Friday, April 16, 2021

Machining The Turntable Base Casting

Now that the turntable base has been cast, it's time to machine the features to make it functional.  I started by setting it up on the milling machine upside down with spacer blocks underneath, and clamping through the middle.  In this setup I faced the bottom contour.

Here is a closeup of the finish, now the base will sit flat for the next setups.

I mention in the platter segment that I revised the spindle design to use bigger bearings.  This meant the original bearing boss casted directly into the base wouldn't be large enough.  Therefore, I had to make a bigger one and attach it into the platter support platform.  Here I've started the first side in the lathe.

Then machining the other side.  I didn't have two identical bearings, so the bores were different sizes.

Next, to mount it in the base, I began machining a hole where the original boss was.  I started by plunge cutting a rough circular shape.

Then I used my big Criterion boring head to machine it smooth.

To mount it, I drilled and tapped three 5/16" holes.  I also faced the area around the bore so the new bearing boss would sit flat

The new boss mounted.

Lastly I faced, drilled, and tapped a 1"-20 hole for the tonearm bushing.

Next Step - Casting The Platter

Previous Step - Casting The Base

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