Myford ML7 mainshaft

[Kevan ShawParticipant @kevanshaw32462]

Hi,

my ML7 has developed a problem. There is slipping between the 3 way pulley and the gear it is supposed to be fixed to. When I see pictures of this part there is often a grub screw visible in the valley of the middle pulley however there is not one on mine.

is this a regular problem and what is best solution? I think the pulley assembly is retained on the shaft by a press fitted collar how can I get that off without damage given I don’t have a press? If it is a hammer job how can I support the pulley assembly so it doesn’t get damaged. The pulleys look like aluminium so I am worried that they may get damaged if I am clobbering the shaft hard enough to budge a steel collar on a steel shaft .

thanks for help with this!

kevan

[Kevan ShawParticipant @kevanshaw32462]

Help with problem

[HopperParticipant @hopper]

Yes this is a common problem, thanks to Myford's cheapo construction. I had the same problem recently. No grub screw on my 1957 ML7 but I drilled and tapped and added one as part of the repair job. Could not believe there was no grub screw or key from the factory. Cheap cheap.

There is no press fit collar holding the pulley on the main spindle. It's just a tightish sliding fit. So pull the spindle out of the lathe, remove the gear and thrust bearings etc from the end. Then bang the end of the spindle on the work bench or a block of wood and the pulley unit should slide off, along with that steel spacer collar.

The thee step pulley was made as a press fit on the bronze gear/sleeve in the centre of it. They come loose with age and use. Mine was loose enough to turn the bronze gear by hand when holding the pulley. The bronze gear can be tapped out using a suitable drift with pulley set on the vice jaws or suitable packing bits of wood etc. I chose to heat the pulley with a propane torch and the gear dropped right out.

I drilled and tapped the pulley for suitable grub screw and drilled a matching divot in the bronze gear sleeve. Note there is an oil hole in the pulley that must line up with oil hole in the bronze sleeve. The pulley is some yucky gummy stuff to drill and tap. Mazak– aka zinc aluminium pot metal. Cheap cheap. Seemed to drill a bit oversize so try a slightly smaller drill first then finish last 5-10 thou with correct size drill. I used Trefolex for tapping goo.

I put it all together with red high-strength Loctite retaining compound. Roughed the surfaces with coarse emery to provide scratches for the Loctite to live in and grip. Then assembled it by tapping the bronze gear back into the pulley body. Again, aligning the oil hole in the process. Left the Loctite to set for 24 hours.

Gave it a test run turning 2" square bar down to 1.5" diameter, interrupted cut, depth of cut about 80 thou, assertive hand feed rate. All good.

Be sure to keep track of the bearing caps and shims so they all go back the same way while you have it apart. And watch out for that tiny round dowel pin that locates the thrust bearing etc. And thrust bearing and collars etc should all be on the spindle when you put it back in the lathe, otherwise you wont get them past the tumbler gears once the spindle is trapped in place by the bearing cap.

Have fun.

Edited By Hopper on 03/07/2020 09:14:05

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