Saw back types, what else have we come up with besides folded and slotted?

So, I've been playing in the machine shop this week making a batch of slotted backs, whilst doing so I've been dreaming up other designs of backs and means of making them grip the plates. I've had some success with mechanically adjustable hinged design but it's in it's infancy and a bit heavy and clumsy, if i get it to a point where i'm happy with it i'll share it here. Anyway, it got me thinking, The only other type of backs i've seen are the excellent self tensioning ones that Shane Skelton makes, either with a built in spring or a hidden screw. I'm curious to know if any of you folk have experimented with alternative back designs?

 

"Folded" is quite a broad term, re: saw-backs, esp. before around 1830 . . . but yes; Mr Skelton's new tensioning-designs appear to permit reliable use of thinner grades of modern saw-plate than slotted-and-pressed backs.

 

Anything that doesn't allow the plate to be held under tension is a waste of time - 200+ years of saw making and material science says so. Tension is essential because it's what keeps saws tracking properly.

Slotted backs are OK for many users, but anything that locks the blade in place (also a rusted plate in a folded back) has very little compensation factor and eventually you'll mung it. Then, how do you fix it?

 

I'm with you Dusty, Although I make a few slotted and bonded saws I do vastly prefer folded backs especially on larger saws, I've had good results with slotted backs on the dovetail saws I make but they're quite shallow depth plates and fairly unlikely to warp, I've never had much luck with slotted designs on saws with larger, deeper plates. The one I'm working on at the moment is 17 inches long and 3 and a half inches deep, I couldn't risk using a slotted and bonded back as it's just too likely to get written off. It's the adjustability and repairability that's got me scratching my head, I really like how slotted and bonded backs feel in use and am messing around with designs which replicate that feel without sacrificing the ability to adjust should it be required. I was just curious to see if any of you had also played about with your own designs really.

 

So here's the design i've been working on.

An adjustable, slotted back.
The back has a slot cut both sides, the plate sits in one side and the other side is drilled and tapped with a grub screw every 20mm with spacings alternating left and right to give a screw every 10mm, when the screws are tightened they force the top slot apart and the bottom together clamping the plate, The top screw in the handle passes through the back and blade pinning it all together, you can then nip up few screws at the toe, pull the blade tight and rely on them to hold the blade stretched between the toe and heel while you tighten the rest of the screws down. The 42 screws are lubricated, m4 and tightened to 50 N.cm, which if my maths is correct gives me a clamping force over the total contact area within the back of 3.2Nmm2 or 464psi. In human terms, it aint moving unless you want it to.

This one was just a proof of concept, forgive me the sloppy execution, i wanted to avoid pouring days and days into a project that diddnt pass go.

In use the saw feels different to either a folded or slotted back, it tracks a line effortlessly, has that zingy feel that a good folded saw has but also somehow feels like a slotted saw. it's just a little on the heavy side for my taste but then again it is a little over 17 inches long, i think if i go down this route again i may taper the depth of the back and adjust the torque of the screws along the length of the plate to compensate for the alteration of leverage and clamping force on the blade, it'll allow me to shave off maybe an ounce and a half from the weight at the toe, perhaps even a make Disston no9 style protruding toe? Perhaps i'll just suck it up and remember that bigger saws weigh more.

I'm keen to hear what you lot think of the design.

Cheers

Matt

 

Hi - great fun, & admirable you've given this slot & counter-slot concept an empirical outing. Interesting to hear your future experiences, as you continue to use & adjust this saw . . .

 

Cheers shoarthing, I'l keep you updated.

 

Matt, the saw looks good but wouldn’t it just be easier to use a friction fit. A friction fit, if done correctly, accomplishes the same thing as a folded back and is allows for removing the spine as well as getting rid of problems in the toothline.

I’m also curious as to how the screws pull the plate and introduce tension. It seems to me grub screws are providing clamping pressure and that compression is directed perpendicular to the tooth line simply holding the plate rigid. Which of course is what most backs on saws do and what they are meant to do. I recently made a dovetail saw that used no clamping pressure on the plate where it was inserted into the spine. I used three screws I made that simply passed through the plate and spine in order to hold the plate in place. The handle hardware didn’t pass through the plate either. Instead it simply applied pressure to the plate to keep it straight and from wandering laterally. The saw worked just fine and since there was nothing passing through the plate in the handle the plate wasn’t being put into compression when jamming up against the flat screws on the push stroke. My thinking is that this sort of system would allow for a plate to heat and cool, stretch and shrink without interference thereby reducing distortion in the saw plate that normally occurs during hard use.

The saw is pictured below. It’s a single piece of bubinga shaped to look like a Kenyon dovetail. It utilizes a patent by Woodrough and McParlin that was never produced, although I’ve taken further than their patent and added a few things of my own.

 

Certainly my view is always different. LOL

I have recently been thinking that over the past most all of the sawmakers have designed and produced saw that could have the plate removed from the back. I attribute the "movable" action of a folded back being one of it's faults.

Recently I started to plan out a knife build and knife makers epoxy that heck out of their knives when assembling so they never coming apart. And it got me to realize...in todays world, saws are much more affordable than in days of lore. If you wear a handsaw out, more power to you...or if you drop a toolbox on your saw and bend the plate, ok...bad hair day, go get another saw. The majority of saws, even the custom ones will last a lifetime with never being taken apart.

For this reason I not epoxy and crimp my handsaws. The hope is they will never come apart or move in anyway to disorient the relation of position.

Maybe a better question would be, "how many craftsmen have had to re-plate a handsaw?". I contend they are in the minority. Most people take care of them like their own baby, and rarely get a scratch...modern craftsmen will fret over something like that...

 

Hey Charlie.
Sorry for the terribly late reply, I've been absent from here for a little while.
I love the Bubinga saw, I'ts beautiful work as always! How does it feel in use? I'm getting curious about other materials for backs now.

As for your question about the screw clamp backed one I built, short answer, they don't. I pulled the blade tight by tightening a pair of screws at the heel end fully, nipping up a pair at the toe end but not fully tightening them, holding the saw in a vice by it's plate near the toe and gently tapping the toe end of the back towards to effectively stretch the plate, then I tightened the screws fully followed by the rest of the screws. The saws got a few months of use on it now and has behaved itself well, I'm going to send it off to a friend who does heavier work than I do to see how it performs under heavier load.

Ps, congrats on the successful rise to fame your saws have seen this last couple of years, it's bloody well deserved. You do incredible work.

 

Thank you for explaining it to me. My one piece saw worked fine but was only used a couple of times before I trashed it. I got a little too obsessed with correcting a mistake on the spine and in the end there was almost nothing left of it. Oh well. Wanted to test a theory so I accomplished that at least.

I appreciate the kind words about my work. I really love making saws but I’m not sure how much fame comes with the job. Most people, woodworkers/collectors/ etc have never heard of me or my saws. You have to be a real fan of saws and a member of the Facebook saws group to have heard of me I think. Which is perfectly fine with me. I just want to be the best saw maker I can and I’ll leave all the rest to others.

Good Luck! with the next field test of your saw. I do this as well- sending them to woodworkers who will use them in a different and heavier manner than I will. I find it’s helpful and definitely provides more insight into the goal you’re trying to accomplish.
Charlie

 

What is wrong with ZTeh method, Lien-nielsen/independence saw uses for 30+ years? Slotted spine and loctit.e