Newbie Sticker still unremoved from my forehead.. Here we go.. with both left feet!

[Turnaround]

Another thought is the material thickness of the spindle is what it is and is in a stress relieved natural state so to speak.

Side stepping...Just out of high school we worked at an engine machine shop straightening crank shafts and cam shafts and tools used were chisel and hammer to change surface stresses to cause shaft to "bend" in the direction needed.

Back to point. ..drilling or reaming the I'd of the spindle MAY cause internal material stresses in the graining of the steel resulting in bending of the shaft which would cause wobble at the chuck ruining the spindle.

These small "hobby" lathes get good money due to small size and easy to move weight.

Clean up the old one and sell it then look for a suitable lathe and upgrade...It is a disease....

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Just out of high school we worked at an engine machine shop straightening crank shafts and cam shafts and tools used were chisel and hammer to change surface stresses to cause shaft to "bend" in the direction needed.

I too ran a crank grinding shop. I soon caught on to the stress riser created when you chisel smack a shaft in a filet (straightening it). Magnafluxing before and after proved the point, and worse, racing those straightened parts usually resulted in broken parts right where the chisel marks were.


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[MetalMuncher]

Post #37 is what I was going to suggest as I got halfway through reading this thread. If you had a secondary spindle you could bore out, you could preserve the tapered stock spindle for use when you need it, or to install if/when you sell the lathe to someone else. I've never used a lathe bigger than my 7x10 mini lathe, but I HAVE often wished I could run larger round stock through the bore! And I don't make gun barrels. Even with the less than 10" projects I have turned, I have wished for this ability many times. For one thing, it consumes less material when you can just turn the end of a long rod, pull out the remainder after your part is made, and save it for next time, rather than having to cut a blank to the length you need + the depth of the chuck jaws, ending up with that extra chuck jaw length left over. Yes, I may need it for something small "someday", but I have a whole box of those leftovers, so "someday" doesn't seem to come that often.

One of the things about being a newbie is the "all things are possible" frame of mind, simply because you have not yet encountered reasons they are not possible. It drives creativity and unique solutions. Were I in your position, and could find a spare spindle, I might try boring it out. As much as I'd like mine to be bigger, I have a hunch it isn't made from all that thick of a rod to begin with in this little lathe, so likely would not hold up if it were bored out. I suppose I could also mention that in 15 years of using and modifying this lathe, I have never put a center in the spindle bore, I've always used a lathe chuck on that end of the work piece. But I suppose that varies a lot with the kinds of things we all make. Overall, I agree with the advice not to bore the spindle you have now. But it might prove interesting to try on a secondary spindle if you feel the experiment is worth the cost of another spindle. As one member mentioned, it is your lathe in the final analysis, to do with as you see fit. If you feel it would be more to your liking to have the bored spindle, why not put one in it?

 

[ghostdncr]

I mentioned making a new spindle from 4140 earlier in this thread and the idea has been rolling around in my head in the days since. Using a much stronger alloy than the originals would allow for a thinner wall wall thickness while still retaining comparable strength, right? Well, I've never had the spindle out of my 12" Craftsman and finally got around to doing some research this morning. I have the occasional job where a bigger bore would completely change the setup and allow for much easier and faster turning.

This idea soon evaporated when I realized the scope of such a project. Here's a photo I found of a 12" babbitt-bearing spindle. There doesn't appear to be much difference between this one and one designed for the Timken roller bearings, as near as I can tell:



In making a spindle to allow pass-through of larger OD stock, the reduced diameter to the right would need to be brought up to near the same diameter as the portion on the left. Looking at the number of parts that sit to the right of that shoulder, we would be looking at extensive modification to a host of components to successfully implement this change. If I'm interpreting the schematic correctly, the small back gear is the last component that rides on the larger diameter. A collar with set screw butts up against the shoulder and changing it's bore diameter wouldn't be much of a problem, nor would several of the various spacers, baffles, dust cover, etc. that sit along this smaller diameter. On the roller bearing headstocks, I'm pretty sure p/n 10A-11C is that lipped bearing that, when found, carries a price tag between $800 to $1600! I was reading about this in another thread but can't seem to find it this morning to use as reference. Now, we're most likely into line boring the headstock to accept an alternate bearing with a larger ID, which may not be a bad idea considering the scarcity of the original part, but still. I think the other components fitted to the smaller OD of the shaft could be modified to fit, but the scope of this project has grown quite rapidly and we're no longer in "swap spindles back and forth" territory. It would be a permanent modification requiring lots of time and money, and probably enough to fund the purchase of a more modern lathe that already has a larger bore.

With the idea fairly-well researched, I can scratch it off my list and move on with my life.

 

[Scott.S]

You have discovered that these machines were designed for certain ranges of use...if your machine has a MT3 taper you will have larger i.d. on the spindle. Kinda like trying to haul a ton on rock in the back of a half ton pickup...it isnt just the rear springs you need to think about. Maybe you need to find a second operation lathe to keep tge footprint small. Good luck