Beginner question: Steel Types

[KillerMike]

I have a question about what TYPE of steel I should use.

I'm going to be making some additional toolholders for my QCTP on my mini-lathe.


I'm just starting out, and this is my first project with my mini-mill.
I'm going to be buying some metal from MetalSuperMarkets, but I'm not sure what TYPE of metal I need. My options are:

Alloy Steel: A steel to which modest amounts one or more alloying elements other than carbon, such as Cr, Ni, or Mn have been added. Alloy steels are workhorses of industry because of their economical cost, wide availability, ease of processing, and good mechanical properties. Alloy steels are generally more responsive to heat and mechanical treatments than carbon steels.

Cold Rolled Steel: Cold rolling increases the strength and hardness and decreases ductility of steel by rolling it at ambient temperature (or below its recrystallization temperature). In addition to improvement of mechanical properties, the cold rolling produces steel plate/sheet of the desired physical dimensions. Steel may be annealed subsequent to the cold rolling process to restore the original mechanical attributes. Even with multiple passes through rollers, cold rolling is more limited in its ability to effect dimensional changes (versus hot rolling) because of the increased hardness and decreased ductility.

I realize that my equipment and tooling isn't top notch, but I have to start somewhere.

Appreciate any input.

Mike
www.ottawawood.com

[Rustybolt]

You could probably get with alum, the forces are so small. as far as steel is concerned Cold finished 1018 is about as cheap as you can get and just about every mill supplier has it.

[sal64]

cold roll 12L14 is the easyest steel to machine.

[whitis]

Alloy Steel
Cold Rolled Steel:]

No, those aren't your actual choices. Those are just categories. With Alloy Steel being rather dubious as the other categories also contain alloys. The hot/cold roll categories there contain low carbon "mild" steel alloy that are not suitable for heat treatment. Your supplier actually has "Alloy Steel", Cold Rolled Steel, Hot Rolled Steel, Stainless Steel, and Tool Steel categories and within each of those various alloys. If you click on the categories on the left hand menu on the main page, you will see each category broken down by alloy, but clicking various other places which are seemingly equivalent does not show you the stock broken down by alloy. Most alloys there are in a rather limited selection of profiles.
Your choices (excluding stainless and tool steel) are more or less A36, 1018, and 4140.

Another vendor provides a little more info, though still scant:
http://www.onlinemetals.com/steelguide.cfm
But more here:
http://www.speedymetals.com/informat...erialframe.htm

Here are some folks who sell metal online:
www.onlinemetals.com
www.industrialmetalsales.com
www.asapsource.com
www.speedymetals.com
www.discountsteel.com
www.fastenal.com

I suggest you compare prices, they differ radically. The same piece of metal can cost 4 times as much from vendor A as vendor B. And for steel, shipping costs can be real killer if you are buying moderate amounts - it may cost as much to ship as you pay for the metal if it isn't a spiffy alloy; try to get steel locally if your order is heavy. ASAP has a good selection but prices tend to be very high. Online metals and industrial metal sales tend to have good prices on aluminum. Fastenal has a limited selection and prices that aren't anything to write home about but they have many local stores, cut to length, and one may be closer than you realize. Discount steel has low prices (for online) for certain standard lengths but they really let you have it when it comes to cutting. However, I see you are in Canada and could really get taken to the cleaners at customs and metalsupermarkets appears to have a store in your city. Lee Valley Tools in Ottawa reportedly has assorted cutoffs from the shop next door.

I am not an expert on the application of steel alloys. You can probably make an adequate QCTP holder out of any of those alloys, untreated. I think people have. I even have some aluminum ones. Use the 4140 if you intend to heat treat. Even without the heat treatment, it may still be tougher than the others. 4140 is one of the alloys used for professionally made tool holders. It is also available from other suppliers in partially hardened form. It is more expensive than the other alloys. If you make insert holders, though, the alloy and heat treatment can be more of an issue due to the concentrated stresses, wear from hot chips, and the set screws dinging the metal the holder is clamped in another tool holder (if separate).

Hot rolled A36 is the cheapest and probably also the hardest to machine. You have scale to deal with (unless pickled). In theory, might have slightly better long term stability due to lower internal stresses. A36 is more for welding than machining parts and seems to be one of the lowest grades of steel.

Machining the stressed skin off all sides of CRS may reduce the tendancy to warp. If you take the stressed skin off one side but not the opposite, this can cause warping.

Aside from one being hot rolled and the other cold rolled, A36 and 1018 are fairly similar in composition.

[Black_Moons]

From a mechanical standpoint, you don't have to worry about anything breaking here, so we'll be looking at rigidity and machinability and corrosion resistance.

Now, as far as rigidity, all steels are basicly the exact same rigidity! go figure! doesnt matter if they are super hardened or boring mild steel. all about the same rigidity, its the point where the metal goes plastic or breaks that is changed by alloy/hardness.

Alluminum however, not being a steel alloy, is not the same rigidity, its much less rigid.

So, aluminum is worse then steel for rigidity.. you do have a decent amount of material there though, and if its a small lathe rigidity might not be a big deal.. but steel would be better then aluminum.

As far as corrosion resistance.. well, aluminum and stainless steel win that, but if you keep it oiled, mild steels will do fine, just get some rust prints unless you blue it or something.

as for machinability.. well, Aluminum wins that, its just a cakewalk. (well, for the standard grades of aluminum), Followed by special alloys of steel designed to be machined (leaded steels, Machines easyer then normal steels with a better finish, some say they have slightly better rust resistance then mild steel.
Cold rolled steel (the process they put 'mild steel through' when forming it) does induce stress that can cause the peice to warp as you machine it (pain in the ass)
Hot rolled steel is typicaly covered in scale that is abrasive, bad on your cutters, turns into dust and gets over your machine (messy), can be removed by grinding outdoors etc.. or wire brush on angle grinder.. but once removed, its gonna machine better then cold rolled because it won't warp on you.

Hot rolled steel is also MUCH cheaper then cold rolled (sometimes 3 times the price or more for cold rolled), and typicaly much less dimentionaly accurate. but you'll have to shave down all its sides anyway.. (though the scale can be left on parts you don't machine, its up to you)

Stainless, is typicaly much harder to machine.. I havent heard of any 'easy' to machine stainless alloys but then, I never really looked.

One thing to note is finish, its typicaly hard to get a nice looking finish without sanding/polishing mild steel (hot/cold rolled). aluminum is easy to get a wonderful finish, stainless... I havent played with much.

All said and done, you basicly have aluminum<cold rolled<hot rolled<stainless in a scale of how good and how diffacult they are to make, Id recommend hot rolled myself, but feel free to try some in aluminum to start with.

[RobbieKnobbie]

For that application any steel would cut the mustard. But since you're going to be doing a fair ammount of cutting with a dovetail, personally I'd go for the easiest thing to machine. That's 12L14.

Since your tool holder will probably have a thin coating of oil on it from day one, I wouldn't fret too much about 12L14's tendency to rust too much.

Second to that I'd go for Hot rolled. It's cheap and pretty machinable.

Someone mentioned pre-hardened -40 or -50 carbon steels. I would stay away from those. The hardness advantage isn't worth the headaches you'll get tapping it, plus it tends to be on the pricey side.

[airsmith282]

i have the same holder you got in your pic and at one time was considering making additional holder for it but then decovered to make them properly it was far cheaper to just go out and by them , but to each his own ,i made my own chipping hammer cause its better, more weight, cooler looking,, and longer life then the ones sold in stores,and the steel i used was free so it only cost me my time..

[Duffy]

I suggest that you go to Loucon Steel and buy a "short" of whatever size and type, (cold rolled, hot rolled,) comes close and wrestle with that. You will get more for your money with enough left over for mistakes. Your words "I have to start somewhere." Loucon generally is MUCH better value, although not always the selection. In this case, you hardly care.

[BobWarfield]

I know you want to make some holders, and I applaud you for the pious thought. If your QCTP is AXA compatible, you should also be aware they can be had for $9 each from CDCO.

Probably not what you want, but just wanted to make you aware.

Sometimes these cheap offers are so cheap you can hardly afford to make your own. I bought a bunch from them 2 years ago.

Nice to have extra holders!

Cheers,

BW

[KillerMike]

Thanks everyone for the advice...

I picked up some cr1014 pieces, and look forward to making chips.

I know I can buy the additional tool holders pretty cheaply, but 2 things are motivating me;

1) its my first real project for my mill, and I want to give it a go..
2) I want to make a custom parting tool holder, that doesn't have as huge overhang as mine does currently. (this one gets held in a quick change toolholder, and ends up hanging out about 1- 1 1/4" and flexes dramatically when being used.)





I'll post a pic when I get it done! (Waiting for my 60 degree dovetail cutter to arrive on Friday)

Thanks again!
Mike