Lefty hefty, righty lighty: reverse threading in the workplace

[bonneyman]

I can think of a few places in the popular world where left-hand threads are standard practice. Wondering if you guys can add to the list.

I know of two right off the bat:
Drill chuck attachment screws are reverse thread.
Bicycle bottom brackets on the drive side (as well as the non-drive pedal, IIRC) are also left hand thread. (These have to do with the forces acting upon the particular part. If the standard rotation of that part would be acting in the loosening direction the part would tend to spin off during use. So they use a reverse threading where such conditions exist.)

 

[bonneyman]

Also, alot of tooling that's used to remove regular forward-threaded parts and fasteners employ left-hand threads to operate.

 

[vavet]

The nut attaching the fan clutch to the water pump shaft on many automobile engines is left-hand thread.
Turnbuckles have one side of left-hand threads.
Some older cars (Mopars in the later 60s to early 70s and perhaps more) had left hand threads on the left side lug nuts. Some of the army's M93X 5-ton trucks also had left handed lug nuts on the left side.

 

[bonneyman]

The nut attaching the fan clutch to the water pump shaft on many automobile engines is left-hand thread.
Turnbuckles have one side of left-hand threads.
Some older cars (Mopars in the later 60s to early 70s and perhaps more) had left hand threads on the left side lug nuts. Some of the army's M93X 5-ton trucks also had left handed lug nuts on the left side.

Good one!
And if you lose that sides' bolt you're in a bit of a pickle, as left-hand threaded bolts are nowhere near as common.

 

[4xdog]

I can think of a few places in the popular world where left hand threads are standard practice... Bicycle bottom brackets on the drive side (as well as the non-drive pedal) are also left hand thread.

As the exception that proves the rule, or at least how good is the idea of the rule, one of my old bikes has a French-threaded bottom bracket, which doesn’t have a left-handed thread. We owe much even today in the bicycle world to the innovations in cyclotourisme between the wars, but a fixed cup that unscrews itself ain’t one of them.

 

[bonneyman]

As the exception that proves the rule, or at least how good is the idea of the rule, one of my old bikes has a French-threaded bottom bracket, which doesn’t have a left-handed thread. We owe much even today in the bicycle world to the innovations in cyclotourisme between the wars, but a fixed cup that unscrews itself ain’t one of them.

Hmm. Didn't realize that.
Most BB fixed cups I've worked on were real tight - almost as if you were cross threading them. Threads on both parts were clean, lube didn't help much. Maybe they made them slightly off to deal with the loosening problem?

 

[4xdog]

There’s a reason French-threaded bike stuff is so hard to find, and installed on no new bikes in decades.

I say that as a Francophile, especially where bicycles are concerned.

 

[malibu101]

Attaching a regulator to an acetylene cylinder.

I don't know if they are all left hand, but, the few ring gears (in an auto rear end) that I've worked on were left hand threads too.

 

[rlitman]

Left wheel on a bench grinder.
The blade nut on my lefty circular saw.
The blade nut on many sidewalk edgers.
Half of a left-right pipe coupling.

 

[drewsifer714]

Bolt that holds the blade on the crankshaft of a push lawnmower. Sometimes. Lol. Had fun with that one more than once.

 

[bonneyman]

This is great, guys!

Next time I have a project to do I'm gonna check this list to see if there's any lefty's in my path.

 

[iajonesy]

True knock-off wheels are LHT on the passenger side.

Mike

 

[59 wagon man]

toilet bowl handles

 

[bonneyman]

There’s a reason French-threaded bike stuff is so hard to find, and installed on no new bikes in decades.

I say that as a Francophile, especially where bicycles are concerned.

I just figured the French stuff got overshadowed by the Japanese on price. I prefer French parts (Huret, Sedis, Mallaird, etc) but once Shimano got going they basically bowled over everybody.

 

[Davefr]

Chainsaw clutch

 

[bonneyman]

toilet bowl handles

Ooooh, that'd be a crappy deal to screw up!

 

[Can I try?]

String trimmer head.

 

[Mick56]

The nut that holds the fan blades onto a vacuum cleaner motor.

 

[bmwrd0]

I just figured the French stuff got overshadowed by the Japanese on price. I prefer French parts (Huret, Sedis, Mallaird, etc) but once Shimano got going they basically bowled over everybody.

French parts are also just slightly different in diameter that English sized parts, ie 22mm vs, 7/8" (which is 22.2mm) As things tend to be sized rather importantly in frame tubes and componentry from the period, this led to the opinion that French parts were inferior.

 

[redmondjp]

Bolt that holds the blade on the crankshaft of a push lawnmower. Sometimes. Lol. Had fun with that one more than once.

Which ones? I've been working on walk-behind mowers since the 1970s and I have never come across a LH thread on a crankshaft bolt. Briggs & Stratton, Tecumseh, Kawasaki, Honda engines are what I have worked on and they've all been standard RH threads.

 

[Mgdoug3]

Left side of a disc open on planters and drills. That way it's always tightening. The right side of the planter unit is right hand threads so it's easy to remember.

 

[paulsomlo]

Belt tensioner pulley bolt on E36 series BMW.

 

[OccupantRJ]

Cross slide lead screw on a metal lathe.

 

[FigureItOut]

The bolt on my miter saw.

Sent from my SAMSUNG-SM-G930AZ using Tapatalk

 

[cjn1014]

operating nut on the fire hydrants in my town. clockwise to open. i think the city got a deal on backwards hydrants in the 1800's, never switched...

 

[Spiffers]

Isn't one set of lugs on dually trucks left hand thread?

 

[Htscheg]

Clutch hub assembly on harley davidson motorcycles

 

[Capt. Spaulding]

I believe most bicycle pedals go on reverse threaded.

 

[Mgdoug3]

Isn't one set of lugs on dually trucks left hand thread?

Older semis and trailers with bud style rims are. My semi trailer has bud rims. The inner and outer nuts on the driver side (I think) are left handed threads. My (2004) semi and dually pickup are all right handed threads.

 

[fourjeepin]

The lug nuts on one side of my M100 trailer from WWII

 

[Fcvapor05]

I believe most bicycle pedals go on reverse threaded.

Only on one side.

 

[bonneyman]

Only on one side.

That's right. Many pedals have an "L" or "R" forged into the threaded shaft end to let the installer know which side to put it on.

 

[alwaysFlOoReD]

1977 f350 drivers side lug nuts.

 

[The Cobbler]

some air compressor flywheel pulley bolts

some faucet stems on one side of a 2 handle set

acetylene hose and tank fittings

 

[TarheelMechanic]

evap test port schrader valve (located underneath the cap)....for those vehicles that still have the evap test port

 

[Capt. Spaulding]

Only on one side.

Ah ok, thank you for the correction.

 

[Mikeske]

I had a 1970 Dodge Dart years ago with LH studs. Tire stop mechanic snapped off 2 on the drivers side front wheel one time. I could not get to him fast enough to stop him after the first one. Made the shop replace the studs with new left handed studs as I felt like being a *****. It cost them double the cost of the right handed threaded studs. It was clearly stamped into the end of the stud "L"

 

[MShaw]

Left side, left hand Chrysler lug bolts were used back in to the 1930s

 

[4xdog]

True knock-off wheels are LHT on the passenger side.

Mike

Exactly. The knockoff nuts are pretty well marked, but there are risks. On Triumph TRs, the knockoffs are splined extensions bolted to the hub studs with special flat nuts. A friend who knows his way around old British cars like I know my bedroom once mounted the knockoff adapters on one of his TRs on the wrong side hubs. So both sides loosened as he drove down the road. He knew he had a problem when one of his wheels passed him on the side...

Here's the knockoff on a D-type Jaguar at Goodwood a few years ago:

 

[bonneyman]

Safety wire on a car wheel sure doesn't inspire my confidence!