Myford QC Gearbox Project.

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Pete W.:
Hi there, all,

I threatened that I'd get to do some work INSIDE my workshop and here I am at last. :bugeye: :bugeye: :bugeye:

About five years ago, I bought a Quick Change Gearbox for my ML7 lathe. Various red herrings and distractions delayed its fitting but it's finally reached the top of the list!

Unfortunately, it turns out that the gearbox that I bought (no fault of the seller) is the Myford Super 7 version, not the ML7 one. The differences are that the Super 7 Gear Cover won't easily fit the ML7 and the Super 7 lead-screw is 3.4" diameter compared to the 5/8" diameter ML7 version.

Part of the fitting procedure is to shorten the original ML7 lead-screw and I could do that. But, somewhere along the way, I bought a gear-box-ready 5/8" lead-screw. I'll get back to lead-screws later, I've decided to start with the Gear Cover.

I was advised that the new proprietors of Myford Ltd. were offering ML7 Gear Covers so I bought one. The snag is that they are raw castings, un-fettled, no holes drilled and/or tapped and un-painted. So the first stage is to have a fettle!

(Before anyone clicks on the PM button, I have accepted an offer for the Super 7 Gear Cover.)

The raw casting looks like this:

and

and

and (on this one, if you look carefully, you might spot little pimples on some of the letters - I guess these are the imprints of the heads of the pins that fixed the letters to the pattern)

and

So I have to transform that to something more like this:

and

and

and

The raw casting doesn't have a dotted line labelled 'File to here', that's why I've taken the photos of the Super 7 Cover. It fitted the back-plate OK so the photos give me a guide as to how much to take off the raw casting.

Watch this space!

awemawson:
Glad to see that you are back in the workshop doing engineering rather than roof repairs Pete. It must be a great relief :wave:

Andrew

Pete W.:
Hi there, all,

I've managed a bit of progress with this project.

I decided that my avatar (the can of peas) was too stationary and was holding me back so I've changed it to something a little more dynamic. It's from a cigarette card and depicts an Alvis TA14 drop-head coupé which happens to be the car in which I learned to drive. It had the Tickfords body.
Wikipedia reckons its maximum speed is in the low 70s but I once had steam coming out of the windscreen demister slots while doing 85 round the Stamford by-pass! :zap: :zap:
Needless to say, that was before the 70 mph speed limit was brought in (but not why!! :D :D :D )

Anyway, back to the project:

Here's a view of the ML7 gear cover after fettling:

And here's an extract from the illustrated parts list (aka 'exploded diagram') showing how this part of the machine goes together:

In addition to buying the gear cover raw casting, I've also managed to acquire some of the minor associated parts from various sources.
Having fettled, I blued the regions that need holes drilling and tapping. I started on the easy one, the 1/4" Whit tapped hole for the knob.

and

That's all fairly straightforward stuff. The casting material drillls and taps quite easily so far, not too soft and smeary! The knob doesn't seat down fully despite my drilling and tapping the hole to a generous depth, I assume there's a swelling where the stud enters the bakelite. I shall add a fibre washer on final assembly to fill the gap.

Another hole needed is to take the 2 BA by 5/16" screw that secures the clip or latch (part nos 225 & 229 on the exploded diagram). Here's the relevant location:

I don't have the spring clip to hand so I can't drill that one yet.

The really challenging part of this process is the location of the two 5/16" BSF tapped holes that take the hinge screws (part number 223 on the exploded diagram). The pointed ends of the screws locate in vee-shaped dimples in the back-plate and I have to transfer the position of those dimples to the two lugs on the gear cover, this photo shows the scene:

Another view:

And another:

The method I have in mind for this operation is to mount the back-plate on a rectangle of MDF so that the points of the dimples (what's the inverse of 'apex'?) align with a line drawn, say, 1.5 inches from the edge of the MDF. Then, with that MDF resting on a flat surface, to set the scriber point of a scribing block level with the dimple centres. Then, I shall place the gear cover in position on the back-plate and secure the two parts together (probably with Gaffer tape). Then, using the scribing block, I shall scribe a horizontal line on each of the outer faces of the gear cover lugs. The next stage is to reset the scribing block to 1.5 inches and to move the MDF into an upright position, supported by a large angle plate, and scribe again on the outer surfaces of the lugs. Where these lines intersect on each lug is the position for drilling the holes for the hinge screws. I hope that the lugs are square enough for the holes to drill true with the lower lug resting flat on the drilling machine table (with a bit of MDF beneath it).

When I get to do all this, I'll take some more photos. I should quote here the military maxim 'No plan ever survives contact with the enemy!'.

When I've done all this drilling and tapping, it'll be time to paint the gear cover. I've got some Hammerite special primer, water-based, brush applied, and I also have a rather old can of Myford grey enamel. I'd welcome any tips and advice on the painting part of the project.

Once the painting is complete, the next job is to fit the change-wheel label which goes here:

rather like this:

The label is supposed to be attached using four very small hammer drive screws. I haven't got the hammer drive screws yet. You can see dimples in the casting marking the notional positions of the holes, I hope they're accurate. I anticipate that care will be required to avoid drilling right through!!

awemawson:
Looking good Pete, glad to see the new workshop roof is keeping you covered :lol:

"I anticipate that care will be required to avoid drilling right through!!"

Drill through a length of dowel, slip over your drill and ensure only what you need sticks through.

Pete W.:
Hi there, all,

I've now marked-out the gear cover lugs for the hinge screws.

Step 1 was to mount the gear cover back-plate on a couple of pieces of MDF. In the event, I drew my reference line further from the edge of the MDF than I quoted in yesterday's post. To get the base-plate mounted rock-free I had to accept more overhang than I would have liked but it seemed to go OK - the test will be when I drill and tap the hinge-screw holes! (There doesn't seem to be a smilie with fingers crossed!!!) Here's photo #1:

It took a while to get the base-plate correctly positioned with respect to the reference line but eventually I was satisfied it was as close as |I was going to get:

and

The next step was to set the scriber point of the scribing block to the centre of the dimple(s) in the back-plate, like this:

Having done that, I attached the gear cover to the back-plate, using Gaffer tape. I inserted a few strips of thin cardboard between the back-plate and the gear cover. Then I scribed a horizontal line on each outer face of the gear cover lugs, like this:

The next step was to up-end the MDF with the back-plate and gear cover and to support them with a large tool-maker's clamp and a heavy angle-plate. Then I reset the scribing block to the reference line on the MDF, like this:

Then I scribed lines on each outer face of the gear cover lugs, at right angles to the previous lines, like this:

and

I've run out of time for today. Hopefully, tomorrow afternoon will bring this stage of the project to a conclusion. Watch this space!!

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