Forging HSS?

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Forging HSS?

This topic has 14 replies, 10 voices, and was last updated 20 December 2015 at 17:32 by Ajohnw.

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19 December 2015 at 14:37 #217053
Rainbows
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@rainbows
Has anyone been able to forge HSS?

I have a boring bar thats wearing down and rather than grind the entire shank down for clearance I was hoping I could heat it up in my coal forge and bend the tip over then once its cooled down grind the final profile in.

Usually if I have to heat treat something I make it really hot then dunk it in oil. Then temper in the oven. Will HSS need a more complicated method for hardening?
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19 December 2015 at 14:37 #29561
Rainbows
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@rainbows
19 December 2015 at 15:54 #217071
Anonymous
Proper hardening and tempering of HSS is non-trivial, and even if you have an electric furnace isn't likely to be practical in the home workshop, which is why it is normally supplied ready hardened. See this link for details of a typical HSS:

**LINK**

Rather than spend ages grinding clearances on the shank rough machine it in the mill. I use old uncoated carbide slot drills to machine HSS. You need high spindle speeds, high feedrates and relatively shallow depths of cut. You want the chips to be coming off glowing red. If the cut is prolonged the cutter will probably be a dull red too. Don't worry about it, carbide will be happy. Just let the tool cool down before touching it.

Andrew
19 December 2015 at 16:18 #217073
Ajohnw
Participant
@ajohnw51620
You could neglect the tempering. I did forge some and harden it during training heating it in a gas muffle. It was quenched in oil – a huge bath of it with plenty of moving it around. I can't remember the initial hardening temperature but it will be about on the web, 1300C rings a slight bell but pass really. The tempering is tricky – holding a precise temperature for some time to let it soak through. I didn't do that and would guess that the job was a foreigner for one of the instructors. A google of heat treating high speed steel will bring up info but there are various grades and that is likely to matter. Cobalt content for one.

Edit – take up the practice of frequently sharpening with a slip stone rather than regrinding. HSS tools last something like for ever if that is done.

John

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Edited By John W1 on 19/12/2015 16:20:35
19 December 2015 at 17:35 #217087
bricky
Participant
@bricky
Let down a square file old by preferance ,forge the ends over in opposite directions.Grind to form a boring bar and the other end for internal screw cutting.Harden and temper. Mine is second hand and was forged back in the 1920,s It is 9" long but works a treat.

IFrank
19 December 2015 at 17:37 #217088
bricky
Participant
@bricky
Let down a square file old by preferance ,forge the ends over in opposite directions.Grind to form a boring bar and the other end for internal screw cutting.Harden and temper. Mine is second hand and was forged back in the 1920,s It is 9" long but works a treat.

IFrank
20 December 2015 at 10:16 #217138
Neil Wyatt
Moderator
@neilwyatt
Some useful comment and further links here:

http://www.iforgeiron.com/topic/12836-forge-high-speed-steel/
20 December 2015 at 12:11 #217165
Ady1
Participant
@ady1
If HSS was easy to forge and heat treat there would probably be a huge range of small quality tools made from it by now, since it's an amazingly tough material when its done right

Garage suppliers like snap-on charge a lot of money for their quality stuff and small garage owners who work 12 hours a day will use anything which makes their job easier/faster

I think the annealing part is a doddle, but the heat treating/hardening part is difficult
20 December 2015 at 13:31 #217186
Ajohnw
Participant
@ajohnw51620
I posted a link similar to this one once – it illustrates the problems well

**LINK**

Part of the problem with hardening is if the temperature gets too high it will burn = nvg.

John

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20 December 2015 at 14:41 #217200
jaCK Hobson
Participant
@jackhobson50760
HSS is always very stiff under the hammer. Doing a neat job of bending the tip over could be a challenge.
20 December 2015 at 15:14 #217206
Jon
Participant
@jon
You would bend it over when hot.

HSS easy to work with far from toughest may need quenching in cool to cold water to get decent strength/wear out of it and a mild temper just above straw.

Quality tools are made using a lot harder steels. Hss readily available easy to work with and can do a decent job.
20 December 2015 at 16:13 #217213
colin hawes
Participant
@colinhawes85982
I have seen HSS forged and hardened by a factory blacksmith in a coke burning forge when I was an apprentice. He used to bend over the ends of boring bars for the toolroom. If I remember correctly these tools were "quenched" in compressed air. Colin
20 December 2015 at 16:43 #217220
jaCK Hobson
Participant
@jackhobson50760
Posted by Jon on 20/12/2015 15:14:34:

easy to work with

Makes me wonder if we are talking about the same stuff.
20 December 2015 at 16:58 #217221
Michael Gilligan
Participant
@michaelgilligan61133
There seems to be a lot of 'forged' HSS around, these days

It's not much like the genuine article

… Just look at some of the comments on the 'Hacksaw Blade' thread.

MichaelG.

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[Yes, I know …]
20 December 2015 at 17:32 #217224
Ajohnw
Participant
@ajohnw51620
Air quenching is mentioned for M42 in the link I posted. That's 10% cobalt. 5% and M2 / plain HSS is available and all will be different. The link also mentions 2ndry hardening and shows what happens with double long term annealing. It's weird stuff.

This shows the hardening problem, it's for steel but HSS is likely to be similar in relation to burning

HSS is heated to 1280C for hardening so my recollection of using 1300C in a muffle looks to be correct. 100C higher and probably oh dear.

If some one has a bent end all round boring bar they might find that only the tip is actually HSS and the bend is actually in the shank that holds it. A test with a file will soon show if that is the case. I have one like this that I bought of Reeves a long time ago. It's a pretty hefty one. Some where I do have small bar that I am pretty sure is all HSS with a daft amount of bend on the end for the size of the bar – eclipse I think, probably sub 1/4" dia bar.

John

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