Finding tool centre height on a lathe

[Pete.]

On my lathe, a previous owner has scribed the center height on the side of the tailstock ram, so all you need to do is slide the tailstock up and set the height of the tool using that mark.

[Bogstandard]

Pete,

On a lot of early lathes, that is how they came from the factory, purely for that purpose.

There is a problem with these early lathes. As the tailstock wears, they get what is called a droop snoot, where the ram starts to hang low the further it protrudes from the main casting, so if you set your tooling with the ram even partially extended, it would be set too low.
The other problem with the tailstock marking system is that most times, the ram can rotate a little in it's housing, so rendering the height marking useless, it could be almost anywhere.

Problems, problems problems 


Bogs

[Pete.]

Gotcha John, I never thought of that.

Easily remedied by marking the nose or side of the tailstock housing rather than the ram, much less versatile though!

[AndyB]

Oops!
I'm with Pete there. I don't extend the tailstock though, so maybe that's why it works...well it does for me.

Thanks John

Andy

[Bogstandard]

Pete & Andy, or anyone else who uses the tailstock method.

I am certainly not trying to say your are wrong in using that method, it has stood the test of time. I was just trying to make you aware that a problem could occur and you need to check if either of the two problems are present on your lathe before you use it.

My last lathe was an old atlas, and before I repaired it, it had those two problems in abundance.

http://www.homemodelenginemachinist.com/index.php?topic=2114.0


John

[Jonny]

The scribe type methods only get you some where near unless happen to drop lucky.
Cant beat taking a face cut and altering height to remove pip.

[Bogstandard]

A bit of a back against the wall statement there Jonny.

What about tooling that can't be used in a facing off scenario?


Bogs

[Stilldrillin]

Most of the tooling I use can be used for facing.

So, I have an (originally), 2" length, of 1/2" dia brass. With a "centre" point turned on one end.

Hold in chuck. Set tool to "centre" height.

Reverse the bar in chuck jaws. Then take a small proving pass across the end face...... 





Unless there's already a part finished component held in the chuck....... 

David D

[Jonny]

Not exactly Bogs i honestly cannot think of any type of tooling where you have to do that way.
May be a knurling tool.
Any type of tool that cuts be it boring bars inc internal thread cutting, grooving can be used to face off, same with cut off and grooving tooling, why settle for second best.
 
Quite agree Dave but i dont bother with a point.
Will also show some weaknesses in setup, whether that be tool flex or beds and slides.

[Bogstandard]

You are quite right, if you put the tooling into a position where you can use it to face off.

Unfortunately, you then have to move the tooling to a position where you need to use it in it's correct mode of operation.

The advantage of a scribed line technique is that you set the tool to the correct height and then it doesn't need to be touched, as it is done in it's working position.

Rather than arguing over it, you do it your way, I will do it mine, and I will waste not one bit of metal by continually facing off.


Bogs

[BillTodd]

Make yourself one of Bogs' tubular squares then cut a groove in it at the right height.

http://madmodder.net/index.php?topic=2175.msg42514#msg42514

Bill

[wanabemachinist]

i know the answer to the boring bars having a negative angle position and still be considered a positive .

BECAUSE!