Need Help Identifying A Mystery Thread

Nogoingback said:
I measured this thread with a Mitutoyo thread pitch gauge. It is definitely not an 8-32. The 30 TPI pitch gauge is a perfect fit to the screw.
Nothing else comes close.
Click to expand...
It is then a thread used by a manufacturer for their own reasons, it is not a mystery merely uncommon.
One may produce threaded products of any combination that you desire, published thread standards are guidelines not laws, the thread police will not turn up to arrest you.

I have been guilty of making parts with uncommon threads just to confuse people in the future for the simple reason that I can.
Producing a 3/8"-15 or 17 thread will cause someone considerable confusion down the road.
 
Wreck™Wreck said:
It is then a thread used by a manufacturer for their own reasons, it is not a mystery merely uncommon.
One may produce threaded products of any combination that you desire, published thread standards are guidelines not laws, the thread police will not turn up to arrest you.

I have been guilty of making parts with uncommon threads just to confuse people in the future for the simple reason that I can.
Producing a 3/8"-15 or 17 thread will cause someone considerable confusion down the road.
Click to expand...

I actually have a couple of 3/8-18 stainless steel studs that I made. I started with 4" cap head screws , cutting the heads off and threading. The threads came out perfect and I was pleased with the work until I tried to run a nut on them. DOH!:oops2:


However, if you really want to confuse them cut a 3/8-12, 2 start thread. It will measure 24 tpi but good luck finding a nut to fit. Left hand threads also serve to confuse.
 
RJSakowski said:
I actually have a couple of 3/8-18 stainless steel studs that I made. I started with 4" cap head screws , cutting the heads off and threading. The threads came out perfect and I was pleased with the work until I tried to run a nut on them. DOH!:oops2:


However, if you really want to confuse them cut a 3/8-12, 2 start thread. It will measure 24 tpi but good luck finding a nut to fit. Left hand threads also serve to confuse.
Click to expand...
This is where people confuse TPI with the lead of the thread.
This is a 4 TPI ballscrew with 4 starts, the lead is 1.000"
 
I've done a little Google search, and in the early 1900's there was an A.S.M.E. standard that included 8-30 as a size.
I found a reproduction of a page in Machinery's Reference Series from 1909 that lists it. (This appears to be the predecessor to Machinery's
Handbook, since Erik Oberg is listed as the author in both.)

This hardware may be older than I thought.
 
Problem solved. I bought a tap to clean the threads on the hardware, and an 8-30 die to make some screws. (I guess they're
really bolts since they were turned from hex stock.)


DSCF7271.JPG
 
I had enough trouble back in the day with British cars from the transition period from Whitworth to Unified threads. ALMOST all the fasteners were 1/2-13, 60 degree Unified threads, but a few were 1/2-12 Whitworth, 55 degree threads. It is just close enough to think the thread is buggered and try to force it or chase the thread with a tap or die, both of which lead to disaster, and some of it on parts that were difficult to replace, obsolete. I quickly learned to see the differences without even a thread gage, just eyeballing the threads. I still have a couple 1/2-12 Whitworth bolts, segregated from the SAE/Unified stuff, and well marked!
 
The reason I bought the tap is that someone tried to brute force some of the hardware with, I imagine, an 8-32. Fortunately they cleaned
up fine.

I feel your pain on the British cars: I worked on them some myself. They were a real pain at times. The worst job I remember was
changing the clutch in an XKE: I had to damn near dismantle the car to get that clutch out. :)
 
Nogoingback said:
The reason I bought the tap is that someone tried to brute force some of the hardware with, I imagine, an 8-32. Fortunately they cleaned
up fine.

I feel your pain on the British cars: I worked on them some myself. They were a real pain at times. The worst job I remember was
changing the clutch in an XKE: I had to damn near dismantle the car to get that clutch out. :)
Click to expand...
The XKE also required the entire front end tube frame forward of the firewall removed to replace the starter. An all day job, 8 hours flat rate. A friend who worked at a BMC dealer showed up hung over one morning to such a job, peeled back the carpet, cut a hole in the sheet metal, removed and replaced the starter, pop riveted a new piece of metal over the hole, hid the sheet metal work with undercoating, replaced the carpeting, and got his 8 hour flat rate job done in under 3 hours.
 
You must log in or register to reply here.
Back
Top