I don’t mind admitting that sash saws confuse me. I’m not talking about the word ‘sash’. Obviously in days gone by, this type/size of backsaw was used to make sash windows and the name stuck. What confuses me is whether it is the length of the saw that defines it as a sash saw or the way it is filed.
When I’m confused about hand tools, I turn to the people I respect in the hand tool world and when it comes to saws those people are Joel Moskowitz, Matt Cianci, and Mark Harrell. The excerpts below are taken from their web sites/blog posts:
Joel Moskowitz (Tools for Working Wood)
Gramercy offer a 14” Sash saw. Here are some quotes from the accompanying text:
“From the late 18th until the mid 19th century the two most common backsaws found in a joiner’s toolbag would be a dovetail saw and a sash saw. The dovetail saw would be filed with fleam so that it could be used for all small work, not just dovetailing, and the sash saw would be used for everything else.”
“We are pleased to offer a 14” sash saw with a traditional combination filing for both ripping or crosscutting.”
“Length of blade 14”, 13ppi, depth of cut at the toe 2.87” depth of cut at the heel 3.29”. 5 degrees negative rake and 7 degrees fleam. Plate thickness: 0.020”.”
On The Saw Blog, Matt Cianci recently wrote an article entitled The Venerable Sash Saw. Here are some picks from it, but I highly recommend you read the whole article.
“Of all the tool forms lost to antiquity over the last century, I think the sash saw is one of the greatest casualties. These traditional 14 inch backsaws are true work horses because they can rip and crosscut thanks to a combination of aggressively raked and moderately fleamed teeth.”
“My own experimentation with sash saws started some time ago when I read about them in Holzapfell. He describes a sash saw as being 14 to 16 inches at the toothline and having a 0.028 thick saw plate, 2.5 to 3.5 deep with 11 points per inch.”
“Over the following few months, I started filing and using 12 and 14 inch backsaws with aggressive rake and moderate fleam to accomplish both ripping and crosscutting. I eventually settled on 8 to 10 degrees of tooth rake and 10 degrees of fleam. I found that saws with thinner plates and finer tooth spacing could handle more aggressive rake with great results (like 8 degrees) and conversely, saws with thicker plates and coarser spacing needed 10 degrees to keep them smooth in the kerf.”
In his reply to one of the comments on this article, Matt writes:
“I’ve found in 9 times out of 10, regardless of plate thickness, tote hang or tooth spacing, 10 degrees of rake and 10 degrees of fleam is the magic combination for sash saws.”
Mark Harrell of Bad Axe Toolworks wrote an article entitled About my Saw Filing Technique which you can read in full on his site. It’s a great article which encompasses a lot more than just sash saws. In the article, Mark refers to his 14” backsaws as sash saws, regardless of whether they are filed crosscut, rip or combination (which he refers to as hybrid filing). Here are the salient points that are relevant to our discussion.
In his PPI table, he lists the 14” sash saw as being 12-13ppi and calls it a “general purpose saw.”
Regarding plate thickness, he writes:
“I find that a 0.020 gauge plate is best suited for dovetail and carcase saw work, less suitable for a 14” saw, and not suitable at all for 16” and above.” He goes on to say that “…length + depth = heat. When you’re ripping big tenon cheeks, the heat generated by the friction of a saw deep in that cut will expand the metal plate, causing warpage and drift along the cutline.”
“At the end of the day, 14” hybrid, 16” and 18” crosscut saws should have .025 plates: that’s just enough thickness to serve as a heat sink and prevent the warpage. 18” saws for hybrid and dedicated rip filings should always have a .0315 gauge plate for the same reason (length + depth = heat).”
Talking about his hybrid filing on his 14” sash saw, he says:
“…I typically recommend a filing of 12ppi hybrid-cut with the .025 plate. Here’s why: a 12 point pitch is fine enough for 3/4 work, yet coarse enough for 8/4 work (and beyond – but that’s where length becomes a consideration too). I’ll file this saw with 17.5 degrees of fleam (more aggressive than a 20 degree dedicated crosscut filing), and 10 degrees of rake (more relaxed than a dedicated rip angle of 6 degrees, but not as relaxed as a 12 degree rake for a crosscut saw). In rip mode, my hybrid filing cuts at about 80% compared to a dedicated ripper. The gullet remains five degrees. I will relax the rake 30 teeth in from the toe, and about 20 teeth in from the heel of the toothline. This eases the start and finish of the cut. … The bottom line with my hybrid filing is you get a crosscut finish – a great crosscut finish – with decent ripping action to boot.”
Having read the above excerpts, you can probably begin to understand why I’m confused as to what constitutes a good sash saw. As I said earlier I have the greatest respect for all these guys, but you have to admit that there is quite a bit of difference in what they deem to be the optimum filing for a sash saw.
Here’s the information in tabular format:
In the past I’ve said that I didn’t really see the point of combination filing on saws. After all, you are effectively accepting less than the optimum for both crosscutting and ripping for the sake of being able to use one saw for both types of cut. This would appeal to me if I had to carry my tools and worked on different job sites, but when you’re working in a small workshop I don’t really think it is that much of an inconvenience to put one saw down and pick up another? The whole point of this journey though was to experiment a bit with different tooth geometries so I had to give combination saws a chance.
I have no doubt that the Gramercy sash saw is an excellent saw. I have their dovetail saw and both of their carcase saws and I like them a lot. However, I have to agree with Mark when he says length + depth = heat. When I built my breakfast bar out of hard maple, the only rip backsaw I had was my Gramercy 12” carcase saw which also has a .020” plate. I used the full depth of the plate to cut the tenon cheeks and I couldn’t touch the plate afterwards it was so hot. If I owned the Gramercy sash saw, I would look at it as a bigger carcase saw. I would either buy the two 12” carcase saws, one filed rip and one filed crosscut, or if I favored saws with a longer stroke and increased depth of cut, I would buy their 14” sash saw. However, I would still be looking for a saw with a heavier back, a thicker plate (.025” to .028”) and a greater depth of cut for larger tenon work.
I’ve never tried the Gramercy sash saw, but I can see how 5 degrees of rake and 7 degrees of fleam would work on a saw with a lightweight back and .020” plate. The saw I decided to try a combination filing on though is a very different animal. Enter stage left, the 14” Drabble and Sanderson that I restored in part 7 of this series. Remember this one?
This saw has a .030” plate and a very thick, extra-heavy brass back. It was filed 12 tpi (13ppi) when I got it. In part 11 of this series I presented a chart showing how I was going to file all the saws I’ve restored and I stated that I was going to re-tooth this one to be 11 tpi (12ppi). I intended to file it using the rake and fleam angles that Mark Harrell uses for his hybrid filing. I might still do that, but first I thought I would leave it at 12tpi and try Matt’s recommendation of 10 degrees of rake and 10 degrees of fleam. My reasoning here was twofold: 1) Matt knows what he’s talking about and, 2) I could easily change it to what Mark recommends if I didn’t like it.
In retrospect, this probably wasn’t the best saw to try a combination filing on. It would have been better to make this one a dedicated rip saw with 11 tpi (12 ppi) and use one of my Tyzacks with a lighter back and .026” plate as a combination saw. Hey who knew?
Anyhow, you probably want to hear how it cuts. I’ve only had time to try it in a bit of quartersawn sapele so far, but I have to say it rips very well. I was particularly impressed with the back of the cut. In fact it was difficult to tell the front from the back as there was no fuzz at all. The surface finish was good too. Crosscutting at 90 degrees to the grain and at 45 degrees to the grain also worked well, although there was a little bit of tear out at the back of the cut. The surface finish on the crosscuts was also very good.
So am I any clearer on what characterizes a sash saw? I think so. Even though today the term sash saw is used to refer to any 14” or 16” backsaw, to me a sash saw is 14”-16” in length, with 11-13 ppi and filed with a combination filing for both crosscutting and ripping. The jury is still out on my preference for rake and fleam angles, but it should have a fairly aggressive negative rake angle and a moderate fleam angle.
In the next part of this series, I’ll try to get some video of this saw cutting. Then I’m going to change it to 17.5 degrees of fleam as Mark Harrell suggests and shoot some video of that too so you can see the difference between the two filings.
Thanks for reading my inane drivel.
-- Andy -- Old Chinese proverb say: "If you think something can't be done, don't interrupt man who is doing it."