Backsaw making

[Sheffield Tony]

Making your own gents saw was mentioned in another thread. I'm tempted. Anyone have some good pointers for help on this ?

I have some saw steel, and 1/8" brass sheet of unknown grade. I presume I'd need to anneal it (sounds like a winter job when the stove is going). Can it just be folded with some angle iron, a vice and a big hammer ? Or is 1/8" too thick ?

 

[woodbrains]

Hello,

I think you would need some sort of bending brake, the chances of folding the brass without introducing some sort of curve or scalloping would be difficult, IMO. Even the slightest imperfection would translate to the blade, which would never be straight. The best back saws had the back of the plate stretch hammered, and folding the brass back over it forced it back flat and in tension, so the blade would remain flatter in thinner plate dimensions. With the difficulties in doing this, I wonder what the point would be in trying your own? I don't want to put you off, but unless you have rather more sophisticated metal working gear, you might just be up for a hiding to nothing. If the plate you have to make the saw is thick, then putting a back on it probably won't do anything anyway ( except make it not straight anymore!)

Mike.

 

[woodiedonald]

well i could be wrong but i think i remember on the two lawyers toolworks saw blog they said they make their backs by cutting a groove in a piece of brass, there was some other small-ish american saw maker (blackburn maybe? not sure) who did this too and said they rounded the edge of the brass to make it look like a folded piece.

Nothing ventured.....

 

[woodbrains]

well i could be wrong but i think i remember on the two lawyers toolworks saw blog they said they make their backs by cutting a groove in a piece of brass, there was some other small-ish american saw maker (blackburn maybe? not sure) who did this too and said they rounded the edge of the brass to make it look like a folded piece.

Nothing ventured.....

Hello,

Yes, it could be done like this, but it is folding the brass that holds the blade in tension. Putting a slotted brass bar on the blade might add weight, and look pretty, but it doesn't do it's main function. It would be a lot of effort making a saw, that wasn't better than a cheap one you can buy.

Mike.

Edit. This is why you shouldn't remove the back from an old well made backsaw when restoring it.

 

[Corneel]

Mike, not wanting to question this, but where did you get your knowledge about how these backsaws were made? I've delved quite a bit into the history of saws but haven't ever found a real description of how they were made. So I'm curious where you heard about this.

 

[woodbrains]

Mike, not wanting to question this, but where did you get your knowledge about how these backsaws were made? I've delved quite a bit into the history of saws but haven't ever found a real description of how they were made. So I'm curious where you heard about this.

Hello,

You are right to question, I am not a saw maker! Like many things, you just absorb information over the years and cannot really remember exactly where, but I had heard/read this more than once. If I was to guess a source it would be Jim Kingshott.

Of course I'm sure there are other ways of fitting a back, but I still think trying to wellie a fold in some brass with a big hammer, would lead to more problems than the benefits of making a saw would yield. Unless the exercise is triumphing over adversity.

Mike.

Edit. Even folding a back over a flat, untensioned saw plate would impart stiffening tension, that merely fitting a slotted back would not, IMHO

 

[Corneel]

Thanks for the info. I'll have to dive a bit into Kingshott then.

I've experimented a bit with folding 3mm brassplate for saws. We used a huge brake. That didn't get the fold really flat, so we turned to the 50 ton press and some massive steel plates. That got them quite flat, not totally though. This was all done without anealing and without the blade positioned in the back. So after that I just tapped the blade between the folded back. I made one 16" backsaw like that and it turned out all pretty well, but was a huge undertaking.

So on a second try I annealed the brass first. Not even redhot, just as hot as I could get it with a small propane burner. It made it much easier to fold the brass. I still started with the brake. Then annealed it. Then hammered it very flat, even so flat I can't see the split anymore. Of course it's hard to keep it straight, but with some hammering in the appropriate spots it is doable. That's where I am now. Other jobs got in between, but the next step is going to be to pry it open a bit again, so I can push the blade into the back!

Overall I still don't know if annealing is a good idea, because I suppose you loose some tension in the pinching of the back, so to speak.

Fun stuff, but I wouldn't follow my lead, I'm far from experienced with this. Almost all the contemporary sawmakers use slotted backs.

 

[woodbrains]

Thanks for the info. I'll have to dive a bit into Kingshott then.

I've experimented a bit with folding 3mm brassplate for saws. We used a huge brake. That didn't get the fold really flat, so we turned to the 50 ton press and some massive steel plates. That got them quite flat, not totally though. This was all done without anealing and without the blade positioned in the back. So after that I just tapped the blade between the folded back. I made one 16" backsaw like that and it turned out all pretty well, but was a huge undertaking.

So on a second try I annealed the brass first. Not even redhot, just as hot as I could get it with a small propane burner. It made it much easier to fold the brass. I still started with the brake. Then annealed it. Then hammered it very flat, even so flat I can't see the split anymore. Of course it's hard to keep it straight, but with some hammering in the appropriate spots it is doable. That's where I am now. Other jobs got in between, but the next step is going to be to pry it open a bit again, so I can push the blade into the back!

Overall I still don't know if annealing is a good idea, because I suppose you loose some tension in the pinching of the back, so to speak.

Fun stuff, but I wouldn't follow my lead, I'm far from experienced with this. Almost all the contemporary sawmakers use slotted backs.

Hello,

It is a shame you didn't get the back almost closed and then insert the plate for the final hammering. I should think some annealing along the way is essential, but you would still introduce some work hardening during the final hammering.

I don't think Kingshott went into great detail in saw making, a treatise or anything, as he was a woodworker and tool user. He did make and modify a lot of his own tools and did a proper apprenticeship in the days when they meant something. He likely knew what he was taking about and knew a lot about other affiliated trades.

Mike.

 

[Peter Sefton]

We undertook a dovetail saw test for British Woodworking back in 2011 and were lucky enough to use eight of the best saws from around the world. We found the English made saws are still made the Sheffield way (bent and folded brass backs) all the other saws we tested from North America had milled brass backs glued on or the moulded Veritas. Much easier and cost effective methods but once glued they cannot be reworked or removed.
A copy of the article if this helps http://www.peterseftonfurnitureschool.c ... icle57.pdf

 

[Kalimna]

Not much to add to the original query, but I found this whilst googling Blackburn saws (thanks woodiedonald). It seems to be a very comprehensive discussion of sawtooth sharpening, though it is something I have yet to attempt.

http://www.blackburntools.com/articles/ ... index.html

Cheers,
Adam

 

[G S Haydon]

Nice article Peter. I have the PAX no1, it looks rather shabby among such an accomplished line up. Glad to see the premium PAX saws had a good report.

 

[Peter Sefton]

Nice article Peter. I have the PAX no1, it looks rather shabby among such an accomplished line up. Glad to see the premium PAX saws had a good report.

Thanks, it was fun to do and very interesting for me and proved useful to the students. I replaced my old Dovetail saw and have not looked back, keep Sheffield and its skills alive.

Cheers Peter

 

[Corneel]

It is a shame you didn't get the back almost closed and then insert the plate for the final hammering. I should think some annealing along the way is essential, but you would still introduce some work hardening during the final hammering.

That's not as easy as it seems! When hammering the back it is quite difficult to keep it straight. So I peer along it and hammer a bit on one side or another. After I am happy I have to clean it up, file away all the hamer marks, sanding, making some chamfers along the edge. All that seems a lot easier to me without the blade allready fitted.

And I am not quite sure what it does to improve the saw. When you first tension the sawblade, stretching it, you create a "frog" in the steelplate. An area that pops in or out. To combine this with a brass back and ending up with a straight blade is completely beyond my meager metal working skills. And when you just leave the spring tempered steel blade as it is, I don't really see how hammering it in place between the brass, makes any difference? All the tutorials floating around on the interweb have you installing the blade in the back after it is finished. But probably the writers haven't a clue either.

Anyway, one thing to remember, the blade isn't installed very deep into the brassback! No idea where I read this, maybe even on this forum, but it is usually installed just a couple of mm, at least not all the way to the fold.

 

[Cheshirechappie]

The only reason for putting a back on a saw is to keep it stiff enough to stay straight during use and normal storage. If a piece of thin spring steel would stay straight without a stiffening back, there would be no back. The thicker blades of longsaws are stiff enough to stay straight, but only because they are made from thick enough (and hence stiff enough) steel in the first place.

The point about backsaws, especially the smaller ones, is that the blade is thin enough to leave a fine kerf. In order to be thin enough (and also long enough to be useful), some stiffening is needed - the steel won't stay straight on it's own.

It thus follows that either a folded or slotted-and-glued back will do the job of providing stiffness equally well. The reason the 19th century manufacturers used a folded back was, I suspect, because it was very difficult to cut a deep, thin slot in a brass (or steel) bar - much easier and more economical to fold, given the technology and equipment available to them.

For someone making a new backsaw today, either method could be used. It would depend entirely on which was easier for the person making the saw. For most people nowadays, machining a slit in a strip of free-machining (CZ121) brass would probably be easier, as keeping it straight would happen almost automatically, given the nature of the machining process. (Not necessarily cheap mind - thin slitting saws are pricey, and delicate.)

 

[Corneel]

Here you can see how they install the back at Gramercy saws, one of the last modern sawmakers using folded backs. At least they install the plate after the back has been finished. http://lumberjocks.com/Brit/blog/33741

I would love to read a report from one of the oldtimers, how they made saws. A bit like how William Armour explained how to make a beech plane in 1898. http://www.handplane.com/32/practical-plane-making-1/

 

[Harbo]

I made a couple of Gramercy saws a few years back but cannot remember now the exact details - weren't that difficult to assemble I think?

Rod

 

[Cheshirechappie]

I've just had a thought on how to use readily available modern technology to make backsaw fabrication much easier. Engineering adhesives.

Take one finished saw blade, two strips of nice straight 1/16" or 3/32" brass or steel for the back, degrease thoroughly, and glue them together using a cyanoacrylate (Loctite 603, perhaps?) or epoxy adhesive. Make the brass strips longer than the steel, and you have something to shape into a tang for the handle of a gent's saw.

No need for machining, bending, hammering or any other time-consuming and patience-demanding skilled work. Just instant saws.

Edit to add - Having done a bit of research, I think Loctite 496 would be a good bet. It's a cyanoacrylate adhesive formulated for bonding metals, and it's available in small quantities (20g pot) from Cromwell Industrial Tools (and probably elsewhere) at £20 a pot.

 

[Sheffield Tony]

I have spotted one on the web made by riveting two strips of brass to the plate. I think if I did it I'd want a traditional appearance though.

I'm feeling less confident now about my chances of getting a straight saw out of my bits of brass, so I think I'll let them sit for a while whilst I get on with some other jobs. But thanks everyone for the interesting discussion.

 

[Isaac S]

Tony, while I have never folded a saw spine, I have put new blades in a few old spines. If you are looking for the easiest way to build a saw, I would suggest looking for an old saw (or a cheap new saw) and using that spine. If, however, you want the experience of bending one, then go for it.

When I hear gent's saw, I think of a saw with a turned handle that is in line with the spine of the saw. If that is what you are trying to make, I think you might want to use a thinner brass for the spine. I have a few of these saws, and on all of them the brass is about 1/16" thick. The lighter weight is appropriate for this style of saw and will be significantly easier to bend.

If you go with a thinner brass, look for 260, not 360. 260 is much more ductile, and you have a better chance of bending it without having it crack.

The best back saws had the back of the plate stretch hammered, and folding the brass back over it forced it back flat and in tension, so the blade would remain flatter in thinner plate dimensions.
Mike.

Mike, I have removed the spine from quite a few backsaws and never seen evidence of this being done. I'm not saying it wasn't (and most of the saws I work on are American), but all of the blades I see are flat when they are removed from the spine. If the blades were tensioned along the back, I would expect them to be concave in one direction or the other.

Edit. Even folding a back over a flat, untensioned saw plate would impart stiffening tension, that merely fitting a slotted back would not, IMHO

I would categorically deny this. There is no mechanical difference between a slotted and bent spine. Yes, some makers use slotted spines and glue the blades in, but you can also squeeze the slot closed and hold the blade in place with friction only (in exactly the same manner as a folded spine). This is the way I make my saws. On several occasions I have removed my slotted spines from their blades, and I can tell you that doing so required much more force than I have ever needed to remove a folded spine.

I would also add that I don't think most folded spines are capable of, or intended to impart any tension to the saw blade. They serve only to stiffen the blade and prevent buckling. To impart tension, they would have to stretch the blade and hold it there. Given how easy it is to remove most of these folded spines, there is no way that enough friction exists between the blade and the spine to actually stretch the metal.

Just so it's clear where I'm coming from, I make backsaws using slotted spines, so feel free to filter what I have said above through that lens.

Isaac

 

[Cheshirechappie]

The best back saws had the back of the plate stretch hammered, and folding the brass back over it forced it back flat and in tension, so the blade would remain flatter in thinner plate dimensions.
Mike.

Mike, I have removed the spine from quite a few backsaws and never seen evidence of this being done. I'm not saying it wasn't (and most of the saws I work on are American), but all of the blades I see are flat when they are removed from the spine. If the blades were tensioned along the back, I would expect them to be concave in one direction or the other.


Isaac

I suspect there is a good deal of long-standing myth about 'tension' in saw blades, probably going back to 19th century marketing hype.

The reason that saw makers hammered their blades in the 19th and early 20th century was to correct the distortions resulting from the hardening and tempering process. Modern steelmakers can supply spring steel in a hardened and tempered state, and flat; there's no need to hammer it flat, and doing so will only distort it. You can't 'tension' a piece of thin steel by hammering part of it. If you need a stiffer sawblade, start with a thicker piece of steel stock. (Interestingly, the thicknesses quoted by Holtzappfel in 'Turning and Mechanical Manipulation' Vol II are somewhat thicker for a given size of saw than most modern premium sawmakers tend to use - not by much, but enough to make a difference.)