Author Topic: screw/bolt specifications for WE 302 phones  (Read 7042 times)

Offline winkydink

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screw/bolt specifications for WE 302 phones
« on: September 22, 2011, 11:17:30 PM »
Is there a Western Electric library document that list the specifications for all the screws/bolts that are used in a Western Electric Model 302 phone.

I don't know about you but the phones that I purchase often have some missing screws.  I never quite know what to use as a substitute.  Today a "misplaced" (re: lost) the screw that bolts the 101A induction coil to the base, and so I need to find a replacement.

If anyone can point me to a document, or list the various screws I would much appreciate it.

Offline dencins

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Re: screw/bolt specifications for WE 302 phones
« Reply #1 on: September 23, 2011, 12:31:53 AM »
Do not know of a document but here are some that I have measured:

Footpad Screws   8-32 x 7/32"
Footpad Screws (Substitute)   8-32 x 1/4" / #8 Lock Washer S/S
Dial Grommet   ID 1/4" OD 11/32" GW 1/16" Hole 1/8"
Dail Mount   4-36 x 3/8"
Metal Switch Bar Top   6-32 x 1/4"
Metal Switch Bar Side   6-32 x 3/8"
Capacitor   6-40 x 1/4" (corrected)
2 Reed Switch Bar   6-36 x 1/2"
3 Reed Switch Bar   6-36 x 3/4"

The one you are looking for is 6-36 x 1/4"

Dennis Hallworth
« Last Edit: September 27, 2011, 12:33:43 AM by dencins »

Offline dencins

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Re: screw/bolt specifications for WE 302 phones
« Reply #2 on: September 23, 2011, 01:11:13 AM »
I should have mentioned that when the Unified Thread Standard (UTS) was adopted in 1949 by USA, Canada and UK, the 6-36 was left out of the general standard so they are not readily available today.  The UTS lists the UNC (coarse) as 6-32 and UNF (fine) as 6-40 and the only provision for 6-36 is UNS (special).

While I have not seen the screws for sale I have seen taps and dies available for 6-36 for people who would like to make their own.

Dennis Hallworth
« Last Edit: September 23, 2011, 01:24:44 AM by dencins »

Offline Brinybay

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Re: screw/bolt specifications for WE 302 phones
« Reply #3 on: September 23, 2011, 01:48:33 AM »
One of my 5302s was missing all three screws.  I took it with me to the hardware store to find some screws that would work.  I don't know what the specs are, the friendly Ace Hardware guy helped me pick out some that would work.  The two I used for the base screws are barely long enough to work.  I think the induction coil screw is often missing because it appears to be a base screw.
« Last Edit: September 23, 2011, 03:30:53 PM by Brinybay »
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Offline dencins

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Re: screw/bolt specifications for WE 302 phones
« Reply #4 on: September 23, 2011, 12:28:02 PM »
I suspect the Ace hardware person used a 6-32.  The strap that holds the 101A is 0.041" thick.  A 6-32 (32 threads per inch) has a pitch (peak to peak) of 0.031" so it would need be 1.3 turns to pass through the strap.  A 6-36 pitch is 0.028" so it takes 1.5 turns to pass through the strap.

It would not take much force to push the peak of one thread in the strap 0.003".  It will work but was not the original specification.

Dennis Hallworth

Offline dencins

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Re: screw/bolt specifications for WE 302 phones
« Reply #5 on: September 23, 2011, 12:55:33 PM »
Two other WECo screws that are difficult to find are the screws that hold the bridge to the faceplate on solid back transmitters.  The  early 2XX transmitter used brass flat head 4-36 x 3/16" and the later 3XX used steel round head 4-36 x 3/16".  These go into a blind hole and unlike the 6-36 in a 6-32 hole, it would be extremely difficult to force the thread.

The 4-36 thread is another one considered UNS by the Unified Thread Standard.  #4 screws available today are UNC 4-40 and UNF 4-48.

Dennis Hallworth

Offline Wallphone

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Re: screw/bolt specifications for WE 302 phones
« Reply #6 on: September 23, 2011, 01:27:05 PM »
Brinybay, Are you talking about the induction coil screw that is inside the phone or the condenser screw that is removed from the outside? I thought so. ;D I have the condenser screw as being a #6-40. I have both WE & AE dials taking a #4-36 screw but the AE type dials that are in the Conn./Signal Corps phones take a #4-40.
Thanks for the chart Dencins.
Doug Pav

Offline Brinybay

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Re: screw/bolt specifications for WE 302 phones
« Reply #7 on: September 23, 2011, 03:26:24 PM »
Brinybay, Are you talking about ... the condenser screw that is removed from the outside? I thought so. ;D

Doug Pav

Yeah, that.  ;D
« Last Edit: September 23, 2011, 03:28:40 PM by Brinybay »
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Offline dencins

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Re: screw/bolt specifications for WE 302 phones
« Reply #8 on: September 23, 2011, 04:39:03 PM »
Brinybay, Are you talking about the induction coil screw that is inside the phone or the condenser screw that is removed from the outside? I thought so. ;D I have the condenser screw as being a #6-40. I have both WE & AE dials taking a #4-36 screw but the AE type dials that are in the Conn./Signal Corps phones take a #4-40.
Thanks for the chart Dencins.
Doug Pav
The 6-40 would make more sense to me since it would be a standard NF (pre-UNF) thread size and I would think the designer would want to get as many turns (or part of a turn) in thin metal.  The 6-40 would be 1.64 turns.

I will go back and measure it again.  I had these specs in a spreadsheet from some time ago.  I do not have a 6-36 thread gauge and do not remember how I came up withthe 6-36 on that one.

Dennis Hallworth

Offline MAin 0-2368

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Re: screw/bolt specifications for WE 302 phones
« Reply #9 on: September 27, 2011, 12:03:40 AM »
Brinybay, Are you talking about the induction coil screw that is inside the phone or the condenser screw that is removed from the outside? I thought so. ;D I have the condenser screw as being a #6-40. I have both WE & AE dials taking a #4-36 screw but the AE type dials that are in the Conn./Signal Corps phones take a #4-40.
Thanks for the chart Dencins.
Doug Pav

Just checked two of my 302s and i'm getting 40 tpi for the condenser screws as well.

Offline dencins

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Re: screw/bolt specifications for WE 302 phones
« Reply #10 on: September 27, 2011, 12:37:13 AM »
I have changed my original post for the capacity screw to 6-40.  Anyone feeling like taking apart some switch bars?

Dennis Hallworth

Offline winkydink

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Re: screw/bolt specifications for WE 302 phones
« Reply #11 on: September 27, 2011, 09:03:41 AM »
I have changed my original post for the capacity screw to 6-40.  Anyone feeling like taking apart some switch bars?

Dennis Hallworth

So am I looking for a 6-36 x 1/4" or a 6-40 x 1/4" ?


Offline Wallphone

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Re: screw/bolt specifications for WE 302 phones
« Reply #12 on: September 27, 2011, 09:18:56 AM »
Wink, If you are looking for the screw that holds down the 101A Induction coil, that is a 6-40 X 3/16".
Doug Pav

Offline Wallphone

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Re: screw/bolt specifications for WE 302 phones
« Reply #13 on: September 27, 2011, 09:35:05 AM »
Dencins, If you are talking about the two screws that hold the hookswitch contacts together, that is a 6-40 X 9/16 (.5625). On a metal 302, three screws hold the metal finger cup on. The hookswitch contacts are mounted to the finger cup. Those three screws are 6-32 X .275". On the thermo 302's the hookswitch contacts trap the cup on. Two of the screws are 6-20 X .600 self tapping. the third screw is 6-32 X .275" w/washer. I hope this helps and I hope I'm right.  :o
Doug Pav

Offline winkydink

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Re: screw/bolt specifications for WE 302 phones
« Reply #14 on: September 28, 2011, 07:55:41 AM »
Wink, If you are looking for the screw that holds down the 101A Induction coil, that is a 6-40 X 3/16".
Doug Pav

Thanks Doug & Thanks Dennis !