Perhaps I should just learn to listen to my body. My best ideas come to me in the shower. My worst ones come while I’m in bed.
This one popped into my head as I was drifting off to sleep this week. Lots of people have seen Frank Klausz’s special bowsaw blade where the toothline switches from 0° to 90° over the space of an inch. The blade allows you to saw out the waste quite quickly.
See the blade in action in this video.
There’s also a rare Harvey Peace saw that does this same basic thing. I snapped these photos of one belonging to Carl Bilderback.
So my crazy idea was to tweak a coping saw or fretsaw blade to do the same thing. I would bend the blade using two pliers so the toothline would change its axis. Then I would drop the vertical section of the blade into my kerf and then push the saw so the horizontal teeth would do the cutting.
Simple, right?
Simply stupid. First I did this with a high-quality Olson coping saw blade. If you bend the blade with the pliers too close together, the steel can rip. And it’s game over. If the pliers are too far apart, then the toothline changes its axis too slowly and the teeth won’t bite. Game overer.
So I fiddled with it until I got the teeth to turn 90° over about 1/16” of an inch. When I put the blade to work, the whole thing went to pot. When I pushed the saw forward (or pulled it back, I tried it both ways), the horizontal teeth didn’t engage much at all. Instead, the kerf in the wood tended to bend the blade just as well as the pliers had. Yup, wood defeats steel in this instance. I could baby the teeth into engaging the side of the waste, but it was impossibly slow.
Then I decided to try something else, and this new tactic seemed promising.
What if I tool a spiral fretsaw blade and “de-spiraled” about 1” of the blade? So I’d have a 1”-long section that was .010” thick. I would drop that section to the bottom of the sawkerf, then push forward and the spiral teeth would engage the waste. I could cut out my waste right along the baseline. Brilliant!
Nope. Have you ever unwound a spiral blade? I got pretty good at it after about 10 attempts. It doesn’t take too long — less than a minute for a blade.
Almost turgid with excitement, I loaded the blade into my fretsaw. It dropped to the bottom of the kerf and pushed forward. Ting! The blade snapped.
I tried another. Ting! Ting! Ting!
My guess: Unwinding the steel blade fatigued the blade. Hmmm, perhaps I could convince a blade manufacturer to make a batch of blades with 1” of the blade unspiraled?
Or instead, I reasoned, I could stop mucking around and finish this dovetailed carcase for the traveling Campaign Bookcase I’m building.
But then I realized that I was already done. During all the experimenting I had cut eight tail boards and eight pin boards.
I need a shower.
— Christopher Schwarz
Chris,
Roy shows a tweaked coping saw blade in one of his early books-I forget which one. The turnover was over a longer distance, though-about an inch or so. It seemed to work for him…..
Have to wonder if you folded it back on the other end?
Then tried a mock up with a long, narrow strip of paper. When I applied tension to both ends it wanted to either straighten out or curl into a tube depending on the direction of the second fold.
I suspect you would need a fairly thick blade for this.
I have thought about doing the same thing since I saw the video, but I would take a wide bowsaw blade for the experiment.
I would start by heating it with a gas torch (annealing I think it is called), then take it to someone with a sheet metal bender (a auto repair shop or a plate metal shop). Make the bend in the sheet metal bender and return to home for a resharpening and resetting of the teeth since the blade will have lost most of the set during the pressing in the bender.
The good theory of this is that with the wide blade, you can still keep the bulk of the blade in the same level, then the 90 degrees part can be left sticking out only 1/2″.
Coming to think of it, I’d better try this when I get home.
Maybe the blade would benefit from rehardening, but I don’t think that it will be crucial.
I forgot, this blade will only work for the pins, so it will be similar to the Harvey Peace saw.
What would this twisted blade give you that you can’t get with a fret saw? Speed?
I saw out my waste using a skip-tooth blade and it’s not appreciably any slower than using my coping saw – and it’s just dropped in the kerf right to the baseline. The blade is set 45 degrees below the direction of travel so all that’s needed is a slight wrist movement to get the saw cutting horizontal right on the baseline. Uri Geller need not apply.
I’ve got to be missing something.
I used a turning saw with an inexpensive length of broken bandsaw blade. I left the far end vertical but turned the closest end 90 degrees. I began the sawing with the far end and when I was ready to make the turn, I forwarded the saw to the closest end. It worked OK but not much difference better than using a dovetail saw to saw the verticals and a fret saw to remove the waste. I still had to do cleanup with a chisel. Moreover, the vertical cuts were much cleaner with the dovetail saw than the turning saw.
In short, I stuck with the old method since time is not my enemy. However, if I had to do production work like Klausz did, I would probably would go with the “turned” blade.
I think Shannon nailed it at #1. You need some space to allow the wood to accommodate the change in direction. And I’m surprised you managed to make the twist without sticking the blade in a torch. Sure that inch or so would lose temper, but you’re also reducing the stress to the steel.
Having said all of that (without having tried any of it), I have tried Mark’s method with much the same result. I concluded that all of the twist needed to be over a short length – but evidently not as short as you managed to make it.
Still chiseling his dovetails,
-Tom
Some days, we’ll do anything to avoid actually doing what we need to do.
I bet someone you could never use turgid in a blog post. Time to pay up.
I love the word turgid. It is one of the those words that you have an idea of what it means even if you’ve never seen it in context.
Tumescent is a good word too.
I did the same thing (minus the analysis) a few years ago after seeing FK ‘s video. I had about the same results with the tight bend. Tore a few blades, then got the bend over a slightly longer distance such that the blade stayed intact. I got it to work nicely in softer woods (East. White Pine and Poplar). I can’t recall ever trying it in harder woods, but I abandoned it as not faster than just using a coping or fret saw after a clean dovetail saw cut. I can see where a harder wood would either tear the blade or un-bend it. I agree with the bottom line: If it ain’t broke…
‘overer’… priceless. Chris, I’ve never met you, but I’m taking a shot in the dark and thinking you write how you speak. It keeps me reading blogs and buying books, so please keep doing what you’re doing. I thoroughly enjoy learning what to do, (and what not to do) through your efforts.
I watched the video. If you watch the section where he’s sawing out the tail board, you can see that the twist in the blade covers roughly the length of a fret saw. On that count, I think you need a longer saw.
Hitting rewind, you can see that he’s really blasting it through the pin board, using the full length of the saw. The full length of the saw has more inertia than the coping saw, which helps. It also leaves room for the three parts of the blade: the wind up, the turn, and the flat after the turn. Score another point for longer saw.
He’s also blasting through pine. Longer, and a thicker blade for blasting away.
I love a good shop experiment as much as the next guy. I made a modified sled once for cutting finger joints that allowed me to cut 4 drawers worth at a time. All of the modifications along the way meant that it was in pretty rough shape after the drawers for that project were cut, and I had to throw it out after that project, but it worked. I need to dust that idea off, I think…
I think the width of the original saw kerf is the key to this. A wide kerf allows a coping saw blade (straight, bent, twisted, or otherwise) to turn more easily in the previously-made kerf and begin cutting the bottom of the tail socket. To be honest, I’ve never understood the need for a very thin plate dovetail saw except for cutting very tiny dovetails. The only thing that matters is the edge of the kerf anyway. Thicker saw plate, finely set teeth, followed by a coping saw and chisel.
I think you should compare blade tension between your favorite bow saw and your favorite coping saw. I think you’ll find the bow saw has substantially higher blade tension, and that tension is what allows the saw to cut rather than bending to follow the existing kerf. Also, the narrowest blade I saw FK using in the video was probably twice the width of your coping blades. Wider blades have higher beam strength which increases resistance to deflection, deflection decreasing the blades willingness to engage the wood (and instead push and twist back into the existing kerf).
All this talk about twisting silly coping saw blades and no comments on Carl’s (now Josh Clark’s) astounding Peace square hole saw?!?!?!?!
You guys are nuts. 😉
-Matt
Yes, more information about the Peace saw. What was it intended to be used for? Seriously, sawing square holes? Does it work?
Dude! No wonder you’re a “Frustrated Furniture Maker”, your saw blades are bent…
Btw, that Peace saw looks like a pruner at the front. Not sure it would do the job as a dovetailer unless you plan on making nailed furniture.
I’d agree with Chuck. Was this saw (the HP Peace Saw) just for cutting a square hole in general, rather than dovetails? With the keyhole saw profile, it looks like it would work great for cutting holes in drywall for receptacle boxes. Although, I’m guessing that Josh Clark won’t be using it for that.
The saw is in original condition and is quite rare. It is factory correct and was marketed to tradesmen like carpenters, not furniture makers. It was indeed intended for cutting a square hole through walls and the like with just a pilot hole to start it ….rough cutting to say the least. And no Chuck, not for doevtails. 😉
I had an email exchange with Josh — the idea was that you could cut a square hole with only drilling one pilot hole, instead of one at each corner. I believe this saw predates drywall by a bit.
I posted a copy of an old catalog entry that shows this saw on my blog. The catalog claims it’s good for dovetail work too.
Log cabin dovetails…obviously.
Ohhh, blind miter log cabin dovetails! I think you’ve hit on a subject worthy of Chris’ research.
The design of Klausz’ “dovetail cutout saw” is in an article by R Mastelli in Fine Woodworking magazine (Wish I could recall the issue). “Methods of an Old World Cabinetmaker” I believe.
Cheers,
Peter