Getting Started With A Lathe

[John Hasler]

Harden steel actually cuts really pretty & is probably easier to get to a spot on target. But... It can also be a pain until you learn what speed to run it at. I've burnt a few pieces of carbide up in unknown metal.

Rust is much harder then the metal so try to get below it when you take the first cut when you can. I usually try to take that first cut with a junk cutter to remove rust then switch to something sharp to finish.

Take the rust off with a wire brush and/or sand-blasting and/or chemicals.

The most frustrating stuff to machine in my experience is the unknowmium that my ag scrap is made of. It *tears*.

 

[kingmt01]

Wire will usually knocks the flakes off but still leaves behind that hard oxide layer I'm talking about. If you're scratching it instead of cutting below it then it's hard on the cutting edge.

 

[John Hasler]

Wire will usually knocks the flakes off but still leaves behind that hard oxide layer I'm talking about. If you're scratching it instead of cutting below it then it's hard on the cutting edge.

HCl will make short work of that oxide. Several other chemical treatments will deal with it more slowly.

 

[Christian Poulsen]

I guess when I talk about cutting some of the hard stuff like prehard tool steels, I should add I have some lathe HSS cutters with severe relief angles I use for plastics.
But I have a diamond face wheel (I like"resin" bond rather than the metal bonds) on a rigged up pedestal grinder I bought to sharpen carbide including my boring bars, some carbide endmills, and mostly a drawer full of 1/4", 3/8, and 1/2 carbide toolbits I have collected over the years...(I don't use insert stuff on conventional(manual) lathes) I have quite a few and various grade Kenametals up to the K11's but my favorites are the old Carbaloy 883's that I use for about everything except the prehards that I use the best (IMO) for steels that are around rc18 up to rc32!): The old Carbaloy 999's

 

[Tozguy]

I will need to look closer at these shafts if nothing else a way to collect some material for future projects. I may be wrong but I had thought some of these types of shafts/pistons had a chrome plating.

All of these shafts are probably not created equal. The 3/4'' plus shaft from a McPherson strut I tried is very hard to cut even with carbide. The shaft was shiny but it was not chrome. My hunch is that it is induction hardened for about 1/8th and ground to very tight tolerances. Considering the job these shafts have to do I can't imagine that any other hydraulic shaft would be easier to cut on a lathe either.

The centre I made from the strut was too hard for the chuck jaws to hold fast so a groove had to be ground near the tip to take a circlip. The clip acts as a stop so the centre doesn't slip into the chuck. As you can see from the picture, the taper could not be cut full length because the last 1/8th on the outside of the shaft was just too hard.

 

[kingmt01]

HCl will make short work of that oxide. Several other chemical treatments will deal with it more slowly.

OK

It's rarely that I need to just skim the surface. If I do then I just do it. I didn't say it won't cut at all. However I still think it's better to take the first cut more aggressively if you have the material.

 

[John Hasler]

OK

It's rarely that I need to just skim the surface. If I do then I just do it. I didn't say it won't cut at all. However I still think it's better to take the first cut more aggressively if you have the material.

Oh, sure. If you're going to cut the stuff get under it. Sometimes, though, the stock I work with is so out of round or pitted that the depth of cut required to get under the crust is more than my machines can handle.

 

[kingmt01]

That's understandable. I also run into times I don't have enough stock to get under it. I can only make a few bearing surfaces. We just call those oil passages.

 

[ericc]

If you have any offcuts of PVC pipe in the garage, these will get you started, and they are really cheap. I made my first cut on a 109 using a junk piece of aluminum (small!) and a junk wood chisel levered against the tool rest. It worked fine just to see what was going on. These lathes will cut steel, but you will have to watch very carefully for issues. There is a lot of low quality stuff that will goof up when you are cutting steel, and the tools need to be sharp and ground correctly. There is not much margin for error.

 

[Christian Poulsen]

Yes, those prehard steels that I like; I "like" Maxel instead of Cold Rolled (seems to come in anywhere from around rc 10-18 (really 4130 to 4140), and Maxel 3 1/2 (around rc28) and Impax Supreme (rc30 to 32) (both really 4150) all have some pretty nasty scale on them....I guess all new stock prehard is that way but its the best stuff for "general purpose", support/compression applications...and pretty good for wear.
I don't feel the scale is much worse than crummy old hot rolled (LOL) (At least to a carbide cutter)...But it's best to properly get that dust off your ways and surfaces eh!?

IMO A2, D2, and S7 are the best all around Tool Steels (in that order with the % of "stuff" like chrome in them),...They have no scale, cut nice, then Heat Treat (for/when and the application usually is wanted/needed) They H.T. with a torch (0xy/acet.) ifn' one has no oven and you can hit your rc hardness up to 58-60 (even 62 with S7) with practice (the colors man, the colors! LOL) and air harden with, well, air from a compressor then you draw back a little bit (temper)...and they return to size (and shape ifn laid down or hung right) so one can just "shine up" with abrasive "paper" ifn one doesn't have Machine Tool Grinders or a bead/sand blaster...(Note: bead/sandblasting also relieves/helps the stresses after Heat Treat)...For small rounds, I like them better than drill blank too.

...all the above also come in plate for milling jobs etc (and plate can and usually is ordered flat ground)....
...the prehards don't like to return to size ifn' they get hot (they like to stay wherever they grow to)
...and all the above can work harden so ya' gotta watch that on the tiny and small stuff

I see/perceive you are starting out but even so, the above stuff from everybody is all good to know and combobulate in the whole thang"