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[737captain]

I’m new, both here on the site and to machining in general. I explained in an introductory post I did time in a machine shop 50 years ago but mostly as a gopher and running machines set up by the tradesmen.

A couple of years ago I bought a South Bend 9” C model lathe with the hopes of being able to manufacture small parts for my vintage motorcycles. I was working full time at the time so didn’t have a lot of opportunity to get it right. Now I’m fully retired and trying to get the best out of my lathe.

im struggling to get good surface finish and good dimensional stability and repeatability. Ive tried various materials, various tool types, I’ve spent hours making sure tool height are dead nuts on center, I’ve cut dry and with cutting fluid, I’ve taken large depth cuts and shallow too. Still not getting there. I believe the feed rate it too high so today I’m going to change gearing to get it as slow as possible.

I don’t want to be the bad workman blames his tools guy but I’ve thought of maybe buying a new PM lathe and start from a known quantity. I’ve read lots on these forums the debates on new import vs used equipment which always comes with the caution to “make sure you have someone who knows what they’re doing evaluate any used Machines” So it occurred to me my SB may be worn out or seriously out of adjustment. I can run a level over the ways but don’t know what is an acceptable tolerance. Similarly I don’t know anything about spindle wear or carriage wear and backlash. Where do I start? Am I barking up the wrong tree?
Thanks in advance.

 

[markba633csi]

Probably it all comes down to your cutting tool(s)- can you post some pics of your results?
What cutting tools are you using? Mild steel often "tears" when cut
Carbide tools often cause issues for beginners
You can't ignore the overall condition of the machine- if gibs need adjustments or if the spindle bearings are shot
you will have a more difficult time
I would chuck up a long piece of sturdy pipe and tug on it to get a rough idea how worn the headstock is
Set up an indicator to measure the chuck movement when you do this for a more precise test

 

[RJSakowski]

Welcome to the forum! I have only bought one used machine; my first lathe. My reasoning was buying a used machine is an unknown quantity and while I could be getting a much higher quality machine, I could also be buying a basket case. A worn out machine could likely be fixed but it could result in many hours of restoration work and possibly beyond my capabilities. My experience is that on closer insp4ction, a piece of used equipment isn;t as good as it first appeared. An exhaustive inspection of a machine is difficult to accomplish at the seller's location as it would involve at least a partial teardown. In most cases, you are buying as-is and even if a seller is acceptable to a return, you have the cost of transportation to and from.

OTOH, buying new Chinese has its drawbacks. They are often referred to as kits because of all the tweaks that are required to make them better than just so-so. My latest acquisition was a Grizzly G0602 lathe. I decided on it because I had previously purchased a G4000, a smaller cousin, for work and was impressed by its overall quality and that of several other Grizzly machines that I had purchased.. I have made upgrades, namely adding a stouter compound clamp, a QCEP, a three axis DRO, an electronic feed screw, and a variable speed motor. I also added a carriage stop and a work stop for the spindle. As it stands now, the lathe meets my expectations.

Were I doing it over, I would probably go the PM route instead. The reason being their reputed customer service and that although the base machines are very similar to those offered by Grizzly, they often have additional features. Grizzly does have an extensive inventory of replacement parts in stock in the US.

 

[737captain]

Welcome to the forum! I have only bought one used machine; my first lathe. My reasoning was buying a used machine is an unknown quantity and while I could be getting a much higher quality machine, I could also be buying a basket case. A worn out machine could likely be fixed but it could result in many hours of restoration work and possibly beyond my capabilities. My experience is that on closer insp4ction, a piece of used equipment isn;t as good as it first appeared. An exhaustive inspection of a machine is difficult to accomplish at the seller's location as it would involve at least a partial teardown. In most cases, you are buying as-is and even if a seller is acceptable to a return, you have the cost of transportation to and from.

OTOH, buying new Chinese has its drawbacks. They are often referred to as kits because of all the tweaks that are required to make them better than just so-so. My latest acquisition was a Grizzly G0602 lathe. I decided on it because I had previously purchased a G4000, a smaller cousin, for work and was impressed by its overall quality and that of several other Grizzly machines that I had purchased.. I have made upgrades, namely adding a stouter compound clamp, a QCEP, a three axis DRO, an electronic feed screw, and a variable speed motor. I also added a carriage stop and a work stop for the spindle. As it stands now, the lathe meets my expectations.

Were I doing it over, I would probably go the PM route instead. The reason being their reputed customer service and that although the base machines are very similar to those offered by Grizzly, they often have additional features. Grizzly does have an extensive inventory of replacement parts in stock in the US.

Excellent input, exactly the sort of thing I was expecting. Thank you

 

[737captain]

Probably it all comes down to your cutting tool(s)- can you post some pics of your results?
What cutting tools are you using? Mild steel often "tears" when cut
Carbide tools often cause issues for beginners
You can't ignore the overall condition of the machine- if gibs need adjustments or if the spindle bearings are shot
you will have a more difficult time
I would chuck up a long piece of sturdy pipe and tug on it to get a rough idea how worn the headstock is
Set up an indicator to measure the chuck movement when you do this for a more precise test

Thank you Mark,
I have mostly been using carbide tipped tools a) because they are available and b) I have yet to learn how to grind tool steel.
I have some brass and aluminum stock I’ll turn and take pictures. I can do the pipe test too.

 

[matthewsx]

Hi and welcome.

My bet is your machine will be just fine as soon as you put the time into learning how to grind HSS.

Getting carbide inserts right isn’t easy for a small machine and can cost quite a bit of money.

HSS allows you to tailor the tool to your work and machine. It’s nowhere as confusing as it can seem when you first start out, arguably easier than selecting the correct insert.

All you need are some blanks and a bench grinder. Also, you can buy some used HSS blanks off eBay which might have profiles that will work for you.

Of course, we need pictures….

John

 

[john.oliver35]

Hi 737! Your frustration is common. I know that first mild steel I put in a lathe and turned looked ridged and rough. Looking back on it, I don't recall what was wrong, but it was likely a dozen things in combination.

I agree HSS is something you need to be able to use, especially with a SB9 (I use a Boxford 10", which is based on SB9 basic design). The lack of speed and rigidity in these little lathes means you have to tinker with carbide just like you would with HSS (at least in my limited experience). But, if you can get a chunk of nicely machining metal, like 12L14, that is large enough diameter to get your surface speed up, say 1.5", you should be able to use carbide and get a nice finish. That could get you a starting point, and some confidence, to start making changes.

 

[Larry$]

I 3rd HSS. It doesn't require being able to grind to some ideal shape to work well. Inserts are great for production work on a production quality machine. There are inserts available for every conceivable use. If you really feel the need for inserted tooling, on a low power loose machine, you will do better using inserts designed for aluminum with their sharp edges. They will cut steel perfectly fine just not last as long. Get some metal and start turning. Mystery metal/scrap is fine for practice but you will get a better feel for what can be accomplished with known grades. Lots available online, maybe locally also. Free machining steels seem like a good starting point. There is a considerable difference in price between grades. A 3' bar will give you hours of practice.

 

[737captain]

Wow, you guys are great. Thank you all so much. I guess I need to learn grinding HSS!

I did do some turning this morning to try to narrow down the symptoms. I started turning brass between centers over a 6 1/2 length. Initially I started feeding manually and got a pretty decent finish, I then used the power feed over the length of the piece, followed by a finish pass. Just look at the taper over 6 1/2”!
i then tried some aluminum over just 1 1/2 without end support and that turned out OK. Following all that I cleaned the machine and put a machinist level on the bed. Over the length it wasn’t too bad but front to back it’s off the bubble at the end away from the chuck and 3/4 bubble off by the chuck. I guess that the first thing I need to fix.

 

[john.oliver35]

Your taper may be more to do with the tailstock side-to-side adjustment rather than the bed being level. Also brass can be great to turn, but it can also be very 'grabby'. Usually you use tools with low or zero top rake for brass.

Not that you can't use brass to learn on, but it is pretty pricey these days and the tool grinds you learn there won't work well on mild steel.

I wouldn't worry about the bed being level until you get some experience getting the surface finish you are looking for. For that, you can chuck up a piece in the chuck alone (no tailstock) as long as it doesn't stick out more than around 3X it's diameter. Then turn away playing with tooling, speeds, feeds. You can worry about long turning and twist in the bed after that. It's all an experiment and learning experience at this point.

I just got a 3d printer about a month ago and every print is a 'why did that turn out like that' experience - when there are no work deadlines it all about journey!