How Would You Lock This Bolt?

[aesmith]

This part of a snowblower. It's a fully threaded 3/8" UNC bolt that holds the impeller onto the gearbox shaft. The shaft and impeller are splined, but the end of the impeller is blank with just thr round bolt hole, the splines aren't visible. There's a heavy round washer under the bolt, and a spring washer.

The bolt works loose. Before the last lot of snow I tightened it hard with impact wrench and it stayed for a couple of sessions but started loosening again.

One idea is to drill through the blade near the root, drill the bolt head, and use lock wire. That (of course) relies on me being able to drill the bolt head.

Or thread lock, but I presume would need some way of degreasing the thread in the shaft.

It's not something that often needs to be undone. If there was anything to key it to then a tab washer would be ideal.

 

[roblane65]

Can you not just take the bolt out and use some thread lock on it ( strong locktite ) is the simple answer .

 

[bricol]

Throw the spring washer - they do nothing other than add another failure point.
Threadlock would seem to be your only reliable way. A squirt of brake cleaner up the hole, followed by compressed air.

I would have suggested a nordlock washer, but with the plain washer under it, it would do nothing.

 

[aesmith]

Cheers. Threadlock is on its way for another job, Green Loctite 275. I thought I had some red Loctite of some sort but can't find it just now.

 

[Dapph2]

To clean the thread hole use an electronic contact cleaner . or a degreasing spry or Easy Start ether spray directly in the hole whilst the hole is upper most . let sit a few seconds , stir it with a cotton bud or similar turn over and empty , if you have an air line blow the hole out.
Then as the guys say ,use a decent thread lock fluid and let it cure for several days especially if it cold weather . or put a 300 watt infra red heat lamp on it for a few hours if you have one to get the gentle warmth to cure it .

Thought .. how much play does the blade have on the shaft ? If it is a fair bit , also clean both parts thoroughly and thread lock it to the shaft .. a decent thread lock can take up 20 thou play .

 

[Agroshield]

Use the weakest threadlock you can find (purple?). The impellor looks to be plastic. How will you overcome super loctite next time you want to pull it to bits?

 

[zzr1200]

Use the weakest threadlock you can find (purple?). The impellor looks to be plastic. How will you overcome super loctite next time you want to pull it to bits?

Those welds look like steel to me, plastic welds are far more lumpy and larger, so to speak, sort of............

Brake clean, then threadlock or studlock up to you which one...

 

[bricol]

Use the weakest threadlock you can find (purple?). The impellor looks to be plastic. How will you overcome super loctite next time you want to pull it to bits?

Most loctites are not recommended for use with plastics - tends to make the plastic brittle.

 

[bricol]

Cheers. Threadlock is on its way for another job, Green Loctite 275. I thought I had some red Loctite of some sort but can't find it just now.

That seems a little excessive - I'd be thinking blue 242/243.

 

[Erie Fred]

Is that dirt on the impeller ?
Only see snow on ours.....

 

[Woody.v8]

https://threadrive.co.uk/nord-lock-...G2bsnGVSd4-uz0fBRwATmKYEeCTwbAs8aAq4dEALw_wcB

These are good.

 

[Turbo]

Blue loctite would be my suggestion. The green stuff (studlock) will not come undone without heat.

But the fact that is it loosening suggests there is some slop in the splines between the shaft and the impeller. It would be a good idea to address that too. Loctite do products for that problem.

But it could also be that they used a rh thread bolt where they should have used a lh thread!

 

[Erie Fred]

Blue loctite would be my suggestion. The green stuff (studlock) will not come undone without heat.

But the fact that is it loosening suggests there is some slop in the splines between the shaft and the impeller. It would be a good idea to address that too. Loctite do products for that problem.

But it could also be that they used a rh thread bolt where they should have used a lh thread!

This ^^^
The bolt should not see any rotation, so LH is not needed if the splines are tight.
Are the spines tapered ?
could be worn and the shim washer might be bottoming out before tightening
up the fit.

 

[Agroshield]

Most loctites are not recommended for use with plastics

I was more concerned about the heat that might be needed to denature the loctite when the bolt next needs unscrewing.

It is moot as the fan is not plastic, as cogently pointed out above.

 

[MoreWellie]

I would use a home made lock washer

it should fold down either side of the flange on both sides of the bolt (for balance) and have one or two tabs that you could fold up on to the side of the bolt head

 

[MattF]

If there was anything to key it to then a tab washer would be ideal.

Why not simply a strip of thin steel, folded over between two of the vanes, drilled for the bolt to go through & then cut a couple of tabs in the strip to fold up the bolt head?

 

[MoreWellie]

Why not simply a strip of thin steel, folded over between two of the vanes

sigh, and as simply as that @MattF got around the patent for my new lock washer

 

[Turbo]

We are also forgetting this is a welding forum!

 

[zzr1200]

We are also forgetting this is a welding forum!

Farmers Agricultural locknut then........