Hi Nick,

It will take considerably longer than grinding mild steel.

Stick with it, don't burn your fingers and don't dip it in water when it gets hot – you can't overheat HSS on a grinder. Try holding it in a clamp rather than your fingers.

Neil

Cubic boron nitride (CBN) plated wheels are the best for HSS but they are initially expensive. However they last a long time.

Which shape are you making ? there isn't much to take off a 'knife tool'.

I've ground some according to 'toms techniques' youtube vids and they work OK.. and he cools his as do I (mine in a mix of collant wash). But it is tedious to do and frustrating if you bog up near the end. I've tried using my tormek wet wheel that i use for wood carving chisels but that really is slow. I've also used my belt sander but you can't get just the edge of the front of the tool at it properly without tripping over the belt sander;s own edges (as in the belt is a centimeter in).

I;ve just ordered a 60 grit diamond disc to try on the belt sanders disc face which has no rim. if that works then i;ll build a holder to sit on the platform there for compound angles. It was about a tenner on ebay from china so it'll be interesting to see what it's like.

As for the cooling argument.. well frankly I don't think that the difference between the heat needed to burn my pinkies and a dunk in room temp water is enough to matter – guesstimating a drop from less than 100C to 20C. And you can dunk before you start.

Use an angle grinder fitted with a thin cut-off disk to rough shape the tool first. Three or four slices at most will get you close and save lots of grinding. Especially once you get the knack of judging angles to slice at slightly too great a clearance angle on the cutting edges so only a small part of the tool depth needs to be ground at the correct clearance angle. A millimetre or so at the correct angle is plenty.

Up-tilted tool holders, Armstrong et al style, make life much easier and more economical because the top rakes are produced by flattening off the top as required rather than grinding down into the tool bit.

You need two grinding wheels. One coarse for rough shaping and one fine for final sharpening. Best to have a slipstone or diamond for the final touches. The finish on the work matches that of the cutting tool so the bits that do the work need to shine.

Clive

Edited By Clive Foster on 20/02/2015 00:12:21

Nick, you may find Harold Hall's book 'Tool and Cutter Sharpening' (Workshop Practice Series # 38) handy.

Best $20 I spent – very educational and easy to follow. Highly recommended reading.

* Danny M *

I use a tangential tool – so easy to sharpen – small tool bits with supplied sharpening jig and to me it is worth every penny I paid for it.

I do not worry about angles – the jig sets them for me with only one face to grind.

My home-made tool rests for both course and fine wheels are both set level

So my 14 QCTP's sit on the shelf and are rarely even looked at.

And now I have made that marvellous tool height gauge from last month's MEW

sharpening and resetting the tool is just a few seconds work.

Richard.

Agreed. I use 1/4" HSS nearly all the tome on my 5" lathe. Just make sure they don't project far from the tool holder or, if necessary, support them with some mild steel bar underneath.

Russell.

Nick, I mainly use 1/4" tooling, although I do have some 3/8", 1/2" and 5/8" stuff. If you look at most tool blanks, you will see that they are cut off at an angle when you get it, and a tool can be ground up from there without much effort, but I agree that with tooling above 1/4", an angle grinder is the way to go, but be careful with the thin cut off wheels, if you use them don't cut on the side of the wheel.

Ian S C

.

I cheat.!!!!

Mostly use the Eccentric engineering tool holder and their associated grinding jig. (I have no shame )

Makes even a tool grinding retard like me able to produce good HSS tools. However I still t times need to grind a 'special' tool.

Nick

On the subject of grinding HSS, does anyone use extraction of any kind for off hand grinders? In particular for dressing wheels?

Thanks,

James

Frequent dipping of the tool in cold water helps your fingers and keeps the grinding wheel sharp by clearing any deposits. Colin