------ Original Message ------
From: "Rogan Creswick" <creswick@...>
To: [email protected]
Sent: Tuesday, 11 Apr, 23 At 05:55
Subject: [SouthBendLathe] Slot-milling worked out on my 10k

I posted a while back about needing to cut a slot without a milling machine; I thought I'd circle back and let you all know how it worked out.

The part I made is the back-gear engagement shoe for a Jet JVM-1044 bridgeport clone milling machine. It lifts a sprocket to engage with the bull gear that drives the quill when in back gears. I'm rebuilding the mill because I couldn't use the "front" gears, due to a horrible racket coming from the head.. the old shoe had broken, and I think it wasn't fully disengaging (although I'm not positive about that... still investigating).

Anyhow, I needed to cut a ~0.300" deep slot, about 0.195" wide, and 1" long. I started by laying it out, then cut three kerfs with a bandsaw, and broke out the two loose bits that remained, so most of the material was taken out that way, but the slot needs a good finish, and it needs to be a good sliding fit on a pin in the milling machine.

I put two 5/16 threaded holes in the T-nut for my tool holder and clamped the part to that, using a stack of shims to get the appropriate height, then used the compound to dial in the surface so it was parallel with the cross-slide.

I dialed in a 3/16 carbide endmill in the 4-jaw to ~0.0005" of concentric, and took three 0.100" deep passes, running as fast as the spindle would go, in the slowest powered cross-feed setting.

I had to adjust shims to get another ~0.010" of width, took three more passes (careful to avoid climb milling) and it was done (well, with the slot).

Here's a video of the milling op on the lathe:

I'm attaching a few photos of the old / new finished parts, and a shot of the lathe setup.

--Rogan