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Sharpening/shaping carbide scrapers

Discussion in 'MACHINE RESTORATION & WAY SCRAPING' started by homebrewed, Jul 30, 2017.

  1. homebrewed

    homebrewed United States Active Member Active Member

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    This post is about a carbide shaping and sharpening system I came up with for my carbide hand scrapers. The motivation: I found a source of inexpensive carbide scrapers, but they had the wrong bevel for metal scraping.

    My setup is a low speed wheel driven by a stepper motor. "sharpen#1" shows the arrangement. It uses a disposable aluminum-foil tray to hold water for lubricating the diamond lapping disks, and a simple tool support to set the bevel angle. The photo also shows one of the scrapers and the tool holder that the scraper is installed into while being shaped/sharpened.

    Not so obvious is the scheme I came up with to get a specific radius on the carbide. If you look closely at the end of the support you will see a fence that is parallel to the lapping disk. The tool holder has a brass insert that has been cut with a specific radius (drawn with a compass & cut out with metal snips). In use, the scraper is run up to the lapping disk and clamped into place on the holder. The brass insert is held against the fence and the tool is rotated around that radius while the lapping disk is rotating. I made a number of brass inserts with different radii.

    I start with a 600 grit disk to shape the carbide, move up to 1200 and finish with the 3000 grit powder. For the 3,000 grit I charged the back of the 150-grit disk using the diamond powder and a home-made charging wheel made from a 1/2" bearing mounted on a handle. I've also got 14,000 grit diamond powder but that would be total overkill for this kind of tool. While I use water lube for the 600 and 1200 disks, the 3000 grit is used dry. I get a pretty nice finish on the carbide. To re-sharpen I do a few passes with the 3,000 grit wheel.

    I used the stepper motor because I had it on hand (I temporarily retasked part of my X2 CNC upgrade kit I'm slowly building up). The advantage there: I can adjust the RPMs to whatever I like. I'm currently using about 100RPM's. Faster than that and the water tends to fly off the wheel.

    I also got a 6" diamond saw so I can -- at some point -- use the setup for a low-speed saw to cut my own carbide. All the diamond items were bought from an online lapidary supply outfit and were quite reasonable in price.
     

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    mikey likes this.
  2. mikey

    mikey Active User H-M Supporter-Premium

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    A lot cheaper than an Accu-finish, especially if it works well for you. Good thinking on the angle and radius adjustment, too. Love it when I see a vision realized!
     

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