How to find exact hight on a lathe

I've seen many, many discussions about the importance of getting a lathe tool/parting tools on center height. True to form, some think its important, others don't. My suggestion is to test it yourself and find out.

I don't like to guess and I don't rely on opinions so I did exactly that and found that going above center causes rubbing and deflection, while going below center increases wear and chatter. Getting on center seems to be the sweet spot where the tool cuts most accurately and finishes best. That led me to make a height setting tool over 30 years ago and I use one frequently.

This works for me but I know of at least one guy on this forum who uses his tool below center and seems to like it best that way, so test it and find what works best for you and go with that.
 
I recently bought a MT3 tool holder so I can drill from the tool post. How can I accurately find the exact up/down centre so I can set and forget the hight on the MT3 toolholder?

Just wondering why you want to dedicate an MT3 tool holder to drilling. I have nothing against it, I have dedicated a tool holder for drilling too but it was not being used for anything else. As a hobbyist much of my time is spent experimenting with set ups and trying different procedures just for the exercise. And my boss is OK with that.
 
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ok here's one tool i will admit to making, and it does come in handy for other things too.i call it an alignment bar,,take a ft long piece of CRS , nice and straight and clean, about 3/4 od, put in 4 jaw chuck , indicate to .000 ,face off, take center drill in tail stock and drill, then FYI put a indicator on that 60 angle, and bet most of u reading this will get .001-.003 runout !! get a piece of HSS grind to shape, and use it to slightly recut the 60 angle, so u have no runout..remove bar, flip around and do other end also..put dead center in headstock,indicate to .000 and another center in MT3 toolpost,after u indicate toolpost holder exactly 90 degrees to ways,put bar between centers,and use indicator with magnet OFF, on the ways across the top of bar,,from headstock to tool holder,then u can raise or lower tool holder till its perfectly on center..this alignment bar can be used to get tailstock prefectly centered ,and also offset for cutting tapers..and as to "set and forget" your tool holder ,dream on !! our home use lathes are not ridged and straight enough,,u may have it perfectly centered at the headstock , and find it .003 low at the end of your ways.best to get it centered in the middle and call it done..good luck..
 
great idea, eastokie!
 
I have to partially disagree with a comment made above. Like all things machining, the context and the equipment you use will cause differing results!

I ran out and tested the \the indicator in the chuck thing... again. I also phoned a friend that has a 'perfectly' centred tailstock. and he used his Mitutoyo indicator and verified my results (to eliminate operator error)...

Using my Mitutoyo tenths indicator, with the sliding dovetails, using the larger spigot (looks to be 9mm, I forgot to mic it) I get no detectable sag. I won't vouch for your setup but by holding the spigot in the 3 jaw chuck, I can indicate my tailstock and on vert and horizontal readings it is exactly the same. the only variance is slight twitch from the surface, but that is barely detectable.

I know this has become a mantra here lately but it isn't always true.
 
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