|gerry madden||23/01/2019 15:20:30|
|48 forum posts|
This topic has deviatingly reared its ugly head in another thread. Rather than perpetuate the error I thought I'd start a new one.
My lathe sits on a metal cabinet on top of a carpet It wasn't "level" on first installation so I fixed it down solidly on large 4mm thick washers at three points. Under the forth foot (tailstock front) I inserted a wedging device along with the pull-down bolt.
Now when I want to do some precision parallel turning, I do a quick machining of my test piece. If there is a difference in diameter between the two ends I simply slacken the bolt on the adjustable foot and pull out or tap in the wedge a fraction. I then tighten the bolt and make a final check.
Its so simple and I often wonder why no one else (or manufacturer) does something similar ?
|3985 forum posts|
It's a good trick, but I feel there are some disadvantages.
Firstly, much depends on the lathe - not all of them are as bendy as others! A Chinese mini-lathe is stiffer than a Myford because it doesn't have a gap. Gap bed lathes are flexible in a good way because they allow bigger work to be squeezed on to the lathe, hurrah. But the gap makes them liable to be flexible in the bad sense too - and usually the more rigid a machine tool the better. A second issue - as Gerry has noticed - is that a deliberately twisted lathe is likely to come out of adjustment, which is undesirable if the machine becomes untrustworthy. Third point is that a correctly installed lathe that's cutting inaccurately probably has something wrong with it, like a worn bed, out-of-true headstock, bent spindle, damaged bearings or duff chuck. It might pay to fix the actual fault rather than hide it by twisting the bed.
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