Toolpost Grinder Part 3: Bearing Caps

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In part three of the toolpost grinder build series, we make the bearing lock caps.

This installment features the return of the dreaded 57/64″ YG-1 taper-shank drill, but this time it does its job without complaining.  Or damaging the lathe.  Because this time I was smart enough to pre-drill first.  I think if I had done this last time, things might have gone better.

I decided to make a single blank for all three bearing caps and thread it all at once.  Three, you ask?  The spindle only needs two.  But for the low, low cost of about a quarter-inch of extra material, I get an extra one to practice on and screw up without wasting a lot of time and effort.  In the end, all three caps came out okay, but this way I got to pick the two that fit the bearings the best.

The threads on the bearing caps are 1-3/8-28 UN.  It’s actually a standard thread, but you’re not going to find a nut to test with while cutting, so I resorted to thread wires.  It’s a simple matter of holding two of the wires in the threads on one side of the part, holding another wire in the threads on the other side with your other hand and measuring across the wires with a micrometer using your other, other hand.  It sounds harder than it is, as long as you let gravity work for you.

Ultimately, I bored and parted off the three caps, leaving them a few thousandths oversize to allow for facing later.

If you haven’t seen the previous videos, I have a Youtube Playlist.

If you’d like to follow along with the build, here are some links to some of the parts and tools used in this video:

External carbide threading tool: (eBay*): https://goo.gl/mtD1DV
Thread-measuring wires (Amazon*): http://amzn.to/2xRoDqG
YG-1 57/64″ taper-shank twist drill (Amazon*): http://amzn.to/2kf1w4J
Noga Deburring Set (Amazon*): http://amzn.to/2xMfiPz
C20-ER20A-150L Collet Holder (eBay*): https://goo.gl/xufUxa
6805-2RS Deep Groove Ball Bearings (eBay*): https://goo.gl/GuCyHu

*These are affiliate links. When you click one of these links and make a purchase, it helps to support projects and videos like this one.