Proper Feeds and Speeds - Steel Turning with Carbide on Taig CNC Mill

[Mike28303]

Hello Machinists,

I just purchased a Taig about five months ago, and am entirely self taught (using what I could find on the internet). I am cutting small molds out of 6061 aluminum, and have made my own alignment pins out of 1/4" mild steel rod by putting it in the mill collet and fastening a tool post with carbide insert lathe tools to the mill bed so it works like a lathe. Here is a video I found that demonstrates what I'm doing:



I also chamfer the pins after turning them to dimension (using a 45 degree carbide insert tool).

I understand that HSS would be ideal, but Carbide is more convenient as my learning curve is already vertical. Of course, if this is the only way to achieve excellent results, I will do it.

My current settings are definitely not correct, although I made them work for my last pins. My fear is that I have dulled the carbide because of my error.


Current settings:
RPM: 10,600
IPM: 12
DOC: .005 to get it close to size, .002" for the finish.

Here are the Mill specs so you can understand the limitations:

Taig Mill w/Ballscrews
RPM: 1050 to 10,600 (There are five grooves on the spindle, so I can do the following: 1050, 1650. 2600, 4200, 6700, or 10,600)
IPM up 100
1/4 HP Spindle Motor

Could someone help me select the best settings?

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[John44]

Try slowing down to 4200 rpm and feed at 5 ipm with maybe 3 for the final cut. If your pins are a couple of inches long you could do a test cut changing feed every 0.5" That way you can choose the best finish from one test pass.

[Mike28303]

Thank you John. While I ended up going for pre-made alignment pins, it's possible I will try turning mild steel again in the future. If I do, I will certainly try your feeds and speeds.