Gallery, Projects and General > How to's
Asian 4x6 Band Saw V belt sizing
superc:
I have a decades old ShopForce brand 4x6 bandsaw. After several decades of happy use it began giving me problems such as the blade not cutting, etc., then the belt finally reached the end of it's stretch and came apart.
I wish to share my findings. First, it does NOT use a 1/2" belt. Use of a 1/2 inch wide replacement belt produces wildly high excessive blade speeds. Instead the saw pulley uses a 10mmx8MM or 3/8" belt. This size of Metric belt is called an SPZ class belt. Your original belt may, or may not, have a 3 digit number on it. Mine had a 559. That is about 22". 559 560 and 562 are all available SPZ belt sizes. Since the pulley arrangement has a lot of play in the adjustment range any of those should work in your machine assuming you too have one of the older metric belt arrangements. I suspect the American 3/8 x 22" size belt would probably also work in my machine.
Be dubious when you read someone else just threw in a 1/2" belt of some kind or another and everything has been just fine since then. Tell them to check their blade speed. :)
tom osselton:
If its turning faster wouldn't that be the proper speed as opposed to a worn belt slipping?
Manxmodder:
Irrespective of how much further out the 1/2" belt sits on the pulleys I think the ratio between driver and driven remains the same so the blade speed would still be as intended.
Or am I missing something here?.....OZ.
philf:
--- Quote from: Manxmodder on April 08, 2014, 11:28:04 AM ---Irrespective of how much further out the 1/2" belt sits on the pulleys I think the ratio between driver and driven remains the same so the blade speed would still be as intended.
Or am I missing something here?.....OZ.
--- End quote ---
Hi OZ,
I'm being a bit pedantic by saying that you are missing something but the difference probably doesn't matter too much.
If you section a vee belt there are tension fibres set below the top (wide) surface of the belt. This usually corresponds with a position inside the vee groove and sets the effective (or pitch) diameter of the pulley. If you use a larger section belt then this will move the pitch line out of the groove and will increase the effective diameter.
E.g. If you have 2" and 4" pulleys (ratio 1:2 or 50%) and you fit a bigger belt you may increase the effective diameter by 0.25" to 2.25" and 4.25" (the ratio then becomes 53%). Not a huge difference but a difference nonetheless.
Cheers.
Phil.
Manxmodder:
superc,is your saw the same shopforce model as this one in the photos I've linked below?
The blade speeds are printed on the motor and it would be easy to check your actual blade speed against the specified speeds by putting a temporary paint or chalk mark on the blade and counting how many times it goes past one of the rollers in one minute.
The number of revolutions you observe in one minute multiplied by your blade length in feet will give you a fairly accurate figure for your actual feet per minute to compare with the blade speed and see if it is running within the speeds specified by the manufacturer.....OZ.
http://auction.ridofstuff.com/details.cfm?ID=1326490#photos
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