Tool holder/carriage angle?

[JeffF]

I have been watching lots of the lathe videos and noticed that the instructors use very different angles on the base unit that holds the toolholder. Tubalcain, for instance, likes to set his at 29%, while others seem to have it set at very close to perpendicular to the work. I know it is essential that the tool make contact with the work at the correct angle (straight in for parting for instance), but does it make any difference what angle you set the carriage that holds the tool holder at? Is it dependent on a combination of personal preference and making sure you clear the chuck when you get close to it? If it makes any difference I have one of the mini-lathes.

TIA,

Jeff

 

[idahoan]

I pretty much leave mine at 45 degs. unless I'm cuting threads; then it is easy to pop a boring bar in the tool post and cut a chamfer.

 

[JeffF]

I pretty much leave mine at 45 degs. unless I'm cuting threads; then it is easy to pop a boring bar in the tool post and cut a chamfer.

Once again, thank you for the response to my very newbie question! Does the 45 degrees automatically set the tool bit to the correct angle for facing and turning? I noticed there is a tab on the bottom side of the quick release tool holder, so you can't really turn that to get a different angle.

Jeff

 

[Swifty]

Hi Jeff,
What you are referring to is called the top slide. I leave mine set at zero unless I'm machining a taper using the topslide or threading.


Paul.

 

[Tin Falcon]

It depends on a few things.
first of all depends what you are doing with the lathe and if you are actually using the compound.
if you are turning and facing and not advancing the compound then whatever angle works for you.
if you are using the compound to cut a short taper. then you need to set the angle for the taper you are cutting.
when threading set at a half degree less than half the thread angle.
IE 29 degrees or 29 and a half degrees for a 60 degree thread.

if you want to take real fine cuts then set to just under 6 degrees then advancing the compound one thousandth will advance the tool one ten thousandth.(arcsin(.1) = 5.739 ) .

some lathes like second operations lathes and jewelers lathe the compound is the only way to get z travel so the compound is set parallel to the z axis of the lathe.
Tin

 

[JeffF]

Thanks guys, very helpful! I knew the angle was important when cutting tapers and threads, but wasn't sure how important it was when just facing or turning. i think I'll leave it at 0 and see how that works out for me before I start getting too creative. I start making my first chips this weekend! I figure some general practice before actually attempting to make any useful parts might be a good idea, so I get familiar with the processes.

Jeff

 

[Tin Falcon]

You do want the tool sticking out of the tool holder as littil as possible . Use the rule of 2 two times the size of the tool is good. and yes position the compound so you reach where yo need to and not hit the chuck or whatever is spinning.
Tin

 

[rake60]

I keep the compound on my 9 X2 0 lathe set at perpendicular zero.

However, all of my tools are mounted in the holders with about a positive 7 degree rake.

It doesn't matter if it is a brazed lathe bit in a 4-position tool post or a carbide inset tool in a QCTP.
That slight angle give the tool the clearance to take light facing cuts without needing to change tools.

Rick