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lbhsbz
12-03-2010, 12:23 AM
Took on a side job to make 4 sockets to service the hubs on an old Italian racecar for a buddy of mine. Decided to make them out of 4140. I ordered 2 12" pieces of annealed material. Made 2 sockets out one piece last night and when went well....hss cut it great on the mill. I went to machine one out of the other chunk of stock tonight....machined ok on the lathe with carbide, but turned roughing endmills red hot taking a .020 pass. I went through about 4 endmills before it clicked......the sent me the hardened stuff. Dammit. I've got 2 hours of lathe work into this piece. Gotta call the supplier in the morning and see what they can do for me.

Ken_Shea
12-03-2010, 01:10 AM
Once again it proves itself to be true "No good deed goes unpunished"

macona
12-03-2010, 01:33 AM
Use a carbide end mill and go or it. Keep the feeds up so the heat leaves in the chips.

lbhsbz
12-03-2010, 03:21 AM
I didn't think I had any carbide endmills, but found a 1/2" solid carbide mill i'n the box of tooling I got from the guy I bought the mill from. I got the big part done....chips were glowing red so I cooled the endmill with cutting oil on a brush between cuts.....worked ok I guess

madman
12-03-2010, 07:40 AM
Always good to specify annealed material. We made a lot of die parts with this material. Then we would heat treat it with a torch. Good stuff. If you get into troubles machining just slow down youre spindle. Glowing red shows a dull cutter or too much speed ect. Take it easy and possibly use coolant? I use a busy bee container with a piece of washer hose stuffed into the nozzle and it works well for controlled coolant squirting on the mill.

madwilliamflint
12-03-2010, 10:43 AM
Use a carbide end mill and go or it. Keep the feeds up so the heat leaves in the chips.

...wait what? Does that work? That seems perfectly counterintuitive to me.

(In the interest of full disclosure I turned my mill on for the very first time last night; so don't mind me, I'm just readin' everything tryin' to learn myself some smartsauce.)

Liger Zero
12-03-2010, 10:56 AM
...wait what? Does that work? That seems perfectly counterintuitive to me.

(In the interest of full disclosure I turned my mill on for the very first time last night; so don't mind me, I'm just readin' everything tryin' to learn myself some smartsauce.)


This is one of those "it depends" questions. You ask 100 machinists and you'll get 100 answers... then they'll all start fighting and bickering and the production schedule goes RIGHT OUT THE WINDOW...

...:p

madwilliamflint
12-03-2010, 11:36 AM
This is one of those "it depends" questions. You ask 100 machinists and you'll get 100 answers... then they'll all start fighting and bickering and the production schedule goes RIGHT OUT THE WINDOW...

...:p

But does the heat leave with it?

*ducks*

ADGO_Racing
12-03-2010, 11:54 AM
4140 HT is machinable with HSS, just goes slower. If you are producing glowing chips, you are running way too fast. Try cutting speeds in the area of 40-55 SPM, Either run some coolant in a spray bottle, or brush on cutting oil. Your HSS Endmills will thank you.

lbhsbz
12-03-2010, 01:29 PM
4140 HT is machinable with HSS, just goes slower. If you are producing glowing chips, you are running way too fast. Try cutting speeds in the area of 40-55 SPM, Either run some coolant in a spray bottle, or brush on cutting oil. Your HSS Endmills will thank you.


I starting thinking about this...and the fact that I drilled a 1/2" hole followed by a 1" hole through it on my lathe with Chinese HSS bits before I started boring. That seemed to work great.

On the mill, I slowed things down to about 800 RPMs and fed very slowly at about .020 DOC with a brushed on cutting oil and the mill got threw about 1 inch of cut before it melted the tip and broke the endmill. Once I switched to the carbide, I ran it about 1500 RPMs and fed 7 ipm with a .100-.125 DOC and while the chips were coming off red, the carbide held up great and the finish was decent. I think I need a carbide roughing endmill. I had to machine a 36mm hex, 1 inch tall out of a piece of 4" round stock. I'd be there till I was dead taking .020 at a time.

I've got to find the book that gives guidlines for DOC and SPM for different materials....winging it will only get me so far I think.