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  1. #76
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    Quote Originally Posted by hiroller View Post
    Ironically,
    I see what you did there - well played.
    Theory and practice are the same in theory, but different in practice.

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  3. #77
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    Just moving on a way from the pundit to the charlatan....

    In attempting to replicate the original Kenyon saws it was apparent that the saw screws were not the standard sizes of later years. In principle Kenyon used two sizes of screw but even they were not all quite the same plus the screws on the open handled saws were distinctly oval. I selected a compromise that had a large screw and a smaller screw as there is a limit to the level of intricacy to which I was prepared to go. However neither was a standard size and I realised, when Ian asked me how I was going to drill the recess for the screw heads, that I had a problem. I think most people use Forstner bits for the recess. I have used them but normally I simply use a spade bit. This channeled my thinking and I decided to go down the same track modifying them as necessary.

    I bought two bits and deliberately selected the type with a winged spur on the outer edge as I felt it would give a cleaner cut with less likelihood of breakout. I bought a 12mm and a 14mm. I actually wanted an 11mm bit but Bunnings did not have one. Both bits were filed down as close to equally as possible on both sides using an old saw file. I can testify that although the corners were gone the face still cut, which echoes the thoughts of several of you that the corners are the weak point and determine the useful life of the file as far as saw sharpening goes.

    P1040248 (Medium).JPGP1040249 (Medium).JPG

    Although the two open handle saws have not had the kerf cut for the blade yet, I went ahead and drilled all the holes

    P1040250 (Medium).JPG

    The two handsaws have one small screw and two large

    P1040253 (Medium).JPG

    The smaller closed handle and the two open handle saws have two small screws

    P1040254 (Medium).JPG

    and the larger back saw has just two large scews

    P1040251 (Medium).JPG

    As you can see in this last pic, some preliminary shaping is taking place. As this is the Silky Oak it was easy to rasp away, but with the harder timbers, which are all the rest, I will be hogging off the corners with a saw or sander to minimise the work done with the rasp. I would prefer to use just the rasp, but the timber is too tough and I value the rasps too much. I want them to last as long as possible. It is much cheaper to sharpen turning saw blades and replace sanding discs than buy more Liogier hand stitched rasps. For the first time I also plan to use the small radius spokeshave I have which was made by HNT Gordon. I think that may work well on some of the medium corners and curves particularly on the inside of the handle hole.

    In the end though it comes down to sand paper, without which I would be well and truly lost.

    Regards
    Paul
    Last edited by Bushmiller; 5th September 2018 at 09:00 AM. Reason: spelling
    Bushmiller;

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

  4. #78
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    I think Paul & I had a discussion on why the bolt head diameters are all a bit different, but for the record, this is my theory: I suspect the bolts all stared out the same, as castings. Casting may seem like a rather cumbersome way of making bolts, but it was the most convenient way of semi mass-producing such things in the days before automatic lathes were perfected. Casting would explain the slightly oval heads.

    All the bolts & split nuts I've seen have a very pronounced chamfer to allow them to be pulled hard into the counter-sunk holes. On assembly of the saw, the nuts were tightened down so that both sides were squashed hard against the sides of the counter-sink holes. When the protruding metal was filed flush, you had a very tight fit of metal to wood, but given there's be a small variation in countersink depth, as well as hardness of the wood, that would provide all the conditions for no two bolt heads being precisely the same diameter as viewed on the finished saw....

    So Paul, for a more 'genuine' set of replicas, we'll have to set up a mini-foundry......

    And you are much gentler on your rasps than I am - mine have been fed some pretty tough stuff over the years I've had them, and all but one are still cutting well. The one that is a bit dull is one of the first Liogiers I bought, an 8" modellers' rasp, so it's done a power of work, & doesn't owe me much by now. I think most of the dulling came from a particular chunk of Qld. Walnut I used for a few handles, some time ago. It wasn't all that hard, softer than Red Gum or She-oak on an ease of indentation scale, but it dulled saw & plane blades like you wouldn't believe! I grew up in the area it grows in & I've always known Qld. Walnut has a fearsome reputation for tool-dulling (Morris Lake goes to great lengths to emphasise that aspect in his book!), but hadn't struck anything as severe as this before. I've picked up a couple more peces since that were nowhere near as hard on my tools (thank goodness!). A nice wood to behold once you get it where you want it, but when every bit you find is a lottery, it makes you a bit wary of it.

    Based on my own rate of production, I estimate you've got about 2 more solid weeks to go to get those handles licked into final shape......
    Cheers,
    IW

  5. #79
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    Thanks Ian

    I was hoping you would put your theory forward regarding the Kenyon original saw screws. The castings would have been quite rough and would have needed to be cleaned up with a file so that might well account for the variations. I am still not quite sure about the oval screws as this would have presented a lot of extra work when drilling the countersink holes. Having had to do some modification with the spade bits to bring them down to size, I don't know how they would have achieved this in 1797. Possibly they drilled a hole and then modified it with a curved chisel. In Beech this would not have been too much of an ask. It may even have been done deliberately to resist the screws turning in the timber as they were tightened. As far as I know the handles have never been removed (for fear of irreparable damage) so we don't know what is underneath, but it is doubtful there is much of a square shank as on the screws you made up. Most split nuts I have seen have only a very slim square shank and I guess relied primarily on the friction of the chamfer against the timber to prevent the screw turning.

    I think the only timber I will be able to "pull" the screws into will be the Silky Oak. I have never worked with it before and was surprised at how soft it is. I am assuming it is Grevillea Robusta (Bootle lists eight different Silky Oaks, but most are denser than the Grevillea species) and while green it weighs in at 1100kg/m3, the dry density is down to 620kg/m3. The difference in ease of working between the Silky and the other timbers is almost mind boggling.

    As to the scheduled time period for completion, I think your estimate relies heavily on an unbroken run at them. Unfortunately during the next couple of weeks I will be away for about a week.

    Regards
    Paul
    Bushmiller;

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

  6. #80
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    All the bolts & split nuts I've seen have a very pronounced chamfer to allow them to be pulled hard into the counter-sunk holes. On assembly of the saw, the nuts were tightened down so that both sides were squashed hard against the sides of the counter-sink holes. When the protruding metal was filed flush, you had a very tight fit of metal to wood, but given there's be a small variation in countersink depth, as well as hardness of the wood, that would provide all the conditions for no two bolt heads being precisely the same diameter as viewed on the finished saw....

    Iím having considerable problems with the idea of nuts being chamfered, if I look at this from a purely theoretical position ,and I am. Now ,if I pull on my considerable knowledge of engineering which is zero.

    We are infect pulling a wedge (yes tho with a flat bottom)through the timber close to the edge of the handle a weak point.
    Yes ,agree the angle is very slight compared to say a log splitting wedge.
    Creating pressure on the side walls of the hole receiving the nut ,possibly causing a fracture in the timber.

    Yet ,I have saws were the nuts are chamfered and all is well that ends well.
    So it must work, because the saws a very old even older than most on this forum,

    I understand why the chamfered is great from a ascetic point of few.
    It makes the hole and nut look tight (I was going to say something else but ,Paul ,would have possibly been given to much ammunition lol)


    Now my due apologies to all who just read my rant.
    And wasted 10 seconds.
    Because yes I have an issue(because I once wrecked a handle I was making with yes chamfered split nuts.)

    Carry on as you were [emoji849]
    I potential feel better now.

    Cheers Matt,

  7. #81
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    Matt

    You have raised a few issues there. Whilst both you and I have pointed out that the screws, by virtue of the chamfer, can be pulled into the timber, the screw thread was coarse and the nut was relatively thin. Even when brand new those old split nuts would not have been able to boast too much pulling power before stripping the brass thread. I think that relatively speaking there would have been a lot more filing going on than compression. So I don't think splitting timber would have been a big issue.

    I don't know what type of saw screw you used to that split the timber. I would lean towards some hairline defect in the first place. Having said that, if you used saw screws similar to those Ian Wilkie and Rob Streeper make, they are a much more robust construction having a thicker shaft and a finer thread, which in engineering terms has superior strength. I may have to be more careful when assembling, but the saw screws I am using are relieved on the inner edge; Not chamfered the whole thickness.

    P1040181 (Medium).JPG

    The greatest issue I am currently having, in my mind's eye, is filing the screws flush when they are in position. I can see myself making a big mess of the surrounding timber if I am not careful even if I file in the direction of the timber grain.

    Regards
    Paul
    Bushmiller;

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

  8. #82
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    Quote Originally Posted by Bushmiller View Post
    .....The greatest issue I am currently having, in my mind's eye, is filing the screws flush when they are in position. I can see myself making a big mess of the surrounding timber if I am not careful even if I file in the direction of the timber grain....
    Nah, you're crossing bridges before you get there. I confess I used to shy away from the flush finish myself, early on, partly because I like to pre-finish handles before assembly. So what I did on the first 50 saws or so was to deliberately make bolt-heads & nuts a little proud, & give them a rounded chamfer, so they looked a bit decorative. But eventually, I found it's not that difficult to do the flush finish. After the saw is assembled & split nuts tightened down, I clamp the saw lightly between my (wooden) bench dogs. Then I take a sharp (i.e. newish) file that has a good bite, but isn't too savage, e.g. a second-cut 10" flat file, and file away, keeping the file contacting at least two bolt heads/nuts as I file, which helps to keep it straight & avoid hitting the wood. I file the brass right down to the wood, then finish off with a flat block & sandpaper to 600 grit, then re-finish the bare wood & the job is done.

    But to get a tight flush finish perfect every time, you really need to use heads/nuts with a pronounced chamfer. Relying on precise counter-sinks in wood is, well, not reliable. Sometimes the drill wobbles or the bolt pulls off centre or something, & I end up with a teeny gap: bolt heads flushed.jpg
    Most folks woudn't notice, but I do!

    P'raps that's why I've swung over to using Glover style bolts this last couple of years.....

    Cheers,
    IW

  9. #83
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    Thanks Ian

    You have in describing your method given us another reason why the Glover patent enjoyed such success. It completely removed the filing step. Something that had not dawned on me before as I was totally focused on the more robust nature of the screws.

    Regards
    Paul
    Bushmiller;

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

  10. #84
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    I'm not sure that having to flush the bolt heads & nuts was the driving reason for switching to Glover bolts, Paul. It wouldn't be a big deal to someone doing dozens every day. There's a bit more faffing about drilling the holes for Glover bolts - three sizes of concentric hole required, instead of two. I imagine that would've been taken care of pretty easily by machines in a factory, but it involves a bit more messing about doing them one by one on a drill press for us 'cottage industry' folk.

    Interestingly, the main thrust of Glover's 1887 patent application seems to be about the solid medallion bolt (apparently medallion bolts were previously made as two pieces brazed together) & makes only a brief mention of the cupped nut (had that been in use before 1887??). The domed heads of the cupped nuts makes it feasible to have a simple slot - no more fooling about with split-nut drivers, which are more awkward to use & (in my hands, anyway) tend to cam out & damage the slot if you aren't exceedingly careful when tightening them down.

    I suspect the switch to domed heads had more to do with appearance (aided by automatic lathes & cheaper metal prices?), rather than any perceived mechanical advantages, but I'd be happy if someone can enlighten me otherwise.....

    Cheers,
    IW

  11. #85
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    Ian

    This is an interpretation from the Glover patent:

    "The primary focus of this patent is on the two-part construction of the saw medallion ("label screw"). In a sense, it can be seen as an improvement on Munger's patent (U.S.P.N 98180), which had no provision for preventing the shaft from twisting independent of the head if the swaged fit failed. The large show surface of Glover's medallion, in conjunction with the shoulder beneath it, allowed for the addition of longitudinal ribs on the shaft of the screw to resist turning.The medallion (figures 2, 3 & 4) and the saw screw (figure 5) shown in Glover's patent drawings both feature the internally threaded construction patented by Henry Disston in 1876 (U.S.P.N. 181648). This form displaces the through screw and "split nut" arrangement which had been the norm. Glover's saw screw differs from Disston's by being formed in a die rather than being cast and having longitudinal ribs on the shaft rather than a square section to resist turning. Also, though not specified in the patent, the shafts of Glover's saw nuts were of stouter construction. Glover's form eventually superceded Disston's.Saw medallions with this patent date have been found on saws from a wide variety of saw manufacturers."

    Glover patent 3.png

    Full description can be found:

    http://pdfpiw.uspto.gov/.piw?PageNum=0&idkey=NONE&SectionNum=3&HomeUrl=&docid=0375350

    The Glover patent should be compared to Disston's earlier, but similar, screws from 1876:

    "The heads of the saw screw and nut are slightly domed, and their outer edges beveled so that they flare outward toward the face. Additionally, the screw is received by a blind threaded socket in the tubular projection of the nut. The tubular projection may, or may not, be long enough to engage the saw blade. Disston expresses a preference for those which are long enough to engage the blade. The overall purpose of this patent is to allow the handle and the saw nuts and screws to be finished and polished prior to assembly, with the beveled edges of the bolts/screws forming their own seats in slightly undersized shallow holes bored into the handle. This also allows for the saw nut to be subsequently tightened without altering appearances.Saw nuts based on this patent were cast, making them relatively expensive to produce. Additionally, the shafts were relatively thin, so were prone to twisting off. In time, they appear to have been superceded by Glover's patent (375350).Figures 4 & 5 of the patent drawing were added to illustrate the common "split nut" arrangement which Disston intended to replace."

    Disston saw screw patent 1876.jpg

    It probably has to be read in conjunction with Disston's description:

    Patent Images

    The earlier Munger patent ( commonly called split nuts) is the really frail version. Your screws, although reminiscent, have a significantly thicker shaft at 5mm and a thicker head and nut all of which make them far superior. The split nut shaft is in fact only just under 4mm (I measured them and it was surprising as they appear much thinner), but at 5mm that represents a 25% increase in diameter and a better thread.

    Regards
    Paul
    Bushmiller;

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

  12. #86
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    You've provided the info I was looking for Paul, thanks! So Disston was using the 'Chicago' style nuts 2 years before the Glover patent which was purely for the medallion bolt, the cup nuts already existed and their patent belonged to Henry. I read Glover's original patent application, and it is all about the rather minor (& seems to me bleedingly obvious!) way to stop the medallion screw rotating if the nut sticks a bit. Never ceases to amaze me how small a thing was considered worth patenting back then!

    So it seems that Disston's reason for changing to the domed bolts & nuts was to avoid having to sand the old style bolt heads & nuts flush after assembly, which does complicate the finishing process slightly. I pre-finish whichever bolt tyle is gong on the saw, but I have to re-finish the cheeks of a handle with split nuts & flush bolt-heads. There is always the strong possibility that the bolts are going to need tightening down the track, no problem with the domes nuts, but it means screwing up (pun intended) your nice flush surface with split nuts. And given that a goodly number of nuts had their slot sanded to a remnant, it's not always easy to tighten or undo the darn things, either.

    You know, I'm not certain that fine threads are necessarily stronger. The root thickness of a fine thread is less than for a coarse thread & my engineering informants tell me that a thread is only as strong as a single turn - once that fails, the next & the next will follow suit. So on that basis, coarse threads should be 'stronger'..... ??

    Cheers,
    IW

  13. #87
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    Thank you you two,

    I have some reading and research to do, before I re design the saw bolt because I think I know better and can improve on the wheel[emoji849].
    Will I never learn I am my worst enemy [emoji849][emoji849].

    Cheers Matt,


    Sent from my iPhone using Tapatalk

  14. #88
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    Matt

    If you come up with a better design at least it is unlikely we will find you face down on the steps of the patent office with Henry's boot prints adorning your back. Not sure we could have reassured you in this way one hundred and fifty years ago.

    Regards
    Paul
    Bushmiller;

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

  15. #89
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    Quote Originally Posted by IanW View Post
    You've provided the info I was looking for Paul, thanks! So Disston was using the 'Chicago' style nuts 2 years before the Glover patent which was purely for the medallion bolt, the cup nuts already existed and their patent belonged to Henry. I read Glover's original patent application, and it is all about the rather minor (& seems to me bleedingly obvious!) way to stop the medallion screw rotating if the nut sticks a bit. Never ceases to amaze me how small a thing was considered worth patenting back then!

    So it seems that Disston's reason for changing to the domed bolts & nuts was to avoid having to sand the old style bolt heads & nuts flush after assembly, which does complicate the finishing process slightly. I pre-finish whichever bolt tyle is gong on the saw, but I have to re-finish the cheeks of a handle with split nuts & flush bolt-heads. There is always the strong possibility that the bolts are going to need tightening down the track, no problem with the domes nuts, but it means screwing up (pun intended) your nice flush surface with split nuts. And given that a goodly number of nuts had their slot sanded to a remnant, it's not always easy to tighten or undo the darn things, either.

    You know, I'm not certain that fine threads are necessarily stronger. The root thickness of a fine thread is less than for a coarse thread & my engineering informants tell me that a thread is only as strong as a single turn - once that fails, the next & the next will follow suit. So on that basis, coarse threads should be 'stronger'..... ??

    Cheers,
    Ian,
    I was of the understanding that a fine thread is stronger because the surface area of the thread area is greater than on a course thread.
    The same principle with spline shafts.
    A shaft containing many small splines is stronger than one only have a few(course).
    Itís do to with surface area realestate.

    Cheers Matt


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  16. #90
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    Quote Originally Posted by Bushmiller View Post
    Matt

    If you come up with a better design at least it is unlikely we will find you face down on the steps of the patent office with Henry's boot prints adorning your back. Not sure we could have reassured you in this way one hundred and fifty years ago.

    Regards
    Paul
    Paul,
    You have given me the courage now to press forward being a coward of a figure [emoji849].

    Cheers Matt.
    Did he have large boots?

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