Machine Bolt Thread Size?

S

Scruffy

Active User
Registered
Joined
Jun 5, 2013
Messages
549
A year or so ago I brought home a brown&sharp model 0 horizontal mill, I have finally got around to tinkering with it.
The power shaft that feeds the table power feeds has a u-joint design I've never seen. It's missing a fillister head machine bolt and I can't figure out what thread size it is.
Looks like 1/4 by 28 but it isn't. None of my thread gauges seem to fit it. The outside diameter of the threads is .235.
It's got me scratching my head more than usual. Any ideas out there?

Thanks ron
 
It is one of brown & sharp's special bolts. There should be a thread pitch gage that will fit the thread pitch. But the O.D. will be small. If you can't make a screw I would consider tapping it out to a standard thread. Your 28 pitch gage does not fit? Does it look like something closer or farther apsrt for the pitch?
 
M6 x 1 maybe? (.239 x 25.4 TPI) Not something I would expect to find in an old B&S, but sounds close.
 
Thanks for the response bill. It may be 1/4 by 28. I didn't have my glasses on and didn't realize my thread guage only went to 20. Thought it said 28 ??
Their's too many horse flys in my shop rite now to fool with it. More later.

Thanks ron
 
Brown and sharpe used their own thread sizes. I had to retap many on an old brown & sharpe universal miller. They wanted $5 each for screws at the time so I just retapped them to standard sizes. It may have a 28 pitch but be major diameter is undersize so that a standard bolt will not fit.
We just went through this on another thread for a tap handle.
 
Brown & Sharpe made their own standard threads before there were existing standards; I had a B&S #2 universal mill that dated about 1906, I used it in my shop for about 35 years, it was a fine accurate machine, but yes, most of the fastener sizes were "different". I remember those little screws mentioned, they had a little teat on the end to help guide them back into the oil holes, and they had a radiused face.
The smaller screws are made in machine screw sizes, not fractional sizes, hence the odd size diameters.
 
It's possible that it is not a nominal 1/4 screw. a #14 machine screw (now largely obsolete) has a nominal major diameter of 0.242. In the past, in addition to the lack of standardization, certain industries used fasteners that are now difficult to obtain. Sewing machines, some locks, typewriters, etc, and even doorknobs had what we now consider "special" screws. Some diligent search might turn up the proper screw, but often it isn't practical, so unless you are a real purist in your restoration or repair, do what you must to bring it compliant with current standards.
 
i happened across some antique/old vintage taps and dies a couple years ago.
there were many size and thread pitches i have never seen before namely
1/2-12 tpi
#14-20 tpi
#8-36 tpi
3/16-24 tpi
 
Ulma Doctor said:
i happened across some antique/old vintage taps and dies a couple years ago.
there were many size and thread pitches i have never seen before namely
1/2-12 tpi
#14-20 tpi
#8-36 tpi
3/16-24 tpi
Click to expand...
Hi Mike,

Don't throw away the 1/2 - 12 tpi tap. I read in a recent thread that the thread is used on a PM lathe. OP posted that he'd measured the thread at that pitch (as I recall) but questioned his measuring. Matt chimed in that the lathe in question does use that pitch. As a side note, my Jet JVM-830 mill has a 1/2 - 12 tpi thread on the quill handle. I broke the plastic handle and ended up making an aluminum replacement (somewhere on the POTD thread).

Bruce
 
Hi Bruce,
i should have specified, it was a 1/2-12 die in the lot :oops:the other sizes were taps and dies
but a 1/2-12 tap is easy enough to make if you have some O1 and an hour (double that in my case ;))
 
You must log in or register to reply here.
Back
Top