Milling Steel on My CNC

[jteneyck]

I'm continually amazed at what I can do on my hobby level CNC.  Today I flattened a blade collar for my RAS to make sure it's parallel with the other face.  I only took off 0.015", nothing serious.  Still, it was a no drama endeavor.  I used a lot of tapping fluid to keep the endmill as cool as I could.  



That circular gauge near the hole happened just from tightening it against the motor arbor shoulder, not even turning the motor on, suggesting the shoulder is not a true surface.  

John

[FrankAtl]

I'm with you John. I love having my CNC for things that would be difficult otherwise. A friend of mine needed to make a chip tray to hold 1000 poker chips. The slots needed to be 40mm wide and around 13" long and he was trying to figure out how to do it with a forstner bit. A 40mm forstner bit isn't common but you can find them. The length of the slots would have required a bit extension and getting the holes straight and correctly spaced would have been a challenge.

It took me a while to figure out how to do it in Vectric Pro but I ended up using a molding toolpath. He's going to build some sort of box for the insert to fit in but I think it turned out great and was easy once I got it dialed in.

   

[stav]

That's a pretty sweet chip tray.  How did they stop them falling out of the ends?

[FrankAtl]

That's a pretty sweet chip tray.  How did they stop them falling out of the ends?

Thanks! That's just the "insert" for lack of a better word. My friend is going to build a case for it.

[jteneyck]

I'm with you John. I love having my CNC for things that would be difficult otherwise. A friend of mine needed to make a chip tray to hold 1000 poker chips. The slots needed to be 40mm wide and around 13" long and he was trying to figure out how to do it with a forstner bit. A 40mm forstner bit isn't common but you can find them. The length of the slots would have required a bit extension and getting the holes straight and correctly spaced would have been a challenge.

It took me a while to figure out how to do it in Vectric Pro but I ended up using a molding toolpath. He's going to build some sort of box for the insert to fit in but I think it turned out great and was easy once I got it dialed in.

That's a pretty nice looking chip tray, Frank.  The molding toolpath would be what I would look to use, too.  I assume it took a long time to carve that unless you were using a pretty large diameter bit.  I did some curved crown molding once just for fun and it took something like 45 minutes to do a piece about 20" long.  

John

[FrankAtl]

That's a pretty nice looking chip tray, Frank.  The molding toolpath would be what I would look to use, too.  I assume it took a long time to carve that unless you were using a pretty large diameter bit.  I did some curved crown molding once just for fun and it took something like 45 minutes to do a piece about 20" long.  

John

This took about two hours. I did a roughing pass with a 1/2" end mill then the final pass with a 1/4" round nose bit. I had to reduce the stepover to 5% on the round nose in order to get a decent finish so that's what added all the time.

But if I ever need to make another one, or ten, no sweat! 

If anyone wants the G-code or Vectric file just let me know.

[stav]

Back to the op. jteneyck, I'm picturing a router based cnc here so I may be off. Did you put an end mill bit in the router to flatten that?

[jteneyck]

Back to the op. jteneyck, I'm picturing a router based cnc here so I may be off. Did you put an end mill bit in the router to flatten that?

Yes, that's correct, except I have a 2.2 KW spindle on it.  I used a 1/2" end mill designed for milling steel.  It worked pretty well with no chattering.  The spindle can't go down to really low rpm, like would be best for milling steel, but I kept it bathed in cutting oil and the bit looks fine.  

John

[tablesawtom]

I think you will find that end mills for wood are the same as endmills for steel. Hopefully it will save someone some money. The speed formula is RPM= cutting speed x4 divided by the cutters diameter and if using carbide multiply the answer by 4. Cutting speed for 1018 steel is 100  So if if a high speed 1/4 inch end mill is used in mild steel the RPM should be about 1600 RPMs and time 4 if the cutter is carbide then the RPM should be around 6400.  Divide in half it the steel is tool steel, or 3200. it a 1/2 end mill was used then the speed should be around 3200 for steel  Other factors are machine rigidity. A Full Metal CNC is a lot more solid than a Bridgeport milling machine. Also spray coolant verses through the tool coolant has and effect, depth of cut and chip load per tooth also inter in. 

There are a lot of other factors pertaining to cutting that also influence things. Carbide end mills can get expensive in a hurry so I wouldn't make cutting steel on a home CNC a habit if you can't get the RPMS correct.

Because of your depth of cut you got away with it. I would never thought of it even though I cut aluminum with a round over or 45% cutter in a hand held router quite often. 

I commend you for doing it but I would caution you to to be very carefull. .

[EdL]

I was told by a machinist & woodworker friend....No problem using an endmill on wood, as long as its new and never touched steel.
For some reason, it won't cut good in wood.

Ed