As mentioned before, the ML7 was purchased new back in 1973 from Reeves when they were still in Acocks Green, Birmingham. They delivered it to Derby free of charge and I think the total cost including 3 and 4 jaw chucks, tailstock chuck, vertical slide, fixed steady, and tools was about £150!
The trusty ML7 (must polish that chuck!)
One very useful modification I made to the Myford was to replace the single phase motor with a three phase motor driven by a variable frequency inverter. This controls the speed of the motor from barely moving to several times normal speed. This makes speed adjustment so easy and saves having to adjust belts everytime you want to change the spindle speed.
I had a trip over to Arc Euro Trade yesterday with my brother to look at some lathes (He's decided he wants a small lathe for turning boiler fittings etc.) and we called in at Myford on the way back. I had decided it was time to fit a new cross-slide leadscrew and nut to the ML7 as the original was very worn. When I came to fit the new parts I thought it would be a good idea to try and make some sort of guard to protect the new leadscrew from swarf etc. The problem is that when you remove the topslide to fit a vertical slide etc. the hole in the cross-slide allows muck and swarf to drop onto the leadscrew underneath the hole. I had got used to plugging the hole with a plastic cap to prevent this, but, depending on the position of the vertical slide, it was not always possible to do this. I hit upon the idea of fitting a piece of plastic tube through the cross-slide leadscrew cavity in the saddle. This cavity has a 1/2" hole at each end so I cut a piece of thin plastic tube to fit between the holes. The only tube I could find was slightly too big so I cut out a sliver down the side to make it smaller in diameter.
The leadscrew now runs inside the tube protected from any swarf etc. I also want to try and make a similar cover to protect the main leadscrew but that will be more difficult due to the saddle movement.
I've made a start on the new stand for the ML7 so that it can be moved into the new workshop. The stand will be made from 50mm square by 2.5mm wall steel tubing welded together.
I had already cut up the tubing to get it out of the way (it came in 2.5 mtr lengths and I kept tripping over it!). The tube would just fit in the power hacksaw fortunately so I used that rather than cut it by hand. The ends came out pretty square so needed no further work before assembly.
The welder I've got is only a Clarke 90 amp MIG so is really too small for this job, a 150 amp would have been ideal. Anyway, I managed to tack it all together ok before completing the full welds.
The stand tack welded together
After checking that it was all nice and square (which it was fortunately!) I carried on and starting doing the full welds on the joints. The welder copes reasonably well with the butt joints on the outside but struggles with the internal corner joints. I had to crank up the wire feed to the max to get enough current to get any sort of penetration and the welds were pretty 'blobby'. Still, I think it will be plenty strong enough. The only joints that I am really going to struggle with are for the square feet that I added to the bottom of the legs. These are 3mm plate and penetration is very slight. Mind you, they are not structural and the stand only sits on them really. I could take the stand to the club and use their stick welder if all else fails.
Before I started on the stand I took my large Argon bottle (now empty) back to BOC with the intention of cancelling the rent on it as it is now very expensive and not economical for the amount of welding that I do. I found out that BOC now do a small 0.5litre bottle at a greatly reduced rental so I swapped the big bottle for one of those. It should last for an hour or so's welding time and will do most of the stand. I know that you can now get rent free gas bottles from places such as Hobbyweld but it was easier to get the small one from BOC. If I do get into welding a bit more them I will consider the rent free bottles. I must admit I would like to have a play with TIG. That would be great for fabrication work. Unfortunately, the welders are extremely expensive!
The stand is now completed and resplendent in a coat of the grey paint which helps to hide my less than perfect welding! The small argon bottle held out just long enough to complete all of the welds. The metal was then cleaned down with thinners, primed, and given a top coat of grey. I've noticed that the top coat takes much longer to dry if applied over the primer than when it is applied to bare metal. The small oil filled radiator was used to help it dry by applying a bit of gentle heat.
The drip tray is not the original Myford one which is quite flimsy but one I acquired some time ago when helping someone clear a workshop. It's a really solid job made from 1/8" steel bent up and welded at the corners.
Yesterday I dismantled the ML7 as much as possible so it could be moved from the upstairs workshop into it's new home. The bare bed and headstock casting are just manageable and I got it down the stairs and out into the workshop fairly easily. Before installing it on the new stand, I blew off all the debris with the air gun and gave it all a good clean. The only problem is that the studs on the raising blocks are too short to go through the tubing under the drip tray so I ordered some lengths of 5/16" BSF studding from a supplier on Ebay to make make some new longer ones.
I decided that during the rebuild I would give the bed some overdue maintenance and remedy the inevitable wear that occurs to the shears near the headstock where most of the work is carried out. I had noticed that when the saddle gibs were adjusted to suit the headstock end, the saddle tightened up as it was traversed towards the tailstock. This was to be expected as the lathe is now 40 years old!
I followed the proceedure outlined by Graham Howe on his excellent website. This entails measuring the width of the front shear and noting the difference at the headstock end and the tailstock end. This relies on the fact that the rear edge of the front shear is not used to guide the saddle and therefore is unworn, the wear occuring on the front edge of the front shear and the rear edge of the rear shear. Myfords do differ as which edges are used to guide the saddle so it pays to check first. I think some use the front and rear edges of the front shear.
Unless it is really worn, the actual wear is very hard to measure. Initially I used a digital caliper which only reads to 0.0005" and I could just detect a difference of that between both ends of the bed. I then remembered that I had a 25 to 50mm micrometer somewhere and then used that. With that the difference was about 0.01mm or 0.0004". I was expecting the wear to be a lot more than this and so was pleasantly surprised. I did discover that the very end of the shear nearest the headstock was unworn as the saddle very rarely went right to the end of the bed.
The next job was to very carefully stone the front edge of the shear to reduce the width at the wide points to that of the narrowest. Care must be taken to ensure that the edge of the shear is kept square to the top.
When the front edge is true, the proceedure is repeated with the rear edge of the back shear. The width is measured from the newly trued up front edge of the front shear to the rear edge of the back shear and the rear edge stoned to remove the high points. I had to resort to the digital calipers for this but the difference was too small to show on the scale. Instead, I locked the caliper to the narrowest measurement and then moved the caliper along the bed 'feeling' the difference in the width.
The saddle was then cleaned up, refitted, and the gib strip adjusted as necessary. The saddle was then slid up and down the bed and I was pleased to see that there was now very little difference in tightness between the ends of the bed.
I then paid attention to the plates that bolt underneath the saddle which stop the saddle lifting off the bed. I noticed that there was quite a lot of lift at the headstock end of the saddle but very little at the tailstock end. The plates have multilayer shims fitted between the plates and the saddle so that the clearance between the plates and the underneath of the shears can be adjusted. You can peel off a layer of the shim and so reduce it's thickness to reduce the clearance. However, it's very fiddly to do and you are liable to remove more than you want to! The layers are very well stuck together and the best way to separate them is with a very sharp modelling knife. I think each layer is something like 0.002" thick?
After much trial and error, I got the front of the saddle spot on but gave up at that point as it was getting late, so I've still got the back of the saddle to adjust next time.
Back to the saddle adjustment and I found that the shim at the headstock end of the rear plate had a small piece of brass swarf embedded in it. When I removed that and refitted the shim the fit was much better so I left it as it was.
The apron was then refitted along with the leadscrew. The saddle traversed up and down the full length of the bed very smoothly with little effort so I must have done something right! Again the leadscrew and half nuts show very little wear although I don't tend to do a lot of screwcutting or power feed work which probably explains it. I do tend to use the leadscrew handle though to feed the saddle by hand when turning as you can get a nice slow, controlled feed using it. The graduated dial on the leadscrew is also very useful when turning something to a set length.
Next I decided to look at the spindle and bearings. Some time ago I did try removing one of the layers of shim on the front spindle bearing but the spindle locked solid so I put it back! I was expecting a bit of wear but it was obviously not very much.
The spindle itself is still in perfect condition with no marks or scores on the bearing surfaces. The rear bearing shells are in very good condition with only very slight scoring on the end nearest the tumbler reverse. The front bearing shells look a bit worse for wear with a lot of scoring in the centre which I reckon has been caused by swarf getting into the oiler. I did find particles of swarf in the grooves in the bearing shells. The scoring is not deep fortunately so I think the shells are still serviceable. Both oilers will get a good clean before refitting!
Spindle - still in very good condition
Rear bearing shells still ok but front ones a bit scored
I tried refitting the front bearing cap with one less shim as before but the spindle still locked solid so there is still very little wear in the bearings. I decided to leave out the shim and blue and scrape the top shell until the spindle rotated freely again. This would also get rid of some of the scoring on the top shell and increase the bearing surface again. I've read several recommendations not to touch the lower shells as this could destroy the alignment of the spindle to the bed.
Scraping the bearing shell took some time as I took it very carefully. Eventually I got good contact over most of the bearing surface but the spindle was still very tight when the cap was bolted down. Rather than carry on scraping ( good name for a comedy film! ) I decided to fit some extra shims made from aluminium cooking foil which is very thin. I finished up with 3 layers of the aluminium foil before the spindle was free to rotate with just a little stiffness. I'll keep my eye on the bearings when I run the lathe next to make sure they don't get hot.
I reckon that the difference between the original shim and the foil ones is a little over 0.001"so I've removed just over 0.001" from the original thickness of the shims. Not a lot so the actual wear on the spindle and bearings is pretty negligible! That's interesting as I have never used the recommended oil for the spindle - usually it's whatever I've had to hand, often 20-50 motor oil.
I left the rear bearing shells well alone as I would guess that they will have worn even less that the front ones.
The lathe is now all back together and ready to go. All I've got to do now is move all the tools and accessories into the workshop which means loads of shelves and storage to be made!
All back together
Last year I purchased a precision level off Ebay so I checked the alignment of the lathe bed. It was near enough spot on in all directions (the workshop floor must be level!) but there was a very slight twist in the bed which was removed by adjusting one of the jacking screws on the riser blocks. At some time I'll turn up a test bar to check that the lathe turns parallel - something I've never bothered to do before!
I've now fitted two wooden shelves on the stand which will hold the chucks etc. for the Myford and the Denham plus other bulky things like vertical slides. Pieces of 10mm ply have been painted and screwed to the wall at the end of the lathe and behind it to hang things like faceplates, tools, drill chucks and chuck keys on. Pretty much the same as before in the old upstairs workshop.
As mentioned on the Eagle mill page I ordered some of the cogged belts to replace the two normal ones on the lathe. They arrived today and I've just fitted them. It's a bit of a pain as you have to remove the spindle and disassemble the countershaft to change the main spindle drive belt but it only took 1/2 hour, if that. The new belts have made a significant difference and the lathe now runs a lot smoother and quieter than before.
The main spindle belt has a direct replacement cogged belt but I couldn't see one for the motor to countershaft belt so I took a chance and ordered the nearest size. The original belt is a Z profile of 10mm wide and 6mm deep but the nearest cogged belt has a depth of 8mm. I guessed that the extra 2mm depth should still fit the pulleys and that proved to be the case. If anyone is interested, the replacement main spindle belt is an AX23 and the motor belt is an XPZ900 (Sounds like a motorbike!)
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