Question for Jet 1236 owners (lost knockout bar)

[Jen Joy]

I have a well seasoned (blue) Jet 1236 that didn't come with a knockout bar. If someone who has one or is better at looking stuff up could tell me what diameter and length the bar is that would be helpful. I know most anything would probably work, but why not attempt to emulate what came with it? I did learn these are also called drift rods. I had no idea. Thanks!

[Tom Rollins]

Scan_0001.jpgI have attached a dimensioned photo of my 1236 knockout bar.

[John K Jordan]

Scan_0001.jpgI have attached a dimensioned photo of my 1236 knockout bar.

That's an odd shape for a knockout bar! Why the smaller diameter on the end? Is there some sort of restriction inside the headstock spindle or does the end of the rod double for some other use, maybe something like to fit holes in the faceplate or another part of the lathe?

As for replacement, it wouldn't be too hard to make one even without a metal lathe. Could buy a length of 3/8" cold rolled steel and see if that would fit through the spindle, or a 5/16" rod should be well strong enough. If the end really needed to be smaller diameter to use as a knockout bar, it is actually not difficult to turn down mild steel on the wood lathe with wood turning tools. For a rod like this I would hold it with some pin jaws on a chuck or even the slides might work without any jaws. If the 0.23" diameter on the end is because the larger rod won't fit all the way through the spindle, I'd probably hold about an inch or so in the chuck, turn down about 1" to .23", then turn off the lathe and saw it off with a hacksaw. Than turn a wooden handle to fit. (I made a short knockout rod for a Nova live center.)

I machined steel like this to customize a set of Nova chuck jaws for a specific precise use. I used a 1/2" Thompson scraper and ground the end as normal but with a slight curve. Using a slow speed the handheld HSS scraper cut the steel OK. I expected as much since HSS is often used for cutting steel on a metal turning lathe.

turning-steel_IMG_20170605_081521_124.jpg

The cut was slow but not the least bit "catchy". The only thing to watch out for is the process creates small "needles" of steel you don't want touch. The machining didn't take long but I did have to sharpen the scraper several times.

JKJ

[Jen Joy]

Wow, Tom -- thanks for the diagram! Above and beyond, and also that is really weird to echo John.

Thank you both for the information.

[Tom Rollins]

The narrow end does fit into the spindle lock/indexing hole; so I suspect that is the reason for it.

[Jeffrey J Smith]

If you're making one, I'd suggest adding about an inch of brass to the end - I drilled mine out and tapped for 1/4-20 threads then cut the head off a brass bolt appropriately sized to the diameter of the ko bar. Just slightly softens the blow. Did that to the jet ko bar and the Robust when I got it...

[Brice Rogers]

Based on Tom Rollins post, you could make the knock out bar just a straight shaft, with no reduction in diameter at the end. Then make a secondary rod for the spindle lock/indexing hole.