Boring with the Lathe

I have been making end plates for my “aluminum frame reel”. I start with a section of rectangular bar, round the corners for lathe clearance, then remove almost all the material with a roughing end mill. Then I make the final cuts (approx. 0.005 inch) on the lathe. Several of these are inner diameters. The right tool for IDs too big to drill is a boring tool.

Here I am working on a rear end plate, holding a round shank boring tool in a home made tool post.
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Sherline sells a boring tool made from a 1/4 inch square HSS lathe tool blank, and it is a work of art. Definitely something that I could not produce on a bench grinder. I save mine for special jobs, and use carbide for most work.

On the carbide boring tools that I have, the side cutting edge angle is adequate but the end cutting edge angle is zero. This is OK for boring a through hole, but on a flat bottomed hole the end of the tool will scrape the bottom of the hole at the end of the cut. When boring the shallow recesses of end plates, I turn the tool post at a slight angle to trade side cutting angle for end cutting, allowing me to go to the bottom without scraping.

When boring small diameters, you will need a set of hole gages. These are by Starrett. The set of four covers IDs from 0.125 to 0.500 inch. A split hemishere is forced outwards by a tapered core, producing an OD that can be measured with a dial caliper or micrometer. I have measured reamed holes with them, and find them to be very accurate and easy to use. Look for them on Ebay.
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When I bought my lathe at an on-line auction, many tools were included. These two round shank tools were part of that, and I assume that they are for boring. If anyone recognizes them, I would appreciate knowing more. They do a fantastic job on Delrin.
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2 Responses to Boring with the Lathe

  1. Rich Bahl says:

    Dave would the hole gages be sufficiently accurate when used with a micrometer with a resolution of 0.0001″ to measure ferrules on a bamboo rod during the lapping and fitting process?

    • dave49 says:

      Rich,
      I don’t think that this would be satisfactory. Resolving 0.001 seems to work OK, but at 0.0001, your have to judge the feel of both the gage and the micrometer.
      For background on ferrule fitting, I refer you to articles by Dempsey and Bogart in the on-line journal “Power Fibers”. I heard Chris Bogart speak at a rodmaker convention and thought that he was knowledgeable.
      At the moment I am at a place with good high-speed internet, so I will send you pdfs to read. These may not be all the articles by Bogart.
      Dave

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