PDA

View Full Version : J-B Weld Experiences



extracash
03-15-2004, 08:15 PM
I posted this thread under the general welding category and received no responses; therefore, I thought that I would try this category. Here's the story:

On one of our mower engines, 10.5 HP/Briggs, the key slot on the main shaft is showing major wear. The drive pulley and supporting key are shot, and obviously, I can replace both of them, but what concerns me is the wear on shaft.

I know that if the new key and pulley do not fix the problem, then it is likely that the 'play' in the pulley will eventually destroy the engine. I can replace the engine shaft for big bucks, replace the engine for big bucks, or come up with some other strategy.

I spoke with a local small engine technician about welding the new key in place. This sounded great to me, but he indicated that the heat would probably be too much for the shaft. He suggested cold-welding with J-B Weld.

Have any of you used J-B Weld for this type of application? Thanks!

david_r
03-15-2004, 08:37 PM
Why couldn't you set screw the pulley onto the shaft?
How much wear is on the shaft?

extracash
03-15-2004, 08:59 PM
David_R,

The pulley does not provide the option to use a set screw. The slot is worn quite a bit. The key is two inches long and 3/16" by 3/16". The fact that the key and slot are fairly large, there is enough surface space to work with to secure a weld. In my opinion!

dulknife
03-15-2004, 09:10 PM
turn it 180 degrees. with a dremall and small cut off wheel cut a new key way
ken

extracash
03-15-2004, 09:15 PM
I considered cutting a new slot, but I was concerned about the accuracy of the cut.

dulknife
03-15-2004, 09:22 PM
go to an automotive machine shop and ask them. they put them in all the time. you can also form a piece of carbon in shape of the key.put it in the wallowed out key and weld around it. i tig mine in but you could use other methoid.

david_r
03-15-2004, 10:30 PM
If you were considering welding on that shaft, adding a couple of set screws shouldn't be anymore difficult. The pulley ought to be able to be tapped easily for a couple of set screws. I imagine a pulley that's tranfering 10 HP would have enough meat to hold a couple.
You can also get larger keystock. Heck, Homedepot can hook you up with that. You'll have to file it down.

Here's the thing I don't get. Why did the keyway or pulley or shaft get bunged up in the first place? Is it a bad design? BTW, what is the design? Is it a tapered bore or a straight bore with a shoulder on the back and a nut or bolt on the front to secure the pulley?


My dad always knew when we hit a rock with the lawnmower. The inertia of the flywheel would shear the key enough that it would run but the timing was too far off to restart it.

Franz
03-16-2004, 12:42 AM
Before doing anything else, the shaft and the pully you intend to put on need to be checked for roundness. If the shaft is out of round it will eat the new pully. If the pully is out, it will tare the shaft and key up more.
Next question, does the pully float or move freely on the shaft?
Is this an engine with a tapped center hole on the shaft that holds the pully on?
How much play is there between a good pully and the shaft?
There are several methids of doing this repair, but what method to use is determined by how the assembly works.

extracash
03-16-2004, 09:47 AM
To answer a few of the open questions, it is not known how the key and slot sustained so much wear. There is little to no slack when the pulley slides over the shaft.

The shaft is vertical with a 2" vertical slot. There is no set screw on the pulley as the pulley is held tight with a 1 1/2" screw that screws into the bottom of the shaft. The pulley does not float freely as it is secured by the key.

The pulley is heavy duty and would easily hold a set screw if that was the direction that we elect to go.

Can a slot be cut without removing the shaft from the engine? I have never seen the tool that cuts the slot, and I was curious if there would be enough clearance to do the job?

enlpck
03-16-2004, 10:14 AM
If the pulley is drawn in with a bolt into the end of the shaft, a setscrew against the shaft is probably not what you want to use-- several reasons: By the time the setscrew it tight nough to hold, you may bind the end bolt by distorting the shaft, may crack the shaft, the bolt may work against the setscrew and work loose more than without the setscrew.


Machining the slot in place will be difficult, but is possible. I would use a die grinder just to even up the edges-- if they arn't straight and parallel, the key will work loose again. The keyslot in the pulley should be widened to match. Then fit a new, snug key. Bluing is your best friend for this... A chunk of key stock, an caliper, and bluing will allow you to get quite a god fit.

The other option, if the slot is too wonky, is to use a setscrew AGAINST THE KEY. The key is then taking the load, and spreading the setscrew load over the shaft. The key won't walk, and is held tight against the bottom of the keyway.

extracash
03-16-2004, 11:10 AM
Thanks everyone for the input. This website was recommended by some members of lawnsite.com. Take Care!

OlPilot
03-16-2004, 02:25 PM
I definitely don't recommend welding on that shaft. Depending on the metallurgy, you could do some nasty things to it. It may be machined low alloy steel, which wouldn't be too bad for welding, but then again, it could be a casting or forging into which you might be inducing cracks, especially since you don't want to disassemble the engine to allow preheat and postheat procedures. But worse yet, the heat might induce runout distortion in the shaft . And, you'd probably cook the nearest bearing and shaft seal to boot.

extracash
03-16-2004, 02:52 PM
Olpilot,
Your note prompted me to research further, so I contacted one of the technicians at Briggs & Stratton. They do not recommend welding the key to the shaft for similar reasons.

Obviously, there are limitations from a liability standpoint as to what they can recommend, but he suggested trying something like the tap screw or even the JB Weld. If these do not work, then he suggested replacing the shaft.

Thanks again! At a minimum, I do not want to do anything that might cause additional harm or potential injury.

Franz
03-16-2004, 10:11 PM
IF both the shaft and hub measure up round, and the same size, you can then align the keyway and do the JB weld on the keyway.
IF either is out of round, or wrong diameter, you have a totally different situation.
The IMPORTANT factor is proper fitup. IF you don't have proper fitup, NOTHING is going to work, and you'll be back to trying another improper halfassed fix.
Measure the thing up, and THEN decide how to fix it.

sscherin
03-22-2004, 06:37 PM
Would it be possible to get an oversize key and have it milled to fit the crank then mill a step down to fit the flywheel?

sscherin
03-22-2004, 06:39 PM
Oh yeah I almost forgot..

Be sure you have the right Key.. they have the aluminum keys and the steel keys.. My 10hp brigs takes the steel key.. the aluminum one is a sloppy fit on one that takes a steel key.