Thread: A question?

I have never done this except as a quick check to see if there's a problem, but on the basis that the carriage holds the tool, and the toolpath is what counts, I have always placed the level on the carriage. As you implied (I think) if there is significant wear on the ways - typically most wear on the front way, near the headstock - that would show a change in level that can't be corrected by "untwisting" the bed. It's nice to see your test confirming no difference in the measuring methods.

Cheers,
Bill

I'm probably not the best qualified to describe this method for checking a lathe bed for twist, but Phil or RC will set it straight, if I get it wrong..

The technique was demonstrated on the scraping course... you make up a support for your level, a good quality sensitive machinist's level, I don't think it matters if it's 0.05 or 0.02, I guess it depends what sort of accuracy you are chasing.

Here's a picture of the setup, courtesy of Phil ( aka Steam Whisperer)



You do the initial setup on on an unworn section of the bed, usually up one end, and let it settle, then slide carefully along mapping the twist as you go. Then you can go about adjusting the levelling screws.. One thing I recall clearly, is that sometimes you need to bolt the lathe down to take out the twist, just gravity alone might not be enough.

Hope that helps...

Regards
Ray

hi mate ive tried both and used vee blocks on the vee ways.
do you have your tail lstock end of the lathe floating?
what sort of lathe do you have?
if its cutting straight it must be ok.
aaron

“Tail stock end of the lathe floating?’ I assume you mean not bolted down. Both ends are bolted down the bed was quite twisted (around .08mm). The bed also drops down slightly over the last 120mm or so, but there is nothing I can do about that, it only affects the tailstock alignment and then only when the tailstock is at the extreme end of the bed, but I’m unlikely to use it back there anyway. The lathe is a 250G which I bought a few months ago, I made a stand for it which is a copy of another members stand (copied a lot of his ideas) and then mounted and levelled it. A week later I tore it apart and fixed the gearboxes and a few other bits and pieces. I also found the headstock off so had to re-align that as well, not really surprised though the 250 is a really rough machine. Then I mounted and levelled it again. A few weeks after that I tore it apart again, stripped it of all the filler and paint, smoothed the castings as best I could and painted it (minus the filler) then mounted and levelled it again. It cuts extremely true now, shame they don’t come out of the factory like that. Whew, I’m all tuckered out just talking about the work I’ve done on it.