washer narrower than thread?!

[bugbear6502Participant @bugbear6502]

[bugbear6502Participant @bugbear6502]

I have a (rather nice) Makita hedgecutter; its only vice is that the screws that hold the blade in place keep working loose, so I have to keep taking the cover off and tightening them.

They're Phillips, which doesn't help.

So I went to my local supplier, and bought some nice M5 pozidrive machine screws.

I removed the old bolts, and attempted to get the washer and split washer off, for re-use.

Uh? They wouldn't slide down the bolt? I assumed the bolt had simply been badly burred, so I used "quite a lot of force". After that, getting the washer off has essentially stripped the thread.

I now believe that the thread was rolled onto the bolt AFTER the washers (plain and crown) had been put on, hence the threaded portion is larger than the shank with the washers.

Has anyone else (ever) seen this – and why would they have done it?

BugBear

[Michael GilliganParticipant @michaelgilligan61133]

Posted by bugbear6502 on 20/08/2016 08:27:23:

Has anyone else (ever) seen this – and why would they have done it?

.

• Yes [and there is a technical name for them, which I don't recall]
• to stop the washers falling off and you losing them … It's actually more likely that they do it for manufacturing convenience; but let's give 'em the benefit of the doubt.

MichaelG.

 

Sems [or more properly SEMS 'cos I'm pretty sure it's an acronym] is what escaped me.

http://www.pencomsf.com/screws-categories/screw-design-guide/#how-screws-made

Edited By Michael Gilligan on 20/08/2016 08:42:20

[MichaelRParticipant @michaelr]

Could be Captive Washers Here

Mike.

[BazyleParticipant @bazyle]

The washers have a single turn thread sort of bent into place (probably self formed) which screws on as it is assembled and then the actin of tightening flattens off that thread start so it won't restart as a thread backwards. 'self retaining screw; extremely common without washer eg the changewheel cover retaining thumbscrew on any Boxford lathe.

[Michael GilliganParticipant @michaelgilligan61133]

Bazyle,

You may find it of interest to follow the link that I provided.

MichaelG.

[AjohnwParticipant @ajohnw51620]

Posted by Michael Gilligan on 20/08/2016 08:50:15:

Bazyle,

You may find it of interest to follow the link that I provided.

MichaelG.

Bazyle is just describing a form that has been around for a long time and might even be more common when they are used to fasten thin items down. The washers can sometimes be screwed off by setting them at the helix angle of the thread but they are still likely to be pretty stiff and need tools.

John

–

[Michael GilliganParticipant @michaelgilligan61133]

Yes, John

[Michael GilliganParticipant @michaelgilligan61133]

Unfortunately, this video is not very well-focussed, but it does give a fair idea of how SEMS are manufactured.

MichaelG.

[Anonymous]

Posted by Michael Gilligan on 20/08/2016 08:35:44:

• to stop the washers falling off and you losing them … It's actually more likely that they do it for manufacturing convenience

That's precisely why it is done; it's all about money. You only need to buy and inventory one part. During assembly only one part needs to be picked instead of three, which then need assembling before installation. It prevents parts getting missed. Can you imagine the outrage vented on this forum if an item was bought only to be found to have missing washers?

Andrew

[AjohnwParticipant @ajohnw51620]

There are some " real " bolt making machines on these. The steam plant seems to be missing,

**LINK**

**LINK**

**LINK**

I haven't seen vibrating hoppers working in the uk for a long time.

John

–

[bugbear6502Participant @bugbear6502]

Posted by Michael Gilligan on 20/08/2016 08:35:44:

Posted by bugbear6502 on 20/08/2016 08:27:23:

Has anyone else (ever) seen this – and why would they have done it?

.

• Yes [and there is a technical name for them, which I don't recall]
• to stop the washers falling off and you losing them … It's actually more likely that they do it for manufacturing convenience; but let's give 'em the benefit of the doubt.

MichaelG.

Sems [or more properly SEMS 'cos I'm pretty sure it's an acronym] is what escaped me.

http://www.pencomsf.com/screws-categories/screw-design-guide/#how-screws-made

Edited By Michael Gilligan on 20/08/2016 08:42:20

That's perfect – and since it appears to be done for stock control and/or manufacturing convenience, it's not something I need to worry about for my replacement bolt.

Thanks to all for the (great) info.

BugBear

[MikeParticipant @mike89748]

Nobody has suggested a practical cure for Bugbear's problem. I'm sure a smear of a grade of a thread-locker which allows disassembly would do the trick.

[Perko7Participant @perko7]

I'd just buy new washers and not waste creative time trying to re-use the old ones.

[Ian S CParticipant @iansc]

I reuse quite a few of these screws , and at times spend a bit of time with side cutters cutting the washers off, I have also used a junior hacksaw, and the Dremmel with a cut off disc. Most of the ones I find are split spring washers.

Ian S C

[HopperParticipant @hopper]

+1 on Loctite. Blue threadlocker should do it.

[bugbear6502Participant @bugbear6502]

Posted by Mike on 20/08/2016 10:59:29:

Nobody has suggested a practical cure for Bugbear's problem. I'm sure a smear of a grade of a thread-locker which allows disassembly would do the trick.

The "cure" is the fact that I don't need to do anything special; I thought it might be a special secure fixing that I didn't know about.

BugBear

[Ian PParticipant @ianp]

Bugbear

Rereading your original post a 'cure' is what you need so you dont have to keep dismantling the hedgecutters.

Mike and Hopper both suggested a thread sealant and I second (third) them.

Nothing at all wrong with Philips screws as long as you have the correct driver.

Ian P

[Neil WyattModerator @neilwyatt]

Posted by Andrew Johnston on 20/08/2016 09:56:51:

Can you imagine the outrage vented on this forum if an item was bought only to be found to have missing washers?

It doesn't seem to be the subject of debate these days but one upon a time ME was full of letters stating washers did not exist in full size, only in (bad) models

Neil

[bugbear6502Participant @bugbear6502]

I can confirm that the original bolt had what I suspect to be thread lock (of some kind) on it.

BugBear

[SpurryParticipant @spurry]

You could always add Nord-lock washers to the bolts. I found them on my mower blade M12 retaining bolts. According to the blurb, they are supposed to be good…but time will tell for me.

There are some on EB: 262489261477

Pete

[bugbear6502Participant @bugbear6502]

Posted by Ian Phillips on 20/08/2016 19:12:21:

Bugbear

Rereading your original post a 'cure' is what you need so you dont have to keep dismantling the hedgecutters.

Mike and Hopper both suggested a thread sealant and I second (third) them.

Nothing at all wrong with Philips screws as long as you have the correct driver.

Agreed – I was so tunnel-visioned on my washer problem, I was ignoring my real problem. Apologies.

However, I taking the trimmer apart to measure/check all this, I've found what I believe to be the fundamental problem – the cutter bar is partially broken.

"darn"

BugBear

[Ian S CParticipant @iansc]

Got a couple of hedge cutters, a Makita battery one uses low profile nylock nuts, the Black & Decker mains unit uses plain nuts, I got it at a garage sale a week ago, I checked the screws when I first got it home as I oiled it, then tried it out on a shrub up the drive way, all ok, so it's put away till the hedge growth starts again. I would reacomend the nylock nuts.

Ian S C

[Dinosaur EngineerParticipant @dinosaurengineer]

If a thin washer is "dished" with a close fitting hole then when the bolt/washer is fitted, the washer flattens and is held capitive.

[Author]

Posts