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Making New Hallicrafters SX-28 Audio Out Bushings

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Making New Hallicrafters SX-28 Audio Out Bushings Empty Making New Hallicrafters SX-28 Audio Out Bushings

Post by Thermionic_Emission on Mon Sep 23, 2019 9:21 pm

These are so often broken as mine were.  The original bushings appear to be a ceramic.  

Making New Hallicrafters SX-28 Audio Out Bushings WmiuczZ



Figured I would machine them out of Garolite LE.  First, I modeled them in Inventor.  

Making New Hallicrafters SX-28 Audio Out Bushings S1DQA1e



Next, I generated the G-code and cut as many as I could out of a 6x6x1/4" thick piece of Garolite LE on my CNC milling machine using a 40k RPM inline spindle and a 1/8" carbide endmill.  

Making New Hallicrafters SX-28 Audio Out Bushings Et9vjLo



The old phenolic washers on the back are shot after all these years.  

Making New Hallicrafters SX-28 Audio Out Bushings A1Gkr2X



So I made enough of them out of super strong G10 fiberglass reinforced phenolic.  These got cut with a diamond endmill due to the abrasiveness of the G10.  

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I engraved the impedance on each one and filled with white lacquer stick.

Making New Hallicrafters SX-28 Audio Out Bushings DpTKt8K



They look very nice installed.  The bottom one looks slightly crooked, but that is the holes in the chassis that they sit in.  My mill easily holds 1/1000th of an inch over this short distance.  

Making New Hallicrafters SX-28 Audio Out Bushings KmCD5gO

Making New Hallicrafters SX-28 Audio Out Bushings D4yWMgb

Making New Hallicrafters SX-28 Audio Out Bushings PDNuxui

Thermionic_Emission
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Post by Chas on Mon Sep 23, 2019 11:30 pm

Hmm, that is the linen filled Garolite, interesting. Nice polished finish too.

The CNC could replicate almost any part for a radio, especially pot metal parts that have gone to crumbles.

But like any service there are costs...

Sure do miss the machine shop, I had access to. The machinist, would make what ever I wanted...

I did all the sheet metal work, custom instrument cases, industrial imaging equipment.

Oh well, on to different things Smile

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Post by Thermionic_Emission on Mon Sep 23, 2019 11:55 pm

The sheet has a nice shiny finish to it. Machining flat areas into it leaves a nice finish though not shiny. The only area I polished was the roundover after I sanded it with 320. The sanding was necessary because of the way the linen filler gets cut and leaves fuzzy edges. After the sanding, a quick hit with the dremel and some rouge was all that was necessary.

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