Thread Identification

[Guest BobD735]

I'm trying to identify a thread used on a map light for my car. I've measured the O.D. of the 1/4" long threaded part, and calculated that the thread is: 11/16-28. The nearest match I can find is 11/16-24.

Do I need a larger magnifying glass, or is 28 thds. per inch a special thread?

Bob

[Guest trainguy]

Tuff to see in 1/4 " of thread.Suggest that you find a thread pitch gauge[a machinest tool]'That will tell you what the pitch is.Phil

[Guest BobD735]

Hi,

Thanks for your response.

I'm trying to determine whether there is an 11/16-28 thread.

Bob

[Guest cben09]

Buy a 1/4" fine bolt at the hardware store,,,american fine is 28 tpi,,use as guage,,,Ben

[Guest cben09]

p/s British fine [cei],,is 26 tpi,,,and American pipe is 27 tpi,,,Ben

[Guest BobD735]

Hi,

From the responses that I'm getting, I think I'm confusing everyone. I have a map light which has, an externally threadeded male end, which I believe to be an 11/16-28 thread. I need to extend the map light and plan to use an internaliy threaded sleeve. I am trying to determine if there is an 11/16-28 thread, so that I can buy the correct tap to thread the sleeve.

Thank you,

Bob

[Guest cben09]

Wrong approach,,,make the "nut" on the lathe,,and thread the hole in the lathe,,,It's called single pointing a thread,,Should be a simple trade school job,,,,Do they have trade schools anymore ???,,Is this to put a metal dash item into a wood dash?? Can you counter bore the back side???another way,,MAKE a nut with a projection to go through the deep wood,,Fun,,Ben

[Guest cben09]

If the sleeve is very thin,,it could come out of the chuck,,Dont use the motor on the lathe,,,better to turn the chuck by hand,,better control,,I made a BSA motorcycle piston into a lenz hood for my camera this way,one dark night,,a piece of electric 3.5"condit made the extension,,,all threaded 48tpi [thread per inch],,Cheers,,Ben

[Larry Schramm]

Do you have a picture of what you are trying to match? It would help a lot with a ruler next to it.

[Guest BobD735]

Hi again,

All I need is to make a simple sleeve about 1" long with an internal 11/16-28 thread (1/4" long)on one end. This will thread into an existing male 11/16-28 thread on a map light. The other end of sleeve with no threads, will slip over an existing map light base, whose outside diameter is also 11/16".

I'm trying to find out if an 11/16-28 tap exists, as my lathe doesn't cut threads.

I'm doing this because I couldn't find a map light for my '20 Chalmers, but I did have the original base. The map light that I did find is the same diameter as my base, but it's threaded, and I have to be able to separate the two parts for assembly/disassembly. I believe my sleeve idea will work, so now I need to find a machinist to cut me some threads.

I really appreciate all of your inputs.

Thank you,

Bob

[Bhigdog]

Yes the 11/16- 28 tap does exist. Yes it is available from MSC Industrial Supply in both plug and bottoming taps. Yes it is expensive @ about $70. Yes they are on line. Or simply Google 11/16-28 tap and any number of suppliers will appear at a lot cheaper prices.........Bob

Edited October 12, 2010 by Bhigdog (see edit history)

[Guest BobD735]

Thanks Bob.

That's exactly what I am looking for. I'll check the sources out.

I really appreciate your help.

Bob