Replacing the bronze worm drive gear on a Greenlee 530/Porter-Cable 724 portable band saw (1 Viewer)

[alia176]

My trusty bandsaw from 1974 finally worn down the bronze worm drive gear and I need to replace it. In our current disposable culture, I know I can go down to HF and get a Bauer unit for not much money but I was really hoping to use this unit another 25 years I bought it second hand in the early '90s.

The actual worm gear is NLA but if I can remove it, then maybe I can find one from Boston Gear. Has anyone ever done this? If so, please let me know some tips. I was able to tear it down but wasn't able to separate the motor drive nut (black nut in the pic) from the motor shaft as the whole thing kept spinning and I didn't find a way to stop it from rotating. Jamming a screwdriver into the cooling fan didn't do it.

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Here's the worm gear that I need to replace:

 

[hotdiggitydamn]

If you can source the ID, OD, length, number of teeth, teeth profile, key type and size, etc you can probably buy one from McMaster Carr, etc. if not a machine shop could probably make one if your willing to pay.

 

[alia176]

If you can source the ID, OD, length, number of teeth, teeth profile, key type and size, etc you can probably buy one from McMaster Carr, etc. if not a machine shop could probably make one if your willing to pay.

Yeah, I am prepared to do any of that but I need to understand how to pull it out of the gearbox!

 

[hotdiggitydamn]

Yeah, I am prepared to do any of that but I need to understand how to pull it out of the gearbox!

Understood. If you spin the nut you pictured does it spin the wheel which turns the blade? If so can you jam the wheel or fab a jig that attaches to the wheel to hold the wheel?

 

[alia176]

Understood. If you spin the nut you pictured does it spin the wheel which turns the blade? If so can you jam the wheel or fab a jig that attaches to the wheel to hold the wheel?

i don't see an effective way to stop that rotor shaft from spinning. Jamming something into the fan didn't work. If there was a way to jam something into the stator, that'd be great but the housing is build super tight with only two holes for the brushes. Brushes are running against a smooth commutator which you shouldn't damage.

I tried using a cordless impact gun but let me fire up air comp and see if that does it.

 

[e9999]

I'm guessing that you can't remove the motor shaft from the housing at all without removing that big nut first. If your worm gear is shot already, can you block it forcefully somehow through the little window? Of course, there is the usual penetrating oil, heat, shock etc to try on the nut as well. But if you do try something like a air hammer, be careful you don't mushroom the shaft end. I'm thinking that penetrating oil, some heat with a big tinning soldering iron, and repeated exposure to a powerful impact gun may be your best bet. Try turning the nut both directions with the impact, counterintuitively perhaps it helps to tighten stuck nuts and bolts. Very long shot as there is very little room in-situ but if you are getting desperate maybe if you could put a small puller in there and there is something to hang on from, and give it a couple of tugs it may help free things up too. Maybe you could also wrap a rubber strap around the commutator through the brushes holes or jam some sort of rubber wedge against it?

 

[alia176]

Made really good progress this morning, managed to pull the whole shebang out of the housing. Now I'll go find a replacement worm gear.

Slowly but surely I'm inching my way!!

 

[e9999]

so you're not gonna tell us how you did it? Enquiring minds want to know!

 

[alia176]

I used a pneumatic rattle gun to zip off the nut. Then I was wondering how to unscrew that bronze nut holding the worm gear onto the jackshaft. Luckily I found a tiny set screw on the housing that I removed and pulled on the sprocket. What do ya know, the whole shebang started to slide out of the gearbox housing I'll clean all this in the solvent tank, take care of the ball bearing, then measure up and order the worm gear.

On a whim, I tried to remove the rotor from the stator and she's a no go. Something is still holding the rotor inside the motor housing and I need to figure that out. If not, I'll pick up a spray can of motor winding cleaning spray and blow out all of the bronze dust out of the motor housing before assembly.

 

[e9999]

Nice. Yes, when at a dead end, I'll check the parts diagram to try to get a feel for all that's there. Won't necessarily show that a screw is preventing movement, but may get me to think about it.
This is being Mr. Obvious, but it's not the brushes that are holding the rotor in, is it?

 

[alia176]

Your're correct, the brushes and the brush holders are not holding on to the rotor.

 

[dragonslayr]

Your're correct, the brushes and the brush holders are not holding on to the rotor.

Hi Ali,,, I just bought an identical problem from a deceased friends widows Auction and found your Post here. Can you tell me if you were successful in finding a replacement Gear? It looks to me like your Worm Gear is fine in the attached pics, which is the same as mine. Is the Worm Gear not made of Steel with the gear it drives being a softer Brass/ Bronze and that it the piece which needs replacing? I hope that you or somebody else here can help me out and if I can make some headway with this project I will post my results. Thanks again, Walt~

 

[PIP]

Gears are complicated. Very complicated.

If you can determine exactly what the gear is then you can try to find one or have one made.

I bet you can buy a dozen of those bandsaw for what it costs to have one worm wheel made.

I have a 1950's Skil 12" Worm drive skilsaw. Like new in the original steel box. It runs low rpm and has a ton of power so I use it for cutting metal. I know how impossible it would be to fix the gears if they failed so I change the lube frequently and check it every single time I use it. The switch went bad a few years back. It took me a year of searching, but I found a 8" skilsaw of the same vintage. Bought it just for the switch.

Maybe you'll get lucky and run across another portaband for parts.

 

[alia176]

Hi Ali,,, I just bought an identical problem from a deceased friends widows Auction and found your Post here. Can you tell me if you were successful in finding a replacement Gear? It looks to me like your Worm Gear is fine in the attached pics, which is the same as mine. Is the Worm Gear not made of Steel with the gear it drives being a softer Brass/ Bronze and that it the piece which needs replacing? I hope that you or somebody else here can help me out and if I can make some headway with this project I will post my results. Thanks again, Walt~

Hello there,

This project stalled and the info on the new gear is sitting in my inbox for the last few months. I did contact Boston gear and they gave me a catalogue of over the shelf options that I need to go through and select a specific gear. I do miss my portable band saw something fierce, while at the same time, I can't get myself to buy a chinese POS unit. I own a rebuildable landcruiser, and the same thing applies to my tools.

Let me move on this and see what comes out of it.