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Replacing Spindle Drive Belt

Slater

Aluminum
Joined
Oct 3, 2007
Location
Oregon
We broke our spindle drive belt last week and ordered up a new belt. How tight should the belt be? We first put it on hand tight (pushing the spindle motor back to get it tight) and you could see the belt whip a little when speeding up and slowing down. Also it would want to run up to the top of the pulley and make a louder whining noise after running for a few seconds. We let it run for about 3 days like this to see if it would get better, no luck. So we took it apart again and made the belt tight, put a bar between the motor and tool release block to make sure there was not any slack in the belt. Now it runs good at low rpms but above 5000 it makes a loud high pitch whine. Also the belt it rubbing on the bottom of the pulley. What it the correct tightness for the belt? or what are we doing wrong.

2008 VF-2 with a 10,000 rpm spindle with about 4000 in cut hours on it.

Thanks.
 
Sorry, but I'm going to give you the best answer. Call your HFO or Haas directly.

If your HFO is anything like mine they will give you clear specific instructions on just about anything. If it's something I can do myself this service is invaluable...if I'm too busy or the job is beyond me, I ask them to come in.

This is why I have several on my floor and will most likely have more in the future..

Why take a chance on what someone may or may not know...I understand in a pinch you have to do what yo have to do to get the job done...

Mine have no tension adjustments...otherwise I would have added in another .02.
 
We did call Haas before we put it on the first time. They said it's kind of a feel thing tight but not too tight. He said some of the techs have a tension tool to dial it in. The spindle motor mounting holes are slotted for adjustment so you can get the belt off and a new one put back on. I will try my HFO, I called Haas direct the first time.
 
Got it figured out now, my HFO walked me through how to adjust it. Just need to talk to someone that's done it a bunch.

Thanks for the help.
 
I just replaced one last week. It's pretty easy, an hour or less. The only thing you really have to watch out for is the tool release button when you pull the spindle sheet metal off. I may have to pull the sheet metal again because I think I have the belt a little too tight. It seems to whine a little more than usual. I guess I just threw it on and put it back together(Rush job on the table). So what was the exact procedure to determine the correct tightness?
 
Basically these belts are designed not to stretch. If they had much stretch they would change the relationship to the cogs themselves.

These types of belts should be installed by taking out the slack then just a smidgen more. They should not be tight as they will distort and sometimes runs off center or shift up or down. If run too tight for long the belt will become warped.

In an ideal world, you would use a force gauge to push on one of the open areas and measure the deflection. I.E. (just for example) a five pound push at the center will cause a 1/2" deflection. Few people, probably even service companies, have the required force gauge. Most will guestimate while pushing with their finger.

Unless you can see deviation in the belt as you turn the spindle back and forth by hand, they will be fine.

Check again in a few months, but the belt should last a long time.

In the end, just don't over tighten. That is much worse than under tightening.

Mike
 
Could we expand on the tension a bit more? My TM1 makes a loud whine at a frequency that would correspond to the teeth on the belt. It does appear to be tight. I also worry about the spindle and motor bearings on a tight belt.
 
Old thread, but I had to do mine on my VF2 today and thought i'd share what the HFO told me. Added bonus that if I have to do it again, I can simply find my post with the data I need.

If you have a gates sonic tension meter like I do (the preferred way of setting tension on a belt), here are the numbers.

Width - 18mm
Span - 234mm
Tension - 33-37lb
 
Why did you have to replace it and how much time was on the belt? I made a plate to cover up the front opening under the cover and it is now quieter to stand in front of.
 
Why did you have to replace it and how much time was on the belt? I made a plate to cover up the front opening under the cover and it is now quieter to stand in front of.

I couldn't tell you how old the belt was since I bought the machine second (or third) hand. I do know that somebody had been in the machine previously. Not sure if it was to replace the belt or to work on the draw bar.

My belt snapped when I was taking a pretty heavy face cut. Their initial tension settings seemed loose after I fired it up. I re-tensioned to 35lbs after 2 cycles and it sounded a lot better.
 








 
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