Welding hss

[Inspector]

Surely brazing it would lose the temper.

HSS was developed for metal lathes and milling machines because it retained it's edge even when it got red hot. As long as it isn't quenched after heating it will retain it's heat treatment. If quenched it gets microscopic cracks and the edges don't hold up. The same reason you don't dip a HSS tool off the grinder, even if it is blue, to cool it. Opposite of carbon steel which you should not allow to get hot enough to see a colour change. So braze away if you want.

Pete

 

[Sheffield Tony]

Surely brazing it would lose the temper.

HSS was developed for metal lathes and milling machines because it retained it's edge even when it got red hot. As long as it isn't quenched after heating it will retain it's heat treatment. If quenched it gets microscopic cracks and the edges don't hold up. The same reason you don't dip a HSS tool off the grinder, even if it is blue, to cool it. Opposite of carbon steel which you should not allow to get hot enough to see a colour change. So braze away if you want.

Pete

Are you sure ? The hardening and tempering temperatures are rather higher than carbon steel, but certainly M2 can be annealed by heating to red heat and cooling in air - I've done it and been able to file it afterwards. And this seems to agree:

Annealing

Annealing is recommended after hot working and before re hardening. Heat the M2 high speed steel to 850°C at a rate of no more than 220°C per hour. Always hold at temperature for one hour per 25mm of thickness (with two hours being minimum). Furnace cool slowly. The annealed hardness achieved should be 248 Brinell or lower.

 

[Inspector]

I'll qualify my statement. Silver brazing / solder flows at approximately 1200F or 650C so is below the temperatures that HSS will loose its heat treat properties. So with the right type of brazing rod HSS can be brazed to a mild steel bar. Now if you take into consideration the cost of Silver Brazing Rod it is probably more cost effective to buy import HSS turning tools or use carbide inserts or HSS inserts that are drilled already. http://www.arwarnerco.com One could also drill a hole in the end of the mild steel bar big enough to put the HSS square or round bar into and hold it with setscrews and put a handle on it. Much of it depends on what tools and equipment we already have, what skills we possess and how much futzing time we have. I think it false economy to try and make HSS lathe tools if we have to go and buy a lot of stuff to do it.

I sit corrected.
Pete

 

[Phil Pascoe]

"One could also drill a hole in the end of the mild steel bar big enough to put the HSS square or round bar into and hold it with setscrews and put a handle on it."
If you go down this route, a set of taps (assuming you've a holder) and five 4.3mm drill bits are only just over £10 + a bit of p&P, and BMS is cheap. Even if you want to go upmarket 16mm stainless is only £16 - £20 per metre delivered. Cheap for what is only a holder, after all.

 

[graduate_owner]

Another possibility - what about using a length of ms for the main shank, say 1 1/2 x 1/4 or so. Take a piece of ms say 2 x 1/2 about 2" long and mill a slot in each end, one slot to fit the ms and one to fit a piece of hss about 2" long as the cutting edge. The slotted ms could be drilled to clamp the hss cutting end, and drilled or welded to fix to the main shank. Effectively joining the hss to the shank by surrounding both with a ms strap all round.

Any thoughts on this?

 

[chipmunk]

Another possibility is to follow the Simon Hope hollowing tool route.

I bought one of Simon's bent hollowers at £25...

and it cut very well indeed. So, I bought a set of M2.5 taps and some TCT 6mm round inserts (RCGT0602) intended for aluminium along with Torx screws and made my own straight cutters (just 6mm silver steel) and some holders with an M6 hole to mount them on my BB. You need a means to mill a flat bottomed 6mm hole for the insert to sit in along with a concentric tapped M2.5 hole which is pretty small.

HTH
Jon

 

[Normancb]

One of my colleagues in SMEE has machined HSS toolbits on a mill using solid carbide cutters to prepare them for our grinding course, but it's very hard on the cutter and produces a poor finish. I've got some early HSS turning tools from the days when HSS was a new idea - they are made just by silver brazing HSS plate into a mild steel blank and they work just fine - if I ever grind away all the HSS I'll just mill a new step and braze in a new bit.