Timing belt noise - motor to spindle

I've got a KX1 mill that I use with ear protection when it's running. It's driving the others in the house nuts when running for long cuts.

It has a timing belt (5m305-15) between motor and spindle - I'm wondering if that's where the noise is coming from.

Anybody have any thoughts on replacing that timing belt with a small "gates" V belt? I don't keep track of spindle rotation for tapping, etc, so I don't really need a timing belt there.

Thanks for any thoughts on how to quiet this machine.

John. (my blog, for those interested: **LINK** 

Hi John

Has it always been so or is it a recent change?

Recently a mate told me of a noisy drive on a machine tool that was tracked down to trapped air.

At high speeds timing belts can trap air under the teeth. this can cause noise when it is expelled, the fix was to mill a tiny groove in the valleys between the teeth.

Does it sound like this one?

**LINK**

You can hear belt noise.

If the timing belt is not needed for the CNC function could you change it to a Multi V Belt

**LINK**

The pulleys are not hard to make on the lathe. You would need to make sure the new drive meets the power requirements for your machine were met. They can carry a lot of power, so you should be able to do it. They do not buzz.

Regards
John

Hi JohnM - That's basically my mill in the first video, but with different control stuff in it. That one is basically idling (it hunts at lower speeds - you can hear that) When I go into the 4,000 to 7,000 rpm range, it certainly is more noisy than the stepper motors!

Interesting about the tiny grooves in the valleys comment. It means that my thoughts about the timing belt being a cause of the noise is maybe not far off.

My Emco Compact-8 lathe uses a tiny V belt, that I've never broken, that seems to work well. They do delaminate every decade or so - I think I'll dig out the old catalogues this coming weekend. More machine repair, less actual model building time again - sigh. (oh well!)

Thanks - John.

John,

If the belt is too tight it will make a devil of a noise, (re cam belts on cars) it should be tightened so that if the belt is held on its edge in the middle of a longest run, you should be able to twist it 90 degrees easily i.e. the tip of finger and thumb should just start to go white.

Hope this helps

Try prising the side shields off the pulleys.

Do one on one pulley and the opposite on the other, this will ensure it won't run off but allow any trapped air to exit from the missing side.

.

John,

Are you absolutely sure that it's the correct belt ... Pitch AND Profile ?

MichaelG.

Michael,

Wrong John but seen a couple of KX1 in my time.

Chinese marking for HTD 5mm pitch 305 long 15mm wide.

JohnS - will try removing the flanges

MichaelG - the belt is the one that came with the machine - certainly it could be wrong, though!

Lofty - I *think* I left the belt fairly loose; it is a bit of a pain to take the cover off and check.

I'll put a sound level meter nearby and see what happens - will try removing flanges, and loosening the belt and see what happens.

Another research project! John.

.

Thanks John,

I half-remembered this development by Gates, which is why I wondered.

MichaelG.

In the car engines who has timing belt, there is the shields in both sides of the pulley at the crankshaft, also the shields is not tight against timing belt to trap the air into the pulley.. with other word the shields is some milimetre wide than the wide of timing belt. No shields in other pulleys such as in cam shaft, waterpump etc..

In case your shields is in same wide as timing belt, add shim between pulley and shield to escape air out of pulley if the other pulleys is without shield.

Long story short - the spindle bearings need a good looking at or replacement.

Belt was as free as could be. Motor as quiet as can be when running through all speed ranges.

They are either adjusted so the spindle is free to turn, or if adjusted so that there is no play in the spindle, are "gritty" feeling.

I've got 3 larger lathes with adjustable spindle preloads, and they are all adjusted ok, so I'm not really a newbie at adjusting the preload on machine spindles.

Anybody ever taken the spindle out and replaced the bearings on a KX1?

I'll keep playing with this little mill. I think that if it needs much work, it'll be going on eBay as-is, which will be too bad, as I like the little thing.

Oh well - JohnS.

Another JohnS.

Ok. After walking away from the workshop for 24 hours, went back in, and spent a good couple of hours measuring, measuring, adjusting, and measuring.

Results, down from 80dB to 70dB, but I have to leave the spindle a tiny bit slack. Oh well.

All the nitty gritty on my blog, for those interested: (http://cnc-for-model-engineers.blogspot.com, - this **LINK** )

Now, back to model building! (I hope)

Currently watching the last of the snow melt - JohnS.

John,

That's an interesting write-up on your blog ... very useful reference.

I admire your methodical approach to reducing the noise, but; I think what you have found is pretty clear evidence that the bearings are pitted, and I suspect you will need to replace them soon.

Out of interest: Do you have a drawing of the spindle assembly, that you can show us?

MichaelG.

Michael - No, no drawings. I'll have to think about how to take it apart, and put it together again.

And, you are right about the bearings needing replacement, sooner rather than later. I do have some engraving to do for a fellow club member - maybe after that, assuming the engraving goes ok.

I purchased this CNC mill to improve my model parts throughput - I think I'm spending more time on the CNC machine than it saves! (smile, but, I'd rather not have to take it apart, if you know what I mean)

JohnS.