Lathe Noob With Some Questions On First Cuts

[Pinresto]

Hello All,
I have some questions to try and figure out where I stand on this lathe. I'm new to lathes. This is my first and over the last few days I've gotten it set up and takes lots of cuts. I'm having some issues I'd like some advise on. I've taken the lathe (SB 9c) apart, cleaned, painted, rewicked, oiled and leveled as well as i possibly could. I read through "how to run a lathe" and many other publications with good info. Not to mention the endless hours of youtube.
I have a scrap piece of solid bar stock 2.25" long x 2.25" diameter in a three jaw chuck. The type of steel is not known. It's magnetic, soft enough for a file to cut it, has no signs of rust and no matter what I do I get a mate finish. I don't know if that will give any clues to the type of metal or not. Anyways. I'm having trouble with depth of cut, feed rate and belt slipping. I'm using an adjustable link type belt from harbor freight. The tool bit is a HSS bit I ground. After a few try's it came out pretty good. I've also tried a carbide tipped bit and a cheap insert tool. All with the same results. I have the gears set up to give me a .0031 feed rate and the belt is on the far right pulleys, 235rpm. All is well if I keep my depth of cut below .008" but anything more then that and the lathe bogs down or the belt jumps off.
I have nothing to compare this performance to so I'm asking, is this typical? I feel like I should be able to take more of a cut. I'm going to try a different material but this piece of scrap is not dulling my tool and seems to be soft enough to machine. It's been in a lathe before based on the marks I see on it. I know it's hard to say with so many variables but, with a slow feed rate and an easily machined steel how deep should I be able to cut on this SB9c?
I apologize this was so long but I wanted to give as much info as possible.
Thanks in advance.

 

[Wreck™Wreck]

I would turn that at 6-700 RPMs with coolant, 300 or so without, .050" DOC at .008-.010 IPR feedrate for roughing, the faster you spin it the better the finish will be with carbide. Finish at the same or faster RPMs , .004-.008 DOC depending on the nose radius of the tool and .004-.006 IPR feedrate.
If it's plain 1018 steel you will never get a shiny finish, as for the drive belt slipping and/or coming off of the wheels that is purely a mechanical problem. Scrap the link belt if at all possible.
Good Luck

 

[Pinresto]

I would turn that at 6-700 RPMs with coolant, 300 or so without, .050" DOC at .008-.010 IPR feedrate for roughing, the faster you spin it the better the finish will be with carbide. Finish at the same or faster RPMs , .004-.008 DOC depending on the nose radius of the tool and .004-.006 IPR feedrate.
If it's plain 1018 steel you will never get a shiny finish, as for the drive belt slipping and/or coming off of the wheels that is purely a mechanical problem. Scrap the link belt if at all possible.
Good Luck

When you talk about .050" DOC what machine are you using? Are you using a 9" SB or similar? I just want to make sure we're comparing apples to apples. If I should be able to take a .050" DOC with this lathe I have a problem. I think I fixed my belt slipping problem. I readjusted my pulleys, shimmed one side a bit and turned my belt around. I didn't realize this belt needed to turn in a certain direction. It still won't take anything more than about .008" DOC. I think I may need a new motor. It runs quiet and smooth but doesn't seem to have the power needed. It's 1/2hp and 1725rpm but it's 50+ years old.

 

[John Hasler]

Scrap the link belt if at all possible.

Why?

 

[Doubleeboy]

I will repeat what was told to me when I started out...... "No mystery metal, cut known good quality , easy to turn stock" 1 inch diameter 12L14 would be fine. Nice sharp HSS cutter with positive rake. I picked up a beater HF 7 x 10 lathe for a bargain used. I can take 30 thousands off the diameter with a sharp HSS bit with positive rake with out it even breathing hard. You should be able to do much better than that, I would start with known parameters, good sharp tool, get help there if needed and good stock, then you can tackle your belt situation if needed.

cheers
michael

 

[Pinresto]

I will repeat what was told to me when I started out...... "No mystery metal, cut known good quality , easy to turn stock" 1 inch diameter 12L14 would be fine. Nice sharp HSS cutter with positive rake. I picked up a beater HF 7 x 10 lathe for a bargain used. I can take 30 thousands off the diameter with a sharp HSS bit with positive rake with out it even breathing hard. You should be able to do much better than that, I would start with known parameters, good sharp tool, get help there if needed and good stock, then you can tackle your belt situation if needed.

cheers
michael

That sounds like excelent advise. I'm about to place an order for an assortment of metals to practice with. I need to decide on a couple starter projects first. I think I'm going to make a set of machinist jacks and some other small useful tools. For now I have what I have. Im new here and trying to find out where all the tool and metal stores are. It's not like back home where I could just use yelp or Google. Here you have to get out, look and ask around. I do have a piece of 1" hot rolled bar stock. I chucked it up and had much better results. I worked my way up to a .050" DOC with no issues at all. I guess it was the type of metal I had after all. Wish I know what kind it was. I have a few sizeable pieces of it.
Thanks

 

[mikey]

Might be the material but it could also be your tool. Would you post a pic of your turning tool?

0.008" DOC on a 9" lathe is ridiculous. I can take 0.025" DOC in 1144 Stressproof steel on my Sherline lathe so something is definitely off.

 

[Wreck™Wreck]

Why?

Less surface area in the V-groove = less traction, can't tighten them as much as a solid belt.
I am also assuming that a SB9 is a 9" swing lathe, 1/2 HP seems a bit anemic for a lathe that size, once owned a Clausing 13" lathe that had a 5HP motor.

.050 DOC at 2 1/2" may be a bit optimistic I suppose (-:

 

[brino]

I try to cut (unhardened) steel with HSS tools at about 80 surface feet per minute.
For 2.25" diameter that comes out to around 136 rpm.
Another advantage of lower speed is more torque (with the same motor).

I would expect to take 20 thou. depth of cut easily at 8 thou per rev. feed rate on my SouthBend 9".
I'd drop to a few thou depth and 2-3 IPR feed for finish cut.
(all with a sharp tool of course)

-brino

 

[Pinresto]

Thanks for all the info everyone. Here's pics of my tool bit and metal I had trouble turning.