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  1. #16
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    Nice looking saw Rob with interesting specification.

    Regards
    Paul
    Bushmiller;

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

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  3. #17
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    So near enough, Rob, the blade of your saw has been reduced in thickness by 20% from tooth line to the top. I guess that equates to my empirical findings that a set which produces a kerf that is between 15 & 20% wider than (untapered) saw plate, runs freely in the dry hardwoods I generally saw & works well enough in pine, as long as it's dry. There is a difference in that a goodly part of the plate in a tapered, un-set saw is still almost as thick as the tooth, so there is going to be more friction than with a typical 'set' saw.

    You probably wouldn't grab one of these saws for general sawing, so perhaps being too specialised was their downfall - after all, it's pretty easy to shoot a sawn mitre, & indeed, I imagine it was deeply ingrained in the work practices back in the day, so p'raps the 'mechaniks' just didn't see there was enough value in having an extra tool to maintain? ...

    Cheers,
    IW

  4. #18
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    Quote Originally Posted by IanW View Post

    ...so p'raps the 'mechaniks' just didn't see there was enough value in having an extra tool to maintain? ...

    Cheers,
    Likely, could also be down to 'good-enough' - ism or cost to produce/purchase.

    When I taper blades it usually doubles the total time I take to finish each piece (plate, not saw). To me however the result is very much worth the extra time.

    I find that a well tapered blade can cut considerably faster than an equivalent un-tapered blade. I have a Wenzloff half-back with an un-tapered 0.032" blade. I made a copy but with a tapered 0.032" blade and it cut about 25% faster than the standard set Wenzloff.

    Tapering plates less than 0.020" is very difficult with 0.025" being the practical minimum. I'm planning to try tapering some thin but narrow plates to see if it can be done.

    Cheers,
    Rob
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  5. #19
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    Quote Originally Posted by rob streeper View Post
    Likely, could also be down to 'good-enough' - ism or cost to produce/purchase....
    Yeah, I reckon those would be among my guesses as to why they perished, too, Rob.

    Mind you, I think "good enough" can be very good, even with an untapered blade. The difference between a saw sharpened & set for a particular job and a not-so-good one is pretty obvious, in my experience. I'm interested to hear you say that the tapered blade cut faster than an equivalent non-tapered blade (were the rake angle & tpi the same??), and particularly by such a big margin. I would've thought any difference would be more apparent in smoothness of cut rather than speed, but since I have no real experience of tapered blades on backsaws, I'm certainly in no position to argue!

    Interesting - it looks like I could have a nice old 77 in my hands for a short while (), so you can bet I'll be giving its abilities some close scrutiny. I might even go so far as to make a saw that is in all respects the same, apart from a tapered blade, and put them through a head-to-head comparison. I secretly hope any difference is not as great as you've found, I have no way of tapering a blade myself, & I really don't want to have to remake all of my backsaws.....

    Cheers,
    IW

  6. #20
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    Both of the half backs were 10 PPI with xcut filing. No idea of the rake on the Wenzloff but the one I made was 21o, dictated by the high and forward set handle. The Wenzloff was a bit catchy in use which I ascribed to the rake angle being a little too steep. I think my comparator has a protractor ocular...
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  7. #21
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    Default First impressions of a 77....

    Well, Zac & I did a little deal - he let me sharpen his saw in return for a little play with it. The saw duly arrived today, and although I am in the middle of something I really ought to be concentrating on, the temptation was too much, so I unpacked the saw (it was very well swaddled! ) and had a look.

    You've done quite a good clean-up job, me lad, and this saw feels very nice in the hand; Good handle, & the heavy steel spine gives it just the right heft, imo.

    So on goes the magnifying headpiece & I takes a look at those fangs.
    First, I can confirm what Zac said about there being no change in the initial tooth sizing. They were too even, and matched the remaining (12tpi) spacing too well to have been modified by a backyard handyman, so the saw may have come that way - were some 77s produced without the reduced tpi at the toe??
    Someone with more enthusiasm than saw-sharpening ability has certainly got at it during its previous life - the first 1/3rd from the toe were filed straight across(rip) while the back 2/rds were all over the place, but with increasing traces of fleam towards the heel, so I think it began life as a crosscut. And there were just too many sad stumps of busted teeth to ignore; one or two, maybe, but there were 3 & 4 in a row in the worst cases, & they were right where a lot of the action happens, so a major jointing was called for.

    I pulled out the digital calipers and took some measurements of the plate, they are marked on the pic (measured in thousandths of an inch, 'cos I'm just too used to thinking of saw plate in Imperial units): saw c measurements.jpg

    So a bit of jointing, some tooth-reforming, a bit more jointing, and all the tooth tips were level again. Yep, this is hard stuff, and it took most of the life from a new file to get them re-shaped. You've probably lost about half a tooth height, Zac, but don't worry, I doubt you will notice the difference in width! I've started with only 25 degrees of fleam. It will be easy to add a bit more, & I'm curious to see what difference it actually makes. The whole job took a bit longer than usual, what with the length (14"), the major tooth re-form (most were still reasonably even, thank goodness!), and the tough metal, but it was done soon enough.

    Then out with some scraps and a few test cuts were made. After each cut with the 77, I cut another slice off with my 'go to' joinery saw, which is also 12tpi, and has about 20 deg of fleam. The first thing I noticed is that the saw is harder to push than my 'set' saw, so I smeared the blade with paraffin & that improved it a bit. But you need a light touch, just letting the saw cut under its own (considerable!) weight was the go - any forcing at all makes it bind. It tracked very nicely, but with the tight-fitting kerf, there is no 'steerage-way' - it goes in the direction you start in, & that's that!

    Comparing the cuts from the two saws, there is no doubt the 77 leaves a far nicer surface - you can see some faint lines in the pics, but they are very fine & you can't actually feel them with your fingers. Here are some samples, in each case, the cut made with the 77 is on the
    First Cherry 1 cherry.jpg

    Then Ash (Fraxinus, not "Victorian'): 2 Ash.jpg

    Now some tougher stuff, She-oak: 4 She-oak.jpg

    And finally, Crows Ash, to see if the oily wood cut easier (it did, a bit): 5 Crows Ash.jpg

    For interest, I compared the kerfs of the two saws - mine is on the left, the 77's on the right: Kerf cf.jpg The kerf from my saw is 33 thou, or 32% wider than the (25 thou plate) saw, which confirms what I already knew, that the saw is over-set, thanks to a blunder at the last major sharpening (I usually aim for enough set to give a kerf between 15 & 20% wider than the plate of a joinery saw). The 77's kerf is 34 thou, i.e. the exact size of the widest part of the plate I measured. I guess that explains the resistance.

    So, so far, a fun couple of hours. Tomorrow, I hope to increase that fleam to 45 as per Henry's intentions, & we'll see how she goes. Stand by for more....

    Cheers,
    IW

  8. #22
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    Wow Ian great job! I'm interested to see if the extra fleam makes any difference...

  9. #23
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    Can you tell the medallion date of the saw? I can't make out enough detail from the picture.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  10. #24
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    Rob; zac provided a close up photo of the medallion further back within the thread.

    Help with a Dodo (Disston 77)-14112054_10154027888171185_1172977262_n-jpg

  11. #25
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    Know anybody who can test the hardness?
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  12. #26
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    Quote Originally Posted by rob streeper View Post
    Know anybody who can test the hardness?
    Rob, the only person I know who might do it is on the other side of the continent from me. I think I'll be satisfied just knowing it's tougher than 'regular' saws - not the hardest saw steel I've ever filed, but going from the 77 to one of my saws (new, "Swedish" saw plate), the difference was very apparent.

    Been thinking about it overnight, and have a couple more things to investigate today, before I pack it up & send it off home. I was surprised at the resistance when it gets 10-15mm into the cut. Waxing certainly helped, so I'm wondering if these saws need a pretty high degree of polish to work properly? Zac has done a good job of cleaning the plate, and I couldn't see any especially shiny spots indicating a dent, but I might try polishing the plate a bit more & see what difference it makes ( don't worry, I'll be very careful with the etch, which is still very legible, despite the neglect it's suffered in the past).

    Once I've tested the polish angle, I will take the fleam to its full 45 & see where we are. Note to Bushmiller: it's not as easy to do as I expected; the combination of such an 'extreme' angle & the habits of years don't combine well! On a practice run with a bit of scrap, I had to resist the tendency to let the file creep back to a more 'normal' angle. I have 20 degree guide lines marked on my vise jaws, which I don't want to change, so I'll put a couple of marked strips of paper along the jaws to keep me on the right angle.

    Ok, off for another go at it...
    Cheers,
    IW

  13. #27
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    Ian,

    Thanks for the information. I haven''t mapped the plates of the two backsaws I suspect may be pre-77's yet but I'm pretty sure that the tapers will be similar to the saw in your hands. I'll also map one of the Wenzloff 77's to see how the grind profile compares.
    The profiles of the Acme 120's are interesting in that the decrement in thickness in the first centimeter above the teeth is quite steep at around 0.003". The thickness uniformity is also better than the 77 you have which appears to have a thick spot a few inches in from the toe.

    Regards,
    Rob
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  14. #28
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    Ian

    I know what you mean about the angles and the muscle memory. You may recall that I have a natural tendency to drop the file handle down, which I think is why the sloped gullets come fairly naturally to me. In fact when filing with zero slope I really have to concentrate hard to resist that dropped handle tendency.

    I have never filed at 45 degs fleam. The most I have done is 35 degs on a mitre saw.

    My only real concern with such extreme angles of fleam is to whether they will stand up to the harder timber species.

    Regards
    Paul
    Bushmiller;

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

  15. #29
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    Quote Originally Posted by rob streeper View Post
    ...... the 77 you have which appears to have a thick spot a few inches in from the toe.....
    Rob, I didn't attach too much significance to the slight variation along the tooth line, I think some of it may be due to deep rust-etching & there are a couple of nasty scabs along the bottom. I may have put the calipers over one of these to get the outlier (34), the other measurements are within a thou of a median 32, which you can probably attribute to operator error.

    Cheers,
    IW

  16. #30
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    Default A wrap-up..

    Well, there's always more to be learned about saws!

    Working on the hypothsis that the saw plate needed a bit more polish, I went at it with some 800 through to 1500 W&D, followed by metal polish rubbed on with scrunched-up aluminium foil. The latter works a treat on new plate, but after a half an hour of effort & impending RSI, I decided Zac had done about as well as the old saw will allow. It did feel a little smoother & slipperier along the bottom inch or so, but I may have been fooling myself to justify all that effort.

    Anyway, on a test-cut, it was even more inclined to bind than yesterday. I gave up pushing it, about 5mm into the first cut on a scrap of Qld Maple.

    By this stage, I'm wondering if I should just stop there, & send it home to put in a glass case as an example of a great idea that just doesn't work. But I decided to press on, and follow Henry's instructions, so I ruled up a series of 45 deg. lines on some paper, folded them over, & slipped them in the vise beside the saw: 45.jpg

    With these as my guide, and a bit lot of concentration, I soon had a set of neat, but rather peculiar-looking teeth, when one is used to the more typical fleam angles: 45 teeth.jpg [edit: I should have brushed the bits of sawdust off, it makes the teeth look uneven!]

    OK, back to the sample, & what a stunning difference! Suddenly, the saw is cutting sweetly & freely. The difference between the action with the 'regular' fleam angle & the 'extreme' angle is almost too much to believe, but there it was. The saw cut as freely as my 'set' saw, still leaving a far cleaner surface. I guess I don't get many Damascus moments these days, but I certainly had one this morning - from a skeptic to a believer, overnight!

    Quote Originally Posted by Bushmiller View Post
    ..... My only real concern with such extreme angles of fleam is to whether they will stand up to the harder timber species....
    Yes indeed, Paul, that may well be the rub, but only time & use will tell. I suspect you are right, and if these saws are used to hack into hard, siliceous woods, they will need constant attention, but if used on 'cabinet grade' woods I think you'll get pretty good service between sharpenings, helped by the harder plate.

    Anyhow, my curiosity has now been satisfied. If a decent 77 ever drops into my lap, I'll probably grab it, and be glad to have it, but I can live with my 'cruder' saws, so I don't think I'll actively pursue one.....

    Zac, thankyou very much for letting me play with your saw, & I'll have it in the post tomorrow, I hope.....

    Cheers,
    IW

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