Old Lathe - Cross Slide Question

I know this is a SB forum, but my 100+ year old lathe may be one of a kind at this point. It is an A.V. Carroll 9" Junior. It is very similar to a SB 9" of similar vintage. My biggest problem is zero documentation. I was hoping guys with an older lathe might know something about how cross slides of that era were designed.

My lathe has a screw in the longitudinal center of the jib that goes through the jib into a hole in the way. It appears to be a lock, but I cannot understand the point of locking the slide in the exact center. The compound has no lock or similar screw, which has me even more confused because it would seem more likely to want to lock the compound than the cross. Any inclination on why it might be this way? It definitely looks original.

All the ways seem oddly designed to me, but I don't know what was state of the art in 1917. The ways are 60 degrees, but the jibs are thin 90 degree rectangular bars. The jibs are too thin to drill a relief for the set screws. Each is held in place by a single relief that goes in deep enough that the drill bit barely penetrated the way side of the jib. If it were any deeper the set screw would drag on the way. They are very bent and need replacing. It appears to be mild steel. Does anyone know if they used a different grade of steel?

I'd be tempted to put in a more modern style jib, but that would require re-cutting a way to fit a thicker jib. I'd probably make it worse in the process. At the very least I would ruin the original hand scraping.

Any additional thoughts are appreciated.

Mike

Without pictures it sounds like a tapered Gib (not Jib)If so? then there should be another screw at the opposite end of the cross slide. The rear one gets loosened and the front tightened a bit until the gibs taper moving inward removes almost all of the clearance, then the rear screw is tightened to lock that setting. Adjusted properly the slide should have a slight amount of drag but not be stiff to move or you put excess wear on the cross slide feed screw and nut. With a highly worn machine it could be tough to get properly adjusted for all positions so a compromise setting might be all you can hope for.If that's not how yours is set up then I can't say for sure what you might have.Cast iron was one of the main materials used for gibs because of it's self lubricating quality's. And steel would be harder than the cast iron used on the cross slide so would wear the cross slide dovetail faster. With a 100 year old machine almost anything could have been done or butchered by past users so it's difficult to be sure of what's OEM and what isn't unless one has the exact same machine. A.V. Carroll doesn't show up on the Lathes UK site Machine Tool Archive so there may not have been many made. Because of that and it's age along with it not being a South Bend then if it were me I'd take some good detailed pictures that clearly show what you mean and re-post your questions here. https://www.practicalmachinist.com/vb/antique-machinery-and-history/ For sure someone there will know the answers.

Technically about 150 years ago and probably only in the UK jib would have been an accepted and understood term. Today Gib is the term used in any English speaking country despite what some forum posters seem to continually and incorrectly use. It's a small detail, but when asking questions using the correct terminology is one of the basics of communication. Today a jib would either be used for a specialized additional boom on a hoisting crane or used on some types of sailing ships.