# Belt Sizing Not Standard



## YotaBota (Mar 13, 2020)

Just thought I'd pass along my fun and games trying to find belts that fit my mill.
I knew when I bought my mill that the belts, B39 and B35, would need replacing. I ordered belts on line that were supposed to be a good brand, Uxcell, and the price was acceptable. The belts arrived and when I tried to install them they were to short, they were a substitute for the brand advertised and they had that raunchy petroleum chemical smell. I reached out to the vender and they refunded my cost and said keep the belts, to much cost and trouble for them to be returned. 
So I went to my local supply house and picked up new belts, Continental, but when I installed them they were to long. Does no one make a belt that is just right? (Goldilocks Syndrome) Even though the old and new belts are all marked the same size, they aren't.
With nothing to lose, one set is to long - one set is to short, I mixed the brands and viola, I now have a working set and a spare set of belts that fit perfectly. 
This has been somewhere between SNAFU and FUBAR but at least I was able to make it work.


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## YYCHM (Mar 13, 2020)

YotaBota said:


> With nothing to lose, one set is to long - one set is to short, I mixed the brands and viola, I now have a working set and a spare set of belts that fit perfectly.



What does "I mixed the brands " mean?

Craig


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## Hruul (Mar 13, 2020)

I assume these are v-belts your working with?  They are expensive, but I bought the linked belt from Lee Valley and I am running it on my lathe.  I like it and can make it any length within the length of a link.

https://www.leevalley.com/en-ca/shop/tools/workshop/tool-maintenance/30051-link-belt-for-power-tools


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## YotaBota (Mar 13, 2020)

I just used one belt from the long set with one belt from the short set. I used a Continental brand belt B39, and one of the belts I got from online B35. Going the other way, using the Continental B35 and the online B39 worked equally as well.


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## YotaBota (Mar 13, 2020)

Yes they are V belts. I looked at the link belts but $15 a foot for 7 feet made me pucker a bit so I stayed with the one piece belts. I use the link belts where I only need a couple of feet but 7 feet was to much. For the cost of two feet of link belt I now have two sets of new belts.


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## David_R8 (Mar 13, 2020)

YotaBota said:


> Just thought I'd pass along my fun and games trying to find belts that fit my mill.
> I knew when I bought my mill that the belts, B39 and B35, would need replacing. I ordered belts on line that were supposed to be a good brand, Uxcell, and the price was acceptable. The belts arrived and when I tried to install them they were to short, they were a substitute for the brand advertised and they had that raunchy petroleum chemical smell. I reached out to the vender and they refunded my cost and said keep the belts, to much cost and trouble for them to be returned.
> So I went to my local supply house and picked up new belts, Continental, but when I installed them they were to long. Does no one make a belt that is just right? (Goldilocks Syndrome) Even though the old and new belts are all marked the same size, they aren't.
> With nothing to lose, one set is to long - one set is to short, I mixed the brands and viola, I now have a working set and a spare set of belts that fit perfectly.
> This has been somewhere between SNAFU and FUBAR but at least I was able to make it work.


I'm also going to replace the belts on my mill. Similar sizes, B34 and B41. 
Who did you order from? (So I can avoid them  )


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## YYCHM (Mar 13, 2020)

Your mill needs a 7' long V belt?  Which belt is that?


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## David_R8 (Mar 13, 2020)

YYCHobbyMachinist said:


> Your mill needs a 7' long V belt?


I think what he meant was that the belts are 39" long and 35" long for a total of 74". That's over 6 ft of link belt. I'm in the same boat. at 75" total length.
Sold by the foot so 7 ft would be required. Basically $100


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## YYCHM (Mar 13, 2020)

https://www.princessauto.com/en/detail/a37k-kevlar-v-belt-1-2-x-39-in-/A-p8859860e

https://www.princessauto.com/en/detail/a33k-kevlar-v-belt-1-2-x-35-in-/A-p8859829e


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## YotaBota (Mar 13, 2020)

David - Amazon vendor Castle Road is who I got the "short" set from. It's not there fault as the belts had the correct length stamped on them, they're just made a bit short. I will stay with a local vendor from now on, at least that way it's easy to exchange and it was only a few dollars more for what I think are better belts.

YYC-  it's actually two belts that when added together (39+35) total 74 inches of belt and as the link belt is sold by the foot you need to buy 7 feet (84 inches) of belt. Which is okay to have a few spare links.

It's almost like some manufacturers the outside circumference and some use the inside circumference.


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## PeterT (Mar 13, 2020)

I went through the same issue on my lathe belt. Couple trips to Napa & other belt sellers. I assumed the markings on the original were enough to go by. but the replacement didn't fit well. I didn't know if the original was distorted or made to a different spec or the new one was off.  In the end I almost think best to bring the old one in & physically match it to whats on the shelf. Even that might not be 100% bulletproof (relying on circumference) because even my V section seemed a smidgen different, which will make fit-up to sheaves different. Fortunately I have a bit more latitude on slack tension so it had to be reasonably close but not bang on.


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## Dabbler (Mar 13, 2020)

Belts are supposed to be measured around a standard radius at each end.  The problem is the SAE radius (around 2.5 inches) is vastly different from the ISO radius (it eyeballs at around 50mm)...  

So I've run across this before as well:  Gates used to have a belt calculator for their V belts that finally worked for me.  In old time garages they had a belt measuring tool with each half circle on the ends and a scale in the center to get you the right belt.  Ah, the good old days!


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