Save me from myself, please!

[westerner]

So- my Millrite is up and running. See my earlier thread in this forum. (Big "high five" to the folks here and at Automation Direct". Bought the GS 2, easy programming, no sweat. GOOD manual)
Now that is done, I am on to repairing my old, WORN OUT,12x36 craftsman/atlas lathe. The bed is worn both on carriage areas, and tailstock areas, of the ways. I am aware of the various options, concerning repair. Am I insane, or just overly optomistic, about my chances to make it better, not RIGHT, but BETTER, by attempting a repair of the bed on the mill? Just take it down, or epoxy back to original, or grind it, or SCRAP it? Max wear about .004 on carriage area, next to the headstock. I aint never gonna get a contract from NASA, I am just intrigued by my newfound options, and the challenge. I look forward to hearing this varied group weigh in. Pull NO punches, please.

 

[markba633csi]

Metal-filled epoxy would be a possible approach, much easier to build up and mill smooth than doing the full grind and all the work that entails.
Still a bit of work but maybe worth it for your situation- but we are talking last-gasp approaches here LOL
Why not just replace the bed with one in better shape?
Mark S.
ps I'm referring to just epoxying the top of the ways and nothing else.

 

[brino]

Wow. That's ambitious.
I bet you'd learn a lot in such an undertaking.

Let's talk specifics:

Is your mill good enough?
Does it have the table length and X-feed to allow you to mill the length of the entire lathe bed in one pass?
Does it have the enough Y-feed to allow you to do the fronts and backs of the V's _and_ all the flats without disturbing the setup?
Does it have the accuracy? I would expect a tool being used to make/fix another tool to be much more accurate than the tool I am trying to make/fix. How much better? Maybe not 10x better, but at least 5x better. Say you want your lathe bed down to 2 thou. So by my math I would want the mill controllable down to 0.0004 inch or better over the entire length of the bed.

Is a milling process good enough?
Although I have seen some amazing finishes produced thru milling alone(by other people), I'd doubt that you could create a surface significantly better than what it is now by milling alone. I would expect some precision grinding or scraping to be required.

Basically, all the above is meant to say that I would not attempt anything so grand until I knew that it had a reasonable chance of success.
I would first have to convince myself that I would not make the lathe any worse.
Some kinda machinist Hippocratic oath......

Run some tests first. Find a stable piece of material as long as your lathe bed and try milling it to thickness. How did that work out?
I also wonder about clamping distortion and perhaps even thermal distortion.

I am not even sure of the exact wear in my lathe.......but I can produce the parts I need at the required accuracy.

-brino

 

[Bob Korves]

Your only real options of repairing the bed are by having it professionally ground, or by scraping it yourself. Scrap is when it gets melted down. Scraping is when you remove metal bit by tiny bit with a scraper and scrape the geometry and the flatness correct again. IMO, the Atlas lathes are not worth that large amount of money or tedious work, so I would sell it and start over with a better candidate. But, that is just me, lots of others would love to gold plate an old inexpensive lathe that was not that special when it was new. Bringing the Atlas/Craftsman lathe back to like new is totally possible, if desired. Flak vest <ON>.

 

[Holescreek]

I hand scraped a .025" bow out of my grandfathers Atlas working a few hours a day for about a week. You should be able to get .004" out in a day. Don't bother trying to use the mill, you'll just make things worse.

 

[menace]

Why don't you just use some well placed machine jacks under lathe bed where the wear is ? The Atlas is flexible enough that you might be able to correct most of the worn area without much hassle? Look for a more robust replacement lathe in the meantime ! Hope this helps.

 

[Holescreek]

The bed isn't the weak point of these lathes, the gears are. Good luck bending the bed right where you need it.

 

[Holescreek]

And no, if it weren't for the sentimental value I wouldn't have spent the time I did restoring the lathe. The bed wear was .025", the carriage wear was about .012" worn underneath. The compound was somewhere around .006". I had to step grind the carriage retainer to get the proper clamp pressure. I'd intended to give the lathe to a family member but onc eit was complete, no one wanted it that wouldn't immediately sell it.

 

[Dabbler]

So I have just donned my Kevlar... How about this? Map exactly the deviations in your bed, every .250.... The use the lathe. When you need to turn accurately, you know the offsets the will occur - you can even find this out by turning an aluminum bar between centers... You will learn some neat skills, get used to lathe operation, then you can sell it to another beginner when you can afford a better lathe.

Many jobs can tolerate the .002 deviation in diameter caused by a .004 dip in the ways. If you use positive rake HSS tools, you can tolerate .004 below center (you might even bias the tools to be +.001 above center, helping to minimize the deviation). Until you regularly need to do work more accurately, I wouldn't sweat it. It does take some time and experience to learn enough to outgrow a little atlas. Heck, some guys never outgrow a South Bend 9/9a or even smaller less rigid lathes! Clickspring on youtube does incredible work on a tiny lathe, for instance...

 

[Doubleeboy]

A lot of times when folks realize their nifty old lathe turns unintentional tapers they figure its bed wear. A lot of times its a combination of bed wear and wear to the carriage top where it rides on the ways. If the carriage has wear it is very easy for the carriage to lift a bit. I have seen on more than one lathe that if you use a high positive rake cutting tool much like Mikey showed in his great sharpening thread you lesson push off of the work, by lessoning this resistance the carriage does not lift or rock as much and you can now do closer tolerance work. Before I got too excited about how bad my ways were I would make sure I had very sharp cutting tool sharpened using Mikey's article as a guide and see if I could turn more accurate work that way. Then following Dabblers advice above you may be able to find some happy spots on lathe where you can do very accurate work when needed.