The bed of the lathe has warn I guess and the centre point of the stock is about 20 thou low on a centre point machined in the chuck. Any advice on how I could rectify would be greatfully recieved Cheers Pete
Assuming that it's not the hardened bed, you could buy "machine tool reconditioning" by Edward Connelly, learn how to scrape and rebuild the lathe. If it's hardened or you don't want to spend several years on a rebuild project, you could search for someone with a slideway grinder.
"Pete" wrote in message news:87e6$5148e41a$43de0cc0$ snipped-for-privacy@news.flashnewsgroups.com...
My trade school South Bend has that problem. The alignment is better with the tailstock spindle minimally extended and the lock tightened. Center drills wobble a little at first, then snap into line and drill true within a thousandth or two, as confirmed by boring. jsw
Crude but effective temporary solution: The tailstock 'lump' is in two pieces, the base being separate from the top. There are machined ways allowing offsetting of the tailstock for turning taper. On these ways, between base and top, you can insert a bit of shimstock raising the centre line of the tailstock barrel. (Front one is a Vee way iirc so you need to be inventive with the shim.)
However: The bed under the headstock obviously is NOT worn as nothing moves on it, so the spindle height in space is where it always has been. The tailstock on a Student slides on different ways from the saddle. Consequently the tailstock ways should see very little wear and are usually in pretty good condition even on old Students. Are you sure that your problem is not tailstock barrel droop from wear in the barrel or bushing?
AWEM
Thank you all for your your interest and suggestions . The lathe is a student Mk1. the rest of it is in pretty good condition for its age. I think its just the bed warn at the chuck of the bed that is where it gets the most use I guess. My plan I think will be to clock the error over a 4" rod between the chuck and tailstock determine the exact error and try and split the tailstock and shim as you suggest. Thanks again I will let you know how it all pans out!
Classic method of estimating bed wear on a Student is to arrange a dial gauge in the tailstock, bearing on the flat way that the carriage runs on, and slide the tailstock gently down it's ways noting any changes in reading. Then repeat in the side (not top!) of the inverted Vee way. This of course assumes little wear on the tailstock ways which is usually true. Clean off the ways first and very very lightly oil with a very thin oil and wipe off to almost nothing, so the tailstock slides freely but isn't raised significantly.
AWEM (who's had a few Roundhead Colchester Students in his time )
Andrew Mawson plaatste dit op zijn scherm :
Another crude one. If the chuck is in fairly good condition you could span the tailstock barrel into it. Then measure any deveation between 1 the barrel and tailstock, 2 upper and lower part of the tailtock. Merely as an indication. On my 1937 Fleck&Co all slideways are worn, even the tailstock ones about a foot in front of the chuck. Reading, understanding and mastering Connelly's book will take a lifetime and the actual re-scraping another one..! Overhere a +/- 0,001 mm lathe bed re-grind will set you back about ?600,-. Best regards, Dirk
Regrinding the bed is the best way to go, but that's not the end of the story. The saddle and tailstock need scraping to the bed, and probably will need Turcite or similar bonding first to bring the level back so that the feed shaft and lead screw ports back into line. Probably the cross slide and top slide also should be done. I've had two Students and one Master 2500 reground over the last few decades !
AWEM
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