Tool sharpening, type of grinders and stones (2024)

HSS takes aluminum oxide wheels. The grayish blue is fine (try Norton). Don't buy the cheapies for your tool grinding. Don't use the white or pink for this. Get a couple of grades, medium and fine. Rough out blanks on your bench grinder by hand, then go over to your good tool grinding wheels.

For carbide, you must use one of these three: diamond, green silicon carbide, or silicon boride (I don't think I got that last one right bit it's something like that and they are very expensive). While you can wear an aluminum oxide wheel down on carbide and eventually do something, it will not be what you want. So buy a green wheel to start with mounted on a standard bench grinder. Eventually, you will realize this is not an ideal setup and your tool performance will lag your expectations so you'll then want to get a tool grinder where you grind on the face of the wheel, not outer periphery. Typically anywhere from $160 at Horror Freight to $300 at ENCO. Bought mine at HF on sale for $130, came with two green wheels. BTW, I took one of the green wheels off my HF tool grinder and made up an aluminum wheel that I impregnate with diamond paste - the kind you get in little syringes. After the green wheel for roughing, the diamond wheel hone puts a super fine edge on the carbide.

You will need to get a diamond dressing point for both types and make up a holder so you can dress the wheels. Wear a dust mask and don't do this near your lathes and mills.

Buy enough grinders so you can dedicate grinders to certain sharpening tasks. Set up one grinder with your two HSS sharpening wheels, make up grinding guides and blocks with your usual preferred angles and then you'll find that sharpening and honing up is a trivial task.

If you get a tool grinder for your carbide, dedicate it only to that.

Ed in Florida

Warning: newbie question.

I bought one of those Baldor-style Harbor Freight tool grinders (parking lot sale, $95 ) with the green wheels. I've been using it for HSS. Honestly, they've been working fine for me. Is there something I'm missing? Would I get a better surface finish if I were to use a finer (AO?) wheel? I've seen the threads over on HSM about the other style wheels and where to get them, but haven't done so yet.

I was impressed with the HF grinder though, mine runs very smoothly and is very quiet (when not making sparks, of course). Not a typical "use the cord as a leash while it walks around the shop" HF grinder.

Green Wheels

Green silicon carbide wheels is what we used to shape our carbide tipped tools in a natural limestone mill I used to work in. They always performed well. You should get a dressing wheel if you use them on a bench grinder though. You'll find it very helpful in bringing the wheel back to shape. Remember your respirator while working with them.

Sharpening, type of grinders and stones

Hello Group, Thanks for the exact info I was after but I still was wondering about a final polishing stone for the very end of the job. Is there such a thing, I was under the impression that you finish on a hand stone for the very edge of the cutter for razor sharp.
a newbie/ beginner
TX Chris

White stones are ideal for HSS, but need to be operated at the proper speed. They can be expensive and hard to find for a typical bench grinder. If you can find them, go for it. They are very good and don't burn the tool as badly as gray wheels.

The biggest help in fast forming of tools is a big honking grinder. I have a 1750rpm 1hp Cincy at home that will eat a bushhog blade as hard as you can push it without bogging. It makes real short work of shaping a 3/8" lathe tool. I have a coarse wheel on one side (60grit Bay state gray wheel) and a very fine wheel on the other (I think it's a 180grit brown/tan colored wheel by Norton, leaves a beautiful polished edge). I hone my tools after grinding. The more polished the edge, the better your finish.

Now for carbide. Green wheels will cut carbide, but from the experience several of us had at the scraping seminar in Savannah, GA a couple of years back, it is akin to sharpening your knife by rubbing it on the driveway. The resulting edge is chipped and ragged, and this will show up in your work. Green wheels are fine for roughing, but diamond is the ticket for a good sharp edge.

The green wheels (silicon carbide) are no good for steel. They combine with the steel and do bad things, as well as disappear at a rapid rate. Same for diamond, but in the other direction... the steel kills the diamond.

Chris

A good grinding rest with decent size table is a great help. If you are on a budget consider something like this:-
http://www.axminster.co.uk/product.asp?pf_id=21251&name=Grinding+Rest&user_search=1&sfile=1&jump=0
or possibly this:-
http://www.axminster.co.uk/product.asp?pf_id=22615&name=Grinding+Rest&user_search=1&sfile=1&jump=0
Your local cheapy chinee merchant will have something similar, expect to do a bit of post delivery rectification.

I got one of the first mentioned ones as a "cheap'n cheerful, will do for now" solution pending getting my Clarkson T&C grinder up'n running. Works well enough although the ally table is a bit rough in the surface so tools don't slide too well. If it were an an "all I have" keeper I'd put smooth 10 gauge steel plates on top. Worth making templates to set the angles you use. I use a cup wheel so I'm grinding on a flat face and can simply set the first one with a machinists protractor then use the tool itself to replicate the angles. Templates better if you use a normal wheel and grind on the periphery.

Normal v cup is pretty much six of one, half a dozen of the other for basic lathe tool grinding. Grinding on the periphery gives a hollow ground shape to the edges so its easier to touch up with a slip stone as much less material has to be removed. Conversely the stone is much less stable so its easy to round off the sharp corner. I don't use one but there is much to be said for having the slip in an angled holder so you can hold the tool down on a flat surface and slide the slip past with it firmly supported at the right angle.

If you use tool bits in Armstrong style holders make one of the SouthBend style grinding jigs which make it very easy to replicate the right angles. I'm sure someone here has links to a design, if not I have something somewhere.

If you've not already got adequate drill sharpening kit the simple swing across the wheel types work well once you figure out the knack.

Should you later venture into milling and need to sharpen milling cutters remember there are several simplified for home use designs of tool and cutter grinder around varying from very basic but good for a limited range of jobs to close to commercial capabilities with corresponding complexity in the build. Come back and ask if the need arises.

Note that you will get best results if the sharpener starts at the edge to be sharpened and moves into the main material. Going the other way leaves a tiny wire edge which is very difficult to shift whilst keeping a really keen edge.

Belt sanders are good for rough shaping, as James says it can be a lot easier to see the angles. However I find that its still necessary to touch up on the grinder before honing as the belt leaves too much surface roughness for the slip to deal with in reasonable time. Excellent alternative to a coarse wheel though and saves working you fine wheel too hard. After the preliminary shaping a coarse wheel is pretty much a waste of space and swopping wheels around should be minimised as you pretty much always have to re-dress. Wasteful and messy, especially if you don't have room for a partitioned off dirty corner. Grinding wheel dust needs to be kept as far as possible away from your (nicely oiled) tools.

Clive

One of the biggest "forward steps" I made in grinding HSS was to build a new pair of rests for my bench grinder. They are quite large, about 4" square, with a deep, tight fitting notch cut out for the wheel. The new rests wind up being vaguely "C" shaped.

The larger rest accommodates the whole tool, making it much easier to keep the desired angle.

My grinder is an older Craftsman model, and had fairly stout rests, so I just welded the new tables to the existing rests. Skimpy rests should be abandoned completely, and new rests fabricated with stout materials.

In addition to Clive's advice on the SB fixture, simply grind the bits IN the holder. If you take the bit out of the holder for grinding, you have a totally different set of angles to deal with (unless you use T type, with no rake). If you leave the bit in the holder, it makes the angles obvious and natural. Once you have the proper angles, remove the tool and use it as a pattern for hand grinding without the holder, if you wish. Holder also saves fingers from heat, lol.

After a while, you will find you probably won't even use the rests, except as a locator. It's pretty easy to hand grind lathe bits and drills without a rest at all.

Yes, grind the bits in the fixture (talking classic Williams or Armstrong tool bit holder). The advice about having several dedicated grinders is also good, and what I have figured out also. Makes regrinding fun, not a chore.

I went into "overkill" mode a couple years ago and bought a used Baldor carbide grinder with appropriate wheels to grind my HSS bits. What a pleasure, and it made quick work of re-grinding. With the availability of the cheapo Horror Freight carbide grinders, the cost of this "luxury" way to grind ordinary HSS bits becomes manageable. With it I find I spend less time at this task.

BTW, I gave up on carbide bits some years ago. My 10L is really not heavy enough to effectively use carbide. I find that cutting edge life is generally poor and ordinary HSS usually works better for anything I am doing (aluminum, brass, steel, stainless).