Lathe saddle gib strips

[GraemeVW]

Sorry to start another thread on this, but wanted to ask about these before I do something bad and would like some opinions of possible.

The front and rear gib strips aren't adjustable on my saddle. They bolt to the saddle with cap head bolts.
When done up tight there is very little play to the bed (none ar the rear) which is good, but no adjustment.
I assume things have worn a little?
This means the front carriage lock, doesn't.
It doesn't lock anywhere on the bed so either just the carriage is worn, or the bed has been reground.

My question is, if the gibs tighten on the bed before they tighten on the saddle, they would be loose as there is nothing to also lock them.

I wondered if they were ground to be perfect when tightened fully. That's pretty much how they are now

But if that's the case, how would the carriage lock ever work?
I could slope it slightly so it just has a tiny bit of clearance at the lock end?

I was toying with removing some from the gib where it mounts to the saddle so I can adjust it, and lock it.

 

[Pete.]

That saddle lock will have a little wedge piece on the end of it, separate from the bottom gib.
Those front and rear bottom gib are never adjustable, except by scraping. They prevent the carriage from lifting but they carry no weight so they barely wear at all.

 

[Brad93]

They're adjustable on some lathes. Using a set of jacking bolts.

 

[GraemeVW]

That saddle lock will have a little wedge piece on the end of it, separate from the bottom gib.
Those front and rear bottom gib are never adjustable, except by scraping. They prevent the carriage from lifting but they carry no weight so they barely wear at all.

I thought that might be the case, having them under size and just hanging on the bolts didn't feel right.

The rear one is spot on then, I'll leave that lone.

The front one is worn, the area that touches the bottom of the bed is ridged.
There is no wedge on the lock though. I cant quite grasp how that wood look/operate though as ibe never seen one.
It just screws into the gib.
The only way it could lock is if the gib doesn't meet the underside of the saddle.
The gib is just solid and the bolt doesn't go all the way through.
The gib must be original as it's cast and properly shaped around the feed for the cross slide etc.

The rear is wanting to lift isn't it, so a tightly bolted gib is needed. The front though the saddle is in compression so may e it doesn't matter if there is a little clearance between the gib and the saddle?

Maybe I should remove the same amount off the top as the wear on the under bed section.

 

[Pete.]

Send it to me I'll surface grind it flat for you.

 

[GraemeVW]

Send it to me I'll surface grind it flat for you.

Really! That's a super kind offer! But...

I've done a little more investigating and took some pics.
This is the rear gib, you can see the wear ridge in this, from nearly nothing at the headstock end to a little at the tailstock end.

If I turn this over (the other side has been planed and has no recess for the cap screws) it removes all play in the saddle at the rear. It also doesn't get tight at the tailstock end, so I guess bed is ok.

This is the front gib. You can see the wear in the running surface although again, very little at the head end.
With this clamped tight there is a tiny bit of play, but this is always pushed down right?
I assume it wants a little taking off the two pads to allow it to clamp tighter.
I think there may be a little wear in the underside of the bed at the front too as it does get a tiny bit tighter at the tailstock end.
I assume it's been used with the carriage lock too tight and has worn both a little?

I also assume the front gib doesn't really want to be loose as such, but maybe just when snugged the carriage moves, and when TIGHT it locks?


The rear gib could be ground flat, but I could just use it upside down and not worry about it.

The front, sending it to you to be ground, id have to work out exactly how much needs to be removed right?

That may be a case of trial and error.

It may be a bit of a bodge, but I was going to put some abrasive paper on a flat surface and just knock it down a tiny bit at a time. Focusing more on the carriage lock end . I'm not touching the running surface, just the mounting surface. And if it needs a tiny bit of clearance, then surely surface finish isn't absolutely vital anyway?

 

[GraemeVW]

I came to the conclusion the front gib doesn't make contact with the bed. It's just a lock, and stops excessive loosenes.
I put a small piece of this feeler gauge behind the bolt so when tightened the strip tips towards the bed and locks the carriage. All working perfectly now.