Oh boy, you guys are gonna hate me.

[RafaelMarujo]

As long as you advance toward the spindle centerline along a straight path, it doesn't matter. The tool path is determined by the cross slide ways path not the bed nor whether or not the lathe is level.

However, I see the wear on the prism surface. It looks like the cross slide would be tilted toward the headstock as well. If I was going to rework the cross slide saddle, I would do a total resurfacing of the prism as well. But as flyinfool suggested, you need to check the bed prism for wear as well. More than likely, you will find excessive wear there which is of more concern,

OK I understand more or less, I'll have to study that a bit more to fully understand, because in my head if the crosslide isn't leveled to the bed ways , the tool cannot be at centerline at all times...
I'd the saddle is 5mm higher towards the back of the lathe, it cannot ever have a straight line between the radius of the workpiece and the centerline of the spindle, or am I missing something?
Now you're making me think and I like that, thank you

 

[RafaelMarujo]

5mm. Maybe something else going on. Are you 100% sure of your observation and conclusion? Sometime, given an observation, different conclusions can be made

Man I am definitely not 100% sure I've measured everything last week, a few days ago, and today... I've been losing my Mind over it, I tried measuring different ways and I'm still not sure, the lathe has such use and abuse I cannot get a good datum for referencing, the best I got are in those pictures...

 

[Flyinfool]

Use the lathe as it's own datum.
Yea its a pain but put it back together and mount a long bar in the tool holder.
Get that adjusted to be on center like if it was a cutting tool.
Now using the flat way as your datum. Measure for changes in height at the end of the bar as you move the cross side back and forth, This will tell you how much the tool tip is moving up and down over the range of motion.

 

[Richard King 2]

Hello, I just saw this. I think I can help you more then you ever dreamed of. I have a student who has been to 3 of my classes who lives in Portugal. He can scrape and he has some straight-edges. He is an excellent scraper and smart as a whip. I will look up his email and private message you. He took a class I had in Springfield VT at the Gear Works and the owner was so impressed he offerend him a job, but it was just after 9/11 and they wouldn't let him back in to work. He has also driven to Germany 2 different times and years and took class once in Germany and once in Austria. He works at a candy factory and is a maintenance manager. I think he lives in Bath. I am positive he will help you as I ask my students to help no questions asked.

 

[RafaelMarujo]

Use the lathe as it's own datum.
Yea its a pain but put it back together and mount a long bar in the tool holder.
Get that adjusted to be on center like if it was a cutting tool.
Now using the flat way as your datum. Measure for changes in height at the end of the bar as you move the cross side back and forth, This will tell you how much the tool is moving up and down over the range of motion.

That's a really smart idea I'll have to do that, but won't it give me the same distance as measuring the crosslide ways inclination?
Thank you fkyinfool that's a great idea tho

Hello, I just saw this. I think I can help you more then you ever dreamed of. I have a student who has been to 3 of my classes who lives in Portugal. He can scrape and he has some straight-edges. He is an excellent scraper and smart as a whip. I will look up his email and private message you. He took a class I had in Springfield VT at the Gear Works and the owner was so impressed he offerend him a job, but it was just after 9/11 and they wouldn't let him back in to work. He has also driven to Germany 2 different times and years and took class once in Germany and once in Austria. He works at a candy factory and is a maintenance manager. I think he lives in Bath. I am positive he will help you as I ask my students to help no questions asked.

Gee thank you so much, that's what I call calling the big guns!!
It's a cheapo lathe and I'll have to buy a better one eventually, I just bought this one bc it was cheap and I had the space, and I'm currently having machining lessons, and it makes round parts that's what matters and the end of the day... I'm not doing precision work, although I want to eventually, I'd just like to tighten up this lathe a bit more without spending money I could save to buy a good one

 

[Richard King 2]

I emailed him (Adam in Portugal) with a link to this forum and I sent Rafael his email address. I will be here to make some suggestions too. Rich

 

[Richard King 2]

My wife wants me to go shopping now. I will answer later. I do have a couple of question now for you. Will you be machining or turning long parts between center? Or will you be turning out of the chuck most of the time? What brand is the lathe? What model is it? Where is it made? I would like to look at the machine on the internet. Many times there are parts manuals online. Or do you have a link to a manual?

Does the headstock sit on a V and Flat way or on 2 flat ways? What do you expect for tolerance's do you expect? Do you know if the spindle bearings are ball or roller bearings or are they a bronze bushing? What is the highest spindle speed on the sign?

Got to go.
Rich

 

[RafaelMarujo]

My wife wants me to go shopping now. I will answer later. I do have a couple of question now for you. Will you be machining or turning long parts between center? Or will you be turning out of the chuck most of the time? What brand is the lathe? What model is it? Where is it made? I would like to look at the machine on the internet. Many times there are parts manuals online. Or do you have a link to a manual?

Does the headstock sit on a V and Flat way or on 2 flat ways? What do you expect for tolerance's do you expect? Do you know if the spindle bearings are ball or roller bearings or are they a bronze bushing? What is the highest spindle speed on the sign?

Got to go.
Rich

It's OK Richard I'm really not in a rush, I wanna plan things out well first.
I'll try and break this down:
I'm pretty sure most of the time I'll be turning out of the chuck, I rarely machine large parts;
The lathe is a Spanish bilcia, I don't really know the model bc I barely find any Info online;
The headstock sits in two flatways as you'll see on the pics attached;
I'm a realist, it's a 500€ lathe and I'm not expecting crazy tolerances to be honest, I'm just expecting a little more accuracy because the dials are almost unusable (bc how inaccurate the cut is) and a Little better surface finish, because with lighter cuts it's terrible... ;
The headstock has ball bearings and they have no play and are in good condition;
I'm not 100% sure but I think the highest speed is 1200rpms, I'm not sure bc the lathe came with no plaques... One of the caveats of being a 500€ lathe... You get what you pay for... I Will have to buy a better lathe if I'm too pursuit a career of machining, that's to me 1000% clear, but for the money this lathe would be sold, I would rather keep it for small jobs and things that don't require atomic precison ;

My wife wants me to go shopping now. I will answer later. I do have a couple of question now for you. Will you be machining or turning long parts between center? Or will you be turning out of the chuck most of the time? What brand is the lathe? What model is it? Where is it made? I would like to look at the machine on the internet. Many times there are parts manuals online. Or do you have a link to a manual?

Does the headstock sit on a V and Flat way or on 2 flat ways? What do you expect for tolerance's do you expect? Do you know if the spindle bearings are ball or roller bearings or are they a bronze bushing? What is the highest spindle speed on the sign?

Got to go.
Rich

 

[jwmelvin]

I think that the “height” of the tool may be misleading. One could certainly imagine a lathe with a non-horizontal cross slide. Let’s say it moves upward along a 10° incline as it approaches the spindle axis. So the tool height would change relative to the (horizontal) carriage ways, but as long as the tool starts in the right place, it will move along a diameter of the workpiece. To set the tool height, one would be measuring from the inclined cross ways, not the horizontal carriage ways.

Such a configuration is perhaps more complicated in some aspects for setup, but should be no different in operation.

It does seem like something is off, as wear alone cannot account for the discrepancy you have noted.

 

[Flyinfool]

I think that the “height” of the tool may be misleading. One could certainly imagine a lathe with a non-horizontal cross slide. Let’s say it moves upward along a 10° incline as it approaches the spindle axis. So the tool height would change relative to the (horizontal) carriage ways, but as long as the tool starts in the right place, it will move along a diameter of the workpiece. To set the tool height, one would be measuring from the inclined cross ways, not the horizontal carriage ways.

Such a configuration is perhaps more complicated in some aspects for setup, but should be no different in operation.

It does seem like something is off, as wear alone cannot account for the discrepancy you have noted.

I was thinking about that too.
In engineering one of the ways I test a theory is to take it to extremes. If it holds true at the extremes them it likely is true at the small scale that is hard to see.
So in this case if the cross slide were at a 45° angle the height of the tool tip above the bed ways would obviously change as the cross slide is moved. Even though the 45° inclined cross slide would function just fine. What is important is that the tool tip follow a straight line that goes thru the center of the spindle. The angle of that line is irrelevant, just like the lathe being level is irrelevant, In theory it would work just as well bolted to the wall. What is important is the the mounting of the lathe does not impart any twist in the bed.

So after more thought, What is important is that the cross slide moves in a straight line that is 90° to the Center Line of the spindle. As long as the cross slide is moving in a straight line it does not matter what angle it is at. Once you adjust the tool height to spindle center line the tool will always hit the diameter of the part it its tangent point, which is what you want.

As far as the dial markings being way off, are you sure the lathe is calibrated in mm and not in inches? Are you taking up all the backlash before you measurement? Some lathes will move the tool tip 1mm per mark which means that it will remove 2mm from the dia. Some lathes are the opposite where the graduations on the dial are for how much is being removed from the diameter of the part. There is usually something real near the dial to tell you what the calibration is, If not then you need to measure it to verify what you have.