Cross slide gib question

[George ScopelParticipant @georgescopel96574]

Good morning

 

I have recently purchased the slides for my lathes cross slide. This slide is adjusted with screws on the body of the slide to make the movement of the slide secure.

The original slide in the machine has angled holes at the same interval of the adjusting screws , I assume these angled holes keep the slide in position in time as the slide gets moved forwards and backwards.

 

Question: how do I have holes drilled into this angled slide guide ? or must the be sparked ?

 

Thank you

George

Edited By JasonB on 09/09/2017 13:11:26

[JasonBModerator @jasonb]

[Neil WyattModerator @neilwyatt]

Hello George,

You can lightly spot them through the screw holes with a hand drill (take care not to damage the screw threads!)

Neil

[Clive FosterParticipant @clivefoster55965]

Many years ago when applying the Geo. H Thomas anti-slip dowel and ball ended adjusting screws modification originally described for Myford machines to a SouthBend I found the smallest centre drill to be a suitable size to pass through the adjuster threads without damaging them. I removed the complete slide assembly and clamped all three components together on a right angle plate with the undrilled gib in its rightful place. I imagine some clamping creativity was needed to get the gib firmly home at the top of its slot with everything held together so nothing could move during drilling.

I think I did the first one on pillar drill so would have used a piece of dowel or steel rod, sized to be a nice fit inside the tapped adjuster hole, to line things up. Then swopped over to the centre drill for drilling into the gib. As I managed to get some ball ended adjusting screws I wanted pure conical, albeit angled, depressions and so ran the drill appropriately deep. A little collar on the drill shank stopped me going too far. Ended up with the extended point of the centre drill creating a shallow hole into the male dovetail of the slide. Like George I found this un-worrying as considering them to be small oil reservoirs.

If you are using the normal pointed adjuster screws you won't want to go so deep and are probably best off with a brand new, good quality, really sharp drill. Or perhaps a spotting drill as these also have plain parallel shank less likely to damage the thread should contact occur. But I have no experience with such so do not know if they will produce a suitable recess. Perhaps John S or another member with relevant industrial experience could comment. Not a job to skimp on as the better the seat between screw and gib the more positive and effective the adjustment. I'd change the screws too as the ends of the old ones will almost certainly have suffered wear and damage over the years. Most likely rendering the adjustment, at best, somewhat imprecise.

Having done the ball ended adjuster and anti-slip dowel modification several times over the years (much easier if you can use a mill rather than drill) I'm convinced of its superiority over the simpler pointed screw in a dimple variant normally found. I find it's much easier and more positive to adjust and allows the gibs to be run tighter without binding. How much of that is due to comparing the old, worn set-up with the new, carefully re-worked system I know not. But it seems logical and when going to the effort of sorting things out its always worthwhile to go that bit further and get them as right as possible. It is, perhaps, instructive that messrs Smart & Brown use that system on my (originally) eye-wateringly expensive and very high quality 1024 despite the common view that a taper gib tensioned from both ends is probably the best system.

At the more model engineer friendly end of the market the simple pointed screw in dimple system is both effective when new and inexpensive to produce. Unfortunately it does tend to wear over the years and is vulnerable to ham-fisted adjustment. The screw points and corresponding gib depressions on the SouthBend slide I first operated on were so badly deformed that effective adjustment was essentially impossible. The screws and dimples being pretty much locked together in one position.

Clive.

[egaParticipant @ega]

As Clive Foster implies, it is well worth reading GHT on this. He explains why the "pointed screw in dimple system" is improved by dowelling.

I have had some success by interposing a steel ball between screw and dimple, an idea gleaned from the Practical machinist site where there was extensive discussion of this issue.

[George ScopelParticipant @georgescopel96574]

Thank you all for the pointers and advice . I most appreciate the information and advice offered by all and will put a plan into action based thereupon.

[Author]

Posts