Quick question: which steel alloy should I buy, and why?

[cazclocker]

I have a small project I want to put together, and it involves drilling & tapping in 1/8" x 1/8" square steel bar.
Looking at OnlineMetals.com, I have four alloy choices: keyway stock, 1018 carbon steel cold finish, W1 tool steel cold drawn, and O1 tool steel.
I plan to hand-file very small V-notches onto one of the surfaces. I want to do the same to two separate pieces, with drilled-tapped holes on both sides of the notches. The V-notches will hold the chucking end of a 0- or 1- sized tap, to prevent the tap from rotating while I hand-rotate the headstock of my watchmaker's lathe.
What I want to end up with is something like this:



My concern is avoiding deformation of the notches over time.
What alloy would you choose of the three I listed? Or will they all work equally well?
Will one of the alloys be easier to tap than the others?
Thanks.
Doug

 

[Razzle]

I would use the O-1. But you should also look at using 4140PH. I like to use 4140 for tools as it is tough but reasonably easy to machine.

 

[cazclocker]

I would use the O-1. But you should also look at using 4140PH. I like to use 4140 for tools as it is tough but reasonably easy to machine.

I've never heard of 4140PH... I'll have to look at that. I only listed the alloys that are readily available at OnlineMetals.com.
Thanks for your advice! If I can find a source for 4140PH in the size I need then I might buy some to try.

 

[Razzle]

PH stands for Pre-Hard. it is basically an annealed form of 4140. Works great for tooling and you can harden it if you so desire. but then you would need to grind it to finished size. My surface grinder is still a work in progress. And i havent needed to harden anything that i have made yet. I have made a tailstock die holder and a multiple position carriage stop from 4140. i have a pile of the stuff just waiting to be made into more tooling.

 

[cazclocker]

PH stands for Pre-Hard. it is basically an annealed form of 4140. Works great for tooling and you can harden it if you so desire. but then you would need to grind it to finished size. My surface grinder is still a work in progress. And i havent needed to harden anything that i have made yet. I have made a tailstock die holder and a multiple position carriage stop from 4140. i have a pile of the stuff just waiting to be made into more tooling.

Thanks for that. I was just about to ask what PH stands for, since I can't seem to find any at my usual online sources.
Looks like I'm going with O-1, since it's almost universally available.
Thanks very much for your help!

 

[Ischgl99]

O-1 is a nice steel to machine and fairly easy to harden. I made a threading tool with it recently and it has held up well, so should work well for your application.

I have found Online Metals prices to be high on the things I purchase, but haven’t compared them recently. Take a look at McMaster-Carr for smaller qualities of materials, they will have just about any material you would want as a hobbyist. Www.mcmaster.com. I have found them to be priced better than other places on some things, but more expensive on others, so you would need to compare each type of product you are purchasing.

Shipping for me is very reasonable from McMaster, but your area may be different, so make sure you include that in your comparison when checking prices. One thing to keep in mind is longer bars cost more to ship, so two 36” bars is cheaper than one 72”. As an example, I just placed a 72” 1” round steel bar in my shopping cart and shipping is $35.08. If I replace that with two 36” pieces, it drops to $12.49.

 

[MrWhoopee]

Some distributors refer to it as 4140PH, but this can be confusing because PH is used to designate precipitation hardening alloys like 17-4PH. It is more commonly referred to as 4140QT (or Q&T) for quenched and tempered or 4140HT for heat treated.

In the case of your little tap wrench it probably doesn't really matter what you use, the taps are so small as to require very little force to drive them. Of your choices, the only difference between keystock and cold-rolled is that keystock is usually zinc plated and a few thousandths oversize to allow filing to fit. I would use O-1 and flame harden it for long term durability. If you don't plan to harden it, chose whatever is cheapest.

 

[cazclocker]

O-1 is a nice steel to machine and fairly easy to harden. I made a threading tool with it recently and it has held up well, so should work well for your application.

I have found Online Metals prices to be high on the things I purchase, but haven’t compared them recently. Take a look at McMaster-Carr for smaller qualities of materials, they will have just about any material you would want as a hobbyist. Www.mcmaster.com. I have found them to be priced better than other places on some things, but more expensive on others, so you would need to compare each type of product you are purchasing.

Shipping for me is very reasonable from McMaster, but your area may be different, so make sure you include that in your comparison when checking prices. One thing to keep in mind is longer bars cost more to ship, so two 36” bars is cheaper than one 72”. As an example, I just placed a 72” 1” round steel bar in my shopping cart and shipping is $35.08. If I replace that with two 36” pieces, it drops to $12.49.

Yes! I have a McMaster-Carr account, but I forgot to look there! Thanks for the reminder.

 

[Ischgl99]

Yes! I have a McMaster-Carr account, but I forgot to look there! Thanks for the reminder.

You're welcome! Another place to add to your search, they don't have O-1, but for future consideration is Midwest Steel Supply if you haven't used them before. I find their prices are the best of anywhere I have checked in the past couple years, but you do have to plan ahead since it takes a few weeks to get an order.

 

[cazclocker]

You're welcome! Another place to add to your search, they don't have O-1, but for future consideration is Midwest Steel Supply if you haven't used them before. I find their prices are the best of anywhere I have checked in the past couple years, but you do have to plan ahead since it takes a few weeks to get an order.

I just checked prices of OnlineMetals.com vs. McMaster-Carr, and they both supply 18" lengths, which is plenty for my needs. The tool I'm envisioning will likely be a rarely-used one, but essential for when I need it kind of thing. All I need to make a completed tool is 5"... 4" for the main secction, and 1" for the other grooved half. The leftover material can be used for another size tap, I suppose.
I checked Hudson Tool Steel, but they're requiring a minimum $150.00 purchase for precision ground flat stock! I don't think so!
Thanks for the suggestion of Midwest Steel Supply... I've got them bookmarked now! I'm in Wichita Kansas, so a midwest source is a good thing for me. I'm just a small-time retired guy who wishes he'd paid more attention in machine shop, so I like to save money whenever possible.