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 Post subject: Is there a cheap substitute for Trimount back fasteners?
PostPosted: Mar Tue 14, 2017 9:06 pm 
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Joined: Jul Sat 11, 2009 1:47 am
Posts: 250
Location: Cal
Have a lot of sets that need those "T" shaped push-in back board fasteners that I believe are called trimounts. Yeah, I could probably buy them, but it's one of those little nagging incidentals and you just HATE to spend more money for a set of trimounts than you did on the whole stinkin beat up radio to begin with. Any ideas greatly appreciated for cheap look-alike substitutes or even a method of "rolling your own".


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 Post subject: Re: Is there a cheap substitute for Trimount back fasteners?
PostPosted: Mar Tue 14, 2017 9:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12728
Location: S. Dartmouth MA 02748-1225 USA
A coarse threaded self tapping screw that cuts its own thread will work but drill size is critical. Too small and hole will split Bakelite, too large and it will strip out. Any drilling of a cast Bakelite hole should be done with bits that have been blunted by stoning the cutting edge at a near 0 deg with shank.

The self tapping screw will be hardened and have a fluke cut into its starting point.

The hole can also be tapped but choose a coarse thread and do not drill to root diameter. With a tapped hole a standard machine screw can be used.

YMMV

Chas


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 Post subject: Re: Is there a cheap substitute for Trimount back fasteners?
PostPosted: Mar Wed 15, 2017 1:17 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4300
Location: Charleston, W.Va.
I have done the same as Chas in the past when I did not have any Trimounts, i.e., carefully drilling and tapping a hole in the bakelite cabinet to receive a coarse-thread machine screw (usually either #8-24 or #10-24). This works fine as long as you are careful, patient and use the proper drill size and a sharp thread tap with plenty of thread-cutting oil, but of course it is not original.

But Ed Schutz now has reproduction Trimounts available at a reasonable price, and this is a far easier and more original solution:
http://www.renovatedradios.com/assets/i ... mounts.jpg
Ed does business as http://www.renovatedradios.com and is a paid advertiser here in the ARF. Click on his ad in the right-hand column. From his home page, click on "Antique Radio Parts", then scroll down the page to the "Hardware" section and you will find the Trimounts listed.

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Poston


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 Post subject: Re: Is there a cheap substitute for Trimount back fasteners?
PostPosted: Mar Wed 15, 2017 5:11 pm 
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Joined: May Fri 20, 2016 7:32 pm
Posts: 656
Location: Illinois 62217
You could go the other way and epoxy some studs into the cabinet holes and use some small acorn nuts (for looks) to hold the back on.

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"I know nothing about everything" Sgt. Schultz.


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 Post subject: Re: Is there a cheap substitute for Trimount back fasteners?
PostPosted: Mar Fri 17, 2017 8:14 pm 
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Joined: Jul Sat 11, 2009 1:47 am
Posts: 250
Location: Cal
I've tapped threads in Bakelite before, but it's not the solution I wanted. Roaming around the hardware stores so far has not yielded any solutions either. I bet 'back in the day these little things got stamped out by the thousands at practically no cost.


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 Post subject: Re: Is there a cheap substitute for Trimount back fasteners?
PostPosted: Mar Sat 18, 2017 2:39 pm 
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Joined: Feb Sun 02, 2014 9:13 pm
Posts: 1856
Location: Roanoke, VA
My solution is one that few people will stumble into. I went to an estate auction whose ad in the newspaper classified named a variety of electronics. It turned out that the deceased was a former radio-TV repairman and some of the auction items were the contents of his business shop, which he stored at home when he retired and closed the shop. I passed on bidding on the tubes, which were largely TV tubes and which two other bidders ended up splitting. I was uncontested for a large assortment (a few hundred packages) of General Cement hardware, the kind sold by parts jobbers in the little plastic boxes with the yellow labels. There were a few boxes of trimounts in various sizes, and I may have enough to last me the rest of my life. They have come in handy, as have many of the other GC parts such as plate caps. I carry a subset of the machine screws, nuts, etc. with me for work. I think I paid $25 for the lot, which would probably cost well over $1,000 to buy new at today's prices - a very good deal.

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Dale H. Cook, Antique Radios / Test Equipment (GR/HP/Tek)
http://plymouthcolony.net/starcity/radios/


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