ML7 compound slide setup

I have been wondering what to do with the four grub screws on the compound slide since I took it off to put the quick change tool post from Arco. There is a metal wedge bit inside I presume to take up slack from wear.

Before I took it off I found the compound handle was hard to turn with a tight spot. Is the a secret to adjustment to get it set up nicely? Maybe an upgrade?

Um...are the grub screws bearing on a strip of metal of parallelogram cross section that fits in the dovetails? If so, the strip is called the "gib strip" and setting it up is critical to getting easy sliding with minimum play. There's no obvious upgrade just patient adjustment until you get reasonably smooth and easy turning requiring uniform torque all the way along the travel. Better a bit tight than a bit loose as you need to minimise play in the slide. When adjusting the screws, have a spanner on the nut so that you can tighten the screw without turning the nut, then hold the screw while you tighten the nut to lock it. Lubricate the dovetails and the sliding face of the jib with some graphite grease or similar as you assemble it.

The spanner size you need for this adjustment is 2BA - and perhaps not so easy to find outside the 'empire' we used to have. The BA series is based on metric dimensions, but does not match any of the 'continental' metric series - French, German, ISO, etc. the dimension across the flats is 8.2mm. Spanners do exist - perhaps you might try an on-line auction site?

hope this helps - Tim

As John said plus the pointy gib screws often have to engage with matching dimples on the inner side of the gib strip. Thus the parallelogram has to be the right way round and aligned so the screws fit properly into the dimples before tightening up. The dimples prevent the gib strip sliding and help transfer screw pressure evenly on to the bearing surface.

Once the gib strip is aligned, I tighten the screws gently by hand until they just resist turning. Then adjust as described by John. It may take several attempts to get the pressure correct across the full range of travel with no tight or loose spots anywhere.

Some people have improved the gibs of Chinese lathes by polishing the running surface, or by reshaping the dimples for a better match to the screw points, or by replacing the gibs entirely with new ones made of brass. I polished the gibs on my mini-lathe and found it made no practical difference, it was OK before and after! An ML7 shouldn't need upgrading, maybe the gibs on your machine have been inexpertly replaced or are damaged. (Who knows what adventures an ML7 has had since new!)

Dave

Dowelling and fitting a clamp screw to the ML top slide is highly recommended and has been covered here before and, of course, in GHT's ME Workshop Manual.

I did the doweling thing on my Drummond top and cross slides but could notice no difference in operation. On the ML7 we just rounded off the ends of the original Myford screw points so they were a dome that located in the dimples in the gib strip and stops them digging trenches in the gib that then allow movement. Works very nicely.

The secret to adjustment is cleanliness and burr-freeness of the gib, dovetails and whole assembly. Then adjust the screw at each end until just noticeable drag can be felt then nip up the lock nuts while holding screws still from rotating. Then do the inner screws, checking as you go that movement is still free and not binding. The handle should not be hard to turn at any point.

If you get one of the old books on these lathes -- my favourite is L H Sparey's "The Amateur's Lathe" -- it will explain a lot more about getting the best out of these old machines.

It also helps to temporarily remove the feed screw for greater sensitivity whilst testing the adjustment.

…or by replacing the gibs entirely with new ones made of brass....

I had to do this on my WM250V-F. The original gib strip was a piece of MS that was off the shop floor methinks.

Original gib strip …



New Brass gib strip... the undercut on the dovetail is obviously too wide but it is a Chinese machine...



George.

To quote the official Myford ML7 maual,, "Careful attention should be given to the screw adjustment to ensure an even pressure of the gib strip.When stripping the compound slides for thorough cleaning and lubrication re-adjust the slides without feed screws and screw support brackets, testing the slides by hand motion, re-assembling the feedscrew units as the last operation" (ML7 manual M.3M/11/64).

The manual also recommends an oil of 30 viscosity on cross and compoud slide ways although I tend to use slideway oil on the majority of sliding surfaces and moly grease on feedscrews.

When you re-fit the feedscrew and bracket keep the 2 bracket screws slightly loose and wind the slide in to the end stop before tightening the bracket screws to ensure best alignment.

Gordon.