Marking Knife Blade & Collet Manufacture
Making the Blades |
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Although for those earning a living a HSS blade is perhaps preferable for stiffness and edge holding I think for occasional hobby use the knife blade need not be particularly thick or over exotic. | I make mine from old worn out Hard Point Saw blades. |
Having sawn the old blade into suitable strips and dressed them to desired width, removing burs etc. I then polish the faces on a diamond and/or oil stone, surprising how coarse the grind is on the average saw blade and it shows up if you subsequently heat treat. I then grind the Vee edge and sharpen the edges with a chamfer, at this point as long as you have not blued the edge when grinding, the blade will hold an edge for a considerable time with occasional use. | |
If however you wish to harden it to retain the edge longer, heat to Cherry Red.----------- and Quench. |
At this point the blade is now very brittle and easily snapped and will require tempering. |
To do this, polish the metal back to a bright finish and reheat Gently at a distance back from the edge and watch for the colour bloom to move towards the cutting edge, when it reaches straw colour immediately re-quench. | The blade can now be polished & cutting edges re-lapped on your preferred sharpening medium, but final sharpening may best be left until mounted in the handle. |
Making the Collets |
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Cut a suitable piece of Brass Rod to length and saw in half lengthwise. | Ensure the inner faces are smooth and flat & glue together with CA with a strip of card sandwiched between. |
Place in Lathe Chuck and turn down one end to a little under bore size required for Knife blade. HSS wood tools are fine for this. | Remount in chuck and turn diameter to a fraction larger than blade bore diameter, dome the end and a few millimetres back from end form a taper down to first turned diameter at chuck jaw face. |
Finished collets should be somewhat like this. | With sharp knife split collets apart and sand off cardboard residue. |
With careful attention to Blade width, drilled blade locating hole diameter and collet diameter, the blade should hold in the handle with just a push fit of the collets. |