Looking for help with Central Machinary 8x12 lathe

[shobley]

I've had this lathe for a while...

http://www.stephenhobley.com/blog/wp...0/03/lath2.jpg
(Harbor Freight)

Up until recently I was successfully turning plastics on it - which proved to be very forgiving of my "newbie" techniques. Today I tried to machine some aluminium and it soon became apparent that my skills were sadly lacking.

The high-speed steel cutting tools lost their edge very rapidly - possibly indicating too much alignment error, or the wrong sized tool.

I no longer seem to have the lathe manual, but IIRC it didn't really cover anything to do with actually *using* it.

So... I'm looking for help in learning how to use this lathe correctly. Either books, online resources or via responses to the thread.

Specifically I need help with:

* Choosing the correct sized tools for the holder.
* The correct way to align tools.
* The speeds to use for different materials (steel or aluminium)

I can probably find some books on technique - but all references gratefully received.

Thanks,
Steve

[underthetire]

I would suspect the grade of the HSS or the grinding technique of them. I had one of those lathes, with a insert tool it even cut Ti pretty well.

[shobley]

Thanks for the reply - I discovered the cause of my immediate issue...

I was trying to enlarge a bore, and the bottom of the tool was catching on the inner diameter, making it look like the upper cutting edge was producing a bad (slanted) cut.

Once I ground away some of the supporting steel I was able to complete the bore successfully.

I do seem to be having chatter issues, so I'm going to test the (runout?) of the chuck with a dial gauge.

Are there other causes of chatter?

Steve

[underthetire]

Tool not on center
Tool radius too large
Tool hanging out too far
Work piece hanging out too far
Speed to fast
Thin wall part
Bad spindle bearings
Loose gibs on the ways
Machine not properly set down (anchored)
and about a 100 other possible causes

[alfiius289]

Hi. Did you find a cure for chatter? Do you have a height gauge? I made one using the mt3 dead center in the headstock for reference. Underthetire gave a lot of good things to check. You want your cutting tool well supported (think rigid), your workpiece well supported close to the chuck (think rigid), and your gibs correctly adjusted (and again, think rigid but not binding).
I get a lot of info (cause I'm a newbie) from Yahoo's 7x12, LatheMaster, and 9x20 groups.
Regards, Al

[Fastest1]

YouTube is an excellent source for instructional videos. I use it all the time. Here is 1 of my favorite guys (Mr.Pete222)

[Crevice Reamer]

MANUALS:

HF 8x12:
http://www.harborfreight.com/manuals...4999/44859.pdf

Lathemaster 8x14:
http://lathemaster.com/images/LATHE%20MANUAL%20PDF.pdf

CR.

[Johann ohnesorg]

Try to find "how to run a lathe" from southbend lathe works. That´s a very good book for beginners. Everything is heavily illustrated and explained in laymans terms. It was written for machinists that bought a lathe and never have owned one. From cutting speeds to tooling, everything is well described.

http://www.bbssystem.com/manuals/Lathe-Tutorial.pdf

Cheers,
Johann