What Steel for a BXA tool holder

Bob N · Sep 12, 2006

I am planning to make a dozen BXA tool holders for my Aloris piston tool post and am concerned that soft steel may result in holders that have a dovetail that will not hold the pressure.
Is my concern warranted?
(The one Aloris holder I have seems to be very mild steel, as I can sort of cut into it with a penn knife or file.)
Any thoughts.

cruzinonline · Sep 12, 2006

4140?

dirty old man · Sep 12, 2006

4140 would be nice, but bear in mind that you gotta dril & tap some kinda small holes!
J C Hannum did an article some time back in Machinist's Workshop Magazine that I was reviewing last night. (I want to make a couple of extras, including the one featured in his article with built in back rake to better utilize HSS).
He used 12L14 leaded stock, and I figured on the same. But I dunno, as I read somewhere else recently that 12L14 rusts very easily?
Dave

dsergison · Sep 12, 2006

you could case harden them.

dsergison · Sep 12, 2006

but you dont need to, I've built a few aluminum ones to hold things like scisor knurling tools.

the dovetail holds up fine.

cruzinonline · Sep 12, 2006

7075 T-6 for aluminum?

As far as 4140, annealed, tapping a small hole is no problem. We make stuff out of it all the time, tool holders, boring bars, wrenches. In fact all we have in our stock is A-36 for plate and weldments, 1018 for stuff we are going to weld and everything else is 4140, and 4340. Lots of 1/4-20 set screw holes, a few #8's or #10's. Yeah you have to be a little more careful with it but we have not had a problem tapping. Machines nice and holds up real well.

tools · Sep 12, 2006

I've also read tons where there isn't a ton of difference in rigidity between common sorts of steel, as in the discussion of making insert tool holders.

To that end, I would imagine mild steel will work fine as long as it fits well. And is exactly what I've decided to make mine out of after doing some research.

ALWAYS interested in hearing where I may have gone wrong before it's too late!

Tools

lazlo · Sep 12, 2006

I've also read tons where there isn't a ton of difference in rigidity between common sorts of steel, as in the discussion of making insert tool holders.

The modulus of elasticity is nearly identical for all steels.

Tool holders are heat treated to improve their wear and strength qualities, not their stiffness.

Cyclotronguy · Sep 12, 2006

Made mine of 8620 and sent them out for ht

Very happy with the results

Gary E · Sep 12, 2006

Are you a hoby guy that tinkers with a lathe? make it from anything...

or are you a shop that MUST MAKE THAT CUT ??
buy them, or make them from 4140 or 4340 and harden and grind them...

actually, if your a shop that is buzy... buy them, it's cheaper.

Gary E · Sep 12, 2006

lazlo

The modulus of elasticity is nearly identical for all steels.

Tool holders are heat treated to improve their wear and strength qualities, not their stiffness.

ohh how wrong you are...

spend some time looking at the properties of heat treated alloys...

cruzinonline · Sep 12, 2006

I have to chime in with Gary E on this. For a quick test, put a piece of 1018 (1/2 x 1/2) in a vise and bend it with a big butt cresent wrench then try it with a 1/2 insert holder or a tool bit. The HSS will of course break before it "bends". We've made a lot of boring bars around here out of bar stock and if you accidently grab the 1018 you'll find out real quick how bad it works as a boring bar vs a piece of 4140. A good old fashioned turbine bolt makes a terrific boring bar.

lazlo · Sep 12, 2006

</font><blockquote>quote:</font><hr /> The modulus of elasticity is nearly identical for all steels.

ohh how wrong you are...

spend some time looking at the properties of heat treated alloys...</font>[/QUOTE]Material.................. Modulus of Elasticity
Cast Steel....................30 x 10^6 PSI
Steel, SAE 950..............30 x 10^6 PSI
1025..........................30 x 10^6 PSI
1045..........................30 x 10^6 PSI
1095..........................30 x 10^6 PSI
1112..........................30 x 10^6 PSI
1212 .........................30 x 10^6 PSI
1330 .........................30 x 10^6 PSI
2517..........................30 x 10^6 PSI
3140..........................30 x 10^6 PSI
3310..........................30 x 10^6 PSI
4023..........................30 x 10^6 PSI
4130..........................30 x 10^6 PSI
4340..........................30 x 10^6 PSI
4640..........................30 x 10^6 PSI
4820..........................30 x 10^6 PSI
5150..........................30 x 10^6 PSI
52100.........................30 x 10^6 PSI
6150..........................30 x 10^6 PSI
8650..........................30 x 10^6 PSI
8740..........................30 x 10^6 PSI
9310..........................30 x 10^6 PSI
9840..........................30 x 10^6 PSI

lazlo · Sep 12, 2006

Ray,

I have to chime in with Gary E on this. For a quick test, put a piece of 1018 (1/2 x 1/2) in a vise and bend it with a big butt cresent wrench

That's Yield Strength, not Modulus of Elasticity (rigidity).

The Yield Strength for alloyed steels is a lot higher than mild steel, but the rigidity for all steels is nearly identical.

The only way to make a toolpost (or boring bar) more rigid is by geometry (increase the diameter) or to go with a material with higher Modulus of Elasticity.

Tungsten Carbide has a Modulus of Elasticity more than 3x steel: 67-97.5 X 10^6 PSI. This is why Tungsten Carbide boring bars are so desirable.

Aluminum is about 1/3 the rigidity of Steel. You don't want an aluminum boring bar

Doug W · Sep 12, 2006

That's Yeild Strength, not Modulus of Elasticity (rigidity).

The Yeild Strength for alloyed steels, but the rigidity for all steels is nearly identical.

The only way to make a toolpost (or boring bar) more rigid is by geometry (increase the diameter) or to go with a material with higher Modulus of Elasticity.

Correct you are lazlo!!

Gary E · Sep 12, 2006

yo Laslo...

Start a boring bar biz makin them from your steel selection if you have some spare $$$$ to toss in the terlet...

if that dont work out... try making Grade 8 bolts...

Or how about aircraft landing gear??

Peter Neill · Sep 12, 2006

Lazlo is right, the Modulus of Elasticity (Youngs Modulus)of steel is typically 190Gpa for all types.

John Stevenson has built a huge number of toolholders for the quick change toolpost he designed many years ago, and I recall him saying he has always used mild steel and had them tuftrided.

Peter

Gary E · Sep 12, 2006

Ok.. another non believer...

Your assignment if you chose to prove your right is to pull the axle out of your car and make another one from anything you want... how about rebar? it's steel to ya know...

dsergison · Sep 12, 2006

GaryE
ridgidity = modulous. of Elasticity

cruzinonline · Sep 12, 2006

Concerning Gary E's post, perchance I came across different than my intent.

Not sure about the Modulus vs Yield discusion as a metalurgist I am not. By no means mean to imply your wrong about the modulus part but I am positive that if I make a bar out of 1018 and a bar out of 4340, same diameter, length and what not, I know which one will chatter, bend, and in general do a poor job while the other will do great. Now the fact that the other one has been heat treated (not hard) but annealed and is around what? 35Rc it will stand up to a cut while the CR stuff won't work with a darn. With the change in properties the tensile goes up, as the shear, so why not the "strength" or "rigidity". Once again, my experience is working with the material not the education behind the material properties.

Concerning the original post, IF, I was making a toolholder I would make it out of the best material available for strength, wear properties, and tensile yield (which BTW affects the dovetail, which is my main concern)and thats why I would use the 4140 over the CR.

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