Using unhardened O 1 tool steel for keystock material? Why?

[i_r_machinist]

We have a gear set that calls for unhardened ASTM A681 O1 tool steel for a 3/8" keyway on a 2" shaft coupling. I don't remember ever seeing this before. What would be the reason, and is there an equivalent steel with that shear strength?
Thanks in advance
have fun
i_r_

 

[EmGo]

What would be the reason, and

Hard to know why someone else does something but if it wuz me, it'd be because O1 is easy to get in small quantities and has a reliable/repeatable strength, so if you are designing to a specified performance, that's a good choice.

Either that or they just thought it sounded cool.

is there an equivalent steel with that shear strength?

Wouldn't that kind of defeat the purpose of specifying O1 ?

 

[alphonso]

Sounds like a good way to beat the keyways out.

 

[eKretz]

More likely that the purchasing department bought some precision keystock somewhere once and it was O-1. Forever after the notation was there. I don't think soft O-1 would be any better than plain CRS.

 

[jim rozen]

Possible they wanted close-fitting keys, and the O-1 was spec'd to a tight thickness?

 

[L Vanice]

One reason to use O1 is that it is available in common key sizes and is precision ground to nominal size (if you don't use the oversize versions, of course).

Back in the 1980's, I bought a bunch of 12 inch lengths of Precision Brand key stock in various sizes. They appear to be zinc plated and I suppose they are accurately cold rolled to sizes to fit standard keyways. They are still in business.

%root_term_title% Steel, Imperial - Precision Brand

High quality steel material. Zinc plated finish. Size is clearly marked on each piece. Precision Brand® Keystock is used to provide driving torque between shafts and pulleys, gears, sprockets, etc. Used for new machinery, general maintenance, and shop repairs. It is a necessity in all...

www.precisionbrand.com

In the 1960's, I bought some "square drill rod" from Cole's Power Models for use as 1/16" and other small size keys. It might be W1.

Larry

 

[i_r_machinist]

More likely that the purchasing department bought some precision keystock somewhere once and it was O-1. Forever after the notation was there. I don't think soft O-1 would be any better than plain CRS.

After talking to the engineers, I think this or the "It sounded cool" reply was the most accurate.
customer

I'm back. Our engineering talked to the current owner of the product line,(two times removed from the original designers), they said they couldn't explain it either and we should just make the keys out of 4140, but don't tell anyone they said so. Our engineer is screwed and thinking about a career change.
thanks for the replies!
Have Fun
i_r_

 

[4GSR]

They said to make it from 4140? That's like finding a needle in a haystack, finding it in a HT condition that small of a square. That's why it was originally spec'd for O-1. Readily available. It's tougher with a tad higher shear strength from that of 1018 - 1040 cold drawn stock IMO.

 

[guythatbrews]

Precision Brand website says they use "high quality steel material". You can contact them and ask. Or maybe your customer wants you to use the "don't ask, don't tell" method.

Seems I remember 1045 from somewhere, but don't quote me.

 

[L Vanice]

After talking to the engineers, I think this or the "It sounded cool" reply was the most accurate.
customer

I'm back. Our engineering talked to the current owner of the product line,(two times removed from the original designers), they said they couldn't explain it either and we should just make the keys out of 4140, but don't tell anyone they said so. Our engineer is screwed and thinking about a career change.
thanks for the replies!
Have Fun
i_r_

So why not just use O1?

Larry

 

[gbent]

If anyone has a site that specifies annealed strengths of tool steels, I would like a link or source. My wag is the shear strength is at least 50% higher than mild steel.

 

[eKretz]

O-1 is around 190 Brinell, soft, as I recall. 1045 CRS (very frequently used for keystock) is hanging right in the same ballpark.

 

[4GSR]

Shear strength is a function of the ultimate yield strength of the materials. Basically 50-60% of that for steel. So for either 1018-1030 CDS or O-1 in the annealed condition, the tensile properties are very close to the same. Really, it would not make a difference which one to select. But if I was to put some $$$ on the table, I would put it on the O-1.
We did have a application many years ago where we had to have a key that would meet the NACE MR0175 requirements and have the shear strength needed. Went to a spring vendor we used back then and got a piece of Inconel X750 square spring material to use for the keys needed for the application. The only problem with that was, the Inconel key was stronger material than the material that had the keyway cut in it! But that's okay, It all goes down hole never to be seen again in the oil well.

 

[DDoug]

This is for a Nuke plant and they are allowing WAG's for material substitution ?

 

[i_r_machinist]

So why not just use O1?

Larry

O1 is readily available. Nuclear grade O1 is harder to find than unobtainium. I guess I should have mentioned that to start with. Sorry. The vendor has agreed to make the keys for us at an astronomical price. Gold would be cheaper per ounce.
Have Fun
i_r_

 

[dalmatiangirl61]

O1 is readily available. Nuclear grade O1 is harder to find than unobtainium. I guess I should have mentioned that to start with. Sorry. The vendor has agreed to make the keys for us at an astronomical price. Gold would be cheaper per ounce.
Have Fun
i_r_

This one shows "back ordered" but would think you could find it somewhere, just cut to length.
https://www.mscdirect.com/product/details/86124005

 

[i_r_machinist]

This is for a Nuke plant and they are allowing WAG's for material substitution ?

Absolutely not. Every other key in this 12 stage speed multiplier is 4140. This is a brand new component. I would love to see the machines that they made this on. Multiple sets of herring bone gears. I don't even know how these were cut and ground. Beautiful work. If they say 4140 keys, I'M GOOD WITH IT.

 

[i_r_machinist]

This one shows "back ordered" but would think you could find it somewhere, just cut to length.
https://www.mscdirect.com/product/details/86124005

In the nuclear world, the first thing you ask is "Is it Q?". Which means "Can you trace the ore that the steel was made of back to the mine that it came from?"
This is to stop parts that are used in your friendly nuclear power plant from being made from ships that are recycled on India beaches.
Have fun and thank you your time in posting the link!
i_r_machinist

 

[triumph406]

In the nuclear world, the first thing you ask is "Is it Q?". Which means "Can you trace the ore that the steel was made of back to the mine that it came from?"
This is to stop parts that are used in your friendly nuclear power plant from being made from ships that are recycled on India beaches.
Have fun and thank you your time in posting the link!
i_r_machinist

Do you have to cut a piece off and send it to a lab for material anlaysis?

I worked for a place in the UK that made CO2 scrubbers for nuclear submarines. EVERY piece of material that came thru the door had a piece cut off and sent out for analysis. Regardless of traceability it got analysed

 

[i_r_machinist]

We have the equipment on site to analyze the material.
Have fun
i_r_