It's 1/2"-12 Ya Dummy, Not 1/2"-13!

darkzero

darkzero

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Many Taiwan made machining machines are made with imperial threads/fasteners. My 7x12 bandsaw has imperial fasteners so I went out to buy a set screw to plug up one of the vise jaw holes when I move the fixed jaw to the other postion. Measured the bolt, 1/2" dia. Ok, sure looks like a common 1/2"-13 thread. Made the trip to a mom & pop hardware store cause big box hardware stores around here don't carry 1/2"-13 set screws.

Had to make a 3 hr round trip to get some parts for my truck so I didn't get to try the set screw until 10pm. Damn thing wouldn't fit! Hmm, is the set screw poorly threaded, nope fits my thread checker just fine. Ok, maybe the hole is full of chips & crud, reason why I wanted to plug the hole, but I just had a bolt in there yesterday. Grabbed my 1/2"-13 thread chaser, wouldn't fit the hole. So then I thought, is it metric? No can't be. I grab a metric thread gauage & measure the bolt, nope definitely not metric. Then I grab the other thread gauge, sure enough it's 12 TPI! WTH is this, I've never ran into this size thread before.

I'm not familiar with all the Whitworth threads & old obsolete US threads so I was confused regarding the 1/2"-12 thread. I get on the Googler & found the answers. 1/2"-12 is BSW, in the early 1900s for the US it was 1/2"-12 but 60° before 1/2"-13 became the standard.

Apparently many mills & bandsaws from Taiwan use 1/2"-12 instead of 13 tpi for all the 1/2" bolts but all the other size bolts are standard UNC/UNF. But why I have no idea & it doesn't make any sense.

All you old timers are probably laughing at me but I learned something new today. It's was a very long day for me & I thought I was going crazy.

:laughing:
 
Like I always tell them in here at work …………………" Whats 1 thread per inch matter in a plant this size " ! :big grin: Can't say that I've ever heard of that before either though , that could really screw you up if you weren't mechanically inclined . ( NPI) ) :grin:
 
I found out yesterday morning that I will have a night-shift pardner for the next 30 days . o_O He has been here for 90 days now and had his evaluation which was not good , so they're throwing him my way for his last chance . Not a mechanic , not a machinist , kinda slow , kinda lazy , always on the phone , etc . I figure we'll get along great . :big grin:
 
Haha, I always wondered how people like that get hired when they're clearly not qualified for the job & there are other well qualified candidates that don't get the job. At my old company there was always a couple of them. Of course they get the boot eventually but new ones eventually get hired. I never had anything against them personally but it was always a headache having to watch over them. It's like my managers did it on purpose & got a kick out of watching me have to manage & try to train them!
 
On my mill drill, one of the handles that drives the spindle drill press-style is badly bent. I read somewhere that they would be threaded 11.5 threads per inch but mine seem to measure 12 tpi. I haven't actually got the replacement piece threaded yet as life got in the way of my hobbies!

Craig
 
WCraig said:
On my mill drill, one of the handles that drives the spindle drill press-style is badly bent. I read somewhere that they would be threaded 11.5 threads per inch but mine seem to measure 12 tpi. I haven't actually got the replacement piece threaded yet as life got in the way of my hobbies!

Craig
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I checked my 40 YO Taiwanese mill/drill handle and it is closest to 12 TPI but not exact. Without resorting to setting up the microscope and measuring, I would guess something like 11.8 or 11.9 TPI. I could cut an 11.8 or 11.9 TPi thread on my Grizzly 602 but on the 6x18, I would cut 12TPI with slightly more clearance.
 
I have some non standard metric taps and dies that came with a budget set (i have quarantined them) , they were not the standard thread pitch.

I was having a hard time getting screws to go into a light fitting (china made) one day and so I tried the non standard thread tap of the correct size, sure enough it fits.

So their might be a few things hear and their using totally made up standards.

Stuart
 
mmcmdl said:
I found out yesterday morning that I will have a night-shift pardner for the next 30 days . o_O He has been here for 90 days now and had his evaluation which was not good , so they're throwing him my way for his last chance . Not a mechanic , not a machinist , kinda slow , kinda lazy , always on the phone , etc . I figure we'll get along great . :big grin:
Click to expand...
These younger folks with their cell phones is a real problem. I have two employees that have to leave their phones in the car. They have such a habit of reaching for it this is the only way they can stay on task.

Could those threads be Whitworth? = 55 degrees??
 
Ugh, yeah ... been there, lol. In 2014 my company purchased 7 new Summit machines and we had to go through that learning experience. Glad I learned at work because modding the coolant nozzle on my PM1236 ran me into a BSP thread. That could have gone sideways if I wasn't prepared.
 
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