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Choose metal type for carbide chisel shaft

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minilathe22

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I have purchased some carbide tool tips, and plan to make my own woodturning chisels with the replaceable carbide tip at the end. I am not massively familiar with metal types and I wonder what would be a good material for the metal shaft from the handle to the carbide tip. Normally it would be tool steel, but I don't think this is needed as the carbide tip will do the cutting.

If it is too brittle there is a risk of it breaking during interrupted cuts, and if its too soft it may bend instead. I want the surface to stay smooth, so I think a stainless steel would be appropriate. Would 316 Marine stainless steel work? Will I be able to tap and drill a small thread for the carbide tip with ordinary twist drills and a tap?
 

Phil Pascoe

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I have one I made to take a tip - I used BMS (bright mild steel) for mine. It's easier to tap than stainless and much cheaper. You'll be using heavy enough stuff not to worry about its bending, and assuming it's kepy dry won't rust. A wipe of microcrystalline doesn't do any harm.
It also allows you to mess about at low cost - these were made from old or broken HSS drill bits for hollowing (stuck with epoxy). Both work, and when I can't grind them any more, so what? :D
DSCF0245.JPG
 

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minilathe22

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Thanks for the replies. I will look for some cheap bright steel to avoid rust a bit. Did you go for 15mm or so diameter?
 

marcros

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mine hasn't rusted, but bright looks a bit cosmetically better. I only made a small tool for turning pens with (although I have used it for some other things), so mine was either 10mm, 12mm, or 1/2". measure your inserts and allow for a bit of side clearance. if you have 15mm inserts, I would go with 12mm or 1/2", or look at one of the commercial manufacturers and see what they use.
 

TFrench

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I just used a bit of mild when I made one - glad I didn't make it of anything nicer as I never use it!


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Robbo3

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The further the cutter overhangs the tool rest the thicker the bar should be. There is a basic rule for this, as well as how long the handle should be to counteract the forces involved, but I can't remember the figures.
IMO 16mm bar is required for 150mm, or greater, overhang.
Square bar is also a possibility but it makes control of the correct cutting angle harder. Mounting the cutter at an angle will overcome this to some degree.
 
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