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  1. #61
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    Iím just going to get a egg [emoji6]

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  3. #62
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    Matt, I was not querying the accuracy of your conversion, it was the size of your slot. Take another look at the Blackburn ad - the slot is 0.3 inches (or 7.62mm) DEEP not WIDE (as you wrote). If the slot was 0.3" wide, the spine would have to be monstrous to accommodate it. I was wondering if you were intending to use recycled truck springs for saw blades!

    I would happily accept a slot 0.3" deep, in fact I usually cut mine a bit deeper than that....
    IW

  4. #63
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    Quote Originally Posted by Bushmiller View Post
    7.62mm sounds like a round of ammunition to me.

    Did Matt mean the thickness of the back and not the thickness of the slit?
    Just a mild case of not being careful about names, posting the ad. removes all ambiguity....

    Paul, your measurements match my experience of small saws very well. The vast majority of saws up to about 300mm long (blade) of all ages that I've measured (with good-quality calipers ) fell in the 0.020-0.025" range, with just a few outsiders. I've seen one or two oldies that were a touch thinner than 20 thou, but only a teeny bit, nothing less than 18 thou. Bigger, longer saws were all in the 30-32 thou range.

    My sample size would be fewer than 50 saws all told, which is pretty small, so there may well have been saws made for particular reasons that were thicker or thinner for a given plate size.

    In my opinion (& it's just an opinion based on my own saw-making & saw-using experience, other mileages will vary), around 20 thou is ideal for saw blades up to about 250mm long, and a heavier gauge is better for 300mm or so. The main concern is how many teeth you can apply to the plate. If you put say, 12tpi on thicker plate (0.030" +) you may have trouble setting them. Thicker plate needs more set to give the same % increase in kerf width, & trying to push over just the top 3rd of thick, small teeth usually ends in a lot of distortion. You can clean it up on the sharpening step, but they don't come out as neat for me as the same size tooth on thinner plate.

    The fashion for "ultra-thin" blades of 0.015" developed a decade or two back & like I have on more than one occasion, I jumped on that bandwagon immediately, uncritically accepting the maxim that "a thin saw cuts faster". For a while was a great advocate of 15 thou plate for small dovetail saws (& I still am, but with a few caveats!). After more experience with saws & novice sawyers, I've revised my opinions a bit, & now tend to recommend 20 thou plate for people with less sawing experience. The bit of extra robustness doesn't hurt, and speed of cut is so close to the same for a given tpi it doesn't matter - I've done several trials with saw plates of different thicknesses but same tpi & tooth configuration, and cannot measure any significant difference in speed of cut. There are minor advantages in the very narrow kerf the 15 thou saw leaves, but it can also be a nuisance for those wanting to use coping saws to remove waste from their D/Ts because coping saw blades are substantially thicker & don't fit well in the skinny kerf of the D/T saw.

    Cheers,
    IW

  5. #64
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    This thread has taken a few twists & turns, but for the sake of completion, Here's my finished 1/3rd scale saw: Mini.jpg

    You might get a better appreciation of its size alongside a bigger brother and the "original": 3 sizes.jpg

    It does actually work, but I can only hold it between a thumb & index finger, so it's not really usable in any serious way.

    It was an interesting exercise. I set out to make as exact a 1/3rd scale model as I could, but I ended up taking several liberties, so it's far from exact. The plate is twice as thick at 10 thou (it should be 5), but 5 was just too flimsy to make a working model from, I decided. The bolts are also too big, I don't have taps & dies smaller than 3mm (or at least I didn't, I've just ordered a 2mm set ), and the handle is a bit thicker at 11mm than the 7.5 or so it would need to be in scale.

    So having taken some lessons from from the gents saw above & still having some scraps of Macassar ebony, I made a 2/3rds scale model with a blade the same length, but a little narrower: 10 thou saws.jpg

    Now we're cookin'. I can actually hold this one fairly comfortably in a standard 3-finger grip (I don't have a very big hand): grip size.jpg

    And with 24tpi, it's a smooth-cutting little beast. Out of curiosity, I compared this saw (24tpi) with the 'gents' saw (18tpi) and the dovetail saw in the pic (18tpi). I made 3 cuts to the line with each saw in a piece of 12mm thick Jacaranda, trying hard to put minimal pressure on the teeth & counting the strokes. Cuts cf.jpg

    The two 10 thou saws took about the same number of strokes on average (~9), with the ebony-handled saw being a half a stroke faster, despite the slightly finer teeth. (I think the reason for that is because of the handles, it was easier to to let the gents saw cut "under its own weight" and not force it). The 'full-sized' dovetail saw reached the line in a touch under 5 strokes despite its plate being 50% thicker. The reasons for that I ascribe partly to its coarser pitch & greater weight, but mainly to its longer blade & stroke.

    So there you go, my curiosity is satisfied; it is possible to make saws with 10 thou plate, albeit little ones. I'll play with the two usable ones for a bit & see how they stand up to regular work, but they seem ok. There is one "but", however. This very thin plate is a beast to cut teeth in & sharpen without getting cows & calves. It only takes a single stroke of the file to cut 24tpi teeth to near full-depth! I had to concentrate like fury on every tooth (all 144 of the damned things) to try & remain consistent - the slightest variation in pressure or length of stroke would make a visible difference to the tooth size. This is as good as I could manage, it's not bad & cuts smoothly, but there are a couple of "funny ones": Teeth ebony saw.jpg

    OK, done with saw making for now - got a few jobs coming up where I should be able to use my dinky new saw to good effect, so I'll report back in a year or three if it turned out to be a good idea or a bad one....

    Cheers,
    IW

  6. #65
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    Quote Originally Posted by IanW View Post
    Matt, 0.87mm is roughly 34 thou which is rather hefty for a backsaw. Be a god starting point to taper-grind a panel saw blade from though. Pity no-one here has taken up taper-grinding. Paul, I'm looking to you to start something, you have a genius for coming up with some nifty low-tech ways for getting the job done....

    Cheers,
    Ian

    This was Disston's works in 1902 with their taper grinding operation:

    Grinding Disston handsaw blades 1902.jpg

    This is the thread Rob Streeper began on taper grinding:

    Taper Grinding Saw Blades (woodworkforums.com)

    Full details can be viewed there, but this was his grinding set up.

    saw blade grinder 1.jpgsaw blade grinder 2.jpg

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

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