SAE hydraulic port troubles

[scattermaster]

Good morning,
I have a chance to add some #6 SAE o ring boss ports to some cast iron valve parts. (#6 has 9/16 UN threads)
I bought a forming tool to get the port profile. The tool is steel but has carbide cutting edges.
My problem is chatter.
I don't have a knee mill. It's a PM 940 V-PDF. (it's not as rigid as a BP type mill)

I have tried various speeds from 1000 down to about 200. Slow seems better than fast.
I tried "free handing" the down feed. That was a disaster. It always chatters.

My best results come when using the power feed set to .10 mm/rev. ( it's finest setting) at about 300 rpm, and stop as soon as it makes a visible counterbore.
doing it like that results in several good ports and then one will chatter. I can't have that happening on customer's material.

I've tried cutting dry, cutting with tapping fluid and cutting with ISO 68 way oil. The -68 oil seems to be the best so far.
I'm considering buying a solid HHS tool with no carbide and trying that, but they are very expensive to buy just to experiment.
What do you think?
thx,
Jim

 

[mmcmdl]

I have the porting tools you speak of . They are carbide cutting edges as you said . Use very slow speed and heavy dark oil for best results .

 

[Jackle1312]

I agree. Use slow speed and good cutting oil. I normally feed by hand but if power feed gives a better finish then use it

 

[scattermaster]

Would bar oil for chain saws be better?

This morning I tried again. Using -68 oil, I slightly increased RPM to 500 from 300 and down feed to .18mm/rev. from .10mm/rev.
I did 4 holes and all 4 look acceptable. Now I'm out of room on practice parts!
Crossing my fingers, I'm running with it.
thx,
Jim

 

[markba633csi]

Tighten every gib on the machine as much as possible and still allow movement. The more rigid you can make the machine the less chance of chatter

 

[Chewy]

Get the sulfur oil for threading pipes. Lowe's carries it even if your local store doesn't have it. I had to go to next town to pick it up.

https://www.lowes.com/pd/Oatey-Cutting-Oil/4752939