Oops it's a left hand thread.

Anyone that works in a machine shop will assume that a thread call out on a drawing unless specified otherwise is RH as 4gsr found out.
Yeah! Machinists will still ask me if it's right hand to this day if it's not specified on the drawing. And customary, it is considered right hand unless otherwise specified. I always put 'RH' or 'LH' on the thread callout on the drawings I do. That way, it takes the doubt out of the equation.
 
Yeah! Machinists will still ask me if it's right hand to this day if it's not specified on the drawing. And customary, it is considered right hand unless otherwise specified. I always put 'RH' or 'LH' on the thread callout on the drawings I do. That way, it takes the doubt out of the equation.
Good on ya, the less ambiguity the better, we do largish jig plate parts for the pharma packaging industry, one customers engineer routinely dimensions parts from all 4 sides of the plate. This may appear to be no problem on paper but when actually programming 70+ holes, slots and pockets at the machine a single o,0 position makes life much simpler.
 
Better yet, try to tap a 3/4-10 hole with a left handed tap. You never though the Bridgeport had so much power either until the magic smoke started to rise from the part! The aggravated part was, I've been pulling 3/4-10 RH taps from that pile for months, too. I kept that tap, too, and still have it today. That was almost 40 years ago, too!
 
I must say it warms the cockles of my heart to find I'm not the only one.
I sped a whole day last week making a new fixing bracket to the fan on my powder coating oven to allow a new motor with a longer shaft to be used.
The centre of the fan is a silicone?? tight push fit to the rough shaft. I thought that a thread would be a rough push fit. BUT, it was a l/h thread and just unscrewed. New design on the way now.
 
Just have to throw in an experience from --way-- back. I had acquired a good bench grinder. Disremember the brand but it did have a "Baldor" motor. The difficult part was the 1/2" shaft. It got thrown out because there was no left hand nut for the left hand side, I guess. This around 1980, when the EPA was taking down foundries left and right.

I turned the city upside down for that 1/2-20 LH nut... to no avail. As it happened, I had both a Dodge Dart and a Plymouth Valiant in my history. The lug nuts were ... 1/2-20. And being Chrysler products, the left side had left hand nuts. A local salvage yard had them by the bucket full, they didn't fit anything newer than ~mid-70s models. I got a handful (doubled) for a dollar. Mostly to pay for them being dug out.

I've used them up making turnbuckles for my tractor. Now I have a tap. But back then, such things were costly.
 
one customers engineer routinely dimensions parts from all 4 sides of the plate. This may appear to be no problem on paper but when actually programming 70+ holes, slots and pockets at the machine a single o,0 position makes life much simpler.

Not just that, but you can run into some nasty tolerance stacking problems if you're not careful. Though they usually deal with that by ratcheting down the tolerances.

One all-too-common problem is when people design, say, a chain of holes, each dimensioned from the next. Ten holes +/- .010", the 10th hole can be +/- .100 from the first hole and still be in spec, much to the consternation of the designer...

Unless you have some specific reason not to, it's usually best to dimension everything from a common origin.
 
Not just that, but you can run into some nasty tolerance stacking problems if you're not careful. Though they usually deal with that by ratcheting down the tolerances.

One all-too-common problem is when people design, say, a chain of holes, each dimensioned from the next. Ten holes +/- .010", the 10th hole can be +/- .100 from the first hole and still be in spec, much to the consternation of the designer...

Unless you have some specific reason not to, it's usually best to dimension everything from a common origin.

That is common actually, you get CAD jockeys with quick trigger finger and had never made a chip in their life. During one small window old company used to send rookie CAD guys down to the "Snake Pit" . They had a tour of duty in all 3 shops ( Elect, Fab , and Machine ) not only did they draw better, but they were also high skilled at sweeping the floor. It built relationships of communication too. Program was dumped by some Dilbert type boss that showed up.
 
My understanding was that using left-handed lug nuts went back to the horse and buggy days when a single spindle nut held the wheel on the axle....
It has since been proven unnecessary provided the lug nuts are tightened properly.

For those situations (like, under the hubcap) where the AXLE has a nut,
there are castellated nuts with cotter pins, and keyed (nonrotating) washers, and a stamped
washer-with-bendtabs gizmo for which I know no name. I'm dubious that there's much advantage
on lug nuts (the wheel can't pivot under 'em to create loosening) though.

A recurrent headache at my PPOE was a slotted bracket secured with a screw
and lockwasher; any movement along the slot was 50% likely to grab the
lockwasher so as to loosen the screw.
 
I can remember Chrysler, Studebaker and International had left hand lugs.
Most had an L stamped on the stud.
 
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