Thread pitch for microphone stand connectors NOPOL

Thread pitch on microphone stands and accessories was 5/8"-27 when I got my phone second in 1963, I don't think it's changed. (I vaguely remember something about a modified thread form too, which might account for the .614" You measure.)

Machinery Handbook shows a 5/8-27 UNS thread. Page 659, 25th Edition.

The standard US thread is 5/8-27. Some lathes include that in their quick-change gearbox, including my 12x24" Clausing 5418. Others don't bother. If you are stuck with one of those, you can purchase taps and dies from MSC (among other places).

It also happens to be the thread pitch for the brass tubing that switched light sockets screw onto, though (of course) the actual diameter is different. (I *think* that the latter thread is descended from gas lighting.)

There are several other European mike thread standards, but most sold here in the USA include an adaptor to the 5/8-27 thread.

Enjoy, DoN.

Thanks for the replies. I wasn't able to set up 27 tpi feed on either lathe, so I tried 1mm. It's not a good match, but I can get about 8 full threads to engage when assembled by hand, so it'll do OK for this application. The purpose is to use the microphone goosenecks to hold a magnifier/flourescent lamp head and another magnifier without lamp.

WB ............

definitely 5/8-27, I have the tap, and lathe turn that thread as well

27 TPI = 0.9407 mm 1mm = 1.000 mm

Error = 6.3%

8 threads = about 0.5 thread error total.

What lathes do you have? While not all quick-change boxes will handle it. even the 6x18 Atlas/Craftsman will do it with the bushel-of-gears threading setup.

Obviously, metric lathes have a problem here, unless you can find the right gear set, or can change the leadscrew and half-nuts to inch ones.

O.K. A reasonable use. I hope that it is stiff enough to support the lamp/magnifier combination.

Good Luck, DoN.

P.S. Beware of putting "NOPOL" in the headers, as it might be trapped by those who are filtering on "POL" (as I am about to start doing.)

The mic stands I've known have been the same as all camera tripods - 3/8" Whitworth (professional/large cameras) and 1/4" Whitworth -(amateur/miniature cameras).

I have seen some odd ones with a fine thread, but they've all had adaptors to the Whitworth threads anyway!.

Dave.

[ ... ]

In an earlier response in this thread, I stated that the 5/8-27 was the standard microphone thread in the USA. I also mentioned that there are several other standards for individual microphone manufacturers (usually Germany, Japan, and the like -- for high-end microphones.

Imported (to the USA) mike stands are often that thread, and come with an adaptor as described. However, every one which I have encountered made in the USA used the 5/8-27 thread.

Enjoy, DoN.

DoN, the lathes I have are imports, a 9x20 and a Smithy. I'm not too swift about figuring out other thread/gear combinations, so I've only used the combinations that are included in the machine manuals. The 9x20 has a QC gear box and extra gears, and the Smithy just has a gear set to choose combinations from.

I was taking part in the Yahoo 9x20 group for a while, and some of the other users provided other thread pitches that aren't printed in the manual. Those charts are on one of my previous hard drives, but I don't recall printing any of them for reference (procrastination again).

The gooseneck for the magnifier lamp is plenty stiff, although it may loosen up with use. I've found with other goosenecks that I've used for other purposes, that they can be stiffened by adding a bundle of solid bare copper placed in the hollow center. Soldering one end of the bundle together makes it easier to pull the bundle into the gooseneck. Of course, that won't work well if a power cord passes through the center.

WB

I have a Smithy AT-300 and an APL program I wrote to compute gear combinations. What model do you have? I also accurately measured the pitch of my lead screw. The combination for my particular machine to get 27tpi is

1 51 33 57 32 0.9409996753 26.99257042 Speed selection:1; Gears 51 33 57 32; gives 26.99257tpi

The gears may be re-arranged if that doesn't fit well. i.e. the 33 and

32 may be swapped and/or the 51 and 57.

Ted

Thanks Ted, I might get a chance to try this combination over the next couple of days.

I believe the model I have, according to the manual, is a version of the AT-300 but it's also referred to as a CB 1220XL in the manual. This may have been a transition model, after the AT-300, but supplied with the longer cross slide and a sector/banjo? for changing different sized gears and also providing leadscrew reversal.

Recalling from (a feeble) memory, I think the lead screw is 2mm x 20mm left hand.

WB .................

You should measure your lead screw pitch. I just re-measured mine since I now have better instrumentation than I did several years ago. I used to think it was 1.994mm. I've revised that to 1.996mm. That was the average of three 20 turn distance measurements each over 2" and progressing along the ways in the most used area. The difference is pretty small and not far off the nominal 2mm but it's nice to know. The measurement setup can be seen in <

Your gear train setup looks pretty much the same as mine after I purchased the left hand threading accessory.

A run with the revised lead screw pitch gave

2 39 49 57 33 0.9408 26.9979 Not much difference in pitch but might be a handier fit for the gears.

Ted

Thanks again Ted, your help is much appreciated. I tried the previous setup you recomended, and it worked well for 27 TPI. The parts fit together to the full depth of the thread.

I probably wouldn't have attempted threading under power with the AC motor since the stop/coasting was unpredictable, but this vari-speed DC motor setup worked well. The rotation stops within about a half-turn of the chuck at slow speeds (not cutting).. that's without any braking resistors or other means to stop rotation.

WB ................

The way the Smithy chuck is mounted, there is no problem running the machine in reverse. For threading, I put the tool behind the work so I thread away from the thread start. I then back the tool out to return to the start so a little overshoot is harmless.

I'm planning to build myself a DC motor setup. Did you build yours or is it a comercial unit?

Ted

I'm replying to an earlier question that I missed

Ted had asked: I'm planning to build myself a DC motor setup. Did you build yours or is it a comercial unit?

The motor drive I'm using is a GE Statotrol Jr, 90VDC, 3/4 HP unit for use with 120VAC line voltage. It performs very well with the Indiana General PM

90V motor I'm presently using. It was problematic with a used PM treadmill motor I tried (rated 7000 RPM, 2.5 HP 130VDC). That motor may have a fault, but I'm not sure.. it was drawing too much current and blowing the 15A fuse in the Statotrol drive.

It's a bit of an odd chassis configuration.. an unusually long rectangular board and heatsink. I had an unused flea market electric service panel enclosure that worked well for mounting the drive, relays, low voltage DC power supply and numerous terminal strips for a remote control box I made from a small aluminum enclosure (originally intended as an Apple disk drive enclosure).

I've got a KB controller that I plan on using for this machine when/if I get around to mounting it in an enclosure.

I started creating a web page for this sort of stuff, but can't seem to keep at it to get it completed. If I can provide any other info, I'd be glad to.

WB