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Making A Full Tang Bolster

Discussion in 'How I Made It: Tutorials' started by dancom, Feb 28, 2021.

  1. dancom

    dancom Dust Maker

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    How I Do Full Tang Bolster in 416 Stainless Steel

    A quick tutorial on shaping and pinning two part bolsters on a full tang blade. But I thought I would show my latest rendition.

    The bolster shape that I chose for the KN48-5 was a shape C in my patterns. These can be downloaded and printed if you want to make your own.

    Starting with some flattened 3/8" 416 stainless steel bar stock I rough cut the basic shape on the band saw. With some layout dye and a scribe I mark the final shape on the steel with the C pattern. (I have a bunch of these made in advance.) I then grind the pieces close to the line on the belt grinder.
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    I use the bolster pin holes in the tang to drill and check the pin alignment. I cut two pieces of plain old 1/8" steel rod as temporary pins to hold the two bolster piece together while they are shaped. I know these pins will be wasted, so I don't use the 416 pin stock at this stage.
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    Once the two pieces are connected with the temporary pins, I use a 2" diameter wheel to shape the backs of the bolster pieces.
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    Using the 45° work table on the grinder, I cut the bevels in the bolster pieces. I have to be careful to preserve symmetry, so I alternate left side and right side. Yes, I am wearing band-aids as I they give better grip and reduce the pain on the fingers from heat build up.

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    Once the bevels are worked to 120 grit, I will push them on some flat sand paper and lightly work each side to remove any lateral scratches.
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    After 400 grit I go the buffer with green compound. Small vise-grips are perfect for holding small things when buffing.
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    I cut the pins to be 2 diameters longer than the the tang and bolster pieces. In this case, I make them stick out 1/8" on each side. This time I use 416 stainless pin stock. It's important to use the same steel as the bolster pieces as this helps hide the pins.
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    The pins are scrubbed with a Scotch-brite pad and all pieces get soaked washed in acetone. Failure to properly clean pins and holes can result in a visible ring around the pin when finished.
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    I make sure the insides of the holes are cleaned as well. Can't stress how important cleaning is.
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    I dry the parts and assemble the bolster and give the pins a little peening with a hammer to keep them from slipping in the holes. I carefully place four #6 flat washers and head over to the hydraulic press. #6 flat washer ID is about 0.15" so there's a little room for expansion.
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    The press hits the pins first then the washers act to press the bolster pieces hard against the tang. I crank it a full 20 tons or whatever the max a 20 ton press will do.
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    The result is that the pins are greatly expanded and the bolster pieces are super tight to the tang.
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    A quick zip on the grinder and any evidence of the pins is gone.
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    At this point I will start shaping the scale pieces to fit
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    Thanks for looking. If you have any questions, let me know.

    Dan
     
    Last edited: Feb 28, 2021
  2. Tom Stegner

    Tom Stegner Member

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    thank you for that.
     
    dancom likes this.

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