only a tiny amount of set, I ended up breaking 2 or 3 teeth off. These two things have led me to believe that it is a bit on the over hard side. I can confirm this with a hardness tester at my work.
What I would like to do is hang it up in one of my ovens at work and draw some of the temper out. The oven is calibrated. I just don't know a good temp at which to start. Any ideas? (I could just be crazy, and if that's the case, it's an acceptable reply)

[george wilson]

The 1095 that I used,and which most others making quality saws use,is 52 R.C.. It is near the top of the hardness a saw can be. I have broken a few teeth myself.

You are liable to hopelessly warp your saw if you attempt to heat it up.I recommend clamping the WHOLE blade between steel plates at least 3/8" thick. Hot rolled steel(with the dark surface and slightly rough surface) is best. It is not full of stress like cold rolled,and won't warp when you get it hot.

Use some old C clamps of all steel construction,and put the whole thing in the oven. Let it cool in the oven after you turn the oven off. Clock spring blue is the color of 1095 when you get it. If you go over that,into a dead gray color,you may have annealed the saw fully soft,so be careful.

Try 700º F. if that doesn't get to blue,go to 750. It will take some hours for the mass of steel to heat up to that temperature,and some hours to cool. The color progression is: yellow,brown,purple,blue,gray.

[Mark Baldwin III]

Thanks, George. 700-750 is more than the oven can do. I think 450-500 is tops for the one that big enough for this saw. I spose I might be better off trying to find another rip saw. I think I will still put it on the hardness tester just to see.
It is FULLY possible that my file was crap and my setting technique needs work!

[george wilson]

It IS possible that the saw is too hard. The saw didn't have darker teeth than the rest of the blade,did it? Some saws have induction hardened teeth,and aren't supposed to be sharpened,OR set. You just toss them and buy a new one. I don't buy saws like that. IF I did,I'd hit each tip lightly on a grinding wheel before I'd toss it.

[Mark Baldwin III]

The patina on the saw hid any signs of induction hardening. It's at least 60 years old, if I remember my history right. I don't know when induction hardening came into common use on western saws, though. At first, I didn't joint the teeth. I just gave it a light refiling and all seemed well. It wasn't 100% though. I decided to joint the teeth and go for a full work up, and that's when the problem started. If the hardness test shows that it is ok, that will indicate that my file was not up to snuff and my setting wasn't either. Either way, I doubt that I would drop it in the can. The worst fate I could think of is hanging it up in my Dad's basement as decoration. Thanks, though, George, you always get us pointed in the right direction!

[george wilson]

I can't recall if they had induction hardened teeth 50 years ago,either.

[Ray Gardiner]

Hi Mark,

Here is the data on 1095 for future reference, I assume your Penn State saw is a similar steel,
http://www.backsaw.net/pics/Tempering1095.jpg

You should be targetting about 52 Rc, so the first check would be to see what the current hardness is. If you refer to the chart of hardness versus tempering temperature in the chart above, you will see that what George is saying is correct, you need to get up to around 700F, hold for a while, and then cool slowly. I would be concerned that you might warp the saw plate in the process...

If it was mine, I would just use it as it is, one or two missing teeth won't affect the saw. They will grow back with subsequent sharpening. And take it easy when setting.. :)

Regards
Ray

[Jonathan McCullough]

52 is very hard, on the upper end of the scale for a saw. Your saw is also likely not made from 1095 but something more like W-1 or W-2, with a lower carbon content of anything down to .70 percent carbon. If you draw the temper out of it, the saw may also warp on you.

[Ray Gardiner]

Hi Johnathan,

Blue Spring Temper 1095 is supplied as 48-51 Rockwell C, this is the preferred stock for good quality saw plate. I'm aware that there are other (lower quality makers) using 1080 and even 1070.. cheaper I guess.

I'm interested in the suggestion that W1 might have been used for saw plate in the 1950's, do you have any references for that.

Regards
Ray

PS Here are some specs for 1095 Spring Steel http://www.victornet.com/report/Blue-Tempered-Shim-Stock/1305.html

[george wilson]

I had a very high class hardness tester at work,the Versitron. Our steel from Precision Steel Warehouse,tested 52 R.C. . It is at the upper limit of spring steel as Ray suggested a few posts ago.

W1 steel ranges from about .80% to OVER 1.00 %.so there is a range of error in it. At any rate,not likely your Penn State saw was made from this highest grade of spring steel,anyway. Too expensive based on the selling price of a saw from them. The steel for 1 of our crosscut saws was costing about $22.00 per blade,in the quantities we were buying it at,which was a $250.00 minimum,PLUS a $75.00 cut off fee.

Even if you bought a LOT more,the metal could get only SO cheap,so,it was probably a lower carbon steel,like 1080,or 1070. It could still be just as hard,but wear resistance would not have been as good without the extra carbon.

[David Weaver]

Any chance of carefully spot heating the toothline to blue temper with a heat gun? That's what I'd try. The saw is as good as junk otherwise, and it won't be worth enough (unless it has sentimental value) to do anything else with it.

[george wilson]

IF you heat the toothline,I'd clamp the saw up to within 1/2" of the tooth line and leave it to cool afterwards. What you are doing is making the steel there swell up longer than the body,and something might have to give. The metal HAS to have somewhere to go,and the distance between the ends of the saw will be a curved line,rather than a straight line.

[Ray Gardiner]

Any chance of carefully spot heating the toothline to blue temper with a heat gun? That's what I'd try. The saw is as good as junk otherwise, and it won't be worth enough (unless it has sentimental value) to do anything else with it.

Hi David...

Outch.... no no no.... if anything is going to warp the plate it's differential heating.. you need to heat the whole thing slowly and evenly. (preferably with clamping and large heatsinks)

As for being "good as junk", sorry, 2 or 3 missing teeth won't affect the saw at all. The missing teeth will grow back in subsequent jointing and sharpenings. :)

Regards
Ray

[David Weaver]

No, what I mean by "the saw is junk" is that a saw that eats expensive files each time you sharpen it and refuses to be set (as this is a budget saw line that was made in york, PA, if I recall correctly) is something you don't have to deal with if it is really something that's hard to sell even in perfect condition, anyway.

I grew up very close to york PA, and as much as I'd like to see them be great saws, they are budget budget budget type saws. They are the kind of saw that is at the silver spring flea market for $2 unused, and they're still there when you go back.

I have a disston #7 that is above and beyond the hardness of this saw, and I'm not too far from throwing it away (I just haven't gotten around to robbing the saw nuts out of it yet) - it eats more in double-cut files trying to touch up the teeth than it's worth in general.

Maybe I'll try the heat gun on it to see how much warpage I get out of that, I'm going to throw it away, anyway. Ran through $15 worth of files on it hoping the files were bad and not the saw. I'll bet it's close to 60 hardness because a single cut file won't even touch it and I can just barely get a double cut file to bite at all (one pass and it was also ruined).

So many saws that saws that behave like this can just be junked after robbing the screws from them, unless they have sentimental value.

I'll report back after I heat the teeth on that saw to blue - at how much it's warped.

[Jonathan McCullough]

Disstonian Institute dot com tested the carbon content of a bunch of Disston saws. As I recall, most were in the .65 to .80 range, including some of the finest they ever made. I think one tested at over 1 percent but it was an outlier. In my experience from cleaning up a range of old saws, the U.S. Steel industry was mature by the 1950s and some of the best, most consistent, and well-tempered steel I've seen in saws were from that era. But ALL saws, I repeat, ALL saws were water quenched, and I don't see any reason they would have made them out of anything other than what they'd been making them for 100+ years. It's only recently that people have been making it out of 1095 because, why not? It's some of the best, hardest steel and it comes pretempered. But it's hardly necessary for a good saw. One exception I've seen was a Pennsylvania Saw Co. at the turn of the century making saws out of W-2, which if I have my facts right, is essentially W-1 with some Vanadium. They called it their "High Speed Vanadium" line of saws, and the steel was from a specialty supplier. I think Disston bought them up around 1909 - 1914, and the Pennsylvania Saw Corp with the Quaker guy is a separate entity. Atkins also experimented with stainless steels but, meh.

[george wilson]

If your saw is about 55 R.C.,or even a little less,David, your files would be in trouble. That is about how hard many anvil tops were made. They won't file.

I think Sandvick(sp?) made a stainless saw,too. I had one in the 60's that looked different. I never got my tools wet to test them,though!

[David Weaver]

George, when I got that saw, it has just the slightest hint of a straw color, but very clean and clear. I thought maybe someone had put varnish on it and not gotten it all off, or maybe shellac. Maybe they did. I hope that's not the tempering color.

I would guess that maybe there's something about it I didn't know, like it was intended for some special use, but it just has the standard disston #7 etch on it, and still has the factory and teeth on it. I just don't know how it ever got out of the factory. The teeth are worn a tiny bit at the tip, just enough for it to cut dull before I went over it and ruined a double cut file on it. It's still not sharp enough to be a nice cutter - but i'm not going to waste another file on it, and the factory set is too much and the teeth will surely break if I try to move them. I'll bet someone bought it, used it until it was dull, and then tried to file it and threw it aside.

The other strange thing about it is it has a broken handle and was reglued (right in the middle of the cheek), but no broken teeth. Someone very crudely glued the handle.

I got it from a tool dealer (as a "good #7 with a full plate and repaired handle") and should've sent it back, but figured I have no interest in spending $15 to send back a $30 saw - they're a pain in the arse to pack and ship. It just isn't worth the time, for $15 difference, I'll avoid the hassle and just have a nice set of saw nuts and disston medallion to use in the future.

[george wilson]

It could have been a special saw for sawing something harder than wood,or more abrasive. There were metal cutting saws made,but they had hacksaw type teeth. There were saws for sawing gunpowder,but they were berillium. Saws for many special apps have been made.

[Mark Baldwin III]

Berillium saws? Sounds like nasty sharpening dust to me! That is one unfriendly metal...in a cancer causing kind of way.

[george wilson]

I found a beryllium crow bar,sawn in half somewhere ages ago. Glad I never turned it in my lathe. Only fairly recently (20 years ago?) did I find out it is very bad.

[Ray Gardiner]

Disstonian Institute dot com tested the carbon content of a bunch of Disston saws. As I recall, most were in the .65 to .80 range, including some of the finest they ever made. I think one tested at over 1 percent but it was an outlier. In my experience from cleaning up a range of old saws, the U.S. Steel industry was mature by the 1950s and some of the best, most consistent, and well-tempered steel I've seen in saws were from that era. But ALL saws, I repeat, ALL saws were water quenched, and I don't see any reason they would have made them out of anything other than what they'd been making them for 100+ years. It's only recently that people have been making it out of 1095 because, why not? It's some of the best, hardest steel and it comes pretempered. But it's hardly necessary for a good saw. One exception I've seen was a Pennsylvania Saw Co. at the turn of the century making saws out of W-2, which if I have my facts right, is essentially W-1 with some Vanadium. They called it their "High Speed Vanadium" line of saws, and the steel was from a specialty supplier. I think Disston bought them up around 1909 - 1914, and the Pennsylvania Saw Corp with the Quaker guy is a separate entity. Atkins also experimented with stainless steels but, meh.

Hi Johnathan,

Thanks for the reply.

The tests on Disstons you refer to I assume are these http://www.disstonianinstitute.com/steel.html The "outlier" you refer to was the earliest backsaw from the 1860's at 1.34% carbon, which was also the most brittle (teeth broke easily) and also the softest, I suspect that it's a reflection on the quality control and production methods used at the time.

Pete Taran's detailed reply on Eric's tests are here http://www.vintagesaws.com/noway/noway.html Interesting reading...

Still on Disston's saw steel... http://www.vintagesaws.com/library/ftj/summer98/summer98.html

W1 (and W2 for that matter) varies in carbon over a wide range, anything from 0.6% to 1.4% (I looked it up), and of course saw steels were always water (or brine) quenched (as is 1095), although, now-a-days, they often use polymer quenchant, the induction hardened steels are almost always polymer quench.

Regards
Ray

[Ray Gardiner]

<snip>
I have a disston #7 that is above and beyond the hardness of this saw, and I'm not too far from throwing it away (I just haven't gotten around to robbing the saw nuts out of it yet) - it eats more in double-cut files trying to touch up the teeth than it's worth in general.

Maybe I'll try the heat gun on it to see how much warpage I get out of that, I'm going to throw it away, anyway. Ran through $15 worth of files on it hoping the files were bad and not the saw. I'll bet it's close to 60 hardness because a single cut file won't even touch it and I can just barely get a double cut file to bite at all (one pass and it was also ruined).

So many saws that saws that behave like this can just be junked after robbing the screws from them, unless they have sentimental value.

I'll report back after I heat the teeth on that saw to blue - at how much it's warped.

Hi David,

If you are going to junk it anyway, there's nothing to lose by trying the heat gun...
Last time I tried something similar (although I was using a map torch, not a hot air gun) I ended up with a propellor shaped saw blade. I hope you have better luck.

Regards
Ray

[Pedder Petersen]

Hi David...

Outch.... no no no.... if anything is going to warp the plate it's differential heating.. you need to heat the whole thing slowly and evenly. (preferably with clamping and large heatsinks)

As for being "good as junk", sorry, 2 or 3 missing teeth won't affect the saw at all. The missing teeth will grow back in subsequent jointing and sharpenings. :)

Regards
Ray

Hi Ray and David,

I did this with a 1mm (0.032") saw blade for Klaus a few weeks ago, because this special blade was wrong hardened. It nearly killed my retoother. It ate sanding belts in dozens and dulled files one per tooth. I was only luck probably, but it worked quite fine for me.

Cheers
Pedder

Disclaimer: I don't recommend to do this with your saw blades.

[Mark Baldwin III]

A hardness test on my saw showed that it is not too hard (RC46-47). I am going to assume it was either my technique or my file that was causing the issue. I'll have another go at sharpening.