Best way to cut HSS tool blanks from bar?

Excuse the newbie question but - is it OK to use a 1mm disc angle grinder to cut HSS steel rod to size? Or does the heat de-temper the metal? Even if it did, would it be possible to re-temper it with the gas torch like other steel, or is HSS steel different?

Thanks in advance, Jim

Cutting it that way will be fine Jim. HSS has to get very hot to loose it’s hardness.

Edited By Vic on 16/07/2019 13:12:29

Jim,

As I understand it, HSS was formulated to avoid the softening that occurs when its predecessor, high carbon steel (silver steel), is subjected to heat. According to T.D. Walshaw (Tubal Cain) some grades of HSS will still work when red hot. Which rather suggests that in the home workshop it will not be that easy to soften HSS! So, as Vic says, go ahead, you won't hurt it.

If you are at all worried, you could do what I did when cutting up an old carbon steel file to use as lathe tools - keep a watering can of cold water handy and flood the job every few seconds.

Peter G. Shaw

Hi Jim, Not a problem, if it is only a small size you can just cut into it a fair distance, hold it in a vice then cover it with a cloth & give it a sharp thump with a hammer & it will snap off... there again just continue with the grinder. As Jim mentions above keep a water supply handy to splash on occasionally.

George.

Jim, I use a similar abrasive disc for slicing HSS. Not sure whether it was ALDI or LIDL but I bought a stand to fit the angle grinder which allows it to be used like a chop saw - it works well.

The only tool steel I know that cuts when red hot is Stellite. I am not aware of any grade of HSS that would cut at those sort of temperatures. In fact, when referring to the cutting/shaping of HSS in the cutter grinding dept. where I laboured a spell the advice given was "if its brown its cooked, if its blue its buggered."

The above refers to the 1980's so apologies if things have moved on.

Rik

From what I've read, heat treating HSS is considerably more elaborate than ordinary carbon tool steel. With the latter, there's a fair amount of leeway with time and temperature, HSS has to be done right.

HSS is specially formulated for hardness, toughness and heat resistance. Getting the best out of HSS involves more effort and careful control of time and temperature during both heating and cooling. Rather than blasting it with a torch and quenching, HSS might be held within a few degrees of a specified temperature in an oven for about an hour, and then held at a different temperature for half an hour before being cooled slowly.

As Vic says it's tough stuff. Despite that I've managed to ruin small bits by overheating due to clumsy grinding! Since that mistake I dunk regularly in cold water. It only takes a little longer. If the worst happened it might be possible to restore some hardness with a torch, but I doubt the HSS would be back in factory condition.

Dave

Thanks for all your answers. I cut one piece with the grinder and the end has indeed gone a bit buggered, to use Rik's vernacular scale. It's only 8mmx8mm - I'll try the 'slice it and sock it' and 'disc it and dunk it' approaches and form an opinion. Many thanks for the speedy replies.

Best, Jim

Edited By Jim Curry on 16/07/2019 13:47:47

I have cut 12mm wide strips of HSS from an old guillotine blade (about 75mm wide and 12mm thick) with a 1mm disc on a 125mm angle grinder - freehand. Slow , but I was careful not to let it get too hot (blue only) as I didn't really know the quality of the steel was. It turned out to be a good lathe tool.

Suggestion.

Don't grind the "just cut" end as the cutting tool end. If the qualities of the HSS have been damaged by the heat of cutting off, it won't be the part that is requred to cut.

Howard

Mechman 48 has the method I would use, if there is any concern about overheating, score deeply using a diamond file all round before snapping off. The advise regarding the cloth is particularly important.

I use a dremel to cut a grove right round, put in vice, cover with cloth and tap firmly with a hammer.

This is a very timely thread, I received today some 6mm HSS rods that I want to cut down. Was wondering how to do it. I had heard of the stick in vice and belt it method. Think I prefer Neil's sounds a little more controlled.

Adrian

I rough out all my HSS tools with a thin grinder disc. It puts much less heat in than the bench grinder. I even made this tool last week by cutting a 8mm drill bit and roughing the shape with my mini grinder before finishing the tool on my grinder to cut a 4TPI Whitworth thread.

Edited By Pete Rimmer on 16/07/2019 18:16:52

Just cut it witth an abrasive disc and do not worry about loss od hardness. I do it often.

Tidy job there, Pete. Did you make the bit-holder too?

Thanks Jim. Yes it's just a bit of inch bar about 8" long, with some flats milled in it and cross-drilled for the tool bits. In hindsight 8mm was a poor choice as it limits the range of HSS tooling I can use (hence the rather nice drill being butchered), but I had a broken 8mm carbide end mill to use in it originally. Broken carbide end mills make for great lathe tools, if it does take a good while to grind them to shape on a diamond wheel.