Page 1 of 1

Edison Standard Model B feed screw

Posted: Tue Oct 05, 2021 6:27 pm
by bartongreg8238
Edison std model B with M8 x 0.5 on it
Edison std model B with M8 x 0.5 on it
I have this rusty feed screw I have been soaking and wondered what type of nut I could use to see if the threads are ok. I found a metric nut that fits pretty good, thought to share. M8 x 0.5

Re: Edison Standard Model B feed screw

Posted: Wed Oct 06, 2021 10:08 am
by Dave D
How well does it fit? I think that those feed screws use a different thread shape. I am sure someone like Jerry Van can comment more intelligently.
Dave D

Re: Edison Standard Model B feed screw

Posted: Wed Oct 06, 2021 10:48 am
by phonogfp
Dave is right - the feedscrew uses a buttressed thread, and it isn't metric. A good soaking in Evaporust and perhaps a gentle brushing with a brass wire brush should accomplish all that's possible in its rehabilitation. It might be better to simply replace it with a good one - which should be readily available from several suppliers.

George P.

Re: Edison Standard Model B feed screw

Posted: Wed Oct 06, 2021 10:58 am
by recordmaker
The lead screw is 50 TPI 3/16 inch as far as I can see the 50 TPI lead screws being coarser are not buttress threads like the 100 TPI on the Triumph and Home designs but there is no reason for them to follow any stock thread standard form of the time either.
The M8 fine 0.5 pitch will be a loose fit on the 7.9375mm thread being a little larger than the 8mm core diameter of a M8 screw and has a pitch of 50.8 TPI but on the narrow nut you show this wont really notice.
However it is possibly not the ideal thing to use as a chaser to clean out the threads as the shape of the thread may be at a different angle.

PS
I have looked at my Fireside leadscrew and it does not look as if it is buttressed and i think it is the same as the standard but i will have to get he microscope out to be sure.

Re: Edison Standard Model B feed screw

Posted: Sun Oct 10, 2021 7:51 pm
by bartongreg8238
Evapo rust is awesome! It really did a great job on the feed screw, although there is a significant amount of pitting. This poor feed screw will probably be a display model


Thanks again!