Chester DB10 setup

This topic has 7 replies, 6 voices, and was last updated 12 October 2017 at 12:57 by SillyOldDuffer.

Viewing 8 posts - 1 through 8 (of 8 total)

Author

Posts
11 October 2017 at 17:15 #321052
Ian Skeldon 2
Participant
@ianskeldon2
Hi,

I have been using my Chester DB10 Super for almost a year now, it has been asked to do a lot and I am generally pleased with it, however I do have a couple of questions that someone may be able to help with.

1, When I take a shallow cut running from tailstock to chuck, if I get to the end of the cut and then bring the carriage back towards the tailstock without withdrawing the tool, I can see the tool taking another small cut as it travels back. Is this backlash in the cross slide?

2. The cross slide is 100% square to the chuck face, it doesn't cause me any problems on small diameter stuff but if I was to face say a back plate, it would be slightlty concaved. Could be me being stupid but I can't see anyway to adjust this out?

Many thanks for any advice offered, PS it runs very accurately down the length of the workpiece using a 0.01mm clock, 0.03 run out over 120mm length.
Advert

11 October 2017 at 17:15 #8906
Ian Skeldon 2
Participant
@ianskeldon2
I think I have play somewhere but where?
11 October 2017 at 17:30 #321055
Clive Foster
Participant
@clivefoster55965
Both normal behaviour.

Shallow cut on return is due to the cross slide twisting slightly under the influence of the feed mechanism which operates on side of the machine. Twist one way on forward feed, twist the other on return feed. Shallow cut is because twisting effect on return is fractionally greater than on the forward feed so the tooltip moves in a touch further. Don't know why the twist effect is such so as to give a small spurious cut on the return but its pretty much always so. High end toolroom lathes in good condition don't usually suffer in this manner.

Lathes are always made to face slightly concave. That way two "flat" surfaces will sit on each other without rocking. If faced convex mating parts would rock. Theoretically things could be made so as to face dead flat but its tricky with no margin for error or wear. Slightly concave is safer.

Clive.

Edited By Clive Foster on 11/10/2017 17:31:40
11 October 2017 at 17:38 #321059
Ian Skeldon 2
Participant
@ianskeldon2
Clive thank you, I shall stop worrying and carry on somewhat wiser.

Many thanks,

Ian
11 October 2017 at 19:20 #321073
Sean Cullen
Participant
@seancullen60833
Ian, thanks for asking the question and live thanks for the answer. I had wondered the same with my lathe.

Sean
11 October 2017 at 20:01 #321079
not done it yet
Participant
@notdoneityet
Apart from the post from Clive, even if it was aligned perfectly it would still likely cut a sliver on the way back – unless a travelling steady prevented any deformation. We call it a spring cut when we want to take off a sliver, so cutting again on the same setting.

Likely a slightly different outcome if the cutter was fitted on the other side of the tool post (but impractical, as we could not cut so very close to the chuck!). There are compromises in most designs.
11 October 2017 at 22:41 #321100
Vic
Participant
@vic
Good question Ian, and clearly answered Clive.
12 October 2017 at 12:57 #321154
SillyOldDuffer
Moderator
@sillyoldduffer
Another reason for getting a sliver on the backstroke is that the other side of the cutter is used. As the edge is different and the spring of the tool is reversed, and for the causes listed by Clive, it's not surprising that a tad more metal comes off.

Dave
Author

Posts