4140

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Hukshawn

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So i have 4140 to make my vise jaws from. I jammed them in the mill and started face milling it with a carbide insert face mill. Aaaaand i get a shower of sparks. It milled like a dream. It was quiet, smooth, with a nice finish. But, i got a shower of sparks which i really wasn’t expecting. The inserts aren’t dull. They’re Chinese, but, new.

Normal? Not normal? I shouldn’t worry about it? I should pack up and run for the hills?


Edit: more info. 2” face mill running at 2000 rpm. Feed rate is unknown, hand cranked, but not overly quickly, not too slow... juuuuuust right.
 
At 2K RPM, that will happen. Also, it's 4140, too. Might slow the RPM's down a little to around 1700 and see if the fire goes away. Might need to feed it a little more too, if the mill can handle it. The stuff must be heat treated, too.
 
Hukshawn said:
So i have 4140 to make my vise jaws from. I jammed them in the mill and started face milling it with a carbide insert face mill. Aaaaand i get a shower of sparks. It milled like a dream. It was quiet, smooth, with a nice finish. But, i got a shower of sparks which i really wasn’t expecting. The inserts aren’t dull. They’re Chinese, but, new.

Normal? Not normal? I shouldn’t worry about it? I should pack up and run for the hills?


Edit: more info. 2” face mill running at 2000 rpm. Feed rate is unknown, hand cranked, but not overly quickly, not too slow... juuuuuust right.
Click to expand...
Way too high spindle speed. About 500 rpm might have been a better place to start.
 
Thanks guys.

I ran fast cause I always read that carbide wants to go fast.
 
Hukshawn said:
Thanks guys.

I ran fast cause I always read that carbide wants to go fast.
Click to expand...
On mild steel, yes, any alloy steel, slow it down a bit. I run my face mill at around 1500-1700 RPM with good results. This is on a Index 645 mill. I think the book says around 1,000 RPM. Also, like Bob said start at 500 RPM and go up on the RPM a little at a time until a happy media is reached if you have variable speed capability. In my case, I just turn the pot on the VFD to a desired RPM.
 
Can you give me the best speed references you guys have? Anything online? A picture of a print out?
 
Hukshawn said:
Can you give me the best speed references you guys have? Anything online? A picture of a print out?
Click to expand...
https://www.actx.edu/machining/filecabinet/4
This is from a college, not a company selling inserts. They are saying 200-400 rpm for what you are doing, per their formula.
http://internaltool.com/docs/reference/speeds-and-feeds.pdf
This is from a tool seller, they recommend 200-600 rpm.

There are some insert manufacturers listing much higher speeds than those. What are you looking for? Pretty? Long tool life? Production speed?
 
Off the top of my head the speed should be in the range 250 - 500 SFM, you"re over 1000 SFM
 
Bob Korves said:
https://www.actx.edu/machining/filecabinet/4
This is from a college, not a company selling inserts. They are saying 200-400 rpm for what you are doing, per their formula.
http://internaltool.com/docs/reference/speeds-and-feeds.pdf
This is from a tool seller, they recommend 200-600 rpm.

There are some insert manufacturers listing much higher speeds than those. What are you looking for? Pretty? Long tool life? Production speed?
Click to expand...
So would 4140 be considered a medium carbon or a tool steel?
 
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