Need Help Identifying A Mystery Thread

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I hope someone can help identify an unusual thread for me. My wife has a piece of furniture with handles secured with machine screws I can't identify.
Some screws are missing, so I'm trying to replace them. The diameter of the screw across the threads is .160 inches and the pitch is 30 TPI. Is this some
old furniture screw standard or what? The furniture was factory made and I imagine made in mid 20th century.
 
A number screw thread has a major diameter of the screw number X .013" + .060"
A # 8 screw therefore is 8 X .013" or .104" + .060" is .164" major diameter. If actually a #8 30 TPI screw it may be proprietary to the the manufacturer of the equipment.

More likely you have measured it incorrectly.
 
Are you sure that it's not an 8-32 thread? If you indeed have an 8-30 screw, 8-30 taps and dies are available from Traverse Tool Co. and I would guess from other machine tool suppliers.
 
If you are not concerned with a cosmetic match, the holes could be drilled and tapped for a 10-32 screw. If you want to retain the 8-30 threads, partially threaded 8-32 screws are available from McMaster Carr. The unthreaded portion could be threaded for 30 tpi.

If threading on a lathe, I would mount the threaded portion in the chuck to preserve the screw head and thread towards the headstock. Position the cutting tool in a groove just under the head and use the half nuts to start and end threading. 30tpi is not common and may not be listed in your lathe thread chart. However, it is often possible to find other gear combinations which will cut 30 tpi. My Grizzly 602 doesn't show 30 tpi but there is agear combination that will cut it.

If threading with a die, I would retain the original threads to provide something to grip. You should be able to rethread over the 32 tpi threads with no difficulty. You could turn down the end of the screw to create a start for the die to make it easier to cut the hread true.
 
I’ve never seen anything 1950s-on with anything except 8-32. Even the m4 is a fairly recent addition.
 
Wreck™Wreck said:
A number screw thread has a major diameter of the screw number X .013" + .060"
A # 8 screw therefore is 8 X .013" or .104" + .060" is .164" major diameter. If actually a #8 30 TPI screw it may be proprietary to the the manufacturer of the equipment.

More likely you have measured it incorrectly.
Click to expand...

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.
 
RJSakowski said:
If you are not concerned with a cosmetic match, the holes could be drilled and tapped for a 10-32 screw. If you want to retain the 8-30 threads, partially threaded 8-32 screws are available from McMaster Carr. The unthreaded portion could be threaded for 30 tpi.

If threading on a lathe, I would mount the threaded portion in the chuck to preserve the screw head and thread towards the headstock. Position the cutting tool in a groove just under the head and use the half nuts to start and end threading. 30tpi is not common and may not be listed in your lathe thread chart. However, it is often possible to find other gear combinations which will cut 30 tpi. My Grizzly 602 doesn't show 30 tpi but there is agear combination that will cut it.

If threading with a die, I would retain the original threads to provide something to grip. You should be able to rethread over the 32 tpi threads with no difficulty. You could turn down the end of the screw to create a start for the die to make it easier to cut the hread true.
Click to expand...


Unfortunately, there isn't enough material to drill and tap for a larger thread: the part is quite thin where the threads go. I've never threaded on
the lathe before, so I'd be inclined to use a threading die. I could turn some screws on the lathe and hand thread them. Thanks for the tip
on Travers: I'll check their site.
 
Update: I checked the Travers site and they sell both taps and dies in 8-30. I guess I'll make some screws.

What's strange to me is that since the tools to make this thread exist, someone, somewhere actually uses this thread.
 
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