Things with reverse threads

I can't remember what things have reverse threads. As in lefty tighty, righty loosey.

Such as a chainsaw clutch retainer bolt/flywheel thing, you turn it counterclockwise to tighten. And lawnmower blade mounting bolts, can't remember about those for sure.

So which things in home, auto, appliances, machinery, the trades, etc., have reverse threads, where you turn clockwise to loosen and counterclowise to tighten, the opposite of normal fastening applications.

Let's list them, so we won't make this classic mistake mistake whatever we happen to be working on.

And if you know WHY it is like that, please explain why it is designed that way.

Done to keep the fastener tight in use.

Turnbuckle has both left and right hand threads.

As far as mower blades, look at the cutting edge - if you were to hammer on the cutting edge, it would make the nut(or bolt) tighter.

So to loosen you always turn the nut or bolt the other way.

Bicycle pedals
Meat slicer blade retaining screws

Early Dodge/Plymouth 1970 or there abouts lug nuts.

Flammable gases in compressed cylinders. Propane, hydrogen, etc.

Should be marked in BIG letters

quote:

Originally posted by blueye:
Early Dodge/Plymouth 1970 or there abouts lug nuts.

Yup, my early Chryslers had them. If one did not know this, it would be a lesson on the lug wrench..

Threaded barrels:

Sig220 - righty tighty lefty loosey.

Sig226 - lefty tighty righty loosey.

I totally don’t understand why these are different. Drives me nuts.

quote:

Originally posted by doublesharp:
Should be marked in BIG letters

Amen!

quote:

Originally posted by blueye:
Early Dodge/Plymouth 1970 or there abouts lug nuts.

Actually, all Chrysler products up to 1975. Some GM products prior to that.

I know at least some if not all HK pistol barrels are LH threads. This prevents suppressors from loosening during firing. It appears to be primarily a Euro thing.
Also several 1960's GM cars (Pontiac and Oldsmobile) had left hand threads on lugs as did cars that had knock off wheels. Corvettes with the optional Kelsey-Hayes aluminum wheels were one and vehicles with wire wheels that had the large single "flipper" style lugs that you hammered to tighten. I seem to recall the lugs on the right side of the car were left hand thread. In my few years I spent in the auto business I only saw one Corvette that had those wheels and there was something on the "flipper" lug that indicated left from right side but for the life of me I cannot remember what was the difference. The car also came with a lead hammer to tighten the lugs.

All semi trucks with bud wheels are lefty-tighten on the driver’s side, and lefty loosen on the passenger side. It keeps the lug nuts from loosening during operation.

The case trimming dimension to the cutter on my Frankford Arsenal case trimmer.

PC

Toilet flush levers, some automobile fan clutches. While not exactly threads, twist ties on loaves of bread are often left-tight, but there is no consistency to it.

Two that come to mind:
bicycle pedals and bicycle bottom brackets.

Why? think of a bike crankset with pedals. The left side (when mounted on the bike) has reversed threads so the action of pedaling doesn't loosen the pedal shaft from the crankset. The bearings in the pedal should prevent overtightening as one pedals.

Some of the screws inside of a watch are reverse threads but they are often marked with 3 lines including the one the screwdriver goes into.

Clarification, I think only one side of the pedals is reverse thread. The other is normal, no?

quote:

Originally posted by r0gue:
Clarification, I think only one side of the pedals is reverse thread. The other is normal, no?

Yes, that is correct. Only one side.

When I was young on the farm, plowshares (the replaceable cutting blade on the plow) came with “left handed” bolts that tightened counterclockwise so they wouldn’t unscrew as they cut through the earth. I found a discussion online that at least some manufacturers have changed to right-hand threads but are using double nuts and the farmers in the discussion didn’t think that worked as well.