Models for grinding HSS Lathe Tools

Lines? We don't need to stinking lines! ;)

Just joking. I think lines are a good idea when you first start grinding tools but you'll eventually get to where you don't need them. Personally, I start grinding the side cutting edge first and try to make the length of that side edge end up about 2 times the width of the bit while ALSO grinding about halfway across the width of the bit for a general purpose tool. Neither goal is all that critical but I've done so many that I can probably hit these dimensions within a few thou. Just start grinding it and don't stress over it too much.

Next, grind the end. Just grind it to produce about an 80 degree angle. You can eyeball 90 degrees with amazing accuracy so just make it a bit less than that and it will be fine. You are simply making sure you can access a shoulder, that's all.

To do the top rake angles, eyeball 1-1/2 times the width and put that estimated point at the edge of the wheel or belt, estimate your back rake angle and just grind until the pattern just reaches the tip, then stop.

Look, I know I gave you specific angles to hit. That's because the tool works well at those angles. My tools will be within a degree or less when I'm done but if you are off a degree or two, I guarantee you that the tool will still work fine. And if it doesn't or you think it might work better with a bit more relief or back rake or side rake then just go back and grind it in.

It is important to realize that all lathes are different. They have different degrees of rigidity, power, speed, wear and a different operator. Accordingly, our tools must differ if we are to maximize the performance of our specific lathe. If you think you need to be able to cut deeper, try more side rake. If your finish could be better, try more back rake (bet you thought I was going to say increase the relief angles or make the nose radius bigger, eh?). Mess with the grind and see what works for you; that is what this whole thread was about.

There are no rules when grinding lathe tools - you just gotta try it and see what happens, then figure out what you did and what worked and what didn't.

As for honing, that is a personal choice. I hone because I feel that a refined edge cuts better and lasts longer but there is certainly no rule that require you to hone your tools. I will say this, though; try honing your tools with your diamond stones, then hit it on a fine India stone and then on a Translucent or Hard Arkansas stone and see what it does to your finishes. It will make you a believer. That tool will also take a tenth off the diameter if you can dial it in. :)
 
I find all this talk of grinding lathe tools by hand very interesting .From the time I was an apprentice to about a year ago I never had access to a belt grinder/sander. I acquired a very small belt sander 1" wide belt. I was taught to grind tools on a pedestal grinder usually 6" x 1" wide Al Ox wheel, usually 60 grit, Occasionally 8" wheel but again 60 grit. I have, since getting my lathe, about 4 years ago, used a box of old tools left over from my apprenticeship and other more recent adventures, and have only rarely needed to regrind a tool, and when needed I have used a 5"angle grinder to rough it out, and then, and only recently, used the small belt sander to finish, this was also a 60 grit belt.

What I find most interesting is all the talk about stoning and hand finish with special stones etc. I was not taught to do this, and as a result I have never done it. remember I was trained in a toolroom, and neither I, nor the tradesmen who were teaching me, ever had a problem with finish. I can only think the difference is HP, large powerful machines can run tools with good sized radius on the nose..

Having said that my lathe is only 1.5HP and single Ph at that, Also I have never noticed single phase chatter, We run 240V 50Hz single Ph here in Australia. Maybe that is the difference. Can any one else also running 240V 50Hz single ph. comment please.
 
Prebuilt belt grinders are pricey. I'm not sure why, they aren't that complex. I built mine from free plans online. Simple cutting and welding. No real critical dimensions, a tape measure is plenty accurate. A bandsaw is helpful, but people have done it with a hacksaw. An abrasive chop saw would work as well.

I do most grinding with 36 grit ceramic belts. Then switch to diamond cards. I did find that using wet sandpaper on glass at about 100 grit helps get the grinding lines out. Just pushing less hard at the end helps a lot as well. I have belts as well, but keeping from grinding facets that way is more difficult and it usually only takes a minute to get to where the cards are the best option.

I also put the cards on a flat surface and run the bit over them. It takes practice to hold the bit at a compound angle consistently, but you get used to it. Use a larger surface than the card, so you can use it as a reference while moving. I usually rest part of my hand on the surface to help keep things aligned.
 
ttabbal said:
Prebuilt belt grinders are pricey. I'm not sure why, they aren't that complex. I built mine from free plans online. Simple cutting and welding. No real critical dimensions, a tape measure is plenty accurate. A bandsaw is helpful, but people have done it with a hacksaw. An abrasive chop saw would work as well.

I do most grinding with 36 grit ceramic belts. Then switch to diamond cards. I did find that using wet sandpaper on glass at about 100 grit helps get the grinding lines out. Just pushing less hard at the end helps a lot as well. I have belts as well, but keeping from grinding facets that way is more difficult and it usually only takes a minute to get to where the cards are the best option.

I also put the cards on a flat surface and run the bit over them. It takes practice to hold the bit at a compound angle consistently, but you get used to it. Use a larger surface than the card, so you can use it as a reference while moving. I usually rest part of my hand on the surface to help keep things aligned.
Click to expand...
No welder.
 
Downunder Bob said:
What I find most interesting is all the talk about stoning and hand finish with special stones etc. I was not taught to do this, and as a result I have never done it. remember I was trained in a toolroom, and neither I, nor the tradesmen who were teaching me, ever had a problem with finish. I can only think the difference is HP, large powerful machines can run tools with good sized radius on the nose..
Click to expand...
The way I see it, Bob, any defect existing on the tool's edges will transfer to the work piece and I know, at least to my eye, that honing produces a better finish. Just as important is that a honed edge lives longer and cuts more accurately. If we are turning a rough work piece for a tractor then this may not matter but if we are turning an arbor that has tolerances in the low tenths then I feel it does make a difference.

I did an experiment with gravers once. I tried turning a brass ball with a graver right off the grinder and that graver was really difficult to use; it dug in and would not produce a decent finish. A few minutes of honing allowed the tool to turn with ease and produced a mirror finish. This just reinforced what I learned with lathe tools - honing does make a difference.
 
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