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Tips/Techniques belt grinder grit

Tips/Techniques

garageguy

Super User
Premium Member
I am getting set up to use a belt grinder/sander to sharpen HSS cutters for the lathe. I used the bench grinder to experiment but found I could be more accurate with my angles on the larger belt sander guide. Anyhow, I am just wondering what grit belt to use for rough shaping and final sharpening ? what do you like to use ?
 

phaxtris

(Ryan)
Premium Member
Premium Member
36 and 80 belts are what i use, more important is the type of abrasive, zirconia or carbide are the only belts worth buying for steel

Edit...ceramic not carbide, derr
 
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trevj

Ultra Member
Y'know, if you really cannot get great results using a rest on a regular Grinder (which you should work towards), I would suggest finding and using what is generally called a carbide grinder, in the interim.

The wheels on a Carbide grinder are face mounted, and generally there is a groove on the tool rest for an angle or protractor guide, in addition to the tilt of the table/rest at each end of the grinder.

The Carbide Grinder were originally meant to turn Brazed Carbide bits in to useful tools (something most sellers of such fail miserably at explaining!) but they work a right treat if you utilize them to rough out and finish,basic angle grinds on say, HSS threading tools, or the like.

So far, the best combo I have found,is to have a decent wheel on one end of the machine, that I can rough out the HSS with, and a diamond grit wheel on the other end, set a little wee bit at a lesser relief than the roughing end, that will allow a touch on the tool that gives it a razor sharp edge, and a mirror finish. Yeah. Diamonds and Steel. It works, if you do it right!

If used for actual carbide grinding, that would be a green wheel on the one end, and the same fine Diamond at the other. For HSS use a grey wheel. Grit isn't as important as availability, as the diamond wheel provides the actual finished cutting edge.

And yep, it flies in the face of "what is known". But it is what I have found works VERY well, as a means of grinding lathe tools that cut like they are scary sharp! Or sharper!

I taught my apprentices that the reason HSS is what it is, "HIGH SPEED STEEL", is that it takes a considerably more intensive heat regimen to soften, than the tools of old, and that getting the tool bit red hot, was not going to affect the capabilities in the least bit! Do some reading on the heat treatment and annealing of HSS, and you will soon become a believer as am I!
I taught my apprentices that the bucket of water near the grinder, was to cool their Fingers, not to cool the blank you were grinding!
My standard HSS grinding demo, was to clamp a bit blank in a pair of Vice-Grips, and have at it until it was well past red heat! Grind the SOB, like it owes you money! A LOT of money!
Per above, about fingers, plonking a hot HSS bit in to cold water, is not the best thing to do. Microfractures may form on the surface, which "Might" cause early failures of the cutting edge. But if you allow the tool to cool on it's own, it will just be ugly. Ugly can be fixed by a quick surface level grind (ie: not very deep!). This gets you past the surface level cracking that may have occurred.
HSS is actually wonderful stuff, if you learn where it fits in the Grand Scheme!

I will endeavor to post pictures of my favorite tools. The most usual one was a combo Boring, Facing, and Turning tool that were all only a wee step away from making a internal threading tool.

Depends where you drew the lines on the Tool Blank.

My Favorite question of my Apprentices (all of whom I am proud of!).
Do you have a Sharpie Marker?

We did a lot with Sharpies. Whether it was a drawing on a piece of paper towel, or drawing your intended results on a tool bit blank!
 

trevj

Ultra Member
Thanks! Really.

I learned a lot of what I know to work, hard! A lot of the folks I see out there, are trying to avoid either learning, or practicing. A lot of my Apprentice Tradesmen and Tradeswomen (though admittedly,FAR fewer of the latter, who generally, were quite willing to read the instructions, then Follow the Instructions!)!

If you do not do BOTH, learning and practicing, you are only screwing yourself! My apologies if it offends, but at times, there is clarity, in blunt language!

There are not a lot of shortcuts available, if you wish to learn a skill. The best shortcut I know for a fact to work, is to listen to the guy that has done it, and to accept that he has had an experience you have not yet had!

For what I HAVE experienced, there is a larger library of things I have NOT experienced! Staying aware of that, is likely a wise move! As is not taking MY experiences, as the end result. There is both a lot I have not done, and a lot i do not know yet!
 

Downwindtracker2

Well-Known Member
A belt sander is a brilliant tool to use on carbon steel, it's much cooler than most grinding stones. If you burn carbon steel, you ruin it. Absolutely great for wood chisels and plane irons. I have rescued alot of fleamarket finds. Lee Valley has the little Veil 1"x42" and the belts recommendations. But for HSS bits , I use a bench grinder. I don't know the numbers on the wheels, but what KBC sold me works great . My instructor in Pre-App constantly told us to "feel" for the hump on the bit and grind along it to get a flat. Looking at my bits from that time, they were still in the big tool box, I didn't do too good, passable with enough honing. However with those wheels form KBC, forty years on, I was able achieve a flat face.
 

garageguy

Super User
Premium Member
@trevj Thanks for your input! It's really good to get the viewpoint of people with lots of experience. One of the things I have been working on is a grinding jig for 60deg. threading tools. I want to use HSS for threadcutting (been using carbide up till now) and my pedestal grinder has junky rests but my belt sander has a pretty good one with a guide "groove" across the middle for my jig to follow. It's working pretty good so far.
 

trevj

Ultra Member
@trevj Thanks for your input! It's really good to get the viewpoint of people with lots of experience. One of the things I have been working on is a grinding jig for 60deg. threading tools. I want to use HSS for threadcutting (been using carbide up till now) and my pedestal grinder has junky rests but my belt sander has a pretty good one with a guide "groove" across the middle for my jig to follow. It's working pretty good so far.
There are any number of different tilting tool rest designs out there for use with a regular bench grinder.

One of the real benefits that I see in favor of the use of a bench grinder, is that it does give you a slightly recessed face on your tool (matching the radius of your wheel), making it super easy to stone to a scary sharp edge!
I happen to like my Eze-Lap diamond files for this purpose.

The times I resorted to using a belt sander, I was not happy with the way the belt left the cutting edge of the tool, as the machine vibrated and it seemed to me, the belt somewhat rounded over what was supposed to be the cutting edge, as a result.

If you do make a decent rest for your grinder, make a holder for a diamond dresser, and clean up the edge of the stone with that.

One little 'dodge' that I use a lot, is to mark out unequal sized 30 degree angles on the bit blank.
Usually I'll run a line from the front, LH side corner of the HSS blank, and then, when that is ground, mark the very small face in the other direction and grind that. This biases the center of your threading tool towards the LH, instead of having it centered, which will allow you to thread that much closer to a shoulder, without having to butcher away the side of your bit blank.

It makes for a very short job of regrinding the tip if you duff that, too, as you usually only have to grind the one side and touch up your tip geometry.
 
Belt quality is gong to be an issue, I've had good and bad experiences with belts from online markets. KBC sells reasonable stuff though they are on the more expensive side, at least if you have issue you have a back up source.

I know buy from an industrial supplier but there are minimums involved. The second item is the ultra fine grit used by knife makers is not available as the industrial side tends to stay below 150 for belts.

One of the things of interest for belt life is lubricating the belt (abrasive side) with wax as it prevents material belt up and reduces heat (I have tried it and depending on the application is worth while doing, I told do it for everything, but I suggest you try it both ways to see what works best for you). The used of a Gummie bar to clean the abrasive is definitely good as it pulls out fine particles and basically give you a near new cutting surface.
 

JustaDB

Ultra Member
OK, from the new guy's perspective...

I sharpen my HSS bits on a 6x48 belt sander w/ 80 grit belts. Now, why?

My bench grinder doesn't have a large tool rest. Yes, I know there are lots of designs out there to make one and, even with my limited tooling I could probably have made one, but at what point do you enter into self-defeating behaviour?

"Gee, I wanted to get started using this wonderful, new to me SB9 lathe, but I couldn't because I didn't have my shiny grinder tool rest made so I could sharpen my tool bits." Wah, frickin' wah.

I looked at the belt sander, saw the tool rest, pulled out a protractor, adjusted the rest to 10 degrees & started burning my fingers grinding. I haven't looked back. Is it perfect? Purdy sure it ain't. Does it work? Made lottsa chips in the last 10 months. Am I smiling? Oh, hell ya!

Wanna make a fancy tool rest for your grinder down the road, by all means, go for it! But don't get frozen into immobility by what you don't have. At the level beginners start at, the mere fact that you can sharpen your own bits & make chips is a huge accomplishment. Got a belt grinder? Use it!

Now, if I could just figger out this damn VHS clock...
 

garageguy

Super User
Premium Member
@JustaDB that's exactly the kind of thing I try not to get caught up in. I can make a good rest for the bench grinder, but first I would like to get some threads cut. Now that the threads are done I can do the grinder rests when I have time, or can get a round tuit. @trevj , I thought that the radius produced by the grinder would have been a negative thing ,but I see your point in being able to produce a sharp edge.
 

trevj

Ultra Member
@JustaDB that's exactly the kind of thing I try not to get caught up in. I can make a good rest for the bench grinder, but first I would like to get some threads cut. Now that the threads are done I can do the grinder rests when I have time, or can get a round tuit. @trevj , I thought that the radius produced by the grinder would have been a negative thing ,but I see your point in being able to produce a sharp edge.
Yeah, at the end of the day, the way most of the old farts that I knew were taught, was essentially that rests were a sin against mankind and the universe, and that you should be able to freehand grind a perfect straight line across the tool blank, without any extra facets or oddball surfaces!

I, on the other hand, figure that anything that makes a good working tool, well.... Didn't use a rest with a miter gage on it, at work, but taught the guys and gals to set the height correctly, as well as the relief angle, and we spent a lot of time drawing on our tool bits with a fine tipped Sharpie Marker, so as to be clear what the desired results were supposed to come out looking like.

You don't NEED a fancy adjustable rest on a bench grinder, but just like how it makes that belt sander that much easier to grind a set angle, a decent adjustable rest on the grinder makes it that much easier to get great results without having spent hours developing the muscle memory that comes with a LOT of practice!

I can, and have, ground a lot of good working tools freehand, with nice clean grinds and straight lines. It just takes some practice, and it's gonna look like the annoyed work of a rabid beaver, while you get started. But if you don't get started, you never get done.
I have used, on occasion, and angle grinder with what was left of a zip disk to sharpen a lathe tool too. Not....optimal! LOL!

Be at least ten percent smarter than the machine, and make it work FOR you, instead of AGAINST you! You don't NEED a fancy rest, but it'll pay back the time you spend on it, in spades!
 

trevj

Ultra Member
I am so screwed...
LOL! Probably not anywhere near as much as you might think!

All of this stuff is just a few basic principle being applied. Simple stuff, like "The sharp edge touches the work first", and "Sharp works better than dull".

You're right about the paralysis that comes out of the perceived need for one thing or another to get things done. Been there, done that! :)

At the end of the day, all I have got to offer, is my past experiences, and which of them worked out best for me.
 
Here is how I started on a 6" bench grinder (and it applies to belt sanders as well).

Marker or layout dye, scribe and a gauge. Mark it, eye ball grind it free hand. Cool often (prevents toasting fingers).

Take your time and don't be scared to restart. Trust me you can get extremely good HSS tooling that way. This is the old school way of doing it.

Final note, do you you want to make lots of tooling that way, hell no, but to get you working its the best and cheapest fastest way while you learn a lot about tooling and cutting edges.

Don't over think it, just do it.
 

Mcgyver

Ultra Member
I am getting set up to use a belt grinder/sander to sharpen HSS cutters for the lathe. I used the bench grinder to experiment but found I could be more accurate with my angles on the larger belt sander guide. Anyhow, I am just wondering what grit belt to use for rough shaping and final sharpening ? what do you like to use ?

That the end gets hollow makes it seem tougher to gauge the angle perhaps. If that is the issue, I suggest not worrying or caring about the hollow ground shape with a bench grinder. This is actually advantageous.....you're best work will come from a light and quick stoning after grinding. With the hollow ground shape this makes much easier; the centre of the grind is relieved so the stoning effort is concentrated on the edge.

A belt sander can be a great thing, but 1) you can get a slight rounding or slight convex shape (the opposite of hollow ground) and they put lots of abrasive into the air (i.e. polishing with emery is tougher on a lathe than grinding).

imo you don't need a rest to grind a tool bit. As a beginner I built a fancy one, only to discover I never use it. Take a piece if sq mild steel. Grind a bit, check the angle. I bet you won't have got 1/2" into the piece before you can grind a pretty good tool bit....and...it doesn't matter than much. 12 degrees or 8 degrees are going to work just about as well as 10.


A belt sander is a brilliant tool to use on carbon steel, it's much cooler than most grinding stones. If you burn carbon steel, you ruin it. Absolutely great for wood chisels and plane irons. I have rescued alot of fleamarket finds. Lee Valley has the little Veil 1"x42" and the belts recommendations. But for HSS bits ,

To add a bit to that, I believe a belt grinder runs at about 3000 SFM. A typical 8" bench grinder is more than double that, 7500 SFM. It turns out, at the point of contact, where a molecule of abrasive meets a molecule of steel, the resultant temperature is almost entirely determined by the surface speed between the two. Even coolant has a negligible effect on that temp; coolant stops heat build up, but doesn't have alter that local temp much.

Thats why the belt runs cooler, the slower speed. If both were aluminum oxide (I think both usually are) at the same surface surface speed you'd get the same temperatures at the point of contact.

You're right, carbon steel can't take much in the way temperature before it affects its temper. HSS does sooo better this and withstanding grinding temps is a good reason for making something out of HSS even if its use doesn't require it (e.g. a tap). Hence slow wheels for woodworking stuff which seems to be mostly carbon. imo it would useful to have a speed control on the belt so you could dial it down even more
 

trevj

Ultra Member
You're right. Then you watch some kid in the Philippines make a lathe out the crap lying the gutter behind a muffler shop and we're reminding of how easy we have it :)
Yeah, or you see what the Indian, or Filipino hillbillies are cranking out, as far as guns, using almost nothing, too.

I have, on occasion, sicced an apprentice on to the task of finding out the heat treat schedule to anneal HSS, as well as to make it hard. It's an eye opener, with some crazy cycle times, going up into days, as well as long terms at fairly exact temperatures, to either dissolve the crystal structures within (solution heat treatment for annealing) or to get the darn things to grow again (precipitation Hardening) with lots of periods and steps in the schedule to keep sorted.
After they see what it takes, they no longer worried about the tool being softened while grinding!

So far as I ever read, the worst thing a fella had to look out for, was to not plonk a red hot tool bit into the tank, as you might create a microfracture on the surface. So you let it cool slowly, and take the black crust off later!
Armstrong, the guys that made the rocker tool holders and tool posts that everyone seems to forget still work pretty well, used to sell holders for grinding HSS tool bits too. Basically a big handle, that you mounted the bit in to grind it. Armstrong put a big ol' ball end, on that handle, so you could lean on the sucker with your hip, and get some use out of that multi HP grinder in the back of the shop, eh!

I have a nice little belt sander that I grabbed with an eye to making a tool grinder out of. It came out of a metallurgical Lab, where it was used to prepare mounted weld section specimens, for the fine polishing before etching. The neat trick is that it is built to be water cooled! Figured it would be a treat for chisels and plane blades, at least for roughing, with not too much to worry about with the heat!
 
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