What a mess, what am I doing wrong?

[100LL]

I got a little shop time today and I’m having a terrible experience.

I got in a piece of 6.5” round durabar (cast iron) to make a chuck backplate and first thing off I went to face it and turn it. I have an aloris turn and facing tool with carbide inserts. First time I’ve used it and I’m also pretty much a beginner.

Well, facing went ok. Sort of.

But turning is terrible. Tiny chips hitting me everywhere. Sometimes a terrible screech. Miserable experience.

I did look up the recommended feeds and speeds for the material and carbide inserts, and mostly tried to use that.

What am I doing wrong?

I took a video and some photos.

 

[100LL]

This is an attempt to post the video.
The piece is roughly 6.5” round and using the formula that called for about 650 rpm I think. I dialed in more like 500 rpm.

 

[100LL]

Upload video didn’t work. Put it on YouTube instead.

 

[rgray]

Way to fast for me.
I would probably turn that at 100 surface feet per minute. That's 61 rpm Course I wouldn't use carbide either.
With carbide and approx 250 sfm rpm would be 150.
http://www.valleytool.net/calculator.php

 

[100LL]

I used this for my speeds and feeds
https://www.dura-bar.com/resources/upload/Dura-Bar-Machining-Guide.pdf

And then from there taking a broad shot in the middle: 800x3.28/6.5= 400 rpm

 

[Ulma Doctor]

Hi 100LL,
nice lathe
the problem with cast iron is that it has a skin on the outside the you need to get under before it acts right and machines well.
the second problem i see is that you are attempting to use a facing tool for work on the od
put the tool on the front face of the toolpost and try again.
make sure the tool is on center

 

[woodchucker]

No, the problem is you have your tool turned wrong possibly.
If you are turning from the tailstock to the chuck, it is facing the wrong way.
The way it is in the pic, you would be turning from the chuck to the tailstock. You want put the holder on the other side of the qcp, and have the cutting end cutting into the workpiece. Usually you want to turn toward the chuck so you are not pulling the piece out of the jaws. You can, but generally you turn toward the chuck. Most most of us turn toward the tailstock, with the tailstock engaged. Or for light cuts.

That's my take on it.

 

[rgray]

I used this for my speeds and feeds
https://www.dura-bar.com/resources/upload/Dura-Bar-Machining-Guide.pdf

I think that is kinda production advertising & sales. I'm not sure 800 sfm for our hobby lathes will work.
Try it at half that speed...see if you like it better.
I haven't seen an insert like that either. something different there would probably help also.

 

[100LL]

I can’t quite get the cross slide far enough away from the work to turn it the other way given the size of this work piece ...I must admit that aloris facing turning tool does confuse me a little.
They market it like you pop it out and go the other direction and all of a sudden your facing instead of turning, but I just don’t see that. Of course I’m a beginner.

 

[Ray C]

Me thinks RPMs should be somewhere between 75 to 125 RPM depending on the grade and if you're using carbide inserts. If it still has the hard outer skin, knock it down to 65 RPM and take several light passes.

Oh, and not only will you get hot chips on you, you'll need to do a lot of clean-up after cutting cast iron. Messy stuff...

(Nice Lathe).


Ray