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Just Another Chuck Mounting Question...

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  • Just Another Chuck Mounting Question...

    First of all, I want to say Hi to everyone here. I've been lurking for the two years I've owned my Logan 200. I hang out on a lot of internet forums to support my hobbies/work, and I have to say this is by far the most civil, knowledgeable group assembled on the internet.

    Like I said, I've had my Logan 200 for 2 years or so, and between it and here, I've been learning a lot. Most of the time I assume that the machine is much better at machining than I am, as its been at it since 1955, and I'm just starting out. I assume when something doesn't work out, its my inexperience, and set out to learn why.

    The Logan came with a Bison 4 jaw, 4304. I assumed all along that the slight taper I was getting was something I was doing wrong. This weekend I decided to figure it out finally. After digging through lots of threads and lots of test setups, the only thing I can find serious out of whack, was the chuck. When indicating the face of the jaws, if I set the #1 at 0, the #2 was +.004, and the #3 was +.008... Eureka! Simple enough, took the chuck off of the backing plate, trued up the face, put it all back together, all four faces are now within .001!

    So I start looking at the backing plate, and the back of the plate is out the exact same amount as the jaws were. While contemplating how the backplate (which looks to be original) is that far out. Then I realize that in all of my surfing, investigating chuck mounting, there was never a mention of welding on the backplate. Mine has 4 small welds around what appears to be a home made, pressed in nipple. I assume the previous owner did this mod after getting a killer deal on a chuck that didn't fit this lathe. (1 1/2, 8 thread)

    Is it safe to keep using this home-brew, or should I just get a new backplate and start over? Thoughts?