Saddle Gib strip tightness wrong?

[NigeParticipant @nige81730]

After stripping the carriage on the ML4 to fit the TDI I reassembled it and today went to adjust the gib strips. I first adjusted the gib on the saddle untill there was no play in it and the carriage moved smoothly. Then adjusted the cross slide the same. Having put the compound slide back and mounted a tool I went to face off a piece of scrap.

Problem is that as I tried to take the cut the tool no metal came off. It didnt matter how big a cut I tried to take. I couldn't work out what was going on until I put my hand on the compound slide handle and realised the whole saddle was moving away from the work piece!!! Although there is no play in the saddle I can push it up and down the bed with light pressure from one finger!!!

I'm guessing this is far too loose?

Do I just tighten the saddle gib strip to introduce more friction ?

[NigeParticipant @nige81730]

[MeunierParticipant @meunier]

I'm only a novice myself, Nige and don't know how an ML4 compares with an ML7 but..did you lock the saddle to the bed first ?
DaveD

[NigeParticipant @nige81730]

Dave. The ML4 is a smaller Myford than the 7. It  doesn't have a saddle lock that I know of!

Edited By Nige on 29/07/2017 21:34:56

[SillyOldDufferModerator @sillyoldduffer]

Guess before bedtime. Lock the saddle by engaging the half-nut with the leadscrew. With the leadscrew disengaged, ie not turning!

Dave

Edited By SillyOldDuffer on 29/07/2017 21:57:10

[Anonymous]

The saddle gibs probably ought to be a bit tighter. But if the tool is pushing the saddle away from the cut then I'd suggest there may be something wrong with the tool geometry or grinding.

Andrew

[HopperParticipant @hopper]

Engage the half nuts and use the leadscrew handwheel to move the carriage toward the job so no backlash is present in the cutting direction. Don't tighten your gibs to act as a lock. It's fine if you can push the carriage up and down the bed by hand, that's how it's supposed to be, ideally. But in the real world, you will probably find the section of bed closest to the chuck more worn than the rest. So i fyou set the gibs on the unworn bed section toward the tailstock, it may be too loose on the worn section near the headstock. Trick is to set it at a reasonable compromise, keeping in mind that you rarely move the carriage very far toward the tailstock for most model engineerring sized jobs. So set it so it moves freely but with no slop on the left hand half of the bed.

That said, a saddle lock is a good thing to add down the road sometime. Especially for parting but also for facing. It can be as simple as drilling and tapping an extra screw in between two of the existing gib adjuster screws. The extra one can be nipped up when you want to lock the carriage or slackened off completely for general work. Or you could make something more substantial modelled on the ML7 lock bolt.

Edited By Hopper on 30/07/2017 05:37:32

[NigeParticipant @nige81730]

Thanks Dave: no access to the lathe at the moment but been thinking how to disengage drive to the leadscrew; tumblr reverse has a mid position of three and hoping I'm going to find that is a 'neutral' 😊

Andrew: Very likely there will be something wrong with the tool geometry😊 I'm starting pretty much again from scratch here and forgotten most of the little I learned, another trip to YouTube planned for today 😀

Hopper: Thank you for the advice. I have been through the gib tightening process a little earlier in this project but not tried cutting at that time. I had noticed a difference in tightness depending on carriage position and had at that point settled on it being tight at the right hand end in favour of something looser on the left. Your idea for saddle locking is good, thank you, and I'll find out how the ML7 does it.

Thank you again everybody👍

[KWILParticipant @kwil]

I am with Andrew, your gib should be a little tighter such that it takes a firm but easy push to move the saddle and the tool geometry, it should be cutting not trying to push its way into the job in hand. I rarely lock a saddle (for facing only), the DRO shows that it does not move away from the job.

[richardandtracyParticipant @richardandtracy]

I lock the saddle for facing if I remember, but always when parting. I've had enough low flying HSS fragments from my parting tool to noisily remind me to lock it every time.

Regards

Richard.

[NigeParticipant @nige81730]

So, one question answered today. The middle notch on the tumblr revers is a 'neutral' position and disengages drive to the lead screw and then engaging the half nuts locks the carriage Original problem solved Thanks everyone.

[Author]

Posts