Top Slide Lock

[Harry WilkesParticipant @harrywilkes58467]

[Harry WilkesParticipant @harrywilkes58467]

I recently purchased a copy of Model Engineers Workshop Manual by Geo.H.Thomas and I am interested in the top slide lock, on page 182 of the book fig 16.1 shows the lock screw with it's end turned down to 1/8 x 1/8 then to the right off the lock screw it's shown with a pointed tip piece. I cannot see anywhere in the text anything related to what this tip should be made of, I was this maybe brass but would welcome comments or suggestions please.

H

[Michael GilliganParticipant @michaelgilligan61133]

Harry,

If I recall correctly, GHT normally specified a Copper slug.

… It's more ductile than brass, and would certainly be my preference.

MichaelG.

[KWILParticipant @kwil]

It is not a separate piece, it looks different in the drawing because drawing lower right is partly showing screw through casting and the tip is in "black" as it is a x section.

It is all one pice of steel with the slightly pointed tip bearing in an indentation in the gib piece. Works a treat especially the pining of the gib to stop longitudinal movement

[Michael GilliganParticipant @michaelgilligan61133]

Posted by KWIL on 28/01/2014 09:20:20:

It is not a separate piece, it looks different in the drawing because drawing lower right is partly showing screw through casting and the tip is in "black" as it is a x section.

It is all one pice of steel with the slightly pointed tip bearing in an indentation in the gib piece. Works a treat especially the pining of the gib to stop longitudinal movement

.

Ah … not the arrangement I was thinking of.

Sorry for any confusion caused.

MichaelG.

[Ady1Participant @ady1]

I think it may be two separate mods

The top right one is a lathe users side view for the dowel which fastens the gib to the topslide

The lower right one is the locking mechanism, turn this 90 degrees anticlockwise to get a users view

Both appear to be solid mild steel

Edited By Ady1 on 28/01/2014 12:06:49

[Andrew Moyes 1Participant @andrewmoyes1]

I did the modification and highly recommend it. Preventing sideways movement of the gib improved the feel of the topslide movement, and the locking screw works a treat.

GHT describes how he made a step in the hole so that the parallel dowel pin is a slight interference fit when pressed fully home. I didn't have the non-standard drill size he used (3.15mm from memory). I hesitate to suggest an improvement on the work of the great maestro but I found it easier to ream a parallel hole in the topslide and gib then turn the dowel with a 0.5 thou step instead. The hole can be reamed with everything assembled and the hole slightly overhanging the base.

Andrew M

[JAParticipant @ja]

I have done this mod twice now (on different lathes) and it is really well worth it.

A couple of comments. GHT was before Loctite. I glued the dowel instead of using an interference fit. There is a good chance that the little handle ends up pointing in the wrong direction. Initially make the screw out of hex bar and tighten it to the gib strip with a spanner, mark the flat most convenient for the handle, drill the hole, machine off the hex flats and fit the handle.

Once you have done this mod there is no excuse for drilling holes in the lathe as GHT did.

JA

[Harry WilkesParticipant @harrywilkes58467]

Hi and thanks for all your replies/comments is it one piece or two here's a couple of pics

[Harry WilkesParticipant @harrywilkes58467]

Oppppps sorry the pics are a little on the large size

H

[Tony Pratt 1Participant @tonypratt1]

The 2BA threaded part is one piece steel with an 1/8" pin inserted at an and angle as the locking lever.

Tony

[RobboParticipant @robbo]

Harry,

In the second pic it does look as though the threaded pin has a separate end, but its just where the diameter changes. It is all one piece as everyone has said.

[Matt DParticipant @mattd]

The dowel and locking screw can be seen in photo 121 on page 185.

[The Merry MillerParticipant @themerrymiller]

Further to the above,

Prior to me carrying out the mod. I noticed that the gib strip had only two dimples for the gib screws but adjustment was applied with four screws!!

Does anybody know if Myford just ran out of dimples or was there an ulterior motive?

Len.

[Clive FosterParticipant @clivefoster55965]

Yet another fan of the gib screw and lock mods. Applied to three Southbends, two 9" and a Heavy 10, on both top and cross slides with excellent results. Heavy 10 is taper gibs so lock only of course. You really should do screws, pin and lock mods because the whole is far more than the sum of its parts.

Do take your time and clean everything up properly before starting. Works much better if the gib is pretty good fit in the gap to start with. Ideally only just enough clearance to slide it in easily. Ten thou or so perhaps. Second SouthBend I did had a rather slack top slide gib and the mods didn't work as well as on first one. After a year or so I made a new gib pretty much as thick as could be slid in resulting in the best performance of any. Its also important that the gib sits properly up into the corner of the recess. The action of the round ended screws in the conical dimple tries to push the gib upwards onto the top of the recess. Obviously things will be much more stable vertically if it actually butts up onto something solid rather than sort of floating on the ends of the screws like standard set-up.

When you come to fit the new set-up do it with the screw removed, plenty of oil and lots of push back and forth by hand, tweak adjustment, repeat cycles. If you get the adjustments even its amazing how tight the adjuster screws can go before things nip up. I used the same ball ended adjuster and pin system on a 6" machine vice obtained right cheap with a" bodgitt up special" gib installed. Its effectively impossible to lock the vice travel by even adjustment of the gib screws. Under test I actually twisted the allen key. Vice action was a bit stiff but not unreasonably so. About 1/10 turn uneven on one screw would lock it solid tho'.

Suitably sized rollers from discarded needle roller bearings are ideal for the dowels and lock screw thumb lever. I try to have rollers fromseveral different sizes about the place as they are so handy for pinning, dowelling and so on jobs.

Reportedly a loose bearing ball and flat ended screw works for gib adjuster duties if the proper ball ended variety cannot be found.

Clive

Edited By Clive Foster on 30/05/2014 17:48:50

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