Cross Slide Lock

G'day all,

Has anyone modified their cross slide so that they can lock it down?

If you did, what method did you use?

Cheers,

Jim

I did what GHT described in one of his books. You drill and tap a hole like the existing gib screws use, and fit it with a suitable screw, with the end rounded a bit so it bears nicely on the gib strip. When you tighten it, it pushes the gib strip harder against the slide, which locks it. I've done that to both the cross slide and the top slide. I used allan screws since that is easier than working a spanner in a confined space.

John

Hi Jim,

Yes I have used the method described in "The MEs workshop manual" by G H Thomas. His was for the top slide on a Myford S7. I have carried out the mod on both the top and cross slides on my S7. I have seen it done on other lathes as well.

Hugh

Thanks John and Hugh, do you use it a lot for turning?

Hi Jim,

Yes but only when I am doing very fine work on small items, top slide is locked most of the time. As John did I also used hex socket bolts, not ball handles.

Hugh

On my mini lathe, having fitted a Saddle lock, at the front of the saddle, I drilled and tapped it, horizontally, so that the knurled brass screw bore on the Cross Slide. So the one fitment perfoms both functions.

A vertical capscrew locks the Saddle by pulling up a pad beneath the bedways, in the same way as the Tailstock clamp.

Howard

Don't need to make anything as my lathe comes with saddle, cross slide and top slide locks as standard. The top slide is locked at all times, except when I need to use it. The saddle is locked during parting off, but never otherwise. I never use the cross slide lock when general turning. It may get used when I'm using the hydraulic copying unit, but it's not essential.

Andrew

My Warco WM250V had saddle and crossslide locks as standard - they're socket head capscrews. IIRC BH has a Warco minilathe - I'm a bit surprised it doesn't have these as standard.

I've sometimes thought about making a tommybar cap to make them easier to use, but there's a potential damaging foul of the saddle lock head with the crossslide gib screws if I did that - the work seems hard to justify.

The devil's in the detail, as usual. If contemplating a locking screw bearing on the gib strip (the usual solution), think hard about the screw/gib interface. This should be such that the gib strip is not displaced in the plane of the dovetail as the locking screw is tightened. The ideal is probably to restrict possible displacement to be normal to the plane of the dovetail. A ball 'under' the screw, bearing on the plane back-side of the strip, does this. Pointed screws in dimpled strips, or flat-ended screws bearing on 'pockets' don't, but are often used. Anyway, it's probably a theoretical worry, since gib strip displacement should be near-infinitessimal.

ISTR the GHT method when I did mine years ago was to drill in between the existing gib screws in the same plane as the gib screws and drill a divot into the gib strip for the end of the locking screw to fit into. Seems to work well.

Why not just point the screw to match the dovetail angle, so that the deflection of the gib is perpendicular (-ish) to its face?

I assume you'd hope that the deflection is elastic, and that the gib will return to its previous condition on releasing the lock screw.

A small plastic ball or a piece of 2mm strimmer line is adequate to lock a shaft for occasional use.

Because it would be devilish difficult to drill and the resulting screw would be inaccessible on a Myford.

I meant cone the point of a screw to be inserted horizontally, so that the flank of the cone makes line contact with the outside face of the gib. I don't know the ML7 series well, but I think that'd work on the ML10 series, or the Warcos.

The Geo. H. Thomas version specifies ball ended screws working in conical recesses. This arrangement tends to push the gib upwards against the face of the slide locking it firmly in place. I've usually made new gibs and drilled the recesses in situ with the gib forced hard up to the top.

I'm convinced that this produces a much more rigid set-up overall. Especially as I make my gibs as thick as will slide in. Perhaps 10 thou clearance maximum. But then I would say that my way is best wouldn't I.

I also find its imperative to give things are really good scrub down. Half the "wear" on slides I've re-furbished seems to be due to hard "old-oil" varnish and other deposits being pushed up to the lesser used ends of travel. A royal pain to shift. If they could bottle it it could be sold expensively as an anti-wear coating!

Clive

'The Geo. H. Thomas version specifies ball ended screws working in conical recesses. This arrangement tends to push the gib upwards against the face of the slide locking it firmly in place.' I don't think this is correct. As far as I can see, the gib strip could pivot on the screw point or ball end, but is constrained to follow the path of the screw's movement. Please shoot me down in flames If I've misunderstood, because I've thought about this subject a bit (and posted previously) and am surprised that a definitive solution doesn't seem to have been made widely known. OK tapered gibs are the answer...

GHT was a fan of dowelled gib strips, which seem to me to be a good idea - or at least some form of gib movement control is. The screw thrust is parallel to the dowel's axis, so any pushing of the gib strip in any other direction (eg 'upwards' would be prevented - but I think that the strip would, in fact, be pushed downwards by pointed screws in conical pockets. (We may in fact agree, but are using 'upwards' and 'downwards' reversed...)

If a ball is interposed twixt screw (flat-ended) and gib strip (not dimpled), the gib should be pushed normal to its surface, so this is a problem for dowelled gibs*, unless the dowel is aligned to be normal to the gib strip's surface too. My ancient Superior surface grinder has its gib-strip adjusting screws arranged so that they bear at right-angles to the gib strips. It's about the only nice bit of design in the whole machine (but that's another story...).

* assuming the dowel fits closely into a hole - a 'vertical' slot would be OK - just constraining 'horizontal' displacements.

Jim

I have fitted a George Thomas type lock on both top and cross slides on my current lathe and have nothing to add about his arrangement.

However there is another very simple locking arrangement that can be used on some Myford lathes. The lathe saddle must have two tapped holes on the head stock side of the saddle. These are for mounting a travelling steady but later lathes (or mine at least) only have one hole. The lock is a simple clamp mounted in these two holes. I have attached a couple of photographs that show the arrangement.

I fitted this to my earlier Myford after the suggested arrangement appeared in the MEW in October 2005.

JA