How to find exact hight on a lathe

Joe Pie has a great video on setting lathe tool height. Not specifically on setting a drill in a QCTP, but the concept he shows will help, I believe.
Dhttps://www.youtube.com/watch?v=1MrjnIcscxI Darn sure took the quesswork out for me, and when the lightbulb lit, I had to grab my shades:big grin:
If the link won't work for ya, because I am a total noob at MANY things, just go to Joe Pieczynski, and look for the "Lathe tool height" video. He has helped me a whole bunch, just because he is a natural born problem solver, and just happens to run a very successful machine shop:cool 2:

+1 I watched Joe's video and immediately went out to the shop and used it to make myself a height setting tool that sits on the flat part of the bed way. Very handy.
 
Swinging an indicator (in the chuck) will not give you center. The indicator will read differently when upside down.
 
I would think indicating would be the most accurate but others have said different. Can someone explain how aligning by eye would be more accurate. I understand indicator sag but I would think it’s more accurate than by eye and feel?
 
I put together a QCTP-mounted drill chuck for much the same reason(s). I got a drill chuck with a straight 1/2" threaded hole on the back so I could use my 1/2" boring bar holder.

To line it up I faced two lengths of 1/2" drill rod and put one in the headstock chuck and the other in the drill chuck. Adjustment is an iterative approach. To start, I back the cross slide out until I can place the two rods next to each other. Then rotate the QCTP until the two rods are parallel, and lock it down. Then move the cross slide and carriage so the nicely-turned ends face each other and adjust the cross slide and tool holder height until you can't feel any step on the sides or top/bottom of the rods. A straight edge would work too.

I also made a cross slide lock so it wouldn't move around while I was drilling.

The arrangement is pretty handy if I'm step drilling -- the length variation in drills as I go from small diameter to large can exceed the range of my tailstock quill so I have to relocate the tailstock partway through the procedure. By comparison, the "quill" of my carriage-mounted chuck is the lathe bed so that problem is eliminated.

I did have to improve the fit between my carriage and bed (the lathe is an old 7x12). The carriage was tipping backwards due to the direction of the drilling force. Also, enlarging holes in brass using unmodified drill bits was far too "exciting" -- the drill would rapidly self-feed as the brass grabbed the drill. I dubbed a set of bits to get around that problem.
 
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I have the same brand/size lathe '97 vintage. I've eyed MT tool holders but don't have one. Does it have tang retention like what is in the tail stock if for example you inserted a large diameter drill with MT shank? Otherwise how does it prevent rotation, just socket friction?

I don't see establishing up/down and in/out center that big a deal because its essentially a point. But I am more curious about how you would ensure the MT axis is exactly aligned with spindle. Even if you rotated a DTI held in the chuck about the crest of an MT center, you would be tricked if the tool was off at an angle. maybe an alternative is insert an MT3-straight shank test bar & indicate at 2 different positions down the length? I bought one like this off Ebay. It was a made in India special but I was actually very pleased with its accuracy for the price.
Let us know how you get on. And some pics of it in operations would be nice.
 
Another way to align the drill chuck is to use a long drill bit and run it all the way into the chuck to see if the bit remains centered in the chuck.
This picture shows the set up although here the drill is too large to enter the jaws in the chuck as shown.
This is eyeballing it but you can get it quite well aligned if you use a test rod instead of a drill bit and chuck up a bushing that barely clears the test rod.

IMG_0138.JPG
 
There seems to be way too much brain power going into this question. Anything over 1/2" I usually drill from the tool post (small drills from the tailstock). Drilling is a roughing operation - even if you had that aligned perfectly and exactly on center - you still would not get a very precise hole.

I have a CXA size PhaseII QCTP. I set the holder height once (using a small pointed piece of rod), I align the holder/drill with the axis of the lathe just eye ball. To set the horizontal position, I set the drill bit with the cutting edge sort of horizontal and just eyeball to get close enough to center (intent is to have two nice chip curls). It works great, very quick to set up, quick to clear chips.

Drill away.
 
when you are wearing green shoes.

I must have been then. I secured a Starret Last Work on the end of a shaft against a pin in the end of the shaft. (Special job, just to check this problem) The Last work had been pointing down. I rotated the shaft 180º, the Last Word, (not really the Most Critical test indicator) moved .008. Gravity affected the insides of the indicator.
 
wow its absolutely unreal all the different ways and added complication and made up tooling and even stands ???!!!!! ,,to find the "center" for lathe turning.. when i went through my 2 year vo-tech school,it took all of 20 seconds for the instructor to show us how to do it, he had a piece of round bar stock already in a 3 jaw chuck ready to cut, he moved the cutting tool close to the bar and then pulled out his 6 inch scale and put it between the 2 and cranked the cross slide so that there was just enough preasure to hold the scale against the bar, if top of scale was tilted back just a little then tool was just under center, exactly where u want it, no need to try and get cutting tool perfectly centered, just under center is good,dont over complicate things, it wasts too much time,, for internal boring u need the tool to be above center, just the opposite."Perfectly On Center" !!!! ????? what for??? it gets u nothing and wastes time..just below center makes sure that only the cutting edge is touching the work, the area below the cutting edge CANNOT be touching the work it will rub, and thats not cutting..sometimes when internal boring u have to raise the tool way above center to keep area under cutting edge from contacting work,,..people KISS ,setup time can be a real time waster..
 
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