Thursday, March 10, 2016

Backsaw with copper back.

I haven't been able to muster any energy for starting the shoe shine box, so instead I have undertaken a different project: A homemade backsaw.

Leif Hansson of Norsewoodsmith has wrote an excellent series of posts regarding how to make a backsaw.
I have used some of that information for inspiration, and I hope I will be able to make a usable saw shaped tool.

We have on board a large plate of 3 mm copper (1/8"). While I know that copper isn't a super traditional material for backs, the esteemed Badaxe toolworks actually make a saw with the back made out of copper. I would have preferred brass, as I like the shiny gold look of it, but copper should be able to do the trick too.

For once there is a slight advantage to working out here compared to at home in my own workshop. Because we happen to have a small hydraulic press, that can be used for bending saw backs.

In order to make my backs, I first sawed out a strip of copper from the plate. I chose to make the strip 4 cm wide (1" 9/16) Because that would give a back of around 3/4" height when folded.
After the sawing, I lightly chamfered the edges to remove any burr. I also scratched a line down the middle to help me determine where to start the folding.

For the first part of the bending, I placed the strip inside the V of a piece of anglebar that I had placed on the supporting blocks for the press. I then pressed a smaller piece of angle bar onto it, and thus formed a V shape from the strip. The small angle bar bent a bit, so for the next back I used a piece of 2" flat bar instead. That actually worked better.

The V shape was further bent by gradually pressing the sides closer to one another.
Once I was past a 90 degree angle, I placed the entire back between the support blocks, and stepped on the hydraulic press with all my weight. That was resulted in the pressure delivering its full potential - 15 ton.

I flipped the back over and gave it the same treatment from the other side, and finally I placed the upper support block something like 1/4" from the rounded side of the back, and pressed again. This resulted in the two sides touching each other nicely.

There are definitely some tool marks left on the copper from the folding, but since the material is so thick, I can easily remove them using a file, and still not compromise the stiffness of the back.
Also the sides didn't end up being exactly the same on each side, so the backs will require a bit of filing to look really nice.

Each of the backs I made are 10.5" long, not because of any calculations, but due to the fact that the copper plate had a section that would allow that specific length. I think they might be long enough for a 12" blade, since the handle also offers some support for the rearmost end of the blade.

My plan is to make a set of 10" saws with small handles that my boys can use in the workshop. One filed with rip teeth, and the other with crosscut teeth.

Ripping out a copper strip for a back.

Scratching a line in the middle.

Initial bending using angle iron.

Still a bit of way to go.

The final and nicest looking back is for Brian Eve.

Teardrop shape.

12 comments:

  1. That looks cool. I'm going to make something really cool with it.

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    1. I'll try to bring it when we come to Munich.

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  2. That's going to turn out great for your boys I'm sure. I look forward to seeing how this progresses, toolmaking seems like a good fit for onboard activities. After this, what? infill planes with pallet wood infill?

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    1. Hi Jeremy.
      Brian has suggested making side escapement planes several times, but I think I'll stay away from the planemaking until we get some better pallet wood.
      In Nigeria, infill planes could have been a possibility, since the pallet wood was all exotic hardwood. But I doubt that a spruce infill plane will work quite the same.
      Brgds
      Jonas

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  3. Nice work, but I would make them flatter. A hammer and sturdy steel surface should take care of that. More toolmarks to remove after that, of course.

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    1. Hi Kees

      I think that the other two backs are a bit flatter, but I read one place, that this teardrop shape was the thing to aim for.
      I can press the backs a bit more together, if I only press at a part of the length. The problem with that is that it could distort the back, so it is not as straight anymore.

      The problem is most likely that 3 mm copper is a bit too fat for a back. But that is what I have on boaard. If it doesn't turn out OK, I can try to find some thin angle bar of steel and make a back out of that, but I think that copper will look better.
      Brgds
      Jonas

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    2. Well, the saw I made are a lot flatter and grip the blade very well! I do put the blade in the back when I hammer it down, you don't want to close it up all the way!

      My older English saws all have very flat backs. Newer ones from Spear and Jackson have more of a tear drop shape. So they both aren't "wrong". I just think the flatter ones look more tidy.

      You need to be able to straighten the back anyway by hammering, bending and twisting (!). It won't come out of the press or from under the hammer straight enough, no matter how hard you tried.

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    3. Hi Kees.

      I'm glad to hear that other home made backs also need a bit of straightening after they come out from the press. That means that my attempt wasn't too bad.

      I'll ask Brian Eve if he wants it pressed a bit more, sine the back on the picture is one that I have promised him.

      I have an old Sandvik backsaw where the back is round. It looks quite different to the usual backs, but it is original. http://mulesaw.blogspot.no/2015/01/sandvik-no-761-tenon-saw-zapfsage.html

      Brgds
      Jonas

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  4. HI Jonas, that tear drop shape is what you are after, it will "grip" better the saw plate, keep it under proper tension etc.

    Your sons are some lucky :-)

    Cheers
    Bob

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    1. Hi Bob.

      I hope the teardrop will work as intended, and your description was also kind of how I had imagined it should work.
      But let's see once I get farther in the project..

      I have to do a bit to keep my sons happy, because they really miss me when I am out here, and they sometime ask why I have to work the way I do. But hopefully a nice set of saws will be fun/interesting for them to use.

      Cheers
      Jonas

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  5. I hear you brother, not easy for the kids for sure, been there, done that.
    Its even worse when they don't know if you'll be back safe or at all... :-(

    But in the end, it will all work out good, im sure you have great kids, they understand.

    Bob, thinking of his sons

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