Myford ML7 headstock belt length

Quick question - looking to replace the drive belt on a ML7 that runs from the countershaft to the headstock spindle. The one that's on it (although in horrible condition) measures 24.5 " around the outside, but I see on the Myford website that they sell a 23 inch belt for this application, but don't state if this is an internal, external or somewhere between the two size.

Having done a bit of measuring around the pulleys with some electrical flex, I don't see how 23 inches would possibly be long enough unless the adjusters are screwed right in and the 23 inches is measured around the internal surface of the belt. Even then I think it would be tight.

Has anyone replaced one of these recently, and if so, what belt size did you use? Probably going to buy from Simply Bearings as they are considerably cheaper than Myford.

Thanks,

Rob

Hi Rob.

My ML7 manual quotes the belt length as 23 inches, inside length.

Best regards.

Alan.

Thanks Alan, it just seems that would be extremely tight, but I'll go and measure again.

Rob

Before I bought a super 7 I had a standard ML7 approx ten years ago and Myford supplied me with a belt that was too tight, I had to use a belt .5 larger than I was supplied, purchased from Simply Bearings at a fraction of the cost!

I would be interested to hear what you go for as I have another ML7 I picked up recently in desperate need of new belts.

I replaced mine a couple of years ago and it was definitely a 23 inch. However, I replaced it with a cogged type Vee belt (AX23 from Simply Bearings) as I have found them to be a lot smoother running than the standard Vee belts.

John

On John's advice , I've just ordered an AX23 from Simply Bearings. I'll let you know what happens.

Thanks for the help.

Rob

I have a 23" AX23 cogged V belt on mine. But I remember when I fitted it, I had to put the locknuts on the tension adjusters on the "uphill" side of the swinging H frame so the mushroom headed adjusters could be screwed all the way in to accommodate the belt.

This puts the belt tension onto the thread in the soft Mazak metal H frame, which tends to distort over the years and eventually stripped one thread.

If I were doing it again, I would go with a longer belt -- maybe a 24" -- and put the locknuts on the "downhill" side of the H frame so the belt tension load is taken by the steel locknuts up against the body of the frame.But that would make the nuts a bit awkward to access with a spanner, so a bent spanner may need to be made up.

Vee belts are usually specified on inside length, so a 23 would probably measure 24.5 externally.

Howard

Happy to report the AX23 fits nicely. Locknuts are on the "uphill" side, but I think that's the normal position. I see what Hopper means though, but I've not gone for guitar string tightness so hopefully all will be well. Also, a longer belt may cause the pulley to foul the guard.

Roughly measuring around the outside with a piece of string (didn't think to do it before I fitted it) give just over 25 inches, which surprises me, but then again, most things do these days.

Thanks for all the advice.

Rob