Re: [CAD_CAM_EDM_DRO] How to scrape lathe ways

Hi,

I would say that the first thing to do is to check that the ways actually
need regrinding or scraping. If wear has been uniform over the length of
the bed you are likely to use, I would say leave well enough alone! So,
first test is to use a test bar between centres to check. Get hold of a
lenght of true ground hard steel with accurate centre holes at each end -
you may be able to borrow one from a local engineers or get them to make one
for you. Then check that the tailstock is in line with the headstock - put a
good true centre in each and, with the tailstock close to the chuck, try to
hold a razor blade or loose 10thou feeler blade between the points of the
centres. If the tailstock is in line, the blade should be gripped and should
sit at right angles to the bed. If not, adjust the tailstock until it is.
Then move the tailstock away so that the tailstock barrel has to be almost
at full extension to again grip the blade as before. This will test whether
the tailstock is lined up so that the barrel is parallel to the bed. Adjust
as necessary. When this is done you can put the test bar between the centres
and a dial gauge in the carriage tool holder so it runs on the top of the
bar and run the carriage from end to end. This should tell you if the bed
has a dip in it which would indicate localised wear - probably near the
chuck. If this is outside an acceptable limit (you need to decide what this
is remembering that the likely effect is only a very slight barrelling on
cuts along the length of a bar due to the tool dipping below centre height
as it runs along the length of a bar, and a limit on the depth of cut you
can take at one go as the wear may allow the carriage to vibrate at some
point of a heavy cut) then you may need to scrape the bed. This is not an
easy job and can take a very long time to get it right and don't forget also
that, unless your lathe has a loose headstock which is clamped onto the bed
ways, any scraping is likely to put the tailstock out of vertical alignment
which can be very hard to correct.

I would suggest that you therefore do the tests and, if necessary come back
then to discuss scraping. The 1/32 lip is not necessarily too significant -
its unlikely the lathe would have worn by this much unless its VERY old and
has been used commercially for grinding or something similar. DON'T go near
it with a belt sander unless you want a ruined lathe!!!

Ian
--
Ian W. Wright
Sheffield UK

----- Original Message -----
From: "Wally K" <cnc4me@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: 21 October 2000 08:46
Subject: [CAD_CAM_EDM_DRO] How to scrape lathe ways


> I have a 10K South Bend lathe that needs to have its ways ground,
> scraped, or both. I can feel a lip of 1/32 or so on the V way of the
> lathe. My local machinery dealer told me it would cost to much to
> have it sent out and ground.
>
> I have never used a scraper before or saw anyone using one. I have a
> feeling that scraping is a learned skill and do not know if i should
> attempt it.