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antique bell collar screw

Postby Donn » Thu Sep 20, 2018 4:55 pm

Looking around for a replacement, for a bell collar thumbscrew for my 1941 Holton, I can see why it has been getting along with 2 for lo these many years, before I got it anyway. The thread is 1/4-24 (looks to me anyway), which apparently was not that uncommon before WWII but hasn't been used since. I found a screw for a Duesenberg generator shaft, but not really interested in that because, for one thing, it's steel. The repair shop around the corner offered to re-tap the screw receiver, I suppose for 1/4-20. I'm thinking I might be able to find a machine shop to make the darn screw. Anyone ever do that? Would I need to bring a spec for the brass, so it isn't harder than the female threads? It has been a while since I visited a machine shop, and I'm not sure they haven't all been displaced by fancy restaurants, but last time it was fairly painless.
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Re: antique bell collar screw

Postby bloke » Fri Sep 21, 2018 5:01 pm

McMaster is only showing 1/4×20 on their website.
I would be willing to take a Conn brass thumbscrew, cut off the threads, counterbore a little bit, and braze on 1/4×24 threads, if that would make you happy. I don't know how closely it would match the other two. If you would like for me to do this, I would be glad to do this as a favor to a fellow TNFJ "bored" member...(??)
If the oem Holton circular thumb part is smaller than Conn, Allied Supply offers a generic one with a slighter design.
The cutting/brazing technique is much easier for me than making one from scratch on the lathe...
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Re: antique bell collar screw

Postby Greenbenches » Sat Sep 22, 2018 7:48 pm

Send me the measurements of a good one or a clear profile picture and I can do it on the lathe in brass or other metal. I may have a 1/4-24 die or I can single point it. No guaranty that I can match the knurl. Brass is not particular about compatibility, I know that I have some 360 on hand.
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Re: antique bell collar screw

Postby roweenie » Sat Sep 22, 2018 9:38 pm

The only place where I've ever seen a 1/4-24 thread used is on the Model T ring gear, where it's screwed (with brass screws) to the flywheel with the magneto magnets -

https://www.modeltford.com/item/3278.aspx

90 cents each, should you be interested in cutting and brazing.
"How many guesses......!"
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Re: antique bell collar screw

Postby bloke » Mon Sep 24, 2018 10:22 am

I could easily run a 1/4 x 24 die down a 1/4 x 20 thumb screw (re-tap)...and it would work fine, but it would be more elegant and less hillbilly to do otherwise (either buy a 1/4 x 24 brass screw, or just run a 1/4 x 24 die down a 1/4" brass rod.
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Re: antique bell collar screw

Postby Donn » Tue Oct 02, 2018 8:35 pm

roweenie wrote:The only place where I've ever seen a 1/4-24 thread used is on the Model T ring gear, where it's screwed (with brass screws) to the flywheel with the magneto magnets -

https://www.modeltford.com/item/3278.aspx" target="_blank" target="_blank" target="_blank

90 cents each, should you be interested in cutting and brazing.


Thanks! I got a couple of those, and managed to bang together something usable. The top was a nut, $1.49 at the hardware store up the street, with the seat filed off, and 1/4 x 20 threads. I cut off the threaded end of the magnet bolt, ran the nut on as far as it would go, and filled the hole with solder.
Image

It's a little longer than it should be - when I cut the bolt, I was hoping I could run the nut on farther - but works OK. (It looks small, and in fact the thread diameter is a hair less than 1/4", but the visible difference is just perspective.)

(And of course thanks to all the rest of you.)
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Re: antique bell collar screw

Postby roweenie » Tue Oct 02, 2018 10:02 pm

Nice job - glad to have been of service :wink: :tuba:
"How many guesses......!"
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