Need some Lathe help? not cutting square.

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I have a 16" southbend that I would guess is kinda rough by machinist standards, but we use it to taper pins and make slugs- just rough work. I am trying to make a small punch housing for my ironworker and I have noticed it is cutting out of square. If i plunge my small boring bar in about a 1 1/2" when I back it out it has tapered in toward the center line. (taken less of a cut). I think I noticed the same thing when I faced something awhile ago? Any input? Thanks for any advice.
Reply:Sounds like you have too much flex in the boring bar. Flex might be because you are using too long a bar, or it might be slop in the machine and you may need to tighten up the gibs..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Check that the lathe is level with a machinist level. If you have any twist in the bed it will cut tapered. Read the part on leveling here:http://pounceatron.dreamhosters.com/...n-127-1930.pdfIt's possible the head stock has been knocked out of alignment. In some cases you can loosen the bolts and it will return close to the correct position. You can then bring to true with a mallet and careful tightening. Depending on the design you may have adjustment screws or shims that may need adjusting. Verify the alignment with the two collar test.
Reply:I think i may have figured it out. My tool post had a chip under it and was rocking slightly. I hope that was the problem. It was tight, but when sent into the part, the boring bar gained leverage. I was only cutting on one direction, sorry if my wording made it confusing. Ive been welding professionally for 20 years- but I sure would love to spend some time with a machinist to gain some of the tips and tricks.
Reply:Eric C An additional remedy, unless locked/cinched/set, its common for the cross-feed to minutely rotate as the apron feeds.  The l/c/s may not be obvious, but commonly has an allen head.Opus
Reply:Originally Posted by OPUS FERROEric C its commonfor the cross-feed to minutely rotate as the apron feeds.  Opus
Reply:zapster  -  A non-problem is not a solution  -  Opus
Reply:might need to adjust the gibbs..   as the machine gets wear on it, the carriage will try to pull to the center when boring, and push outwards when turning...   at a point, if the gibbs are worn out you would have to replace the gibbs/gibb, if the ways are just worn out your sol and have to make do...tackleexperts.comwww.necessityjigs.comhttps://www.facebook.com/groups/mach...dingequipment/
Reply:What model SB lathe is this?- MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.
Reply:A quick way to find out what is happening is to make your cut then stop the lathe and slowly move the carriage or cross slide back to the original position.  If the tool bit drags back across the work making a slight mark it indicates that there is "spring"  in the boring bar or tool holder.  If it comes back without leaving a mark at all likely there was movment of the slide that was supposed to be stationary.  If that is the case often you will see a gap between the work and cutting edge near the original start of the cut.   From these indications you can start your hunt.  Note that it is common to have some amount of spring especially if you are taking heavy cuts.  Often after heavy cuts an operator will take a "free" cut not advancing the tool bit but running over the work.
Reply:boring bars can tend to gradually ride up out of the cut giving you a tapered hole,  especially if they are not ground properly or are less than sharp.  a couple spring passes with a sharp tool usually will straighten them back out.XMT 350 MPa, w/D52-DTA 185 TSWHarris of
Reply:What 7A749 was talking about is "backlash" (mechanical slop).Check the Practical Machinist forum South Bend section for info specific to your lathe such as manuals and what to adjust for best performance.http://www.practicalmachinist.com/vb/south-bend-lathes/You will find that tools work most effectively when taking off enough metal to make nearly continuous chips. Not so light a cut that tools "wipe" and deflect, or so heavy a cut that they flex or flex the workpiece.Check as lotechman describes.