.

• 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

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.

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

–

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

MichaelG.

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

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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.

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

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

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

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