Problems with first steel cut on 1130v lathe

[rronald]

Looking at pictures is always a little challenging to be sure, but it looks to me like the tip of your cutting tool has been destroyed. That would be consistent with only cutting some small distance before "rubbing".
When cutting in rusty metal or HRS scale, you want to slow your RPM down quite a bit to get any tool life on that initial cut. Possibly as low as 60-80 FPM. 20 thou depth of cut or more, depending on what your lathe motor will handle. Really you are trying to get down to clean metal all the way around in one cut, but how deep of a cut that takes depends on how well centered and round your stock is. Or just sand/grind the shaft clean first as others have mentioned. Just remember to protect the ways on your lathe so they don't get saturated in abrasive residue.

Random (mystery) metal may also have been hardened (like the printer shaft). That can play havoc with HSS. Learn to use a file as a basic hardness test, a file will easily cut in soft metal, and will skate across hardened metal without biting in. Some feel is involved so don't be afraid to try it on several pieces of steel to get an idea of how to judge.

You're the first person to suggest slowing down below normal machining speed to deal with the "crust". I like that idea.

I have already gone out and emery-paper sanded off the rust this afternoon, so almost all of the bad stuff is now gone and it actually looks like steel. I did the sanding of the first section before I realized I needed to protect the ways...but I've cleaned them and will clean them again. I put a paper towel in place for the rest of the rust removal project.

My first step with this bar was to cut it with a hacksaw. Based on that cut, I'm relatively sure it's not hardened. If it is hardened, it's not very much.

I agree that the bit is not likely to be at its best anymore. I ordered some inserts, but they'll take a couple of weeks. I guess I'll give grinding a try to see if I can clean up the cutting edge. And I might switch over and cut some 12L14 first...it should be here late tomorrow.

Thanks to all!

 

[rabler]

You're the first person to suggest slowing down below normal machining speed to deal with the "crust". I like that idea.

I suspect many just take that as common knowledge, something that goes without saying. Speeds are a starting point, machine, material, cutter, etc all can have an impact, a big part of manual machining is learning to get the feel for when you need to try something different. I'm still learning myself so it's easy to see how that gets left unsaid.

Any pre-ground bit is likely in need of some finish work on the edges. A diamond sharpening stone works well for a little manual touch up. Working with HSS is a very useful skill, so I would encourage you to not set them aside completely based on this and move on to using only inserts.

 

[jwmay]

How far does one need to turn "back" before moving forward to get rid of backlash. I'm familiar with the concept and I was going back perhaps 1/2 a turn on the slide before coming forward to end at the number I wanted. Is 1/3 to 1/2 turn far enough?

The answer to that is “it depends”.
Generally you would be able to feel the difference. It’s not a matter of how much the crank is turned. It’s a matter of whether or not the forces of cutting are being resisted by the nut bearing on the screw in the compound. I’ll try to look up a good description. I can’t think of a good way to explain it thoroughly without a ton of words.

 

[Larry$]

Your cutting tool photos show a very bad condition tip. Grind the tool to a point (a slight radius will give a better finish but not necessary for now) with some clearance, 7º or more will work. It isn't critical at this point. Rust is a HSS killer, it doesn't do carbide much good either. HSS will cut fine at almost any surface speed until you get so fast it over heats. Too slow is unlikely to be a problem. (Threading is run quite slowly. ) I'm not a fan of Chinese carbide inserts. I've had variable luck with them.

In one of the first posts you mentioned shimming the tailstock? Am I correct in thinking that means you raised it some? If so get rid of the shims, they serve no purpose unless the lathe is way off. Front to back is important and you will be able to easily dial that in when you do the two collar tests. There are adjusting screws on the tailstock.

Someone suggested using a steel rule for a quick way to center the cutting tool on the stock, do that after you have sharpened the tool. It is quick and easy. Your first facing cut will show you how well you did on centering.

Projectnut had some good points to do.

As a newbie, don't assume the machine has a problem until you've learned to use it. Using a level is for checking twist, not how level the lathe is with the world. The more sensitive the level the easier it is to see any discrepancies. To tell the truth I wouldn't worry about the twist until you've got some experience and understand that a Chinese? casting may not have been totally stress relieved. It may continue moving for a while.

 

[ttabbal]

Hmmm, links don’t work. “Access denied”

They should work now. I forgot I had to specify the sharing settings.

The other points mentioned are good places to start working on things. Fix up the tool as the tip does look a bit burned. They also look just rough ground, though it can be hard to tell in pics. If that is that case, honing them with diamond cards is cheap and works well for me. It's not required, but does help with finish and the ability to shave small amounts off.

While I do use and recommend HSS for most things on smaller machines like ours, I use carbide inserts for removing that mill scale. It's a great use for questionable import inserts.

 

[rronald]

Well.....good news!

Yesterday I sanded off the rust. Ordered some tools. Noted that my "good" L1214 steel would be here soon.

But this morning, I realized that the inserts and holders won't be here for a couple of weeks, my nice steel hasn't made it anywhere close to DFW (the promised USPS delivery date is not going to happen), and I don't want to wait. The only thing that's stopping me is that the tool bit is likely dull. And I should be able to sharpen it. There are only two reliefs (both straight lines), to sharpen...and maybe a tiny radius. between them. With the rust removed (both where clamping and where cutting), and a (poorly) sharpened bit, running around 300 RPM, I was cutting. No drama. At times, with a 10 thousandths cut, I made a chip that was roughly 8 to 10 feet long. Surface finish isn't great, but it's not terrible.

I did the first two-collar cut. Indicating down the length of my old 3d printer 1/2" shaft and adjusting that straight seems to have helped get the alignment very close before any cutting. Removed a single shim under the tailstock and retested....and the head end was .0001 bigger than the tail over 4". Seems pretty good and about as equal as I can measure at this point.

Now I need to make some jacks to simplify my shimming. And need to make a drive pin and setup for turning between centers for tailstock centering. Maybe buy something bigger than my 5" grinder (with 30-40 year old crappy wheels for sharpening bits). Lot's to do.

Thanks to everyone for all for the help! And kudos to this site for sticking with a "forum" format rather than something like Discord. Forums gather collective wisdom and store it so that current and future users can learn. Discord is great for the moment, if the right people are online. But a few days later, that information gets hard to find. Even if you know it's there and especially if you don't. I've been using the PrintNC Discord for my CNC mill and it's a great community. But I think that's despite the format of the site. Hobby-machinist has a much better format...or maybe I'm just an old guy now.

 

[verbotenwhisky]

Carriage was unlocked during first facing cut, but locked after that. Still seemed to move. I even locked the cross slide during the OD cuts (after the first or 2nd attempt). Didn't seem to help much if at all.

Tool was adjusted on center line by alignment with point of center.

RPM for facing was started at ~250, but quickly adjusted to 500. RPM for OD cut was done at 400-430 (since oil seems to fling starting at about 450).

These are the first cutsI've done in about 40 years on a lathe. So anything above 20 thousandths is a bit scary. Is it reasonable/safe to do more to remove the oxide layer?

Some of your issues may well be things you could do better; but from the frustration I am reading in your post a bit of the issues may simply be using a machine you are not yet familiar/comfortable with.

I use HSS tooling for certain things and I like carbide insert tooling for certain operations. When I first started getting use to my machine I used exclusively carbide insert tooling because, for me, it removed an unknown factor, the did I properly shape, cut and/or use the HSS correctly.

 

[rabler]

With the rust removed (both where clamping and where cutting), and a (poorly) sharpened bit, running around 300 RPM, I was cutting. No drama. At times, with a 10 thousandths cut, I made a chip that was roughly 8 to 10 feet long. Surface finish isn't great, but it's not terrible.

Yep, cutting slow has the tendency to give a poor finish, and to make long ribbons rather than nice chips. As you increase the RPM you get better (shorter) chips and better finish, but more heat and thus wear on the cutting tool. Of course you've now seen what happens when that wear dulls your cutter. Some material, like 1018 or hot rolled steel (A36) is difficult to get to make chips rather than long ribbons, at any speed. Those strings can be dangerous as they are sharp and can get wrapped up in the chuck/stock and spin. Don't ever use your hands to clear them when the lathe is running, use a long nose pliers or a chip hook (rod with a hook at the end).

I'm just talking speed here. Other things like cutter material, depth of cut, cutting tool geometry (chip breaker), etc, make a difference too. The trick (art) is to learn how all of these different things play together so you can adjust the right one. Lots of experimenting and you will start to develop a feel for it.

 

[verbotenwhisky]

Yep, cutting slow has the tendency to give a poor finish, and to make long ribbons rather than nice chips. As you increase the RPM you get better (shorter) chips and better finish, but more heat and thus wear on the cutting tool. Of course you've now seen what happens when that wear dulls your cutter. Some material, like 1018 or hot rolled steel (A36) is difficult to get to make chips rather than long ribbons, at any speed. Those strings can be dangerous as they are sharp and can get wrapped up in the chuck/stock and spin. Don't ever use your hands to clear them when the lathe is running, use a long nose pliers or a chip hook (rod with a hook at the end).

I'm just talking speed here. Other things like cutter material, depth of cut, cutting tool geometry (chip breaker), etc, make a difference too. The trick (art) is to learn how all of these different things play together so you can adjust the right one. Lots of experimenting and you will start to develop a feel for it.

I have a long set of locking surgical forceps I sue to clear the strings, they work very well.

 

[Larry$]

I made a chip that was roughly 8 to 10 feet long. Surface finish isn't great, but it's not terrible.

Just stop your feeding for a second to break the chip. Those rat's nests can be dangerous!
Turning between centers is a better way of dong test bar cuts. A chuck may produce some forces that distort the test part. Put a dead center in the head stock. You can leave the chuck on , just back the jaws away from the work. The chuck jaws can be used to drive the lathe dog. It takes less material length if you use a face plate to drive the dog instead of the chuck.
Ideally you shout turn the taper on the dead center while it is mounted in the spindle. That ensures that it is running concentric. I still don't under stand shimming the tailstock?? A few .001" up down has very little affect on the diameter turned. Not measurable with the means you likely have.

If you are feeling the need to check everything, make sure the head stock is aligned with the travel of the carriage. You should find the recommended method in the paperwork that came with the lathe. A headstock misalignment will cause a taper to be turned on a bar just held by the chuck. It will also affect the test cuts when the work is held by the chuck and the tailstock. That's why you should do test cuts for tailstock alignment between centers. You will need a bar about 2 1/2" in diameter x 12" long, sticking out 10". Lock the compound and cross-slide to make the cut. If both ends of the cut don't measure the same your headstock needs aligning.