Wrong steel or harden it??

[Davek0974]

Hi all,

I've been making and selling some keys that are 3" long with a T-handle. The working end is a 7mm square peg a bit like a chuck key.

I was checking my ebay feedback and noticed that one customer had not left any, i sent him a gentle nudge and he replied that he was disappointed with the tool as it was too soft. I apologised, added that he should have contacted me straight away and thanked him for his input.

I am using EN16T steel 7/16" dia. Is this a good choice or should i be hardening the tips?? If so, how do i do that?

Thanks in advance.

Dave

p.s. no other customers have complained but naturally i am concerned that it is too soft.

[Paul F]

I'm unfamilliar with "EN16T" steel...

You can do a quick test to see if you're using a hardenable grade of steel or not...

Torch heat a piece of the steel to red-and-slightly-orange, and quench in water.
If it's hardenable, that should do it. If it's an Oil hardening steel, it may not just harden, but crack as well.

Slide an old file over it, and see if the file cuts.
If it cuts easily, it's not hardenable without some sort of case-hardening or case-carburizing and hardening.
If it cuts reluctantly or not at all, you have a hardening steel.. now you just have to look up the exact heat treat regimen for that particular steel for it to have the hardness and toughness you need.

Hope this helps.
Paul F.

[clutch]

http://argent.fia.com/web/fia-public.nsf/BDCD3AEB4AA7E420C125739A003DB378/$FILE/05_RecommendedMaterials_a_2004.pdf?Openelement
Applications:
Free-cutting, medium strength, medium carbon steel for machined components. Similar to BS 970: 1983 606M36T, Hitenspeed 55T.
Chemical composition:

C 0.38-0.43%
Si 0.25%max
Mn 1.5-1.70%
P 0.04%max
S 0.22-0.3%
Mo 0.25-0.35%
Fe remainder

Heat treatment:
Quenched and tempered to T condition.
1. Heat to 820-870oC for 1hr
2. Oil quench.
3. Temper at 550C for 2hrs
4. Air cool.

Properties:
Tensile strength 850MPa
Tensile modulus 196GPa
Yield strength 700MPa
Elongation 18%
Shear strength 561MPa
Shear modulus 76GPa
Fatigue strength (@ 106 cycles) 430MPa
Hardness 261-319Hv
Charpy impact 55J
Density 7.89gcm-3
Linear expansion coef. 11.5x10-6 oC-1
Characteristics and suitability for processing:
Resistance to atmospheric attack: poor, requires protection .
Machinability: good.
Adhesive bonding: good.
5 fc – 05.03.04

[Davek0974]

ok so my spec sheet states...

"A manganese molybdenum higth tensile alloy steel, hardened and tempered to the 'T' condition. Excellent ductility without brittleness. Readily machinable."

So what does that mean? It says hardened and tempered so should i harden it again?? But then says ductile, which to me says it will bend before breaking.

So should i heat treat or look for a better spec??

Dave

[Lynn Standish]

Lead is very ductile, but not very good if you don't want something to deform. I'd try some S7 or other variety of stressproof.

[clutch]

Lead is very ductile, but not very good if you don't want something to deform. I'd try some S7 or other variety of stressproof.

P = phosphorous
Pb = Lead

Did the end deform or did the buyer go nuts with the torque and twist it? I've made keys out of 12L14, treated tips with kasenite to put a case on them and they held up.

Clutch

[Davek0974]

Thanks guys

This is getting daft,

I cant find any reference to a BS number for S7 or stressproof anywhere.

I have found 12L14 but it seems to be the same as our 230M07 or freecutting leaded steel, which cannot be case hardened and is very soft due to the lead.

EN16T is a high tensile moly alloy steel. My application is mainly torque transmission as in a chuck key, deformation by using it as a hammer is not my problem or worry, the tip twisting off is so case hardening will not help at all.

Any suggestions?

This comes at the end of a *very* bad day and i'm just about ready to throw in the towel and take up painting and decorating:mad:

Thanks
Dave

[Davek0974]

Apologies for the last post, as i said, it has been a very bad day or two.:o

Still need help though:)

[clutch]

Dave,

Did the customer twist the driving end? What torque value do you expect your wrench to transmit?

If you have a value in mind, you could set up a fixture to proof the part using a torque wrench.

Does your ebay buyer want to return it for refund, shipping at your expense?

I wish I could determine the what the alloy and treat is of the common hex key (allen wrench). It sounds like you want something with similar torque transferring ability.


Clutch

[Rusty Marlin]

ok so my spec sheet states...

"A manganese molybdenum higth tensile alloy steel, hardened and tempered to the 'T' condition. Excellent ductility without brittleness. Readily machinable."

So what does that mean? It says hardened and tempered so should i harden it again?? But then says ductile, which to me says it will bend before breaking.

So should i heat treat or look for a better spec??

Dave


Based on what's in it and the Hv number it looks like a material very similar to ANSI 4140 pre-hard at 28-32 HRc. That's some fairly rugged stuff, as in rifle and hangun recievers, but its not really a steel for making hand tools. Its meant to take structural loads things like aircraft landing gear, rifle barrels, engine mounts etc etc.
I believe you would be better served by a 1085 material, plain high carbon spring steel. You can HT this at home with a MAP torch, a bucket of water for hardening and the wifes oven (if you don't get caught ;) ) for tempering.

[Davek0974]

Thanks all,

The torque figure will be low, as much twist as a human can apply to a 3" t-bar tool - the t-bar is about 4mm dia, but it is all applied to the 7mm square tip.

I took one of tools, fitted the bolt that they are made for into a vice and set about it like a gorilla.

I could have no effect at all using it as designed. I attached an 8" bar across the T so i had a bigger T, with two hands I managed to put a barley-twist into the tip and bend the T-bar.

I was quite impressed with my product.

I have sent him a free tool with a covering note explaining this to try and gain some outside input.

There is a vague possibility that hiss tool was one of my original ones made from EN8 or even less.

Time will tell.
Dave