An interchangeable tool holder design

The next few parts on the Glass Engine are brass. For that I need to grind some cutting tools, the geometry for brass cutting is quite different. While I have a Quick Change Toolpost, every cutter more or less needs its own holder. This gets pricey at CA$20 each. Plus the growing collection needs a storage solution.

On YouTube I had seen an interesting solution while browsing for tool grinder videos. Luis Ally uses round tool bits for his machining. Well worth a watch. Basically you make a holder for round tool steel, and replace the ‘inserts’ as needed. Since I have a Tool & Cutter Grinder and I have 6 and 8mm round tool steel, it was just the solution.

I used some .5” square stock, drilled a 5.5mm hole and reamed it out to 6mm. Then using a slitting saw I cut a groove on one side. This allows the clamping force of the tightening screws to lock the tool bit in place.

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Of course there is as usual a diversion, to add a degree marked wheel to the grinder work head. Using the dividing head I marked +/- 15 degree marks on the 4 90° segments so that I can angle the work as needed.

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Once back to the tool holder, I ground a bit to see how it would work. 7° relief angles were used on top and side with 5° top rake. End clearance was ground by hand. A bit of honing with a fine stone and off to the lathe.

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I took a skim cut on the outside surface, then a 0.1” deep cut. Both performed wonderfully resulting in good chips and smooth surface.

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There are a few refinements to make, adding a set screw to help align the initial flat ground on the side of the tool with the tool holder. And of course making more cutting bits.

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