inverted v templates

I'm getting a visual on the direction you are going here and what I'm proposing is to only get you close in seeing how much work you need to do. This is only a ballpark or basic start, and maybe you don't need to do as much as you think.

I get lots of folks walking through the door with products to bend and I need to determine the angle(s). If it's bent then it has a radius and if it's rollformed it usually has even more radius. An example might be a roof flashing for a penetration through a metal building roof panel. There are usually some constants here, like center-center of the ribs, height of the ribs etc and I have to take into account any stretch or distortion. My reference here are ribs that are truncated cones, or in your case, the Vee's. With that said; I begin with getting an approximate angle using the flat of the panel up the side of the rib. I take the centers of the ribs, the base dimension of the ribs, the flat (truncated) across the top and with a little math determine what the angles are, what the stretchout of the flat piece should be (hopefully).

Now to your project; After the preliminary task of getting close, I shear, notch, and spotweld a template that fits the panel shape before I shear and bend the real thing. I think you can see an end view of a one piece template that fits the bed as Bob explained, and if you need any help with coming up with a template just PM me. Many times I take strips of metal (16 ga.) and vicegrip them together as I work through the angles, by placing the pieces against the shape I'm measuring or attempting to determine an angle. If you get a good fit across the unworn section of the bed, then you will see the daylight on the worn sections.

As I stated, this is to give you an idea of what's on the road ahead, before you go to Bob's #9 post. Okay, and I see I missed Ken's attachment for the fixture, and in essence that's my idea but at a basic level to start.
 
I'm getting a visual on the direction you are going here and what I'm proposing is to only get you close in seeing how much work you need to do. This is only a ballpark or basic start, and maybe you don't need to do as much as you think.

I get lots of folks walking through the door with products to bend and I need to determine the angle(s). If it's bent then it has a radius and if it's rollformed it usually has even more radius. An example might be a roof flashing for a penetration through a metal building roof panel. There are usually some constants here, like center-center of the ribs, height of the ribs etc and I have to take into account any stretch or distortion. My reference here are ribs that are truncated cones, or in your case, the Vee's. With that said; I begin with getting an approximate angle using the flat of the panel up the side of the rib. I take the centers of the ribs, the base dimension of the ribs, the flat (truncated) across the top and with a little math determine what the angles are, what the stretchout of the flat piece should be (hopefully).

Now to your project; After the preliminary task of getting close, I shear, notch, and spotweld a template that fits the panel shape before I shear and bend the real thing. I think you can see an end view of a one piece template that fits the bed as Bob explained, and if you need any help with coming up with a template just PM me. Many times I take strips of metal (16 ga.) and vicegrip them together as I work through the angles, by placing the pieces against the shape I'm measuring or attempting to determine an angle. If you get a good fit across the unworn section of the bed, then you will see the daylight on the worn sections.

As I stated, this is to give you an idea of what's on the road ahead, before you go to Bob's #9 post. Okay, and I see I missed Ken's attachment for the fixture, and in essence that's my idea but at a basic level to start.

I've got a lot of thought to figure this all out. All three of you are so far out ahead of my comprehension. But the roof ribs and flashing make sense to me.

So in order to get the correct dimensions am I to measure the vee's bottom and top. This being at the tail stock end where the wear should be almost non-existent?
What I don't understand is that the beds on these were supposed to be hand scraped. I can't seen any scraping marks. Not one.

I really have to look at Ken's drawing again. I don't quite understand how to get a reference from a rolling jig if the non-bearing machined surfaces are on the vertical sides? Assuming the machine is working position horizontally and correctly leveled. Wouldn't a rolling jig like that end up riding on the bearing surfaces and throw off the measurements of wear? I'm guessing my thought process isn't complete due to lack of experience.
 
I do not think sheet metal shapes would do a very good job of mapping the wear on a lathe bed that is measured in thousandths. But, Russ is a pro, and I could be wrong. Ken's setup was an experiment designed for grinding a lathe bed with a normally handheld grinder mounted to a trolley, which was also used to map the existing wear and the progress.

Bed ways become swaybacked typically from use, with most work done near the chuck and therefore more wear in that area where the saddle typically moves back and forth a lot. The ways also wear sideways from side loading from tool to work loading. Before we start removing metal, we need a map of where things are at the start so we can make plans to remove the minimum amount of metal to get the desired results. We also need to test the progress of the work as it progresses, and finally we need to be able to know when we have accomplished the repairs to within the required tolerances. We make jigs and templates to assist with those measurements, which cannot be done with a ruler or other simple everyday tools.

In earlier times, lathes were expected to be hand scraped, that made them "professional", like the big guys used. Of course, expecting a scraping job on a $300 lathe was ridiculous, even in those days, so they just put some random scraping marks on it after it was planed, milled, ground, or otherwise manufactured using machine tools. It was scraping, and it was done by hand, so the lathe was advertised as "Hand Scraped" in the promotional material. A lot of machines are "reconditioned" today by people with scrapers who make them look nice and pretty. They also put a nice coat of paint on the machine. It is still a worn out POS... Of course, some of the best machinery in the world is also finished by scraping, carefully and to very tight tolerances. A "reconditioned" $2000 Bridgeport series 1 is not one of the great ones... Caveat Emptor!

Edit: People who have the skills to do that work also have the skills to know the difference between fine work and a con job...
 
I do not think sheet metal shapes would do a very good job of mapping the wear on a lathe bed that is measured in thousandths. But, Russ is a pro, and I could be wrong. Ken's setup was an experiment designed for grinding a lathe bed with a normally handheld grinder mounted to a trolley, which was also used to map the existing wear and the progress.

Bed ways become swaybacked typically from use, with most work done near the chuck and therefore more wear in that area where the saddle typically moves back and forth a lot. The ways also wear sideways from side loading from tool to work loading. Before we start removing metal, we need a map of where things are at the start so we can make plans to remove the minimum amount of metal to get the desired results. We also need to test the progress of the work as it progresses, and finally we need to be able to know when we have accomplished the repairs to within the required tolerances. We make jigs and templates to assist with those measurements, which cannot be done with a ruler or other simple everyday tools.

In earlier times, lathes were expected to be hand scraped, that made them "professional", like the big guys used. Of course, expecting a scraping job on a $300 lathe was ridiculous, even in those days, so they just put some random scraping marks on it after it was planed, milled, ground, or otherwise manufactured using machine tools. It was scraping, and it was done by hand, so the lathe was advertised as "Hand Scraped" in the promotional material. A lot of machines are "reconditioned" today by people with scrapers who make them look nice and pretty. They also put a nice coat of paint on the machine. It is still a worn out POS... Of course, some of the best machinery in the world is also finished by scraping, carefully and to very tight tolerances. A "reconditioned" $2000 Bridgeport series 1 is not one of the great ones... Caveat Emptor!

Edit: People who have the skills to do that work also have the skills to know the difference between fine work and a con job...

OK a grinding trolley makes more sense to me now. Also, looking at it again I see it rides on the center flat of the vees.

They were $300 lathes you got a point there. So more likely it was some flaking at best? I did read that in a promo I found so you got me there. I can say my "rebuilt" Bridgeport should be awesome when I'm done. But I know exactly what you mean. Probably won't ever sell that once I get it done.

I could start bringing parts over for "us" to work on? :) (No pressure...please help me.) lol

Here are some pictures of the Logan bed to firm up what profiles I'm looking at here.

Paul
 
The saddle on my Jet lathe was so poorly fit that the inboard side was 14 thousanths above the way unless a heavy load, like a deep cut, was placed on it.
I could bump it with a small dead blow and hear it smack the way.
The feed and threading rods actually lifted the OB so when machining it could pivot on the V-way and get some contact on the IB flat way.
Except the way wipers were so stiff and ill fitted that the saddle road on them...........
Then there's the problem that the saddle had no true reference points to measure from. Everything was convex and/or out of square to the ways and the dovetails which
were so bad I didn't even keep a record......
Very poor finish quality and loved to chatter.

The point is that everything has to be checked and understood before starting such a project. Everything!
I also found the tools I had weren't very good " actually they were crap" for getting into the V-way to scrape it.
Got it done and properly aligned after multiple tries. I think!
At least its solid and finishes are greatly improved plus other problems I listed are corrected.
It's amazing how the V-way can support an off-sided load and I had to role or re-align the saddles V to get the IB side to ride on the flat way and give me a square
or very, very slight concave face.
Had the lathe not been really crappy I wouldn't have attempted such a project with the limited " almost none" experience I had.
Wish I'd had the opportunity to start small and work up.

Now I know that I'm not ready to try a lathe bed.
 
OK a grinding trolley makes more sense to me now. Also, looking at it again I see it rides on the center flat of the vees.

They were $300 lathes you got a point there. So more likely it was some flaking at best? I did read that in a promo I found so you got me there. I can say my "rebuilt" Bridgeport should be awesome when I'm done. But I know exactly what you mean. Probably won't ever sell that once I get it done.

I could start bringing parts over for "us" to work on? :) (No pressure...please help me.) lol

Here are some pictures of the Logan bed to firm up what profiles I'm looking at here.

Paul
Paul, your lathe bed does not show much wear visually in the photos, though the pics are not taken in the usual most suspect areas. You are not looking for wear at the sides of the bed, you are looking for it on the V's and the sliding flat ways themselves. The saddle contact on the V prisms does not normally extend to the bottom of the V. If there is heavy wear, you will normally see a step on the angled surfaces between where the saddle slides and where it does not slide. You can also feel it with a fingernail. It is usually worst about 12-18 inches from the headstock. Same for where the tailstock slides. It does not slide on the full width of the way, so you can see the wear versus the unworn areas. The tailstock wear will be farther to the right end on the ways than the carriage wear is, due to how they work together. The unworn areas are reference surfaces, as are all the unworn surfaces that were machined in the same setup when the bed was originally manufactured.
 
Paul, your lathe bed does not show much wear visually in the photos, though the pics are not taken in the usual most suspect areas. You are not looking for wear at the sides of the bed, you are looking for it on the V's and the sliding flat ways themselves. The saddle contact on the V prisms does not normally extend to the bottom of the V. If there is heavy wear, you will normally see a step on the angled surfaces between where the saddle slides and where it does not slide. You can also feel it with a fingernail. It is usually worst about 12-18 inches from the headstock. Same for where the tailstock slides. It does not slide on the full width of the way, so you can see the wear versus the unworn areas. The tailstock wear will be farther to the right end on the ways than the carriage wear is, due to how they work together. The unworn areas are reference surfaces, as are all the unworn surfaces that were machined in the same setup when the bed was originally manufactured.

Oh I wasn't trying to show wear. I will take those pictures later today. These pictures were to show where my reference points are and just general overview of where I would somehow have to measure from. I can tell there is considerable wear by messing with the carriage lock. If not loosened enough the carriage will quickly start to drag as you get away from the worn areas on the bed. Not really a very good test. But it's evident when using it.

One other issue I have is that the compound has enough slack in the vees to twist it by hand. This can be seen visually and heard to click as you do this. It has new gibs and I'm sure that could be tightened. But doing so limits the travel too much. Of course not tightened leaves it to have a lot of chatter.

But before anything can happen with the bed I need to figure out the replacement chip pan and get the legs done. Then properly level and wait and level again. I understand the extreme importance of leveling now. Can't be done until those parts are replaced.
 
So more likely it was some flaking at best?
Flaking and scraping are quite different things. Flaking is deeper cutting done for oil retention pockets (and decoration.) It is also often mistaken for scraping, Flaking is also used to turn a sow's ear into a silk purse. The scraping done on the old Logan and SB lathes, when you see it unworn and pristine, is done by a scraper with very little nose radius, making flat cuts that cover a wider area than usual, and with areas between the marks that are not scraped at all. I suppose someone might say that is to "final fit" the lathe, or to add oil pockets, but I call it decoration. The lathes I am talking about here are typically smaller ones, built to a price point, often from the 1930's, 40's, and '50's. Earlier lathes were planed and then completely scraped in, later ones did not bother with 'scraping' at all, left them shiny.
 
I do not think sheet metal shapes would do a very good job of mapping the wear on a lathe bed that is measured in thousandths. But, Russ is a pro, and I could be wrong. Ken's setup was an experiment designed for grinding a lathe bed with a normally handheld grinder mounted to a trolley, which was also used to map the existing wear and the progress.

My sheet metal proposal was intended as the first step as a visual inspection tool to see how much wear may be on the ways. I agree, the bed looks good from the photos Paul posted so my template was also a prevention tool; Don't try to fix something that isn't broken. :big grin:

I think we agree that some things can be made worse by trying to get it as perfect or accurate as possible when there's no real point or value. e.g. On my 100 year old Lodge & Shipley I do a basic check on the ways for wear. I chuck up a piece of 1/2" drill rod with a drill check in the tailstock. I set up a dial indicator and run the carriage end to end. I get about .005" low spot where wear would be expected. I loosen the drill chuck, turn the rod 90° and do the same thing, with the same results +/-. My first thought was; I must be doing something wrong, there should be more wear for a machine this old. I think I'll leave it because I'm not sure I can get a cutting tool more accurate and a .005" drop on the centerline isn't a deal breaker on this machine.
 
The saddle on my Jet lathe was so poorly fit that the inboard side was 14 thousanths above the way unless a heavy load, like a deep cut, was placed on it.
I could bump it with a small dead blow and hear it smack the way.
The feed and threading rods actually lifted the OB so when machining it could pivot on the V-way and get some contact on the IB flat way.
Except the way wipers were so stiff and ill fitted that the saddle road on them...........
Then there's the problem that the saddle had no true reference points to measure from. Everything was convex and/or out of square to the ways and the dovetails which
were so bad I didn't even keep a record......
Very poor finish quality and loved to chatter.

The point is that everything has to be checked and understood before starting such a project. Everything!
I also found the tools I had weren't very good " actually they were crap" for getting into the V-way to scrape it.
Got it done and properly aligned after multiple tries. I think!
At least its solid and finishes are greatly improved plus other problems I listed are corrected.
It's amazing how the V-way can support an off-sided load and I had to role or re-align the saddles V to get the IB side to ride on the flat way and give me a square
or very, very slight concave face.
Had the lathe not been really crappy I wouldn't have attempted such a project with the limited " almost none" experience I had.
Wish I'd had the opportunity to start small and work up.

Now I know that I'm not ready to try a lathe bed.

Was the Jet lathe new? Or 2nd owner? Thanks for taking the time to explain your convex issues. First time I've read about someone with 1st hand experience with that.
Just wondering but were your scraping tools made at home or ebay brands?

So you only scraped the the saddle's Vees? So the bed is still convex or perhaps twisted?
Paul
 
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