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Your Go-to Materials On A Pm-1236

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tino_ale

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#1
Hi guys,

So I know this doesn't sound like a machine thread but I think it actually makes sense to approach the material discussion based on a specific machine. What machines beautifully on a huge CNC with fast, constant surface speed, coolant and carbide tooling may not a a smaller manual operated with HSS tools equiped garage lathe.

So I have a PM-1236 equiped with a good BXA QCTP and carbide tools. I have steel inserts as well as aluminium specific inserts. No coolant yet. Obviously no CNC, no variable speed etc. 1800rpm is the max I can crank it up. Machining mostly around 1" to 2" parts.

Aluminium is easy : 6061 default, 7075 if something nicer is needed. I don't like to have too many stocks so I stick to those two only.

Now,
I am looking for an all around, defaut go-to steel alloy that :
- machines to a nice finish
- machines easily or reasonably easily on this class of machine (drilling ? parting ? threading ? tapping? ), no headache, chips fine... remember : I have no cooling
- is no too bad regarding rust
- mechanicaly good enough for general mechanical non-critical parts. Serious step up from 7075 aluminium expected.

I have easy access to 4140 pre-treated (medium hardness) and 1035.

4140 looks like the way to go but is it going to machine well on this setup ?
Any other recommendation ?
What is you go-to material on this class of lathe.

Any input appreciated.
Cheers
 

Bob Korves

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#2
If you want easy and friendly to machine, go with 12L14. It has lead in it, so does not weld well. 4140HT is good, strong and tough but expensive, and unforgiving if you work harden it. It depends on what you are making...

I use a fair amount of O-1 drill rod where I want stronger steel with decent machining and it is fairly close tolerance as purchased.
 

Dan_S

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#3
The big thing is getting the right inserts, and getting your sfpm as high as you can with out going over the insert recommendations. On my 8" machine I've been using ccmt finish inserts that let me feed slow (0.004"/rev), and take shallower cuts.

I've had no problem with any of the following, ad long as my doc, feed, and sfpm are reasonable.

  • 12L14
  • 1018
  • A36
  • 1144 stressproof
  • 4140
  • O1
  • 8620
  • 416 (stainless)

4140 will work fin on your machine.
 

wrmiller

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#4
What Bob and Dan said. For just 'making stuff' 12L14 is hard to beat. I do a fair amount of 4140, 1018, 12L14, and some stainless and titanium on my 1340 and most everything comes out fine. Unless I screw up of course. :)
 

Muskt

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#5
12L14 works wonderfully on my 12x36 - also on the 9x20 I used to have. BUT the original poster said he wanted to avoid rust. 12L14 rusts almost immediately. I have never favored 4140, but it is better than the generic CRS that is commonly available. I have a couple of pieces of 1144 that also work nicely. There is a metal yard near where I live, & he offers "surplus SS". No indication of what it is, but some machines well, & some not so well.

Just another opinion.
Jerry in Delaware
 

tino_ale

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#6
Thanks for your replies.

I have easy access to "C35E" steel, apparently it's called 1035 on your side of the pond, but can't find any feedback on this one.

Would you say 4140HT is significantly tougher to machine than, say, a milder steel like the 12L14 that you recommend or are they pretty much in the same leage in regards to how easy they machine ? For example, is it going to make a big difference in terms of tapping, parting, threading... ?

Easy access is convinient but maybe I'm shooting too high with the 4140 pre-treated ?
 

T Bredehoft

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#7
Pieces made form 4140 are tough, wear like leather, are great for fixtures, etc. 12L14 is a free machining steel, (yes it has .3% lead, that's point three) It will do well for pieces not subject to wear/friction. They are not for the same products.
4140 is considerably toughter to machine, but then almost any steel is tougher to machine than 12L14. Tapping and parting of 12L14 is at least as easy as 6061 aluminum. It's really "free machining."
I do not experience rust in my shop, very low humidity, so I can't discuss that.
 

ch2co

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#8
OK guys, now from the standpoint of a COMPLETE novice when it comes to machining steel. I work with aluminum, brass, plastics, and a little stainless steel.
I know what to expect from various grades of these materials at least the ones that I have worked with. I recently delved into the machining of steel for the first
time when I made a new base for the compound on my G1022. I got a couple of pieces of 3/4" x 4" x 4" "cold rolled steel" from a local supplier, and went to work
on the project. First milling the piece to square and properly dimensioned size on my mini mill, then used the 10-22 with a four jaw chuck to bore a stepped
center hole through the piece and finally back to the mill to mill down the two mounting edges to the correct thickness and open a slot on the front for viewing
the compound's angle scale. My only challenge in the whole operation was which cutting fluid to use. By trial and error using every oil that I had in the shop, I
finally settled on using canola oil from the kitchen which worked wonders. Thanks to whoever suggested it in one of these forums. Everything machined almost
as easily as aluminum. The finished part looks fabulous, absolutely fabulous, and what a difference it made in rigidity of the compound.
Now comes the question: Hot Rolled, Cold Rolled, I understand the difference between them and their manufacture but are the various alloys that you
are talking about available in both Hot and Cold rolled forms? I've only known a choice between hot and cold rolled but not their alloy specifics.
Would I order a piece of 4140 cold rolled or 12L14 hot rolled? Does any of what I'm trying to say make sense to anybody?
 

mikey

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#9
Now,
I am looking for an all around, defaut go-to steel alloy that :
- machines to a nice finish
- machines easily or reasonably easily on this class of machine (drilling ? parting ? threading ? tapping? ), no headache, chips fine... remember : I have no cooling
- is no too bad regarding rust
- mechanicaly good enough for general mechanical non-critical parts. Serious step up from 7075 aluminium expected.
My go-to for steel with your requirements is 1144 Stressproof. This is a semi-hardened steel with good toughness that machines nicely with sharp tools. It has a machinability rating of about 83-85% VS 12L14's rating of 170%, so it is about twice as hard to machine as 12L14 that machines like butter. It contains sulfur so it doesn't weld well but makes it nicer to cut. 1144 likes to rough at lower speeds and finishes to a nice satin finish at high speeds and light depths of cut. It is MUCH easier to work with than 4140. Note that it does work harden so your tools need to be sharp. I much prefer to use a good HSS tool rather than carbide; I can cut deeper, size better and finish much nicer than with any carbide insert I've tried. Carbide does not like to go slow and 1144 does not like to go fast so ...

I love 12L14 but when I need a threaded stud with some strength or something that will keep its dimensional size under stress, like a bearing housing, I use 1144. It is cold worked and then stress relieved so it tends to warp less after being worked; on a shaft that has to be straight, like a leadscrew, this is important to me. It is one of my favorites to turn. It does rust if left untreated but is less rust-prone than 12L14.
 
Last edited:

MarkM

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#10
I would agree with mikey. Match the material to the function of the part as the go to material. Could be Strength, weight, corrosion etc,
 

Tony Wells

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#11
Bottom line to me is function of the part. You can work with virtually any material with your machine. The tools and techniques are what change. Yes, some are clearly going to be more difficult, but it really is right to sacrifice ease of manufacture to practical application.
 

springer

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#12
Another vote for 1144. I really like using it because it machines well and had good strength
 

Bob Korves

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#13
1144 is nice steel to machine, does not warp much, and has good strength, but there are a few practical issues with it. As near as I know, it is only available in round bars, mostly meant for shafting. It may not be available locally, many steel suppliers do not stock it. It is comparatively expensive. It is not considered to be weldable.
 
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