Is 4140 the best to use....

[ferryman]

....for making a morse taper?
I have some that I am planning on using for making a MT slot saw arbor.
I just happene to have some 4140 the right size. Do you think it will be ok to use? I am going to drill and tap it for a draw bar to fit on my mill, as well as drill and tap the "big end" for a screw clamp to hold slotting cutters.
Should it be ok to turn a taper on my lathe? Also thinking about oil dipping, (heat to red, and quench in old oil), the arbor after its finished to harden it a bit and stop it from rusting. Or will this warp it too much?
Thanks Phil

[Sunset Machine]

It'll work fine, but you're making work for yourself with no gains in the end. I'm assuming it's half-hard scrap? I usually anneal the stuff, it's tough and slow to work with even at that. I'd probably prefer a low-carbon hot roll 1018 for a project like yours, or ramp it up to W1 drill rod and skip the heat treating. Stressproof 1144 is pretty nifty too. 4140 would be at the bottom of my list for this one.

[f350ca]

I like machining 4140, gives a beautiful finish, but have heard its hard to work with small machines. (could be hear say) As for heat treating I've never needed to yet, for a slotting cutter in a home shop environment your great grand kids wouldn't wear it out. I think you want the bright surface on the taper to get the best grip, any irregularities from treating will reduce contact and cause problems. Your into a project I need to follow some day, have a chinese R8 one that has way to much run out.

[PixMan]

I too like machining the high alloy steels. they break chips and can offer a nice finish with the right tooling run at the right speeds and feeds. Carbide insert turning tools and solid carbide (and/or carbide insert) milling tools rule the day for machining it. With HSS tooling, things can take 4 to 10 times longer, and I'm not getting any younger while watching HSS tooling plod along. ;)

I tend to go for the pre heat-treated varieties as that usually meets most requirements for material tensile strength. True Stressproof 1144 can be hard to find, as many sellers try to pass off regular 1144 as being stress proof. When you do get it, it machines like butter. Common 1018 cold rolled steel is worse to machine (IMO) than most other steels unless you can really apply carbide and get some heat into the chips. With HSS the chips stay cool and never harden up enough to break. I do machine 1018 from time to time, but not if I have a choice of instead using 12L14, 1117, or the 414x alloys.

[Sunset Machine]

(08-18-2012, 08:43 AM)f350ca Wrote: I like machining 4140, gives a beautiful finish, but have heard its hard to work with small machines. (could be hear say)

Definitely - with HSS tools, my old 1/2 HP lathe just stops and hides from it. My 3/4 HP lathe does a little better, but .030" DOC maximum. In soft steel, .125 DOC max. So, half the RPM and 1/4 the DOC means it's time consuming stuff for me.

[TomG]

Phil,

4140 is probably overkill for an arbor. A better bet would be mild steel, or 12L14 for a super finish. Whatever you use, don't harden it. You want the taper to be softer than the spindle it fits into so when (not if) it spins, it won't cause damage. MT adapters are always left soft for this reason.

Tom