Making Lathe Bits Without the "Right" Tools

Angle grinder with a thin cutoff wheel works for gross shaping, like making a grooving tool out of a 3/8" blank. I use a 1x42" belt grinder for general tool sharpening, then touch things up with a diamond hone afterwards. For a real finish, I use the hard Arkansas, like for midget threading tools. Use a coarse belt on the belt grinder, 40 grit or so.

Stan

Which Makita?

I grind them roughly to shape with an angle grinder, 7" to cut fast and 4-1/2" for more control. The bits stay in place better at the end of the vise jaw if the jaws are padded with sheet aluminum the bit can press into and there is another bit taped in place on the other end to make the jaws close parallel. Then I can really lean on the bit with the coarser grinder and form the basic shape quickly. I try to grind both sides and the end without having to move it because pliers slip on the extremely hard metal and I don't want it melting through my shoe.

Some examples:

The smaller inside threading bit was cleaned up on the bench grinder, the larger one still has some angle grinder finish.

The concave rounding bit was finished with a small conical stone in a die grinder. The other end is for pulley grooves. The two half-rounds were matched by eye to the holes in a drill gauge.

The One Right Tool would be the 4-1/2" grinder, the 7" one is too heavy. It's fine for horizontal weld grinding because the wheel supports its weight but I can't be accurate with it for long on a vertical surface.

The cheapie $20 angle and die grinders are OK for short jobs like this. They heat up quickly so I use them with specialized wheels and burrs for small details, but not to smooth the larger welds.

Jim Wilkins

Tim, If you heat the bits enough to change the color, you are ruining the temper of the steel and defeating your purpose before you start. Buy a bench grinder, quench often and be patient. Steve

Very true for carbon steel. HSS doesn't anneal that easily and quenching can cause cracks.

Jim Wilkins

A good bench grinder is what I use. There are a lot of underpowered bench grinders out there, and I suspect that is what you have. You should not be able to stall a bench grinder. And with a coarse and fine wheel, you should be able to grind a tool bit about as fast on it as using a angle grinder. Faster if you count the time to get the angle grinder and the time to put it away.

The wheels that come with most grinders are not great. But if you buy a coarse wheel that is about as coarse as the wheel on the angle grinder, it will cut quickly.

Dan

But I'm still left with rounded-off corners on the wheel, which offends my aesthetic sensibilities. That's primarily what I'm trying to avoid -- I like maintaining the wheel so its flat all the way across.

(Yes, I'm picky).

I have acquired a gearmotor. I've known of these and seen plenty, but I have no idea what this one would be good for:

1/2 HP 30 RPM 6" single-groove Vee-pulley.

The only thing comes to mind is a power hacksaw. What sorts of things would such a motor be used for?

4 X 36 belt sander with 6 inch disk. Use zarconia [blue] belts to rough grind and a fine grade disk to finish grind. With a fine grit on the disk you can get a literal mirror finish. example of sander of zarconia belts [scroll to bottom of page] of disks car parts places that have painting supplies will have even finer ones down to 2000 grit for a super finish.

The protractor on the fence/table is OK for wood working, but an improved holder and accurate guide will give you better and more repeatable results. for my solution see

Also get one of the machining textbooks that discusses lathe tool geometry and nomenclature. Moltrecht vol one is good. [get both volumes when you order.] Frequently on sale from Enco and Amazon the reprints from Lindsay books are very good and are priced very reasonably. any of these lathe books will be very helpful. Just make the tools look like the pictures to start. angles have been developed over 100 years are more. After you get this down, you can vary to see what works best with your machine and way of working. Be sure to keep a notebook and sketch what you do for easy reference.

A tip -- regular M2 is both easier to grind and cheaper than 5 or

10% cobalt, and will be more than adequate for your initial projects. Also for the typical hobby/home shop lathe, rake at the high side of the recommended range, or even above can be helpful as this reduces the cutting forces. The trade-off is shorter tool life, but this is not a major consideration for home/hobby shop use.

Unka' George [George McDuffee]

------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).

Rock tumbler?

The difference is between holding the hot bit versus the grinder. They slip in Visegrips. An Armstrong type holder works well for roughing if you don't mind scratching it with the wheel occasionally, but they don't give a good sensitive feel for finishing.

My photo shows smooth continuous ground surfaces without the usual multiple small facets from hand grinding. I do that by letting the bit float slightly in my fingers so it touches the wheel all over. I press the end against the motor housing first to align it and try to hold that angle while grinding. The hollow-ground ends are easy to hone at only the cutting edge.

Jim Wilkins.

I'd make you buy a surface grinder and a sine vise. But you might never talk to me again...

One can get spoiled by the tools that are available sometimes.

More seriously, look into something like a "Tinker" cutter grinder jig from our friend Mr Lautard. Dedicate a decent straight cup wheel to tool grinding and don't quench HSS.

regards Mark Rand RTFM

That'd gear down my band saw so I could cut steel. Totally useless to you though, just taking up space and gathering dust..

So send it to me, already. :)

--Winston

How to RUN A LATHE 1942 is as good as any. The changes in the later edition are specific to South Bend lathes.

I vary the shape the book shows for the Side Tool slightly and use it for most everything. My lathe won't take such a deep cut so I center the point, shortening the main cutting edge and lengthening the other downward sloped one, which can make nice smooth shearing cuts if the bit is raised slightly.

Jim Wilkins

I replaced the disk on a $49.95 one of these;

with a home-made pulley plus 1-1/4" arbor that takes an Enco face wheel for a Baldor-clone tool grinder. The tilting table is too flexible for serious rough grinding but adequate to finish the edges.

Jim Wilkins

A) T&C grinder B) Belt sander

Not with high speed steel, Steve. Its tempering temperature is in the neighborhood of 1050 - 1100 deg. F. When HSS was used in production, machinists typically would grind it until it was *dull red*, let alone showing tempering colors.

This is a common misconception about HSS. But if you can run it to dull (very dull) red while turning with it, you can grind it to the same temperature. And if you try it, you'll find that you can hog metal that way with far less wear of the grinding wheel per unit of steel removed from the tool.

Just don't dip it in water, because HSS can develop cracks if you do. If you grind it hot, expect some deterioration (loss of temper; tiny microcracks) about 0.001 - 0.002 in. deep. Grind that off cool, or, better, hand hone it off when you give the tool its final sharpening.

-- Ed Huntress

Elevation screws on a band mill.

Wes

I just hold the bit in my fingers. The only time you really hog the metal is when you are starting with a new piece that has never been ground. And a new bit is fairly long. So you hold it in your fingers, and when it get too hot, you drop it in the water container right in front of the grinder. Sure you may get some surface cracks, but you are going to do some finish grinding on the fine wheel. So it makes no difference. Tool steel does not conduct heat as well as plain steel, so you can get the end being ground pretty hot without burning your fingers.

Well at least that is what I do. I ground a lot of bits before I ever owned an angle grinder, so that is what I got used to. The bench grinder I first used was a belt driven 8 inch grinder that W.W. Grainger used to sell. So the wheels were bigger than the common 6 inch grinders, and the wheel rpm was between 3400 and 1750. Which made the surface feet per minute about right for an 8 inch wheel.

Dan

How about power feed on a cheap mill?

A cordless drill and an angle grinder head worked for mine.