V Belt Size

[John ShepherdParticipant @johnshepherd38883]

I want to replace the v belt on my drill press. The old one is showing signs of wear and I suspect it has stretched because the tension adjustment is towards one end.

The old belt is marked M37. It appears that the M section has been replaced with Z so I ordered a Z37 belt only to find it is too long. (X section is OK)

Having checked the internet, I am now totally confused on how to determine which belt I need. Calculators I have found show measuring the two pulleys and the centre distance but don't say what part of the pulley to measure.

Specifications talk about Li (inside diameter). Some say measure in metric, take 22mm from the outside diameter and then convert to inches which I think gives the datum diameter and others say just measure the outside diameter.

As I can't use my original belt as a standard, can any one please tell me how to measure the belt length and convert this into the right belt number

Thanks

[John ShepherdParticipant @johnshepherd38883]

[Ian ParkinParticipant @ianparkin39383]

I have much the same problem many times

even 2 belts (new) having same numbers on differing manufacturers though will be so different in length

If you need to buy online its just looking at your too long belt and deciding how much shorter it needs to be and ordering the shorter length

so your z37 is supposedly 37 inches so if it looks like an inch too long then z36

I do have a local supplier so I cut an old belt to the correct length and take it in they have a jig on the wall to measure it

Ian

[MuzzerParticipant @muzzer]

I've used these boys to reasonable effect:

**LINK**

Note that they have one of those belt length calculators to help estimate the right belt size.

Murray

[BowberParticipant @bowber]

Try bearing boys as well. I think the M series must be measured on the pitch if you've found a Z too long. From buying lots of belts I would recommend you just get the next size down unless it was a lot longer. I also tend to buy 1 up and 1 down from the size needed as the postage is usually more than the belt.

Steve

[John ShepherdParticipant @johnshepherd38883]

Thanks everybody.

I took the practical advice and sacrificed the new belt that was too big and confirmed that I needed a belt just 1 inch smaller. So I need a z 36 instead of a z 37. The theory still doesn't add up though. (BTW I meant circumference, not diameter in my original post). Pleased I am not alone in experiencing problems with this and will try to make sense of it for the future.

Regards

John

[Ian PParticipant @ianp]

Posted by Ian Parkin on 27/05/2015 09:35:37:

I have much the same problem many times

even 2 belts (new) having same numbers on differing manufacturers though will be so different in length

If you need to buy online its just looking at your too long belt and deciding how much shorter it needs to be and ordering the shorter length

so your z37 is supposedly 37 inches so if it looks like an inch too long then z36

I do have a local supplier so I cut an old belt to the correct length and take it in they have a jig on the wall to measure it

Ian

If you have cut an old belt to the correct new length why do you need to take it with you to the supplier? surely all you have to do is measure how long the piece is and take the measurement with you.

Ian P

[John ShepherdParticipant @johnshepherd38883]

Ian Philips

The problem is that it appears that belts are measured in three different ways, inside circumference, datum circumference or outside circumference. For example in my case, I had two belts that were marked as size 37 but they were different sizes so I presume each is being measured to a different standard.

Ian Parkin is lucky in that he has a local supplier and his approach is a totally practical and sensible one.

[Ian ParkinParticipant @ianparkin39383]

Absolutely John Shepherd

if only belts were all made equal

I do have large stocks of belts and usually ordering online as they so much cheaper order ones around the size I think I need

problem gets worse when you need matched sets of belts….they very expensive

[Nicholas FarrParticipant @nicholasfarr14254]

Hi John and Ian, the info below may be helpful.

Regards Nick.

[Ian ParkinParticipant @ianparkin39383]

Nick

Thats all well and good

but if you order a belt online using the size you have determined it may not fit ,particular on a machine with limited adjustment

Different manufacturers have different ideas on what makes a say A36 belt

[Ian PParticipant @ianp]

Posted by Ian Parkin on 28/05/2015 19:01:25:

Nick

Thats all well and good

but if you order a belt online using the size you have determined it may not fit ,particular on a machine with limited adjustment

Different manufacturers have different ideas on what makes a say A36 belt

Ian

Do you mean that different manufacturers measure and state the length be different methods? Mentioned in this thread have been references to inner, outer, and centre lengths (of the belt section). Each would obviously all give different results.

I only ever seen belt lengths specified by the pitch (which might not be dead centre) so surely if a manufacturer says a belt is 36" and it measures differently then surely that is a product quality problem?

The real difficulty here is when does not know the pitch diameters of the pulley or even the belt section type. The best option is then to use old belts and test for best/correct fit in the groove followed by the belt cutting and measuring technique mentioned earlier. In practice one could probably get away with using a length of electric cable that drops half way down the grooves and measuring that.

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian Phillips on 28/05/2015 20:37:53:

… I only ever seen belt lengths specified by the pitch (which might not be dead centre) so surely if a manufacturer says a belt is 36" and it measures differently then surely that is a product quality problem?

The real difficulty here is when does not know the pitch diameters of the pulley or even the belt section type.

.

In principle, it is easy to locate the pitch line in the belt; especially if you have an old one to cut up … It is [or a least, it should be] where the reinforcing cords are positioned.

A look at the cross-sections in any of the reputable manufacturers' catalogues will show that this is quite 'high' in the profile.

MichaelG.

.

P.S.  … There is a useful diagram on this page.

Edited By Michael Gilligan on 28/05/2015 23:22:23

[Ian ParkinParticipant @ianparkin39383]

Posted by Ian Phillips on 28/05/2015 20:37:53:

"Do you mean that different manufacturers measure and state the length be different methods? Mentioned in this thread have been references to inner, outer, and centre lengths (of the belt section). Each would obviously all give different results."

All I know that the times I have looked at a machines belts seen a number either imperial or metric sizing and have got a new belt same number on 50% of the time it hasnt fitted or is longer or shorter by more than I would expect

So I always take an old belt or a cut one the right length to be sure of an adequate fit

My local supplier a bearing and power transmission specialist always measure a belt rather than relying on the numbers

Maybe its a quality issue at the belt factory or a differing set of standards

I do buy quality european brands for my day job

 

Edited By Ian Parkin on 29/05/2015 16:06:08

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