Did they change how V-belts are measured?

[bulgie]

I'm replacing the belts on my '80s Enco 10x24 (Taiwanese). They're clearly marked B-45 and B-40, but the replacement belts I see available are larger than mine. My B-45 for example measures just about 46" on the outside circumference, where the ones I see for sale called B-45 all say they're 48" O.C.

I'm guessing that 48" belt must be 45" on the inside circumference. That's difficult to measure directly, but I calculate the I.C. as 45.2", based on O.C.=48" and my belt's height of about .440", so that checks out for a first order approximation.

So, maybe my B-45 really is 45" on the pitch diameter, is that a thing? Somewhere in between the inside and outside circumference? Or maybe it used to measure 45" on the O.C. when new, then it stretched in use?

Is this just an '80s Taiwan thing, measuring a different way than we do in USA?

And if they changed the way the circumference is measured, what else did they change? McMaster shows a B-45 as being 13/32" (.406") tall, where mine is definitely over .430", more like .436". Again, hard to measure precisely, being rubber, and worn. I can measure the height and width of the belt cross-section easily enough, but do I need to worry about the included angle of the vee also?

I'm not too worried, I'll just order the closest thing I see to the size of my existing belts. They put the lathe about halfway through its available belt adjustment range, with a fair bit of leeway in both directions, so I'm sure I'll be OK. Just thought I'd ask the large brains here, because I'm curious.

Thanks!
Mark

[Bill Shields]

USA standard of how belts are measured has not changed.

V belts generally do not stretch.

A belt that is wider than intended can appear to be 'short'

How Taiwan interpreted these numbers is another kettle of fish

[Steggy]

I'm replacing the belts on my '80s Enco 10x24 (Taiwanese). They're clearly marked B-45 and B-40, but the replacement belts I see available are larger than mine. My B-45 for example measures just about 46" on the outside circumference, where the ones I see for sale called B-45 all say they're 48" O.C...

Asian V-belt standards are not like North American ones (scroll down a little to read about it).

[bulgie]

Thanks Bill Shields and BigDumbDinosaur. I have what I think are the right Gates belts coming from O'Reilly. I just ignored the part number starting with "B" since that's not useful here, and just went with actual measurements. What a concept!

Happy New Year
Mark

[liveaboard]

If you take the old one(s) to a belt/ bearing shop they can measure with a special belt measuring thingy and match it up.

[Bill Shields]

You do realize that many belts are A B or C cross section of the same length. So there are A45 belts and B45 belts that are the same length but will not fit the same application.

This cross section is determined by the width of the pulley groove.

Get the cross section wrong and the belt can appear to be the incorrect length..or spill out of the pulley groove and wear prematurely.

[backgear66]

V-belts are measured from the flat side ( OD ). Make a mark and carefully measure the circumstance around the outside until you get back to your mark. Of course if you try to put. 30B belt in place of a 30A belt it will be too short because it rides too high in the pulleys.

[LouStule]

I've got a bunch of 3L's and 4L's. IE. 4L360, 3L380, etc. It seems like every manufacturer has their own way of measuring the exact same thing! I still don't know what the numbers actually mean though.

[Bill Shields]

No ..manufacturers of belts in the USA are built to standards....or what became standards. All that you have mentioned are straight out of a power transmission catalog.

A 4L360 from one company will be the same from another.

A B C 4L 3L are all industry standard designations and are designed specifically for different pulley geometries.

True...some were originally from Germany...but have been adopted as standards since before I was born.

Have you looked up the poly v?