H80 bandsaw: bronze dust in gearbox

Opened the worm gearbox in my H80 to replace the OEM oil with trusted quality oil. Found at the bottom a not insignificant of bronze dust mixed with the oil.

Bandsaw has only seen light use: is this the gears wearing in as they do or a sign that something is dodgy?

Hello Rainbows,

Not a good sign I'm afraid. I had the same trouble on a similar far Eastern bandsaw, traced to poor assembly of the shaft with the worm on it, the bearing nearest the worm had failed. A second problem was with poor alignment of the bronze gear wheel with the worm being offset to the side so that wear was taking place with the worm running off axis.

I covered my repair in an article in MEW 247 if you have a copy, or can look it up in the digital archive

Regards

Brian

Hi,

Bronze dust would be common in a basic worm drive gearbox especially one that had been assembled but never "run in". I would drain it, wash the dust out and re-assemble with good quality worm drive oil.

I worked for a company where we made worn drive gearboxes for aerospace use and the worm and wheel were lapped in in a jig. When they were assembled and run on the test rig for a couple of days, They were then stripped and if any bronze dust was found, then the whole procedure was repeated (many times!)

The inspector's criteria was that his white glove had to be absolutely clean when he rubbed around in the gearbox to allow the "run in" certificate to be issued.

It must have cost a fortune!

Never thought to check that on my bandsaw. Think it might be a bit late now? [How many years ago ?,dont even ask !!! ]

I hate reading things like this !!!

Don't panic! I opened my gearbox a few months after purchase because the rubber gasket started to weep oil. Inside I found obvious signs of bronze dust but no obvious wear on the worm. I changed the oil and bodged the gasket.

Because it was a bodge, the gasket leaked again after about a year. Re-opening the gearbox I again found traces of bronze dust but much less than the first time. Again no sign of damage to the worm. I'm pretty sure the dust was due just to roughly made and assembled gears bedding in.

My bandsaw is the crudest of all my Chinese tools by far. It wasn't lovingly fettled by master tool-makers to meet precision specifications! Nonetheless it works a treat, far better than appearances would suggest possible.

One problem with inexpensive equipment is that what you get is inconsistent even between tools from the same batch. You can't assume because my saw is OK that yours must be too. I'd check the gearbox after some months cutting to make sure it doesn't need remedial work. With luck you'll find nothing wrong.

Dave

Be cautious about the make-up of oil used to fill a gearbox containing yellow (brass, bronze) or red metal parts.

Additives in EP or Extreme Pressure gear oils (sulfur, chlorine, potassium-borate ...) can cause rapid wear.

Examine the product data sheet looking for results of the Copper Strip Corrosion Test (ASTM D130) or whatever the equivalent test is in your part of the world.

When I opened the gearbox of mine it was full of 'liquid gold'.

The gear is badly worn, but I did my best to improve alignment and it has lasted years now and the oil is clear of dust.

The situation is helped as the gear only turns in one direction

At some point a new gear will be needed, though.

Neil

Probably the oil should be changed early in the life of the saw, after which it should do a good few hours without any trouble, maybe a check / change every couple of years. Mine has been going about twenty years on the original oil, and at this stage I'm not looking inside.

Ian S C

The oil? came out gold coloured suggesting I should have changed it earlier. As there is no filler orifice they must fill it with the saw on its side as it was virtually full. If I am able to repair it then an orifice will be provided.

I have e-mailed Chester on the off chance they will have one somewhere otherwise it is going to give me a headache finding one. It is probably beyond my ability to make one. I will have to make a puller to remove it and although it will come off fitting the new one will require me to remove the worm first. Happy days.

Mine is a Taiwanese made item, but i guess the same as the rest. It too had a small amount of dusty gold in the bottom. No signs of any problems & runs great. I would not worry too much. Try it again in a year & see if it is less. A good gear oil is the way to go.

Steve.

Mine is a Taiwanese made item, but i guess the same as the rest. It too had a small amount of dusty gold in the bottom. No signs of any problems & runs great. I would not worry too much. Try it again in a year & see if it is less. A good gear oil is the way to go.

Steve.

Eddy -

Thank you for that tip about corrosion..

Although I don't think it contains many bronze bushes (the main bearings are all ball or roller types) I used a mixture of automotive gear-oil and some sort of regular lubricating oil in my Harrison lathe headstock, thinking that being more viscous it will stay in there longer!

I ought therefore take the lid off and take a close look.

.... and while at it, have a look at the gearbox on my 'Alpine'-badged bandsaw's gear-box. Though from a previous owner I can trust, I don't know when that was last done. Not by me, in the 5 or so years of my ownership, so due. Luckily I don't give it all that much work to do.

David,

..as you already have the worm, replicating the wheel shouldn't be to difficult - it could (is likely to?) be an off-the-shelf-item in any case..

I must go to work, hopefully this post will help prompt a response to help you.

Oh, the optimism, finding an off the shelf item. I faced the same problem a year ago with my bandsaw. I searched high and low and in the end made a new worm and worm wheel as I concluded the original items were rough and poorly fitted.

The yucky mess once the glittery oil had been mopped out:

The worm wheel was so worn that it wouldn't drive the blade. Fortunately my M300, with the right changegear, can cut worms of specified MODs, so I made a worm and a hob. I made a new wormwheel by the free hobbing method, having gashed the blank first to ensure it started hobbing correctly first time:

And while the gearbox was apart, I changed all the bearings just for good measure. A lot of work, and not what I wanted at the time, but I failed to find an off the shelf spare.

As these bandsaws are quite generic, may I suggest Machine Mart and their Clarke brand as a source of spares? The other option is Sealey.

I regard worm drives as high wear items and one part is sacrificial

So you reduce the wear with good oil

It's just the nature of the component IMO, we have a small simple arrangement that achieves the same effect as the backgear does on a lathe

The wheel is probably just a normal bronze or even brass. Many years ago we had a wheel go in a servo driven rotary table. The shop made a new wheel from a plain bronze, it lasted about a week, then they asked what it should be made of, aluminium bronze, was still going years later.

Chester responded today with the good news. Part No BAN-SAW-H80-S-052 H80 Brass gear. So I will get one and spend my energy replacing it. Thanks for all the advice.

I looked out the Instruction Manual and leaflet for my vintage Warco machine and was interested to see that the gear is steel and the worm wheel bronze.

The Manual specifies SAE -30 oil "to lubricate the components" and says that "the drive gears will not require a lubricant change more often than once a year, unless a leak or overhot [sic] occurs." I assume from this that the Taiwanese makers did not think that an EP oil was necessary.

The machine has served me well over decades of light use and I shall probably leave well alone.

I purchased a Clarke Metal Bandsaw earlier on this year. On assembly I noticed a tight spot accompanied by a "scraunching" sound when I turned the drive pulley. When I removed the gearbox cover I saw that there was a rough spot on the worm which I dressed out with a needle file. If left it would have destroyed the worm wheel in a short time. Worth checking for if you have not already done so.