Finding lathe center height the easy way.

Jimsehr

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Use height gage touch top of stock . Take half of stock dia away and you have centerline. Mark this size on tool post and you always know true center.

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This is the easy way, determine a distance from the ways to center and then use a ruler to measure the tool, I have done this for years without ill effect.

If one is truly determined to have the tool on center (parting to 0 for example) just run it across the face of a part and adjust it until the nub disappears, this approach is fool proof
 
I made an aluminum gauge rod that gives me the centre height as a fixed gauge. I can feel within .002 quite easily to make sure the tool is on centre.I usually achieve closer to .001.

I measured using an electronic vernier the height from the saddle top to the top of a known gauge block in the chuck, then the height from the flatway to the saddle, and subtracted 1/2 the diameter of the gauge block.

That established the length of my aluminum setup rod.
 
Watch Joe Pie's video. In general, 1/2" diameter in the chuck, 1/4" diameter on top of your height gauge. Sweep across the top of both, adjust the gauge until equal. Pretty easy conceptually.
 
The thin steel rule between the stock and the tool edge can be fairly accurate if your ability to judge a vertical condition is decent.

Another way that I have found to be accurate is to use is this low cost tool. eBay cost is under $10. I found that it would detect a change of less than .002" in tool height. One requirement is the lathe must be level front to back.
https://www.ebay.com/itm/Lathe-Gage...l-center-height-setter-USA-MADE-/370592279135

Finally, I made a gage and calibration standard which allows me to set tool heights with .001" repeatability. An advantage is that I can set repeatable off center tool heights. A description is found here: https://www.hobby-machinist.com/threads/making-tips-for-a-dial-indicator.67209/#post-561864 post #3.
 
I don't believe it's all that critical. I've found some materials like the tool slightly above center others slightly below. Wherever it's happy is where my tool sets.
 
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Yep, happy is happy, regardless of what things say should be. Center is just a good starting reference point.
 
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