Sheldon Exl-56-b Lathe Crossfeed Questions

W

Wireaddict

Active User
Registered
Joined
Oct 24, 2013
Messages
149
I'm quite familiar with the controls on this lathe although I haven't used it much until now but I'd like to lock the crossfeed while making longitudinal cuts but I can't find a square head locking bolt for it like there is for the longitudinal feed. There is a crossfeed gib adjustment screw on the right side of the crossfeed dovetail that binds it up when I tighten it [it requires a flat-bladed screwdriver unlike the other locks & hold-downs]. Is there another way to lock the crossfeed?

Another question: is there a way to tighten the screw & nut for the crossfeed? Mine has about 0.060 inch of play. I have a manual but it doesn't address either of these issues. Thanks!
 
Dave
Have you tried the Sheldon lathe group ? John Knox is a member and worked for Sheldon and has a wealth of knowledge about them, as does the other members. I owned a Sheldon for a short time and found them to be very helpful. I am sure they will answer all your questions.
Tomh
 
Wireaddict said:
I'm quite familiar with the controls on this lathe although I haven't used it much until now but I'd like to lock the crossfeed while making longitudinal cuts but I can't find a square head locking bolt for it like there is for the longitudinal feed. There is a crossfeed gib adjustment screw on the right side of the crossfeed dovetail that binds it up when I tighten it [it requires a flat-bladed screwdriver unlike the other locks & hold-downs]. Is there another way to lock the crossfeed?

Another question: is there a way to tighten the screw & nut for the crossfeed? Mine has about 0.060 inch of play. I have a manual but it doesn't address either of these issues. Thanks!
Click to expand...

No, other than tightening the gib screw, there is no way to lock the EXL-56 cross-slide - in general that is not a necessary feature on any lathe. If locking the slide is of importance to you, you could make a custom gib locking screw with a knurled handle on the end extending far enough out from the slide to be conveniently accessible :)

You cannot easily improve the backlash on the cross-slide, which is caused by the wear on the cross-slide lead screw and the mating nut. A fellow on eBay makes/sells both the lead screw and the nut for old Sheldons. The nut is semi-finished and will require a bit of milling to get it correctly sized. My old EXL-56B also had about a half-turn of backlash and I ordered the eBay parts. Although the parts were pricey, I was happy with the results which were described here:

http://www.hobby-machinist.com/threads/old-sheldon-still-going-strong.34932/
 
I'm not personally familiar with the Sheldon. But on most lathes, there are two sources of "backlash" in the cross feed mechanism. One is the clearance between the threads on the cross feed screw and the threads in the nut attached to the cross slide that the screw drives. Unless the nut is one of the adjustable ones, this is never zero due to thread allowance. And as the nut and the screw wear, it will increase. (And if you install a "zero backlash" nut on a used screw and adjust it for minimum backlash in the most used area, it will lock up when you try to move the carriage out of that area.)

The other source is end float (axial movement) in the cross feed screw. This can account for half the apparent backlash on a well worn lathe. But on most machines, it can be adjusted to very close to zero, and this adjustment is good over the full movement of the cross slide. I don't know how it is accomplished on the Sheldon, but on many machines, the adjustment mechanism consists of a nut on both sides of the cross feed crank or handwheel To adjust it, you first run the cross slide off of the screw so that the nut is not engaged. Then you alternately loosen one crank nut and tighten the other until the end float is essentially zero but the screw still turns freely or with minimum drag. Then re-engage the cross feed nut with the screw and see what backlash is left in the most used area.
 
On the cross feed lock question, the most common method is a gib lock. In place of one of the gib adjust screws and nuts, you will have a T-handle screw. The nose of the screw should look like the other gib adjust screws. The screw length is typically about twice that of a standard gib adjust screw. The outer end is cross-drilled for a short rod that is pressed through the cross-drilled hole. On an Atlas machine, the milling attachment comes with a gib lock screw. You can also install one of them in the cross slide (which I've done on my machine). The only problem that you may have with doing this is that the rod may hit the saddle wings in certain positions of the screw at the extreme travel of the cross slide.
 
I was hoping to hear that there was a backlash takeup adjustment in the nut like some mills use I suspected there wasn't. I'll look for a screw endplay adjustment in the next few days or possibly shim it. As for the crossfeed lock, I think the feature is as valuable as the longitudinal travel lock on this machine & the X, Y & Z axis locks are on mills to improve accuracy, particularly with the play in the screw. That sounds like my next project in the shop. Also, I joined the Yahoo! Sheldon lathe group that John Knox belongs to before I moved from MI several years ago but never visited it since I joined this forum. Thanks for the info!
 
Wireaddict said:
I was hoping to hear that there was a backlash takeup adjustment in the nut like some mills use I suspected there wasn't. I'll look for a screw endplay adjustment in the next few days or possibly shim it. As for the crossfeed lock, I think the feature is as valuable as the longitudinal travel lock on this machine & the X, Y & Z axis locks are on mills to improve accuracy, particularly with the play in the screw. That sounds like my next project in the shop. Also, I joined the Yahoo! Sheldon lathe group that John Knox belongs to before I moved from MI several years ago but never visited it since I joined this forum. Thanks for the info!
Click to expand...

If the mechanism is not too worn (my EXL-56B was not and it was made in 1944) it is simple to minimize end movement in the lead screw. There is enough play in the internal parts to allow them to be re-assembled more tightly. There isn't any adjustment mechanism, you just eliminate the slack to the desired amount when putting the shaft components back together before tightening everything.

I just looked up my notes from rebuilding the cross slide and found the following: "replaced cross-slide lead screw and nut on 2 Nov 2014. Backlash reduced from .070 to .003". (FWIW, if the lead screw nut is slotted and compressed a bit, it is possible to obtain zero backlash, however there is no need for zero backlash and the process increases wear on the nut.)

I posted the process on the Yahoo Sheldon group but if it has a search function, I have yet to find it. It would be worthwhile for you to go to the lathes.co website and get a manual for your EXL-56, both operator's and maintenance manuals are available.

Honestly I don't get the need for locking the cross-slide. No lathe manufacturer that I know of has ever found that to be a useful feature. But you could, as I suggested, make a new gib lock screw that would allow locking :)
 
I just re-read wa5cab's second post more carefully and I'm going to retract something that I said.

If a milling attachment is used on a lathe, then it is desirable to prevent cross-slide movement ... so there is an application for a gib lock. I had an Atlas milling attachment for my little 6 inch Atlas lathe, back in the 'sixties, and used it a number of times without a cross-slide lock - I just tightened the gibs and went at it.

A cross-slide clamp would surely have saved time :)
 
Thanks Randy, I got my EXL-56B manual from lathes.co; they seem to be the only source for them now. I'm interested in clamping the crossfeed gib because I got a noticeably better longitudinal cut with the gib tightened. And with a separate clamp screw, simply loosening it restores the gib adjustment to its normal setting. There's also a good place to add this clamping screw between the ways where it'll clear the apron with the crossfeed fully retracted & still catch the gib when tightened.
 
One other operation where a cross feed lock would be desirable would be if you are using the compound to cut a taper
 
You must log in or register to reply here.
Back
Top