Old-school lathe tool grinding

[Nick]

"I'm a bit perplexed at changing from a horizontal to vertical grinding surface..."

Horizontal surfaces run side to side. Vertical surface run up and down. Hope that helps.

With all good wishes ,

[drewa]

George (and all),

Can I suggest for the procedure you are using for grinding chisels that you invest in a "green stone." There are a variety of grinding stones out there in the market one of them is called a green stone and it is less aggressive than the gray stones and will not produce the heat the gray stones will create.

Do some "lookin'-up" on it. You will get better results.

Be good,

Drew

[edflorence]

However, there is no pivoting jig for sharpening a roundnose- do you remember how it was done in PTWFE?

While on the subject- are a roundnose and gouge the same in cross-section, so that one could be reground into the other?

No, you can't morph a round nose into a gouge or vice-versa. The stock of the round nose, behind the cutting edge, is a rectangle in cross-section, while the gouge is a thick-walled "U" shape.

I took a look at my older PTWFE's last night and found out that in the earliest versions they recommended sharpening gouges on the inside of a "cup wheel" which is a cup shaped grinding wheel. Later on, the cup wheel disappears and either a regular grinding wheel or the sanding disk is recommended. The grinding wheel will leave a hollow ground, of course, and it was advised that this sort of edge might be a little fragile for turning. The current thinking on the gouge is to use either the sanding disk or the strip sander for sharpening.

As for the round nose tool, the early PTWFE's simply advised that a stone be used to touch up the edge and to keep the back flat. It wasn't until I read the instructions that came with the sharpening jig that I learned that the factory angle on the round nose is too steep and needs to be flattened to about 15 degrees. This makes sense when you look at the typical angles on other scraping tools. I don't think that 15 degrees is a real critical number, the angle could be a little flatter or even a bit steeper without hurting anything. I used the pivoting arm on the jig to change the angle, and it worked slick. However, I think it would be pretty easy to "free hand" it as well. You might try tilting the table to 15 degrees and bringing it up close to the sanding disk, then lay the roundnose on the table with one hand on the end of the handle and the other applying a little downward pressure at the ferrule. Then, you should be able to pivot the tool by swinging the handle, using the other hand to keep the tool pinned down at the pivot point. Unlike the gouge, sharpening the roundnose all takes place in one plane, so you won't need to twist the handle while the tool pivots. I have never actually tried this, but it seems to me that it should work. I would be interested in hearing if anyone has ever sharpened a round nose this way.

Nick...thanks for sharing the excerpts from your book. Much appreciated.

Ed
Idaho Panhandle
MkV 505 +/- etc

[Randy]

George (and all),

Can I suggest for the procedure you are using for grinding chisels that you invest in a "green stone." There are a variety of grinding stones out there in the market one of them is called a green stone and it is less aggressive than the gray stones and will not produce the heat the gray stones will create.

Do some "lookin'-up" on it. You will get better results.

Be good,

Drew

1) Gray, brown or black is usually Aluminium Oxide and used for general purpose grinding
2) Green is usually Silicone Carbide for finer grinding and some sharpening
3) White is usually for HSS and Tool steel sharpening and grinding
4) Pink, Red or Ruby is usually for hardened Steel and Alloys

For sharpening the best is white.

[solicitr]

OK- I slept on it, and woke up realizing that to sharpen a gouge you need two things: an angle relative to the wheel, and a means of restricting the tool's movement to rotating about and moving along its axis (I.e. thrust and roll, with no yaw or pitch).

The angle part is easy- I've got a miter gauge which locks and clamps (don't throw out the old-style hold-down!). As for the guide- why not a hole? I measured the SS gouge and found it's just oversize*- .55"- so I bored a half-inch hole at one end of a piece of 2x4 and then reamed it out with the gouge itself, making a tight fit (wax helped a lot here).

All right: set up the disk just beside the table, clamped the MG (reversed) in the near slot, set to 45 degrees, and added my 'jig' so that it just cleared the edge of the disk. Insert blade in hole.

I found it does require a bit of 'touch', because the fit is tight enough to resist in-and-out, and it's easy to grind a straight-sided cone. But after a little playing it came out very nicely.

This evening I'll do the same with the one-inch.

*IMPORTANT- the number you want is the tool's outside radius, NOT its width.


(As for the confusion on roundnoses- my problem was that I got a dog's breakfast of lathe tools with my Mk V: the original SS 1/2" gouge and parting tool (the latter ill-ground on the faces, discolored and probably ruined); three good heavy carbon steel Buck Bros (1" skew, 1" gouge and another parting tool); and three no-name pieces of garbage that look like they were hammered out of leaf springs. The three gouges had such an insane variation in bevel angles I assumed one was a 'roundnose'- when in fact I don't have one at all)

[drewa]

I stand corrected. Thanks for the info.

Drew