FP1 Lamp Holder Thread?

[adh2000]

Does anyone know for certain what the thread is in the FP1 lamp holder? Mid 60s two dial machine. It's a female thread and there's only about 10mm of it so it's difficult to tell. Possibilities include:
3/4-16, seems unlikely being a metric machine but a 3/4-16 bolt goes in without binding, loose though so IDK maybe they used an English thread for the US market.
M20x1.5, maybe, but I'd have to order a bolt to check it, nothing around here with that thread on it.
PG13.5, God I hope not. The PG threads on the electrical cabinet and motor housing were nothing but a pain.
Some metric pipe thread. Do they have those? Never ran in to one but a tapered thread could make sense here.



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[cwilcox]

I don't have an FP1 but if 3/4-16 threads in maybe it is M19x1.5?

 

[ballen]

Does anyone know for certain what the thread is in the FP1 lamp holder?

Post a photo here. If it's the same part as on my FP2, I have a labeled tap that fits, because I made a replacement which also holds the coolant tube.

 

[AlfaGTA]

Believe its 20x1.5 for the thread.
But its more complex than that if it follows the other machine families.

The nut is used as a compression "B" nut that tightens against a nylon ring that fits tightly over a circular extension of the lamp bracket.
The tubular section is 16mm in diameter and extends to the bottom of the lamp mount. The nylon ring is located using a round wire snap ring below the nylon ring.

Its made sort of like a plumbing connection that uses compression fittings...
The point is that the nut holds everything down, putting pressure on the nylon ring . Believe the ring seats in a relief in the bracket. Allows the base of the lamp to rotate and be adjustable
by tightening the nut against thee nylon compression ring....

Cheers Ross

 

[adh2000]

Yes. Thank you for taking the time to post that, very helpful. I'm going to customize to fit a different lamp but will use this strategy.


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[DJ2]

That is what we did.

 

[AlfaGTA]

The important thing here is that the lamp support or stability is a function of the extension that enters and is supported by the mount. The nut just retains the package and
provides some tension to keep the lamp bracket from swinging freely. (holds position)
Cheers Ross

 

[ballen]

My FP2 lamp holder also has an M20x1.5mm thread.

Ross, your picture is interesting, because my unit no longer has the white plastic ring. Adding it would provide some tension to make rotation less free. Perhaps I'll turn one from delrin and add it in.

 

[AlfaGTA]

Bruce:
Think the plastic ring is square on one side (against the retaining ring) and tapered where it bears on the threaded piece.
Cheers Ross