From Manual to CNC - Sherlines

[kvom]

If it's > radius of stock that's all you really need.

[zeeprogrammer]

If it's > radius of stock that's all you really need.

 

[Kim]

Your software background is showing!  Still got your copy of K&R?

Left it at work for the next poor soul.  Nearly memorized anyway.

I wound up keeping my copy - had it since college, couldn't bear to leave it behind. Though I have not opened it since!

Everything I did in school was in Pascal.  I didn't learn C till I got out on my own.  Picked up a copy of K&R and never looked back.  C is still my favorite

Kim

[Jasonb]

If you are going to be playing with aluminium and non ferrous then also change the insert of a VCGT as it will cut better and put less load on the machine so you can run higher feed or deeper cut. Same with the mill get a few aluminium specific cutters if you are going to be working that regularly.

Apart from that looks like you will soon have a set of pins

[Jo]

Your software background is showing!  Still got your copy of K&R?

Left it at work for the next poor soul.  Nearly memorized anyway.

I wound up keeping my copy - had it since college, couldn't bear to leave it behind. Though I have not opened it since!

Everything I did in school was in Pascal.  I didn't learn C till I got out on my own.  Picked up a copy of K&R and never looked back.  C is still my favorite

I burnt mine when I retired    I have kept all three volumes of Ward and Mellor 

Jo

[zeeprogrammer]

If you are going to be playing with aluminium and non ferrous then also change the insert of a VCGT as it will cut better and put less load on the machine so you can run higher feed or deeper cut. Same with the mill get a few aluminium specific cutters if you are going to be working that regularly.

Thanks all.

Jason...How did you know to suggest changing to VCGT? The ones I have are VCMW (HSS) and VCMT (carbide).

I've been searching for information on inserts...how to identify, how to choose, etc. but am having difficulty finding something simple enough for me to understand.

[Jasonb]

VC was easy enough just looking at the shape, it's the GT part that makes them suitable for ali etc. In fact they work well on steel and stainless too but that will wear the sharper edge slightly quicker. I tend to use 0.2mm tip radius but you may be better with 0.4 as it is a bit more forgiving until you get the hang of things.

The other advantage they have over the coated carbide that you have there is that the aluminium will be less likely to stick though I would suggest a dab of Kerosene or WD40 which will stop that and also improve finish

The chart I tend to use is in the MSC catalogue, this is the UK one and you want pages 390 & 391, don't spend too much

https://edition.pagesuite.com/html5/reader/production/default.aspx?pubname=&pubid=9c3eabd2-e3ba-4a9f-8bd3-aa6475bd6e37&_ga=2.33452094.1270605157.1588173128-37005281.1586275050

[zeeprogrammer]

Thanks Jason!

[zeeprogrammer]

Went for the bowling pin.
All went well until the last finishing pass.
Then it got caught and yanked out of the chuck. Got a little dent in the ceiling. 
I suspect my X zero was slightly on the other side of the center axis so when it moved out, the part was in the way.
Maybe reduce the plunge cut depth as well.

I need to figure out how to get X at zero. Z is easy enough.
To get X at zero would it be to touch the stock, measure the stock, and move half diameter? Seems inaccurate.

Still...this is considerable progress for me.

I need to play with the lathe some more but I'm noodling on whether or not to move on with converting the mill.

This is the start of the first of two finishing passes.
<a href="https://www.youtube.com/watch?v=m6xBnCLySTQ" target="_blank">http://www.youtube.com/watch?v=m6xBnCLySTQ</a>

1st two pics show the roughing process.
Last pic shows the 'result'. You can see the damage due to getting pulled out of the chuck and the damage at top of pin where the cutter got hung up.

It's always the last cut, the last hole, the last operation...then blooey. 

But I'm still 

[crueby]

Nice!  Run off some more, add a ball bearing, and your elves can start bowling. Anyone have plans for a mini pin setter?

[Jasonb]

Even without CNC that is a far amount of stick out for a small chuck so could have happened on any machine. Apart from that it's a big step in teh right direction.

Have a look at Dave's answer yesterday about using the jog functions in Mach3 to take a skim off some scrap then measure that and enter the valve in mach.

J

[kvom]

For X0 do what Dave suggested.  Turn the end of the stock using the jog function.  Back off in the Z direction without changing the X used to turn.  Measure diameter with a micrometer.  Set X DRO to that value.

[Dave Otto]

Hi Zee

Not sure how CAM Bam works but maybe there is an issue with your lead in or lead out settings, or depth of cut, or not the correct insert for aluminum, or....
That is a pretty dicey setup, given how tiny the chuck jaws are, at what point in your finish pass did the part get pulled from the chuck?
I think as others have indicated before, the 4 jaw chuck will probably hold better.

One ideal that I had would be to drill and tap the end of your stock and use a bolt through the spindle to pull the stock tight against the back of the chuck; it would be pretty hard to rip it out then.
Then that part could be waste as you part off the finished piece.

Looks like you are hiving fun,
Dave

[zeeprogrammer]

Thanks.

Chris: The shop elves can just juggle the pins.
Jason: Yes, still sticking out a bit. Not sure how I would do this different.
Kirk: Yep. Gotcha.

Crud...
For another test I chucked up a 6" length of 5/8 diameter aluminum along with a live center in the tailstock.
Sheesh!
I used a depth increment of just 0.003" and a cut feedrate of 8 (it was 5 in an earlier test but got the same results).
Looks like it was threading (horrible noise) and then everything smoothed out.
The pic is after 3 passes of doing that.

Part of the problem too is that the live center would loosen up.
I'm suspecting the cutter was pushing the part into the chuck slightly.
Certainly, when I tightened up the tailstock, the part was getting pushed into the chuck.

I couldn't tighten the chuck any further without bending the tommy bars.

Not sure what's going on here.

Just saw your post Dave. As you see above, I had trouble with that chuck again. The 4-jaw needs to be tried. What a pain though.
The part got pulled out at the beginning of the last finish pass, at the tip of the pin. I'm pretty sure my X0 was slightly off (past centerline) and the depth of cut too much. So the cutter was coming out in X and a little in -Z. Because the cutter was 'past' the centerline, it was taking too much of a cut as it move out in X and in -Z.

I'm going to wait on converting the mill until I have more success with the lathe.

[crueby]

Seconding what the others said, with softer metals like ali and brass, tailstock use is very important unless the bar is small enough diameter to go all the way past the chuck jaws. The jaws are shallow enough that they can dig in and twist under a cut an inch or two out. One thing about cnc is you don't have the same feel for pressures on the cutter as working manually. Small machine, light cuts, proper support.


(Written before your latest post)