Monday, December 13, 2010

First lathe experiments

I finally got a few days off, so this morning I began to do things with my new lathe.

My initial motive in getting the lathe was to have the capacity to make my own extruder hot ends.  Given my total lack of experience with lathes, I decided to see if I could try sinking an 1/8 bore in a piece of aluminum round stock using a fixed drill bit in a chuck inserted into the tailstock.  An idea of what I did can be seen here.

After a considerable time, I was able to sink a 50 mm hole into the centre of the round stock.  The steady rest that you see supporting the end of the aluminum round stock nearest the drill bit reduces vibration and misalignment.

When I worked with Tommelise 1.0, I used a 5/32 inch braised copper tube (1/8 inch ID) hot end several inches long with its top only heated using nichrome wire.  I was able to get well past the whole issue of having filament melt in the PTFE thermal break with that approach.  These days, I hope to do something similar using aluminum.

Here you see the drilled round stock after I've trimmed it down to 12 mm outside diameter and trued up the end.  It takes a nice finish.


AKA47 said...

Forrest, looks like fun. Something to watch with aluminium, drilling is OK but be careful parting and turning. Most especially parting. Aluminium has a very bad habit of grabbing the tool and going through a nasty runaway spiral of destroying itself and potentially sometimes the tools or supports.

It seems to grab the tool and being soft bends very easily out of true and grabs the tool some more going in a runaway state of getting worse until it jams solid all in a very short time.

Keep the tools you are using sharp, and clean the tips with fine wet n dry (or better still a fine oil/whet stone) regularly whilst working aluminium. You will find that a small quantity of aluminum adheres to the tool tips. It pays to advance slowly as it starts to grab. It does this most often at smaller diameters.

I have managed to mangle parts I had spent a lot of time on many times particularly machining cooling fins in to hot end cooling barrels.

Acetal (Delrin) is very cheap and works easily, Brass is expensive but excellent to work with. Neither of these share the grabbing problem with aluminium.

Forrest Higgs said...

@AK47 Thanks for the tips on working with aluminum. They are especially timely in that the next thing I want to try is doing some cooling fins. :-)

AKA47 said...

I made a screw on heatsink from 30mm aluminium bar stock. It was to cool a stainless steel M6 feed barrell. The hot end was the other side of a thermal break. It looks like a dalek gun.

Drilled the centre to 5.xmm (taping drill for m6) tapped it to m6.

Faced the exposed and and sides of the rod.

Then used a parting blade/tool to to cut fins in the 30mm bar cutting to a depth of about 15 to 20mm (depends how brave you are).

For measuring the fin thickness I just went with the thickness of the parting tool blade. Cut every other one.

When I had enough length of heatsink I set up as if to cut a final fin but parted the piece right off.

It grabbed several times even with care. So progress was slow and patience was needed.

when it grabbed I hit the emergency stop withdrew the tool, cleaned the tip and then repaired the damage by cutting/turning the aluminum away that had bent into the tool path.

They do look really good when finished and are worth the trouble.

Forrest Higgs said...

Did it work? Got a Link?

AKA47 said...

Its one of those many not completed because something else took priority jobs.

It is waiting for a heat shield to be added in Peek.

At the moment I am concentrating on getting my Huxley built. It is about time after three years or so of experimenting with lots of bits that I actually completed a full machine and gained the ability to print.

I will take some photo's though and put them up on my blog in the next few days.

Forrest Higgs said...

@Ak47 "It is about time after three years or so of experimenting with lots of bits that I actually completed a full machine and gained the ability to print."

I came to the same conclusion a year ago and bought a Rapman. Actually being able to print gives you a completely different outlook. :-)

BodgeIt said...

Aluminum seems to grab on any cutting tool chop saw and angle grinder, grinder they all require eye protection.

During my apprentiship I dont remember having any of these problems so it could be related to having the right cutting speed and the correct rake angle for Aluminum on the tool.

Forrest Higgs said...

It's kind of strange. I've read all about the nastiness associated with working aluminum and I've certainly had my share of unpleasantness working with it with hand tools.

Oddly though, so far I haven't had a single problem with it on this lathe. Mind, I had to clean the flutes of the drill bit I was using because the tiny flakes of aluminum tended to melt together and clog, but other than that it's been smooth sailing.

I even used the parting blade that AK47 warned me about with no trouble ... so far.

Possibly, my lack of trouble has stemmed because I've been taking things VERY slow and making very shallow cuts with my tools. I tend
to be very conservative when getting used to a new tool, especially an expensive one like this.

AKA47 said...

Nastiness is a harsh phrase. In
reality I think you guys have it.

Slow and steady is the way.

If you do this and clean the cutting tips often then aluminium is indeed beautiful. Every material has it's ways.

Rush it and it will screw you over big time.