Chris Schwarz's Blog

Spiral Blades: Good for Dovetailing?

While packing my tools to teach a toolbox class in Germany, I knew two things:

1. The students had to cut a lot of dovetails in 7/8”-thick material.

2. Coping saws are uncommon on the Continent.

So I packed an extra coping saw blade in my luggage, which turned out to be either a stupid or brilliant mistake. By the second day of the class, the students had snapped both of my blades. I’ve never snapped a coping saw blade. So then we had two choices:

1. Bang out all the waste with chisels (the European way).

2. Use the school’s fretsaws with spiral blades.

Half of the students opted for the banging; the rest picked up the fretsaws. I was building a tool chest along with the students that week, so I also had to make the choice. I’m already pretty good at removing waste with chisels, so I decided to use the fretsaws and see if I could do two things:

1. Stop breaking so many fretsaw blades.

2. Cut so close to my baseline that I could simply pare out the waste without any chopping.

After a week and 50 honkin’-big dovetails I did master the fretsaw with a spiral blade. By the end of the week I was almost splitting the baseline in half with the spiral blade. So all I had to do after that point was drop a chisel in the baseline and push down. Nice.

But this accuracy comes at a price.

Spiral fretsaw blades – at least the ones I could find – are slow. The Dictum school had coarse, medium and fine spiral blades, but I wanted ones that were even coarser. In fact, I got to the point that while I was sawing out the pin waste I could take a sip of coffee while sawing. That’s how slow it was.

But I had almost zero chopping to do. So my gut feeling is that it was a wash for time.

I’ve prepared the following short video that demonstrates the two blades in 1/2”-thick pine for a drawer side. The coping saw blade is an Olson 18-point skip-tooth blade – the best coping saw blade I know. The spiral blade is a Ryobi 41 tpi blade – the only spiral blade I could get at the home center.

So here’s another tool to add to my wish list: an aggressive spiral coping saw blade with pin ends – or perhaps just a more aggressive spiral fretsaw blade. There is a spiral coping saw blade on the market already (see the details here), and they had some of these at Dictum, much to my surprise. But they clogged quickly with sawdust and resin.

If y’all know of other blades I should be looking at, leave a comment below.

— Christopher Schwarz

Other Dovetailing Resources
• Glen Huey’s “Cheating at Hand-cut Dovetails” DVD is an excellent group of tricks to help you get faster at dovetailing while preserving the hand-cut look. Check it out here.

• Have you ever seen Chuck Bender cut dovetails? He’s amazing. We have his two DVDs in our store: “Dovetailing Apprenticeship” and “Dovetail Mastery.”

15 thoughts on “Spiral Blades: Good for Dovetailing?

  1. mdgarnett

    A question about the Knew Concepts saw: have you tried both the aluminum and titanium versions? I got to try the aluminum one recently and felt it might be a little too flexible tho’ I didn’t have any trouble with it. Just wondering if the extra for the titanium is worth it if you care to express and opinion.

    Thanks

    1. oldster

      There is some flexibility side to side, but I have never seen anyone use the saw in the fashion that you describe.

      When the blade is tensioned, and you are using the blade to do the work, it is extremely rigid where it is important.

      I’ll be at the WIA conference in Cincinnati, and I will have both the Titanium and the Aluminum frames there.

      Since Chris seems satisfied…..

      Lee (the saw guy).

  2. oldster

    You might try these blades:
    These are spiral blades made for cutting wax (jewelers use them). The one shown in the video appears to have a very fast gain (relatively few tpi), and appear to be different than the ones that I suggest below.
    They are available from:

    http://www.Riogrande.com
    light duty #2 110-065
    med. duty #3 110-066
    hvy. duty #4 110-067

    They are sold in one doz. packages

    Also available from http://www.Ottofrei.com
    http://www.ottofrei.com/store/home.php?cat=1142

    These are made in Germany, and may be the same as what Chris was using.

    Blue tape on the saw frame?
    I have added a blade checking gauge to the saw frame by adjusting the laser cutting pattern for the frames so that it include a pair of parallel edges that are 5-1/8″ apart on the rear spine of the frame. The blue tape was to show Chris this new feature.

    Lee (the saw guy)

  3. woodgeek

    I get my spiral blades from Lee Valley. I believe they’re Olson’s.

    Deneb turned me onto using spiral blades for dovetail waste about four years ago at a woodworking show.

  4. Frank Strazza

    Hello Chris,

    The blades that I use for coping out the waste are found at….Sears, of all places! I get the fine coping saw blades. They work great, they are thin in the direction from teeth to the back of the blade, so you can make a pretty easy turn. Mine just develop that “twist” as I use it, but I suppose you could twist it with a pliers. I use them on the push stroke, you will have some tear out on the back side, but the knife line keeps that from causing any problems. I can cut right above the line with them. Give it a try, a pack is only $2.50!

  5. TheHoneyBadger

    Dear Chris,

    Will look for blades over here als well, but as you know you guys over there have way better supplies. When your video finishes theres this link to another video about a guy who makes dovetails in 3,5 minutes….. DAMN, oooppps, I’m sorry! Gonna have dinner now, chicken(s)!

    All the best man, Erik.

  6. pmcgee

    I am remembering Frank Klausz with a ?bowsaw? blade with a ninety-degree twist in it. A very cool video.
    He pushed the vertical section into the saw kerf, and continued to push forward, using the horizontal teeth of the rest of the blade. I always meant to try to butcher up me one of those.

  7. Andrew Yang

    I’m still working away with my coping saw. Even then, I don’t think I manage to cut through quite as quickly as you do with the spiral blade.

    Question regarding the spiral blade, do you have any problems with the blade marking up the side of the tails when you drop the blade down into the kerf?

    1. Christopher SchwarzChristopher Schwarz Post author

      Nope. No marking on the tail board. The trick is that the spiral blades have a section that has no teeth. So you start the blade moving against the work and it doesn’t cut until you get 1/2″ into the blade. Try one. You’ll see.

  8. Dean

    What was the tpi of the coarse spiral fretsaw blade at Dictum? I did a quick search and noticed that Olsen sells a 30 tpi spiral blade, and that Flying Dutchman Spiral saw blades (see link below) have 27 tpi blades from 0.011 to 0.015 inches and 0.030 to 0.037 kerf size. Just wondering how a Flying Dutchman 27 tpi at 0.015 inches thickness would have held up cutting dovetails in your toolbox class, or if they would have been too coarse and too thick. I’m guessing that it would be way too big for cutting the waste in your blog video, but then I’ve never seen various spiral blades sizes “in person”.

    http://www.scrollsawbladespatterns.com/new_spiral.htm

  9. patriarch

    In my experience with fret saws and coping saws, normally that’s the trade-off; coping saws are great for dovetails, whereas fret saws are better for finer pattern work. That being said, I’ve had pretty good luck with Lee Valleys #3 spiral fret blades (part # 02t16.12). Not as aggressive as most coping saw blades, but decent for what they are.

    -Simon

  10. Steve_OH

    After watching the video and listening to the music, I think I’ve got the spiral fretsaw blade blues…

    It seems to me that all you’re really looking for is a blade that will (efficiently) cut a tighter radius. The minimum cutting radius is controlled primarily by the distance from the tips of the teeth to the back side of the blade. The spiralocity of the blade isn’t directly a factor–that just makes it more steerable. But the size (and therefore aggressiveness) of the teeth is a factor, and so is the width (and therefore strength) of the blade.

    So, it’s ultimately a trade-off. Reducing the cutting radius means reducing either the aggressiveness of cut, or strength of the blade, or both. There are ways to make the blade stronger, but there’s a limit to what you can do about the aggressiveness of cut. Maybe a blade made up of a high-strength alloy steel wire and studded with small (but not too small) carbide teeth.

    -Steve

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