1/4 in shank or 5/16 th shank lathe tools ?

TQA222

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These will be used on a 7 x 12 mini lathe with the stock tool post. The tool post limits me to 5/16th max in tool shank size.

Is there any benefit with going for 1/4 in shank tools with packing or should I stick with 5/16th ? Or is there little difference.

Light hobby use only, no production runs.
 
Unless you need to hang the tool way out of the holder, there is no good reason to use 5/16" tools, added rigidity with long projections is the only reason that I could see, and the 1/4" bits are going to be easier to grind and cheaper.
 
The 5/16 tool is a bit stronger than the 1/4 inch so should flex less and may improve the finish. Having said that, I use anywhere from 1/8 to 5/8 tool bits on my lathe depending on the exact project and tool requirement for the specific operation. But in general will go with the larger tool bit where possible.
 
5/16 seemed to be the correct size for my lathe, as just needed a little shim (maybe .010") to get on center. Thats with the 4-way turret tool post.
 
My 11” Logan came with Armstrong tool holders for 1/4 “ bits . I use These bits almost exclusively. I changed to an Aloris axa tool post and still use the 1/4 “ bits .
 
The 5/16" bits are not nearly as popular as the 1/4" ones. I've seen really good ones sit on ebay , making it easier to find high quality bits for cheap. They don't take much time to grind and will give you greater stiffness and reduced resonance so I would go for the larger bits, too.
 
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