Mk1 Super 7 - What colours ?

Did you check the fit of the saddle at the chuck end of the bed compared with tailstock end i.e. does it tighten up? This would indicate bed wear which would arguably respond better to a regrind. Worth checking particularly on an older machine without an induction hardened bed.

The way to check the bed is to strip the bed including the headstock. If you have a good long straight edge, I used a 900mm Moore & Wright, Look for wear with feeler gauges under the first 150mm of carriage travel, particularly front shear. I can send you the wear pattern I found.

Had the bed ground on a surface grinder about 40Km from where I live. Think it cost me $80Au about a year ago. Cost more to get the saddle machined for conversion, $120Au, from another shop.

While the bed bed is probably not perfect, it is a lot better than before the regrind.

Thanks for the responses.

I removed the saddle assembly and tailstock to lighten the machine for transport home. On inspection the original saddle was obviously massively worn, on closer inspection the oilers were full of hardened grease so no idea when it last had a proper oiling.

I was OK with scraping the bed, but the saddle would need more serious work so I bought a used (late model, wide guide) saddle with virtually zero wear - factory machine marks still very obvious - hardly any visible wear. Should save me a lot of time in the long run.

So I didn't try the saddle to bed fit before the bed scrape, but after many, many hours of tedious scraping I got the bed flat - Well as flat as I can and a whole lot better than it was previously. The main wear on the bed was on the front edge of the front rail, starting around 1 1/2" from the headstock end.

I made myself a carbide scraper, used a thick sheet of float glass as a surface plate and it took around 3 weeks scraping for 2 or 3 hours most evenings until I got even blue spotting all over the top of the bed. Obviously most of the hard scraping work was at the unworn tailstock end, and more on the rear rail than the front.

I decided not to scrape under the headstock, so as to leave the original reference there, thinking that I can shim up the tailstock later if required so the centres match. I realise this isn't 100% perfection but I think I can live with it. I can always revisit this in the future if It throws up noticable errors.

I miked up the verticals measuring from the untouched rear one, not too much wear there but to correct it I welded up a square steel frame, bolted 2 sealed bearing races on the back and a piece of square section aluminium tube on the front. I then stuck some sandpaper (the Klingspor self adhesive backed stuff that bodyshops use, not regular stuff), to the ali extrusion, put plastic pads underneath so not to mark the freshly scraped bed - then slid it backwards and forwards along the bed using the bearings as rollers against the rear vertical, and the sandpaper to clean up the other verticals till they all came in parallel to the rear.

As for the undersides of the rails, after a good clean up I went round with a micrometer and got good readings all the way along. As I was going from narrow to a wide guide I didn't need to check the inner ones.

I had problems when fitting up the apron to the new wide guide saddle, the handwheel wouldn't turn and the split nut wasn't centred on the leadscrew. Turns out the bolt holes in the later saddles are approx 2mm further inboard than the early one, so I have had to slot out the holes and make up some custom washers. That's all working nicely now, no tight spots taking the saddle end to end. I just used the shim stacks that came with the later saddle I bought, they seemed loose before I oiled it up so I tried peeling off one shim, refitted them and it clamped up solid, so I have put the shims back and all free again, now I have oiled it I cannot detect any play by hand.

A question though - If I was to check with feeler gauges, what sort of clearance should I expect between saddle & bed in a perfect world ?

I'm currently working on the headstock assembly at the moment - all looks good so far except the rear bearings have also had a dose of grease instead of oil although they seem fine by hand. I am seriously considering the taper roller conversion (what do you chaps think ?) - but I'll need to get it running first so I can machine the collars to suit.

There's also the drip oiler. I unscrewed the sight glass whilst stripping for clean up & paint - Unfortunately the white plastic insert behind it has cracked, I would be amazed if they are still available, but although I could make a replacement I cannot get the brass drip tube out, and that holds it in place. Does anyone know how the brass tube fits to the headstock casting ? I'm guessing it's on a taper. ?

At the moment I have used a bolt, a large washer and a big nut as a spacer to put some tension on it, given it a good dose of plus gas but still no joy. I have tightened the bolt down as far as I dare, but I don't want to do any damage.

I'm leaving it under tension overnight - well you never know.

Was thinking of applying some gentle heat but then if I understand correctly brass expands more than cast iron so that's probably going to make it tighter ?

Any suggestions / ideas welcome.

Cheers - Dave.

Edited By Dave Whipp on 03/12/2018 23:56:14

Edited By Dave Whipp on 03/12/2018 23:58:03

I would not remove the Oiler tube. Had a look at my lathe and the tube is tight. I have a drawing that shows it has 2 different diameters, but without a photo cannot say accurately. If you made a new insert, referred to a a thimble with a slot in the back the shape and size of the oil nozzle. When I looked at the thimble on my lathe it is not tight and the hole in the top is much larger than the nozzle thimble.

An alternative option would be to leave the thimble out, machine a piece of tube to hold a sight glass cover and loctite it to the housing. The white Plastic makes it easier to see the oil, that is all.

I have just finished the Taper Roller bearing conversion. If you are doing the conversion look for good quality bearings, SKF, NSK, RHP etc. Do not use cheap bearings, there are differences. Also watch the recess machined in the retainers, for SKF bearings the bore had to be 48.5mm or it rubbed on the bearing cage. The original spacer was used.

The Myford shim packs are comprised of 0.002" shims. you should be able to close the gap to less than 0.002". This is assuming that the bed has an even thickness and carriage does not jam as you get closer to the tailstock. Normal practice is to remove the headstock put the bed upside down in a surface grinder, and grind the bottom of the feet. the bed is then turned up the right way and the top is ground including the headstock end. The biggest issue is finding a surface grinder with enough travel.

From the grind marks on the bed under headstock, the bed was ground on a vertical spindle surface grinder similar to the Churchill Snow grinder.

That colour was known as Straw, anyone who worked on telephones in the 60s / 70/s would have seen equipment racks painted in it.

This might prove useful. https://www.youtube.com/watch?v=XVdM1ZI3hEQ

Thanks for the video link - yes, that will come in handy - thanks.

Light Straw. Yes, I work for BT and there's still plenty of ironwork painted that colour in the exchanges. Maybe that is what my "custard yellow" was intended to replicate ?

However, colour wise, I've settled on Grey & red.

Re. the bearings, yes, will get SKF ones, Hopefully should last me out. Ta.

As for the saddle to bed clearance, Ive gone over it with my 2 thou feeler gauge and I can't get it in anywhere so pretty chuffed about that. There's the odd place I can just about squeeze the 1.5 thou feeler in (the thinnest I have)

I have given up on trying to extract the brass oil dripper tube from the headstock - it is indeed very tight and if I force it more something is going to break. I will attempt to make a replacement plastic "thimble" from nylon bar and slot it at the back to go around the tube, like you say. I am tempted to make it a fraction longer and put an O ring under the bezel. I will have to wait till the lathe is up & running first, so I'll just put some tape over the hole in the meantime.

The thimble has (as far as I can measure) a 22mm X 0.7mm thread. Does that sound right for a Myford of that era - I would have expected imperial measurements ? Or am I measuring badly ?

If so, should I be able to cut such a fine thread on my S7 when I get it running ? I'm a complete newbie to threadcutting though I have watched a fair few youtube videos on the subject.

Dave.

Could be 36tpi, if you have a QC Gearbox that is a standard thread and more likely to be used in the 6 years that this initial style of headstock was built. The thimble is an odd size as 21.9mm OD, so could be 22mm. What is the bore in the headstock for the oil thimble?

Remember that the Idea is not to fill the sight glass, but rather to have a steady drip of a good quality Hydraulic oil. Myford recommend ISO 32, but I have always run ISO 46 as it as felt to be better in warmer areas such as Australia. Also at the time easy access to that oil as where I was working used large quantities for steam turbine lubrication.

Hole in the casting measures 22.1mm or .87 inches.

I don't have the gearbox on my lathe, but I do have plenty of gears. Will have to work that one out later I suppose.

The thread is so fine I could just put a slight taper on, and push the bezel over the plastic with some sealant on it but I'd like to make a proper job of it really. I will have a look at my thread gauge and see if 36 tpi seems a better match than 0.7mm

I have just bought a 5L can of 32 hydraulic oil so should be OK for a while there.

Cold & damp in the UK at the moment - I don't need to worry about the oil being too thin !

Dave.

The pitch for .7m is .0278" and for 36TPI .0276", a difference of .0.78%. Cut which ever you have the change gears for.

Thanks Peter.

Dave,

I am entering this conversation without reading it all so just three points:-

1) The yellow down the middle of the bed depicted an unhardened bed. A hardened bed was painted red.

2) A wide gauge saddle will not work on your early bed. The leadscrew claspnut will not line-up.

3) The Brass tube on the drip-feed is a push fit, straight sided arrangement. You need a good BSF bolt (1/4 BSF I think) that will screw in the length of the thread so as to have a fair chance of not stripping it. Set up a lever arrangement to the back side of the oil well and pull straight up; it gives way very suddenly - frightening!

As to your cracked white back piece. Once you have it out, assuming it has not been bodge-glued in before, apply some Araldite or similar to the cleaned-up outside of the crack and that will do the job. I just run a bit of oil via the tap at start of session and that works fine. The sightglass was never meant to be filled, so no need for an oil-tight fit.

Dennis

Many thanks Dennis.

1- Very interesting to know the history. My bright yellow had been sloppily painted on top by the guy who was selling it. I wire brushed it all down as it looked terrible, there was traces of cream / light straw paint underneath the several layers that were there though. Today I painted the inside of the bed red, so that was a nice easy way to harden my bed without even realising

2 - I found that out the hard way and have modified the wide saddle - it now lines up and works well.

3 - I gave up on removing the tube - I was getting very near to thread stripping time with the amount of force I was applying and decided to leave it be before something broke and ended up giving me an even bigger headache. The plastic thimble was loose and a section of the threaded edge had cracked and a chunk was missing, so I have pulled out the plastic remnants and will make a new one from some white nylon, and slot the back so it goes in over the tube.

Thanks - Dave.

Have a look at this YouTube video on the Headstock oiler

https://www.youtube.com/watch?v=F9KU-liSGNk

Thanks for the link. I think I now understand why the Mk 2 Super Seven is thought by some to be inferior in this area.