View Full Version : All in one lathe tool grinder jig project.

08-18-2009, 03:04 PM

First let me thank Brian Rupnow and Loose Nut for the ideas.

I don't have a proper tool grinder so I'm going at this for my belt-disc sander.

My plan is to be able to grind 1/2" HSS stock into the most common turning tools I use for exterior work, including threading. I don't want to spend $120+ for a bar and $22+ for inserts of all different pitches.

Here's my idea. Make one of these plates out of aluminum to fit on the top of, and into the miter gauge groove, on the table. I can't get put the tool where Brian does on his top grind because of the disc part of my sander. In order to do this I thought about milling the jig to 7 deg and leave the table horizontal. This way, I can turn it 180 deg and be able to grind the top since it will be +7deg.

However....I haven't ground enough to know if the top grind position is correct...or does it need to be on the other side?

Any ideas or comments welcome!!



Bill in Ky
08-18-2009, 03:23 PM
Your idea would probably work but I think most folks think tool grinding is harder than it really is. My mentor use to free hand grind everything from tool bits to drills to end mills, and I do to. Use you eye to get the angle right and there is nothing you can't grind.


08-18-2009, 03:36 PM
I agree completely. I'm barely beyond newbie myself, and I still clearly remember my own confusion and concern with my ability to hand grind lathe bits. However, I quickly overcame that after only a few initial attempts that came out remarkably well. I then experimented and "researched" (read Harold's treatise on the other HSM board!) to expand my understanding of the interplay between relief, clearance, rake, and lead angles, combined with chip breakers and other modifiers. I now have a lathe that LOVES carbide, but I still use HSS quite frequently. And *none* of it is ground in a TCG or with any sort of jig.

The sole exception would be for threading bits. I have (and do) hand ground them, but a jig is a welcome aid there, with a TCG being even better if you actually want to produce correct thread forms. But thankfully those days are mostly behind me now that I have a selection of Kennametal Top-Notch threading/grooving inserts that cover most of my needs. But even then, for brass/bronze a HSS bit is often superior, and for me, that means hand grinding...

Forrest Addy
08-18-2009, 03:56 PM
That aluminum grinding jig looks like it will work slick as a whistle. There's no problem at all with your engineering or your desire to relieve the learners of the agony of getting the angles right on lathe tools/ Problem is it's training wheels. Its very convenience stands in the way of senses development needed to equip a home shop machinist with the skills he subconsciously employs doing every little task.

The jig could be a great aid to tool grinding but it doean't do anything for you the little protractor thingy won't do better. And it get in the way of learning the EYE and its value in producing accurate tools and angles with only occasional reference to the protractor or the optical comparator.

Kinda boils down to "control the variables or the variables will control you." Learning is in some respects learning the variables singly and in combination then putting them to work for you.

As an apprentice I ground way too much clearance in my tooling and failed to consider the importance of the last final touches with the stone. It takes practice. Now after 40 odd years (by cracky) I have a couple of drawers of tooling most of which look machine ground but I distinctly remember off hand grinding most of them on the Hammond grinder next to Column C-9 and the 12" Century grinders on the other side. That was when I was in my '30's and '40's and had the eye of an eagle and Euclid's head for angles. When I was 19 my eye was undeveloped and my powers of visualization was devoted to prurient interest. My off-hand lathe tool grinding left a lot to be desired.

Between aged 19 and 24, I worked full time in a pressure-cooker apprenticeship but it still took a year before I was up to snuff on a bench grinder; you noobs shouldn't sweat a little anguish developing the skills needed to run your shop to its potential. It's an obstacle course we all have to run.

08-18-2009, 03:59 PM
I know how to grind a tool. No, I'm not the greatest, but my flycutter and cutoff tool work just fine. I can sharpen a drill bit and end mill on the sander and have sharpened an annular cutter with a dremel tool.

I just dont' think hand grinding is as accurate or as quick as using a jig, and being able to put this jig on and get a perfect (err very close to) 60deg v for threading would be great.

So, as long as I've got the material on the cnc mill, why not cut three more grooves to make the other edges just as close to "perfect" as the threading tool?


PS WHOOOO HOOOO, I'm a Senior Member 8>)

08-18-2009, 05:44 PM
If you make the fixture, keep this in mind:
If you machine special angles in your fixture, those angles change as you tilt the table.

08-18-2009, 07:54 PM
If I decide to change some angles I'll add a sine bar or use bolts to lift or lower the front or back.