Backs for Stewies Disston #70 clone

Discussion in 'Saw Makers Forum' started by ray, Mar 18, 2012.

  1. ray

    ray Administrator Staff Member

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    652
    I'll post this here, inspired by Alan's thread on making slit brass/bronze backs...

    They say it's third time lucky,

    This was the third attempt to make these for Stewie, he wanted a lighter and thinner back than the 1/4 x 3/4 brass I've used previously, first attempt was set up on the mill, and everything looked good until I removed the back from the vise, and it sprung into a banana shape that resisted all attempts to straighten it, evidently there is considerable internal stresses still in the extruded brass even many years after manufacture...

    Next time I will put the brass into the heat treatment furnace and do a proper stress relieving cycle.

    For this one, however I setup the surface grinder, which is much less stress than milling and took even amounts off each side.

    [​IMG]

    The slitting set up is a bit primitive, and only allows shallow cuts, unlike the old system I used previously, I think I need to make some new jigs.

    [​IMG]

    Here are the finished backs, so now it's up to Stewie to make something out of them... :)

    [​IMG]

    I chamfered and polished one, but I'll leave the others.

    Regards
    Ray
     
    Last edited: Mar 18, 2012
  2. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    Glad to have inspired you, I do remember when you first got started with this I tried to be helpful, as a couple others were to me. Your first drill press setup wasn't bad, IMO. You may have been inspired by the mini-mill setup, I am not sure...I was working with my mini-mill back then and had a friend help me with the slotting fixture. Mike Wenzloff helped me get to the final level of making saws, and getting everything to fit right...this means the gaps around the split-nuts, gaps around the mortise in the handle, etc...each piece has a learning curve of it's own.
    There are days I'm slower than that.
    That's why it's hard to imagine doing for a living for me. I do the same. I'm sure if I was doing it all the time I would get better at it, but the metalworking is a constant learning process for me.
    This is something I feel everyone has to go through on their own. Recently I was trying to explain this to Matt, but he knows what he wants and will go through the same process as most all of us have. There is NO RIGHT ANSWER, it's a personal choice. I was merely trying to explain that 1/4" x 1" is a big piece of brass. I can see using it for really big, thick bladed saws. Those are not the saws I make most of the time, though. For me I do like a long saw, but don't like it too heavy. The natural weight of the saw should cut well, no added weight should be needed. The saw should be balanced, so there does get to be a point that a saw is too long for certain people, length is also a personal choice as well. Again, no right or wrong.
    Don't feel bad, I just screwed one of the backs up that I was going to send Joe...hehehe :p

    I have some 1/4" x 5/8" that I'm slotting a 12" today with .025". I only have a screw slotting saw, so will run it at my highest speed.

    Some blades don't leave much room, heh? It's challenging to match up the blades, bore, thickness, etc...to have enough clearance and enough blade to cut the depth desired. I have a 1" arbor.
    I wouldn't recommend it. Work it dry, and keep the speed down. Brass gets spongy, so you need to keep the speed/rpms down.
    I'd like to see that better. I'm looking at a bevel/chamfer machine for the chamfers. What size chamfer are you grinding? Is it about 1/8" wide ?
    Tooling is everything, heh? It's worth getting setup properly, IMO.

    This is what I would like to use:

    (linky pic)

    [​IMG]
     
  3. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    Ray,

    Curious what size brass are you using for these Disston No 70 backs?

    Probably should be 3/16x5/8, IMO.
     
  4. planemaker

    planemaker Active Member

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    Nice work with the brass backs Ray. Apologies for the extra work it took to size them down. What lengths are you supplying Ray. . Stewie.
     
  5. ray

    ray Administrator Staff Member

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    652
    Hi Alan, Stewie,

    I made all three 12" long, and there are two different types, the first was using some 3/4 x 1/4 already slit and resized to 4.5mm x 13mm, the other two were from some 1/2 x 1/4 stock that I had, but not slit, so those two have the shallower slit.

    I'll be dropping them into the post tomorrow, so you should have them by the weekend.

    Regards
    Ray
     
  6. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    181
    Wow, you had a perfectly good piece of brass, in impreial and you screwed it up by taking it down to metric! :p j/k

    I just got some 3/16x5/8 and I do think that is the correct size for the No. 70 back. It's not clear to me how 4.5mm x 13mm works out...let me see if I can convert on my calipers to metric...

    EDIT: Yeah, that's pretty close to the 3/16x5/8, 13mm is actually just about 1/2", and they should be slightly smaller than 3/16" thick.
     
    Last edited: Mar 21, 2012
  7. planemaker

    planemaker Active Member

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    39
    Hi gents. I have attached a completed open handle dovetail saw thats been fitted with 1 of Rays light weight brass backs.

    As for details on the rest of the saw. The handle is made from Tas. Tiger Myrtle. The blade is 10" long and 2 2/8"deep below the spine. I used 0.015 saw plate, and its been sharpened 14tpi rip tooth.

    I hope you like the end result.

    Regards; Stewie.

    [​IMG]

    [​IMG]

    The next dt build will be a closed handle version.

    [​IMG]
     
  8. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    Curious what Ray slotted it for if you used a .015", as there are no .015" saws.

    Ray, what did you use? (.014" ??? .016" ???)

    Saw looks great Stewie!
     
  9. planemaker

    planemaker Active Member

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    39
    Hi Alan. Ray slots the hardback to take 0.020 saw plate. You can use the thinner gauge plate by adding some drops of Loctite or Epoxy Glue along the length of the slot prior to fitting the saw plate. You end up with a very secure fitting.

    Regards; Stewie.
     
  10. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    181
    Wow, you put a .015" plate in a .020" slot? I probably wouldn't do that myself, I was cautious about putting a .015" plate in a .016" slot...:confused:

    I use loctite/epoxy (both work fine for me) on all of my saws that I've built. I don't want any of them coming apart unless they need to, and in that case it can be heated and removed. I have seen people state they use a press fit, but not me. The big plus about a slotted back is that it will not move if the saw is dropped and I want to make certain of that. All of our mileage varies in that regards I 'spose...;)

    As I said before, great looking saw!
     
  11. ray

    ray Administrator Staff Member

    Messages:
    652
    Hi Alan,

    Stewie beat me to the answer, I use a 0.5mm slitting saw (20 thou).

    I've never had a loctited blade come loose in normal usage.

    Regards
    Ray

    PS I've used press fit as well, you can close up the slit a little in a smooth jaw, or if you've got a good anvil and a good eye you can tighten it up by light hammering... you might need to fettle it afterward.:)
     
    Last edited: Mar 31, 2012
  12. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    181
    Ray,

    My issues with using a slot that is larger than the plate is that it is easy for the plate to get off center. The same as bending/pinching the back together to get the slot tighter, you can't dictate which side will move in and there is a chance the slot could be off center, pointing the blade at an angle. That angle, while small, accentuates the farther you get from the spine.

    That said, I don't know that it is a problem or not, just sayin'...

    I often get a slot that is less than perfect, and it still seems to make a good saw, but I would like them to be perfect.

    As a side note, the first tests with the bur-beaver are not too impressive, I think the best results may be had with the dual cutters at a higher speed. I'll have to swap out the pulley this weekend and see if I can get a decent cut from them. May need to modify my jig...
     
  13. planemaker

    planemaker Active Member

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    Hi Alan. From my experience so far using loctite on the 0.015 plate, you end up with an even film on each side of the saw plate after the brass back has been fitted. This can be validated by looking at the common patches of squeeze out each side of the saw plate. I am quite sure Pedder & Klaus use the same method for their backsaw assemblies. I concur with your comments about the problems associated with pinching or hammering folded hardback to get a tighter fit on the saw plate.

    Ray. I completed the 1st stage of shaping on the new closed handle. The grip and finger hole feels very good within the hand. Being a smaller sized handle, getting it near right at the design stage is fairly critical as there is little margin left at the shaping stage to alter the hand fit. A satisfactory day in the workshop.

    Stewie.
     
  14. pedder

    pedder Active Member

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    Hi Stewie.

    I like the low hang of the handle and the shape. This gives you a lot of forward power and less downward. So this saw could take a heavier spine. Than it will be a powerfull beast running through 1,5" wood liek nothing.

    Let me add: your saws deserve prettier screws.

    Cheers
    Pedder
     
  15. pedder

    pedder Active Member

    Messages:
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    Hi Alan,

    since we have a new maker for our spines, who cuts the slots on a cooled mill, we have some problems to fit a 0,3mm (0.012") blade in a 0,3mm (0.012") slot and add loctite. I don't think 0.005 will be a gap to big for loctite.

    Cheers
    Pedder
     
  16. TraditionalToolworks

    TraditionalToolworks Most Valued Member

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    I haven't seen that problem, albeit you have made more saws that me. I like to squeeze it into the slot, along the opening and then push the plate into it.

    .005" is a lot in machine world...not so much in woodworking, but still, in my mind it seems easy for the plate to tilt in the slot.

    I know it will work, just sayin'...that is an advantage with a folded back, but then they suffer from having the plate/spine move over time and need maintenance done to them. I'm a firm believer in the slotted back in that regard. I have yet to see a plate warp like they do in a folded back. I have seen the backs bend on slotted saws, brass is soft...