Lathe / Milling question

[BrentD]

Got a combination milling machine/lathe from Harbor Freight a while back but haven't played around with it much yet. I've got a couple of projects that I need to undertake eventually, but both projects have brought up some technique questions that don't have answers that are obvious to me.

I'm perfectly comfortable making flat and strait-line cuts both on the lithe and the mill, but I've been trying to figure out how to mill smooth curves with the mill or how to do smooth tapers and rounded ends/edges on the lathe.

Looks to me like both techniques would require moving the X and Y axes at the same time and varying the rates accordingly. I just can't quite see how to do this accurately and repeatably by hand, though it would be easy for a CNC machine.

I'd appreciate any tips you can give, and if there is a tutorial you can point me to it would be great.

 

[kennyd]

On a mill you use a rotary table (ROTAB for short)...Tapers are done a lathe with either the compound or a taper attachment depending on the length of the taper.

But CNC is the easiest

 

[kthompson]

It has been years since I ran either but did you see if your manual covered this at all? It would seem if you could they would give directions. Your thoughts seem correct.

Kennyd came to the rescue while I was posting.

 

[BrentD]

It has been years since I ran either but did you see if your manual covered this at all? It would seem if you could they would give directions. Your thoughts seem correct.

The machine came from Harbor Freight.... The manual is incredibly basic.

I kinda theorized that a dividing head or rotating table could be used. Didn't even think to google "taper adapter"until KennyD's post but once I did I found a nice site that shows you how to build all sorts of useful gadgets for the lathe:

GadgetBuilder's MiniLathe Site

 

[DanD78]

If you need to turn a long taper on the lathe you can put it between centers and off set your tail stock a little. You will be pretty limited on what you can do on a home owner machine like that. You can make or buy cutting tools that will round over corners or do form cuts on either machine. An Enco catalog would be helpfull. You can free hand cuts on the lathe and finish them off with a file using a radius gauge or a card board pattern as a gauge.
Wear your safety glasses...

Dan

 

[n6ckv]

Check the Home Shop Machinist web site for some information .

The Home Shop Machinist and The Machinist's Workshop

 

[Kernopelli]

Brent, I too have one of the bigger HF lathe/mill combos and it is very handy, I got mine "used"( actually brand new but never used) off Ebay for $300. That said, it isn't a high quality unit but for my basic needs/skills, it has been a good purchase. I am like you and have been looking for a way to cut accurate arcs and tapers without buying X/Y drives ( too much $$$) I have resorted to cutting freehand and file as mentioned by DanD78. I haven't had to do this for a precision application but have had pretty good results so far. I have also been buying the HF indexable carbide lathe tool sets, I prefer the 1/2" over the 1/4". They aren't too good on hardened steel but on other metals work fine and are pretty dang cheep compared to brand name items.

 

[kennyd]

I just remembered I had a link to these video's...they are OLD but the info is still current for manual lathes.

South Bend Classic Films

This site has some excellent text on cutting tools:

Cutting Tool Basics

This is an excellent resource also:

Virtual Machine Shop

 

[sandman2234]

Probably not an option with H/F's finest, but I have a Volstro rotary head that will do arc's and curves rather nicely while hanging on my Bridgeport. They make an extension to allow the same head a little longer reach. Take a look at them and see if you can adapt one to your use...
David from jax

 

[laurencen]

there are radius attachments for the lathe that fit into the toolpost, it works good to make shaft ends round and even ball ends, if you just want to say radius a flat bar end say 1 1/2 by 3/8, drill a 1/4 hole 3/4 from the end, put a 1/4 bolt in the toolpost and a carbide burr in the chuck, now little at a time rotate the flat on the bolt while cutting with the burr, this process will also work on the drill press and milling machine, for tapers on the lathe, you can get prety good, if you practice it will be close to perfect

LN

 

[laurencen]

To cut a radius in lathe these work good

Jabus ball-turning tool - stock code 3707

 

[3RRL]

Tapers can be cut using the compound on the lathe or tilting the head on a milling machine is yours let you do that. But you can also "step off" the taper ... or radius. There are "Radius Cutting" tables available that can be used in the lathe or milling machine. Or you can calculate the "X" and "Y" coordinates for any radius you want. Before CNC, that's how we did it. The smaller the steps the smoother the contour and you have to file in the steps. Using the same set up and calcs, you can repeat accurately.

You can make all kinds (or buy) radius cutting attachments too, but I always like to make my own. You can cut spheres either convex or concave using the step off technique in the lathe. You can also cut spheres on the mill with a rotary table and a fly cutter by setting the radius of the fly cutter and tilting the head. There is a formula for doing that. I have cut many many different shapes and contours on conventional milling machines and lathes way before CNC by using those techniques.
Rob-