Need Help In Selecting Proper Varispeed Belt For A 3hp Bridgeport Clone "millport"

[737mechanic]

I have a millport 3hp varispeed bridgeport clone mill and it has a vibration when running that I think is coming from the cogs on the varispeed belt. It will also develop a squeal when cranking up the speed but immediately goes away when belt dressing is sprayed on the belt. The belt that is on it is a gates 2322V364 belt. The manual that I have shows a G-830 as the belt but I can't find any reference to that number anywhere on the net. I found a part number for a varispeed belt for a 3 hp bridgeport that is 875vc3830.

After doing some research I found there are three common belt angles some are 22 degrees, some are 28 degree, and some are 30 degree. The 2322V364 belt that is on it is a 22 degree belt and the 875vc3830 which apparently 3hp bridgeports use is a 30 degree belt which leaves me wondering if that is what should be on it.

Does anyone have a 3hp variable speed mill and if so what part number does your mill call for. I am not having any luck finding an exact part number for my mill.

 

[derf]

Best bet is to check the angle of the pulleys.

 

[JimDawson]

I just changed out the belt on my 3hp Eagle. The number is 2430V354. Seems to be a 30° included angle
http://www.vbeltsupply.com/variable-speed-belts/2430v354-1.html

There is no guarantee that your belt is the same.

 

[737mechanic]

Thanks Jim for the info I think your number would be a better fit then what I currently have on it.

I got a 15 degree gauge block in there and it is 15 degrees without a doubt. So now the question is since it currently has a 1-7/16 wide by 37.5in. long 22 degree P/N 2322V364 belt on it now, will a 1-1/2in by 35.4in. long 30 degree belt work.

BTW I measured the RPM's with my portable tach and when the speed is cranked down to the lowest setting of 60 RPM on the machine dial it is actually running 100 RPM. When it is cranked up to 4250 RPM it is actually running 4800 RPM so something is either out of adjustment or maybe the belt that is on it is the wrong one for sure. Not sure how the variable speed adjustments or a wrong size belt would effect the speed.

 

[JimDawson]

Not sure how the variable speed adjustments or a wrong size belt would effect the speed.

It could be that the belt is running in a different centerline in the pulleys than expected because of the different angle. Thus the dials would be off. There is also an adjusting screw for fine tuning the speed, the screw sticking up between the motor and the spindle on top of the housing.

 

[derf]

Worn belts will make for more RPM, as will the incorrect belt. The speed dial can be adjusted to match the RPM's, however it will only match exactly at one particular setting, because the belt size/condition will throw off the ratio proportionately. Usually it's not anything to worry about. The most important thing is the contact area of the belt. Typically the edges break down first letting it drive deeper in the pulleys, and subsequently on the hub itself. Once a belt gets that far, it develops thin spots that create the vibrations and thumps. You'd be surprised how much smoother and quieter things get with a new correct belt.