Myford ML7 1956 ... Question on drive belt and Stalling when cutting

Hi

I am the new owner of an ML 7 standard lathe from 1955 to 1956

Got the lathe home yesterday and assembled it today. A few teathing problems but generally ok

Clutch wasnt engaging properly but that was solved through adjustment

The drive belt to the chuck is similar to a fenner zero downtome belt in appearance but black and it doesnt have the twist connectors

Ive tensioned this belt but it still can be stalled quite easily. Doesnt seem to ve contaminated with oil or anything

It means that only very small cuts can be taken of say 5 tho at a time

Is this normal for this size of lathe ... looks a pain to change the belt unless i use another jointed belt

Any thoughts would be appreciated

Monty

It's not normal, should be capable of much bigger depth of cut. Stalled means the motor slowed and then stopped. Is that what happens, or was the belt slipping instead?

Andrew

What's stalling? Does the motor keep turning but the countershaft stops, or is it that the spindle pulley keeps running but loses its drive to the spindle. If it's this last there is a drive dog in the bull wheel (the gear behind the chuck) which must be engaged. Has it slipped out of the drive position - perhaps to use the back gear.

You really need a copy of the user manual.

5 thou a time for the best you can do is definitely wrong.

Its the belt driving the chuck that slips

Its tensioned coreectly .... the motor keeps running fine

Amyone recommend the best belt to replace this with ?

1 With the belt de-coupled, does the spindle revolve freely when chuck spun by hand. If not, find out why before proceeding.

2 check for any obvious oil contamination and clean.

3 If you have, as I think, a link style belt, bear in mind the tension may often need to be much higher than for a normal A section V belt, and the cheaper the replica belt the higher the tension required, usually.

4 Replace dodgy belt with standard or segmented A section belt for little cost, or if you have to, get a genuine Fenner product replacement. You should then be good to go with 40 thou cuts (if you want to be brutal).

BTW a suitable basic 23 inch A section V belt should cost about a fiver plus delivery from any number of  bearing, drive, belt, motion  factors  on the net.

Edited By Martin of Wick on 06/03/2022 18:28:37

ill replace it with an endless belt and go from there i think

Thanks for responding good advice 👍

Cheers

Ian

The black link belts commonly available from a certain supplier are completely useless and you will never get them to work because the plastic is slippery. As Martin says, get a Fenner of the correct size, RS have them, and fit it quite tight, and note that it has a right and wrong way of going on. IIRC, the links are formed so one end is sort of an arrow head in shape and that should point in the direction in which the tension from the driving pulley is being applied. So the belt should be fitted so that the points on the lower part of the belt as you look at the h/s assembly point towards the countershaft.

The belt you need is an A 23/A620. On an ML7 it is easy to change ! The belt to the motor is A34.5 inside length. I would NOT recommend a link belt. Good luck. Noel.

Edited By noel shelley on 06/03/2022 18:27:40

Thanks John and Noel

Good to get support from the community

Regards

Ian

You have got the belt the right way round have you?

**LINK**

regards Martin

Hi Martin

ive cut the belt off and ordered a fenner endless replacement

it was the right way round just a cheap imitation of the fenner zero,down time belt

thanks for responding

I found that the standard V belt was heating up the spindle pulley, to the point that the bush inside would come loose. Apart from securing the bush better with loctite, I made a new set of pulleys for it that use a poly V belt, which does not heat the pulleys. As a bonus, I was able to squeeze in an extra step and widen the range of ratios slightly, because poly V will drive satisfactorily around a smaller diameter. Hemingway does a set for using Poly V on the Super 7, but not for the ML7.

John

@ Ian Montana,

I like that name. (Big country/State).

If it's not been mentioned, are the belt pulleys secure on their respective shafts, really secure.

Good luck.............

My 1957 ML7 will happily take 100 thou deep cuts with carbide insert tooling all day long, and more with a well honed HSS toolbit.

Sounds like the slippery plastic link belt is your problem. But while you are at it, check the condition of your pulleys. The V grooves can wear to a sort of round profile and let the belt slip. The smallest diameter V groove on the headstock spindle pulley wears the most for some reason. I had to replace mine as it slipped in the highest speed when taking heavy cuts.

Also, a common problem on the ML7 is the cheapo diecast headstock spindle pulley coming loose on the bronze bush/gear that is pressed into the middle of it. Cure is to pull it apart and reassemble with Loctite and maybe a grub screw.

And of course make sure the drive dog for the back gear is firmly in place on the bull gear and the allen head screw holding it is well tight.

The Myford Users Manual PDF is widely available for download on the net for free. Well worth getting. As is L H Sparey's book The Amateur's Lathe andalso  Ian Bradley's Myford Series 7 lathe manual. All still in print, cheap as chips and invaluable.

Edited By Hopper on 07/03/2022 09:21:22

Thanks Hopper - I'll check when I fit the new belt

Any idea where the PDF is located that you mention

Thanks

Ubiquitous. I found mine by googling Myford ML7 Users Manual.