Straight Edge

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The V ways on my 80yr old lathe has about a .005 dip near the chuck (as close as I can measure). They're hardened ways, so I'm toying with the idea of truing it up using a grinding stone in a dremel tool for a scraper.
But, before I can move forward with my fevered dreams, I'd need a five or six ft straight edge. Buying one for this one-off job is a non-starter. But, it would work if I could borrow or rent one.
 
I've got a 6 ft Starrett here out in the Honda at the moment . Don't know how I could get it to you but it's here if needed. I think John is correct , more damage .
 
Find a metal fab shop and get them to shear you a 1 1/2" wide piece of 1/4" steel. Cut it at home to the length you desire. Good enough if you decide to proceed with your original plan for scraping.
Which I would not attempt either. But at least you'd have a straight edge.
 
To take out your .005" dip near the chuck, you will need to remove that much material from the remainder of the ways. It would be difficult enough to do on flat ways but keeping everything in alignment across the entire bed would be torture. I would live with what I had.

edit:If it is truly bothersome, send the bed out to a professional for regrinding.
 
Stop!

Follow me for a moment, use pencil and paper, or a BASKETBALL.

Now that I think about it, a soccer ball would be better.

Place the ball in your lap and get a level, whatever level is handy.

Hold the level true vertical, now place it along SIDE of the ball.

Make a mark where the level touches the ball.

Now, hold the level horizontal, and place the top end edge on the mark you just made.

The level represents your cutting tool.

The ball represents some round object being turned in the lathe.

Draw a horizontal line where the level is touching the ball.

Place 1 piece of folded paper on top of the level and draw another line.

Imagine now, the difference from the center of the ball between these 2 marks.

Squat...

If you are good at math, you could do a bunch of math to get an exact number, and there will be something.

Now, last point, this is a hobby. Your best work you will ever do will likely be less accurate than that number.

Most of us are working to maybe 0.001.

There are many other places that can induce errors that cost nothing to correct. Methods of work is one.

Fixing this would cost a substantial amount of money, but your return on investment would be zip as the other things are still there.

If you are aware of the possibility of error from this, then you compensate by correct methods, which would be the same if this was perfect.



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Taking your lathe to bits is probably not getting you closer to your machining goals. Although it may be possible to grind the ways back, it will be a lot of work. If you're not willing to spring for a straightedge, this may not be the job for you.

Consider making some way covers. They will prevent further damage. Search McMaster for "fabric" and get some of that nylon core neoprene. It's about 0.022 thick. ROBRENZ has a video about it.
 
I like treadmill tread for way covers. Extremely resilient, and free.
I get that it will be a lot of work, but if I'm going to clean this lathe up and make it look pretty, painting it and such, then I'm going to want to go all the way. I've looked at sending it out to be ground. The shipping would be hundreds, and the work would be thousands. I'm a hobbyist and I only paid $600 for the lathe, so that ain't happening. Spending time on it is part of the hobby. Money. . . look guys, she'll only let me have so much!

But, I don't get the immediate jump to "a dremel will ruin the late." Scraping is the process of determining the high spots, whether bluing with a straight edge, an optical flat or some other method, and then scratching them off. The question that needs to be answered to determine if an alternate to the hand scraper would "ruin" the piece is, "How much does each "scrape" remove from the work item?". If the alternate method is less aggressive, then one would be more likely to ruin it with the standard method. A dremel is a fairly weak tool. I can't see it eating through through metal as fast as even a hand scraper would.

But, I think I'm ready to stop talking about it and put a pre-project on the ToDo list. Get a set of I-beams from my uncle, and then hand scrape them into a set of straight edges. Nothing but time involved, and if it works, I'll have a story to tell.
 
There's a video of a Japanese worker using a small air-powered angle grinder to rough in a surface which he eventually scrapes flat. So it's certainly possible. Just don't dig a hole. A Dremel disc is small so the contact patch will be even smaller. When you're roughing with a scraper, a wider tip with large radius is used to avoid digging in.

Do you have a mill handy? For a project like this you'll need some tools specific to your lathe. An angle template, for example. Also, you might need a short and long lap when you're getting close to the right dimension. There's a bunch of errors that do not show up with a straightedge that are related to the alignment of the ways compared to each other. So a tool like the saddle might also be needed, to check distance and level between... Anyway, if you decide to do it, take a few pictures so we can see how it's going.
 
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