Hardening Silver Steel

[garethp]

Hi,

I've been having variable results when hardening silver steel, anything I can find on hardening says 'heat to red and then quench' but the time at red is never mentioned. I've always heated to bright red (carrot colour?) and plunged into cold water - should I keep it red for roughly 10 seconds before cooling or a longer / shorter period of time?

Regards,
Gareth.

[brozier]

What problems are you having?

Are you tempering after hardening?

Silver steel should be hardened at Cherry red (770 - 790 degrees Centigrade).

Time depends on size of workpiece - you want the whole thing to have reached the same temp.

Do you stir the tool as you quench so it cools rapidly?

The Tubal Cain book on hardening is pretty good if you want to know chapter and verse. (Workshop Practice series).

Cheers
Bryan

[weldsol]

Hi Gareth
According to UK special steel stock holders.
They state the following -

Heat to 770 - 790 C and thoroughly soak.
Quench in well agitated water or preferably 10% brine solution
check their site fir colour chart for tempering

www.westyorkssteel.com/Product_Info/Tool_Steel/silver.htm

Paul

[garethp]

Sorry - should have said that I don't seem to be getting the steel hard, I've made a few tool bits (mainly D bits, a rounded end cutter for cutting a rough round bottom groove and a cutter for machining a small dovetail) The D bits have been reasonable but some deformed slightly after use, the round end cutter appeared to be still soft and the dovetail cutter was the most successful. The dovetail and the round end cutter were made from the same bar which was 1/4" and the largest I've used is 8mm. I haven't tried stirring the bit in the water, I guess oil would cool it more rapidly as well?

[Richmond]

My understanding of this is that the temp must be kept up for 1 minute per cubic inch of material to be hardened.

Also, my local sources swear by brake fluid as a quenching agent. Cheap, and easier to deal with. Also, adds a nice patina to the work after polishing.

Keith

[jonkett]

As i remember it is esential that when quenched it is necessary to agitate the hot metal, especially in water. This is because as the metal heats the water and steam forms, this acts as insulation, preventing hardening taking place. Also, with a long thin piece quench verticaly, hottest part first.

Regards
John K.

[SteveW]

Jul 29, 2008 13:34:16 GMT garethp said:

I guess oil would cool it more rapidly as well?

That's a NO.

The hardest quench is in brine and oils provide the softest quench.

It's also important that once fully hardened and cool the part is cleaned up to a shine and then heated from away from the required edges. Colours of oxidation will then travel out from the heated bit.

These colours provide a very actuate idea of temperature. As the required colour reaches the bit you want then quench. This freezes the amount of relaxation of the original hardness. If you don't temper you can leave the part too brittle.

It's important to plunge vertically as bending can occur due to the differential cooling and as said above, keep the part moving.

[ravensworth2674]

Gareth,
Might I ask the awkward and probably offensive question? Why are using what is nothing better than a carbon steel for your work?
OK, I use 'silver' steel which doesn't contain silver for 13" lengths of say 1/8th-3mm to bore African blackwood. There really is no cheapish alternative and I use it for boring bar shanks but I bung in HSS inserts or if I am cooking on gas- sweat carbide inserts to do the cutting bit.
I points out( I think) that you might be overheating and softening the temper of the tool.
In some of my work, it is difficult not to but you are using using 7mm stuff and - every cheap HSS drill set has a 7mm drill. In all probability it will be a lot better and----- cheaper.

And you do know that you can even drill the other end of HSS drills?

Cheers

Norm

[abby]

Silver steel should be more than adequate for most of your tool making needs but the tempering is more critical than the hardening. For small stuff when no temperature controlled oven is available a bed of sand heated from underneath or a tin of molten lead or solder will allow accurate tempering . It is some years since I worked in engineering but I believe that 1 hour per inch of section was the soaking time at hardening temperature for most tool steels although I can't be sure.

[ravensworth2674]

Abby,
there is nothing wrong with your points. The only flaw, apart from the likelihood of not having sand or lead baths in a home workshop is price.

Whilst 'my bit' was running, I went back to local and current price lists and found that there are really much cheaper alternatives.

We 'did' this exercise years ago when an old tool room fitter explained his somewhat bizarre tooling. Dear old Jack has long gone but his exhibits at Harrogate will linger on. Jack used high tensile bolts as tooling. he used bike spokes for boring bars and made a Quorn from welded sections. Old Ted was another of these men and he case hardened his mild steel tool blanks.
Where they wrong? Were they getting bette or worse results from their approaches?

These fine old men are gone now but I watched French TV3( I'm into such things) and found a knife maker who was using broken lorry coil springs as his raw material.

I came in for some stick about my thoughts on other things. Alongside the 'Oz' in the Western Desert, Spitfires were taking off in their defence with what would we would regard as gimcrack bearings in their worn out main bearings on the Merlins. The bearings were made out of bits of spare aluminium which was lying around. Jack, Ted and now another of my Club take full stage.

Excuse me, but I have a chunk of wood tool holder on my tool and cutter grinder which could do with a pennyworth of attention. Must make something a little better but what the Hell?

Norm

[Noddy]

One test to see if you have achieved the necessary phase transformation at cherry red is to see if a magnet will stick to the tool, if it does, it hasn't been at heat long enough. don't leave the magnet on for more than a fraction of a second though, or you'll destroy its magnetism.

I'll second Brozier's recommendation. get Tubalcain's book, life's too short to be messing about.

Keith

[ravensworth2674]

Keith,
Ah, the Irish contingent! So we can introduce the Irish tempering technique.

Heat to cherry red and plunge firmly into a 'tattie' and allow to cool.
Is it a slur against the occupants of the Emerald Isle? Not a bit of it, the humble potato is both water and near pure carbon. And there you have it.

Isn't science a breeze?

[abby]

Norm your points on economy are noted and agreed however the question was specifically regarding silver steel.
Personally I use whatever I have in stock , being employed for several years as buyer for a very large scrap metal company in Birmingham , and operating my own scrap business for a few more years I have enough silver steel , ground stock and gauge plate to last the rest of my life and like in the song it didn't cost me a dime.
I also keep all my broken drills and endmills to use as tool bits if they can't be rescued on my clarkson cutter grinder with genuine clarkson drill sharpening attachment. I am also rather lucky in so much that my dear old dad - now pushing 90 - following his stint in the RN and being torpedoed twice in the Atlantic , shot to pieces in the Scheldt by our own rocket firing vessels , and wounded during the D-day landings worked at Clarkson's for well over 30 years , so I have a stock of endmills ,slotdrills , chucks both dedlock and autolock , collets drills and taps down to 14 BA.
Other members of the family were killed at Salerno , taken prisoner ( and escaped ) at Arnem and hit in the chest by a panzer shell in Normandy - he survived.
This week I are mostly into investment casting ! but am interested in extruding brass sections and copper tube so if you have any knowledge that might be helpful I would be pleased to learn.

[ravensworth2674]

Abby, glad to agree about economy and most other things. One of my friends is the little Dutch girl who tended our boys when they were wounded in Arnhem. We have a VC in Oosterbeck. I still have 'shares' in my Squadron. I suppose that it will last to the end of my days.- we must keep the flame burning. Meanwhile, back at the Ranch.
Well, you can emphasise to a younger crowd how good the old Clarksons are- and just how things improve with something similar. Actually, I have 'rather more clarkson bits' than hinted but we have to encourage others to progress.

Back to casting? I'm not an engineer. Always wanted to be one but that's show bus.
I have done a little light alloy casting but it is my wife that you should ask about investment casting. She was an orthodontist and consultant. Daughter has just done her 'final written exams' as a special registrar. So if you have any gold/platinum which would be lying around- no, well, I am trying( very)

Gathering my remains of a brain, the guys into extrusion were Metal Box and those in Ordnance. I saw it done at MB but really, I'm nudging senility as it as so long ago.
One thing- Yea, I can panel beat and wheel is that copper has to be annealed repeatedly by going red hot and quenching.

OMG- you are NOT into musical instruments? My missus has just got a new Selmer Alto clarinet today. And -yes- I do know locobuilders/musical instrument repairers. Please--- no!
Must have a go at that jammed trombone mouthpiece.

And these guys are writing for advice.
On that note-oops

Cheers

N

[garethp]

Thanks for all the replies!

Thats interesting about the oil, I'll keep on using water - no burning oil smell either! I have been plunging vertically as to keep things straight but i'll start stirring as well. I've been using silver steel as generally I have pieces in 'stock' and for the odd reamed hole or one off cutter I think its more than adequte - for heavier use I'd get a hss reamer.

Just to let you know, I'm constructing Geo Thomas's rear tool post which grips the blade in a slot which has 7deg dovetails, the cutter that I made for that was the most succesful - it was the one which I kept 'red' for longest.

From the replies I think that I've not kept the bits 'red' for long enough and I need to stir the bit in the water. Next step is to perfect the tempering once the bits are hard! I'll get a copy of Tubal Cains book - life is indeed short enough.

[ravensworth2674]

Abby,
A flash of memory( they are getting fewer)
Google 'Ferees' who make musical instrument repair stuff in the US.

If it helps, my missus has a book on musical instrument repair as well.

Apologies to the rest- but I am having a spot of
Damn, it's gone again

Norm

[chris vine]

Hi All,

I find that for tempering, the domestic electric oven is remarkably accurate. (German). However you could do a colour test to see what you have to set it to to get light straw etc etc..

The beauty is that it will hold temperature fairly stable so that it is not just one part of a tip which is as you want it.

Note to self: Only do this when swmbo is out.

C

[abby]

Sorry Norm but you have totally lost me -who mentioned musical instruments ?

[Old Biker]

Depending on what the tooling is for you can avoid the problem of tempering all together. An engraver of my acquaintance re-hardens his gravers by quenching in a block of paraffin wax. I have had success quenching knurling wheels (specifically for brass & nickel silver) & very small cutters (eg. for ivory, ebony, boxwood etc.) in cooking oil.

[petercolman]

There is no point in tempering a tool that is not hard, if you have got thre job hot enough without roasting out the carbon by holding it at too high a tempreature for to long, quech in brine (higher boiling point than plain water) and see if the thing is hard by attacking it with a file, if all ok get it clean and polished.
Now gently temper by any of the methods- heatibng in a box of sand or brass swarf, in the oven by colour etc and quench, if too soft you over temperd, if it breaks then not enough. one point to remember, in the Birmingham gun trade, the spring makers who made v springs from carbon steel by hand, making them straight and bending after tempering, were not allowed to temper a spring until after 10. am whern the daylight was bright enough to see the colour!