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Myford ML7 - Top-slide Lock, Top-slide Gib-Strip Pin, and Findings

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I installed a top-slide lock and a top-slide gib-strip pin.
I roughly followed the procedures outlined in the book 'The Model Engineers Workshop Manual', by Geo. H. Thomas (GHT).
The text is on pages 181 to 183 in his book.

Before I committed to drilling into the top-slide, I spent a long time fussing over and marking out the eventual hole positions. Whilst I pondered the task at hand, I made some fairly precise measurements and found a bit of a problem with the top-slide.

There is a lot of text on this page. You might want to just look at the pictures!

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MYFORD ML7 TOP SLIDE - MARRED SURFACE AND ROCKING QCTP


↓ The top surface of my top-slide is marred and battered.
I assume that the badly marked and dented surface was caused by the original tool clamp, and the tool clamp adjusting screw assembly.
Quite some time ago, I purchased a QCTP from Chronos, and did away with the original tool clamp affair. I ignored the marred surface at that time, fitted the QCTP, and moved on and got turning.

While doing the topslide lock I ran a DTI over the marred surface and tested the height of the surface at many locations. Despite the heavy dents, the surface was fairly flat and parallel to the bottom surface of the top slide. However, the surface was distinctly raised around the toolpost hole in the middle. Worried by the finding, I laid the QCTP in position on the marred surface and carefully inspected it. The QCTP rocked. However, it was stable when the toolpost nut was tightened.
I will have to skim around 0.5mm to 1mm off the marred surface.

 

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MYFORD ML7 TOP-SLIDE LOCK AND GIB-STRIP PIN


Continually having to loosen and tighten the gib-strip adjusting screws and nuts, to lock and unlock the top-slide became a nuisance. I needed a top-slide lock.
GHT did the gib-strip pin modification at the same time, and I decided to follow suit.

The gib-strip adjusting screws are 2BA. Going against the grain, I made the lock with an M5 thread, and the pin with a 3mm diameter. I have put a note in my Myford documents, to bring this to the attention of the next owner.

↓ I used a toolmakers surface gauge to scribe the layout line for my new holes.
I have since got a digital height gauge. I find it easier to use.

I put the gib adjusting screws backwards in their holes. I lined up the scribe, on the toolmakers surface gauge, with the centre of the dimple on the end of one of the adjusting screws. I verified the height by checking against the other adjsuting screws to be sure. I scribed the line knowing it was at the same height as the centres of the existing tapped holes.

 

The distance between the centres of the adjusting screw hole is 1.1/2 inches, so I stuck to imperial measurements when marking out.
The gib-strip pin is central between the two middle adjusting screws i.e. the pin is 3/4 of an inch from each adjacent adjusting screw.
The M5 lock hole is then 6/16th inches to the left of the gib-strip pin hole.
I followed the GHT arrangement, and placed the gib-strip pin in the centre of the gib-strip, and the locking screw to the left of that.
I used different sized components to GHT, and I did the gib pin differently. Here is my method which is a copy of GHTs method:-

[] Mark out the positions of the gib pin hole and the locking screw hole.
[] Secure the component with the outer dovetail in the mill universal vice.
[] Use good quality sharp drill bits. Things need to be accurate.
[] Drill the gib pin hole undersized, using a 2.8mm drill.
[] Drill the locking screw hole undersized, using a 3.5mm drill.
[] Remove the component from the vice.
[] Carefully remove all the burrs around the holes. Just remove the burrs, and not any other material.
[] Reassemble the top-slide components, but don't fit the feed screw assembly.
[] Carefully adjust the gib-strip, so that all parts are how they should be. The gib-strip has to be perfectly in its usual position.
[] Secure the work in the mill universal vice.
[] Drill through the gib pin hole using a 2.9mm drill. Drill through the outer dovetail. Continue to carefully drill through the gib-strip. Drill into the inner dovetail, by around 2 or 3 mm.
[] Use the depth stop indicator on the mill. Pass a 3.5mm drill through the lock screw hole in the outer dovetail, and carefully drill into the gib-strip for a depth of 1.5mm ONLY. Don't overdo it!
[] Disassemble the cross-slide assembly.
[] Carefully remove all the burrs around the holes. Just remove the burrs, and not any other material.
[] Secure component with the outer dovetail in the mill universal vice.
[] Drill through the gib pin hole, using a 2.9mm drill. I figured that the 2.9mm drill will drill slightly over 2.9mm, but not 3mm.
[] Using a 3mm hand reamer, carefully open out the gib pin hole, in the outer dovetail only, to 3mm. Leave the hole in the actual gib-strip at 2.9mm.
[] Drill through the locking screw hole using a 4.2mm drill. 4.2mm is the tapping size drill for an M5 coarse thread.
[] Carefully put a good thread in the locking screw hole, using quality M5 taps.
[] Remove the component from the vice.
[] Carefully remove all the burrs around the holes. Just remove the burrs, and not any other material.
[] Get a piece of 3mm diameter silver steel.
[] In the lathe, carefully stone or file the end of the 3mm silver steel, for a length of around 5mm. I reduced the diameter by around 0.5mm, using a small flat diamond pad. You are looking to press this end into the 2.9mm hole on the gib-strip. The pin has to be tight press fit in that hole.
[] File or sand the end of the silver steel pin to 60 degrees. I sanded mine on a Record DS300 sander, using a 60 degree protractor as a guide. It came out well.
[] Cut the 3mm silver steel to length, and round the cut end to your taste.
[] Press the 3mm silver steel pin into the gib-strip. I left the end of my pin, that has the 60 degree profile, just short of the surface of the gib-strip. I had to tap the pin in using a small hammer and it was a good tight fit. I frimly held the pin in the vice soft jaws, and twisted the gib-strip, so that the end with the 60 degree profile was orientated correctly in the gib-strip. I also applied a small drop of super glue for good measure.
[] Make the locking screw, and the locking screw handle. I made my handle from 5mm silver steel. I tapped the locking screw head M5, and put an M5 thread on the end of the handle. So, rather than being a press fit, the handle screws into the locking screw head. I found it necessary to have a removeable handle, just to make the assembly and fitting easier.
After tapping the hole in the locking screw head, I made small recesses at both ends of the threaded hole using a 5mm end mill. This tidied up the ends of threaded hole, and also allowed to the handle to fit snuggly into the locking screw head.
I adjusted the length of the locking screw, until the handle was in the correct 'out of the way' position in relation to the top-slide and QCTP.
I put a small ball bearing in the locking screw hole. The ball bearing is squeezed between the end of the locking screw and the gib-strip.

In the 'The Model Engineers Workshop Manual', the author mentions ... 'a pair of pliers with brass or German-silver lined jaws is useful for this kind of work as they do not mar finished work'. I must admit, when I first read 'German-silver lined jaws' I dismissed the advice as old has-been stuff because I did not understand. Now, having done this modification I see what GHT means (apologies to that good man!).
I did not have any pliers with German-silver lined jaws, so I tried using my plain flat nosed Kennedy pliers and a coil of resin cored solder wrapped around the handle. The idea worked well, and I managed to tighten the handle without marring it. The soft resin core solder worked great.

 

 

GHT gives some good sound advice regarding the final setting of the top-slide gib-strip:-
''Fit and adjust the gib-screws before replacing the feed screw. It is so much easier to obtain a correct sliding fit overall without the feedscrew in place.
Replace feedscrew and endplate leaving screws slack until the feedscrew is right home as far as it will go. Then tighten the endplate screws.''

I would also advise that any of the four adjuster screws is only adjusted when it is opposite the inner dovetail. It is no use adjusting a gib screw if there is nothing behind the gib-strip!.

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MYFORD ML7 TOP SLIDE - SOME PICTURES DURING THE MAKING

 

↓ Here is the topslide on its own, secured in the Universal Vice.

The holes had to be drilled in the topslide. The topslide was then removed to mark the gibstrip.
To ensure the topslide went back in the same position for further operations, I used the Vice Stop.

 

↓ Here is the topslide and base, secured in the Universal Vice.

 

↓ Here is the topslide and base, secured in the Universal Vice.

 

↓ The pin in the gibstrip.

 

↓ The pin in the gibstrip.

 

↓ The pin hole in the gibstrip.

 

↓ The lock.

 

↓ The lock.
The gibstrip pin is to the right of the lock.

 

The gibstrip pin is to the right of the lock.

 

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