"Slow speed" grinder

V

vahpr

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Dec 31, 2017
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Hi,

Just picked up an 8" Rikon slow speed grinder on sale, wondering if this is suitable for grinding hss lathe tooling blanks?

I could use recommendations on what wheels to use as well.

Thanks!
 
It seems like its made for woodworking tools, I suppose to lessen the tendency to overheat tools, drawing the temper; one thing to consider, for lathe bits, is that the speed of grinding may be significantly less than a full speed grinder of the same wheel size capacity. Given the same wheels possibly being used on either grinder, slower speed makes a wheel seem of a softer grade, that is breaking down faster than when running slower, that will make a wheel cut better and cooler, at the expense of wheel life. I have a Delta pedestal grinder that I bought perhaps 25 years ago, it still has the same white wheels on it that it came (used) with. Without knowing what grade (hardness) of the wheels, it is not possible to say which is best for lathe bits, but my guess is that the high speed motor with a correct grade of wheel is best for the machine shop, the low speed unit being best for woodworking tools.
It is heart warming for me to read a person's post who is contemplating grinding HSS tool bits, with most singing the praises of carbide inserts; they both have their place, but aspiring amateurs should learn how to grind all sorts of HSS tools, especially for hobby use.
Bottom line, a wheel that is selected to sharpen high carbon steel tools may not be the best choice for HSS.
 
John, what grinder wheel would you choose to grind HSS?
There are so many choices it is confusing.
 
In one of the HSS grinding threads, a member here reported having excellent results from a Tormek. I think it would be slow for roughing and great for finishing and resharpening. It would certainly work.
 
For a grinder with high speed motor (for 6" wheels) 3450 RPM, I'd be looking at perhaps grade (hardness) in the K-L-M range; for cutter grinding, J or K; as to grit, 46 or 60 for roughing and 80 to 100 or 120 for finishing, abrasive aluminum oxide, 32A being common.
 
I have a slow speed grinder. I only use it for fine dressing carbide like Micro100 and modifying inserts. Too slow for HSS in my opinion. It doesn't get used as much as I thought it would when purchased. ;) I have a normal tool grinder that I use for HSS.
 
I have a Tormek (have had it for years). If you wanted to “re-grind/sharpen” HHS no problem. If you are shaping HHS cutters from blanks I’m sure it will do it but you’re going to be there a long time.... like “cut the lawn, start grinding, cut the lawn again, keep grinding, cut the lawn again, finish grinding”. I bought a Toycen Journeyman for doing end mills and the like and thought I’d try doing HSS Lathe Tools on it with a 5C 3/8 Square Collet. It’s a DC drive and I can grind at under 1000 RPM with the variable speed drive...... yada yada yada...... my point, grind on the grinder, sharpen on your sharpener. Sometimes I do ramble on.....


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@benmychree, which wheel would be the best at cool running, i.e. transferring the minimum amount of heat to the work?
 
Rikon makes two 8" slow speed grinders, one with a 1/2hp motor, and one with 1hp. I bought the 1hp version specifically to grind HSS tool blanks for my lathe and have been using it with the white 60 and 120 grit wheels it came with.

When the wheels wear out I've been looking at replacing with a set of CBN wheels which should outlast me.

I've been happy with mine, it is well built, with almost no vibration when running. I do plan on building a better tool rest for sharpening, but the ones it comes with are fairly solid and have been working for me.
 
Thank for the feedback guys. Although I have woodworking tools, I'm no turner so have a WorkSharp for my flat chisels and plane blades which works pretty well. I might have checked here first, as it seems the 1/2 hp Rikon won't be optimal for what I want. And John, yea, I like carbide inserts plenty but it seems a really good idea to learn to grind your own tools for those odd jobs, just a good skill to have.
 
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