A three-part series (1, 2, 3) from Mikey over at MachinistBlog.com, a great site for hobby machinists we’ve linked to many times in the past. Mikey has been a machinist for 15 years, and has come ’round to the belief that high-speed steel (HSS) cutters, rather than the pricier, lower-maintenance, carbide-tipped bits, are the way to go on a hobby-sized metalworking lathe. He also makes a compelling argument for using a belt sander, instead of the traditional bench grinder, for making, shaping, and sharpening HSS lathe tools:
A far better option for grinding lathe tools is a simple belt sander, preferably one that uses 2” wide belts. These machines are cheap, widely available and surprisingly capable for home shop use. The smaller machines with 1” wide belts don’t have enough width to grind a tool evenly, the platen is too flexible, the belts wear too quickly, and coarser belts are harder to find. As a tool grinder the belt sander is almost ideal:
- Belt sanders cut very fast and very cool when you use the right belt and a wax stick lubricant. Average grinding time for a 3/8” HSS tool is under 4 minutes and less than 2 minutes for a ¼” HSS tool.
- With their wide flat platens they allow for simple tool alignment so facets are easy to avoid. This is far, far, far better than trying to realign a tool to a narrow round wheel that requires frequent dressing.
- Belts are widely available, cheap, and do not require dressing, balancing, or conditioning. They also have a very good service life if used with wax lube.
- Changing grits takes seconds and going from shaping to a mirror finish by stepping up through the grits takes a few minutes. Honing to a final polish is less than a minute away.
- Belts will snap at the splice occasionally, especially if they are old. This will scare the crap out of you the first time it happens but I find that preferable to an exploding wheel.
Mikey goes on to talk about what belt sander should be used, how common models can be modified and/or upgraded for lathe-tool work, and why the details of tip geometry are important, before stepping us through the manufacture of a general-purpose lathe tool on his belt sander. Great information, with great attention to detail. [Thanks, Mike!]
8 thoughts on “Grinding Lathe Tools on a Belt Sander – Why and How”
He makes a really strong argument for HSS, with which I agree. I use carbide (or even diamond coated) end mills at work, because it requires a diamond wheel to sharpen them.
Carbide’s tough… about 2x as hard (1200HB vs. 700HB) as M2 HSS(M2 is about as hard as a standard issue “mill bastard” file, but stronger). Unless you either buy off the shelf everytime, or have a diamond wheeled T&C grinder, (google: deckel SO) HSS is your man!
Have you seen the 3M diamond abrasive belts? They are pricey (around $75 USD for what they use in the article), but look like they would let you use a little sander like this to grind carbide tooling. Still, I’ve never tried these belts.
I do run some diamond lapidary plates in a DIY potters wheel for wet grinding glass. Works so good I destroyed a carbide router bit trying to sharpen it. I mostly use carbide insert tooling, but if I need to grind some custom profiles for the lathe, I’ll have to try my diamond lap disk next time.
I have a permanent mark on my belt sander angle gauge, and an angled line drawn on the table itself. It takes a little practice to learn the motion of lifting and rolling off, but provides the proper alignment for sharpening twist drill bits. There is a really good description on sharpening drill bits in:
Home Shop Machinist Vol. 26 No. 5 Sept-Oct 2007
Well, interesting post,
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