Questions on cutting steel

[mrscheider]

Hi group,

My plan is to make a steel mold. I want to take a 2 inch bar, cut a 1 inch deep, 1 inch wide, 14 inch long rectangle cavity into it and then bolt on a second 3/4 inch steel plate to that face. This will serve as a mold for me to pour molten aluminum into to make new machining stock.
I have cut so much brass and aluminum in the past that I have 5 gallon buckets filled with chips. In addition to machining, I do allot of casting. So naturally I would rather melt down the chips and mold them into 1X1 stock to machine on my mill. I have NEVER cut steel on my Taig (except a few runs into the vise! ). I don't have a coolant system so Im looking for your suggestions about how to address the heat and maybe a few feed speed suggestions. Can this even be done at all on this machine?
I don't know what kind of steel it is. I got it from the shop at my job.
thanks!

Mike

[5artist5]

Man that is a big deep pocket to cut from steel!

I am nowhere close to being in a position to try that on my Taig.
If I "had to" for some reason and I had no coolant system, I would get a bottle of tap cutting oil and squirt in in there by hand or from a spray bottle or something.

Really I though I would just get someone with a knee mill to do it for me.

[mrscheider]

Hi Artist5
Yeah, one inch is deep but obviously I will do it in a great many passes.
Even to do 1/32 each pass would only require 32 passes per tool width to get to that inch. I'm willing to do the work, I just want to know if I will damage my machine. So is the Taig just not capable of this? I though on the website it stated it did cut though steel.
I'll have to double check.
Anyone else ever try it?
Thanks!

Mike

[5artist5]

Again, I am no expert here, but when I use a 1/4" diameter flat tip cutter on 6061 aluminum I have been taking .005" depth of cut for roughing and .002" for the finish pass.

If I were going to try it I would start at .001 or less and see how it cuts and then up it from there.

[escott76]

Originally Posted by mrscheider Hi Artist5 Yeah, one inch is deep but obviously I will do it in a great many passes. Even to do 1/32 each pass would only require 32 passes per tool width to get to that inch. I'm willing to do the work, I just want to know if I will damage my machine. So is the Taig just not capable of this? I though on the website it stated it did cut though steel. I'll have to double check. Anyone else ever try it? Thanks! Mike

You can of course make the cuts, it will just take a lot of them, and it will take a long time. Check your cutter diameter, and calc the speed and feed to get there. I'd derate from the ideals a bit, to compensate for the smaller machine, and take light cuts. 1/32" is .03125 which might be a bit optimistic given your machine size. Make a test cut .005, .010, .015 deep and see how the machine handles it. Ramp into the part with a 4 flute.
The biggest problem (aside from the time) is that you don't know what alloy you are talking about. "Steel" covers a wide range of materials and a wide range of feed rates. See what a hand file does to it, and compare the results against a known sample of mild steel or similar. At least if you have a horrible time denting it with the file you'll know you have something tough on your hands.

[escott76]

Originally Posted by 5artist5 Again, I am no expert here, but when I use a 1/4" diameter flat tip cutter on 6061 aluminum I have been taking .005" depth of cut for roughing and .002" for the finish pass. If I were going to try it I would start at .001 or less and see how it cuts and then up it from there.

FYI you should be able to take much more than .005" in 6061 with a 1/4" tool in a roughing pass. You can do passes of .005" if you like, but there is no reason to take that little.

[DeusExMachina]

Originally Posted by escott76 FYI you should be able to take much more than .005" in 6061 with a 1/4" tool in a roughing pass. You can do passes of .005" if you like, but there is no reason to take that little.

Mine with a 1/4" Finish end mill will take 0.03" doc with very low chip loads in 6061, the issue is the motor though, not enough power...

Your best bet would be to get a chunk of steel and take some lite cuts with a 4 flute cutter to figure out what chipload the machine can handle then go from there.

[Andre' B]

Now I do not have a Taig and normally run a much larger machine so!!
I would start with something like this.

1/4 carbide ALTIN coated 4 flute with 0.030 corner radius.
3800RPM 23IPM 0.003 Z steps
On the machine I normally run that would be 6000 and 50 and the steel would be 60Rc tool steel.

Just enough of an air blast to get the chips out of the way.

The program in the zip does a pocket 1.04 wide 4.0 long and 0.52 deep with 2° taper on the sides. Move the part down and rerun for a longer pocket.
Make 2 and bolt them together for a 1 by 1 finished bar.

[youngjim]

What about investment casting? Make a positive out of a scrap of something with a nice surface finish, cast ceramic around it, pour your scrap into that. I don't know if that would be cheaper but it would save a lot of time on your mill.

Jim

[mrscheider]

Excellent discussions folks. Thanks allot.
Let me get some clarity on a few things, if I may?
First, the concensus is to use 4 flutes. I have a carbide TIN 2 flute 1/4 flat.
No good?
The steel is definitly an unknown. It was stuff the shop had laying around. I threw it on my chop saw and initially, the first 30 seconds made a good bite in it. I stopped before finsihing that cut because too many sparks were flying around giant piles of sawdust. lol
Artist 5, I'm a little surprised about your cuts in Aluminum. My taig goes through it like butter. I generally use 20% of my tool diameter on a rough cut through 6061 at 5 ipm sometimes faster. Most commonly I use a 1/4 flat so that would be .05 per pass.
In steel, perhaps 1/32 was optimistic.. it was just an example.. Im sure I would have found out the hard way to thin it out.
YoungJim, Excellent idea regarding the investment casting. I actually thought about it but the ceramic wouldnt hold up to repeated castings of molten aluminum or brass, plus I would have to detroy the mold to remove the part.
In the steel mold, I could simply unbolt the face and remove the casted part, rebolt and reuse.
Andre, Thank you for the program, I already have the code to do the design I first conceived but this is a definitly Plan B. Much appreciated!
Kind Regards,

Michael

[escott76]

Originally Posted by mrscheider Excellent discussions folks. Thanks allot. Let me get some clarity on a few things, if I may? First, the concensus is to use 4 flutes. I have a carbide TIN 2 flute 1/4 flat. No good? The steel is definitly an unknown. It was stuff the shop had laying around. I threw it on my chop saw and initially, the first 30 seconds made a good bite in it. I stopped before finsihing that cut because too many sparks were flying around giant piles of sawdust. lol Artist 5, I'm a little surprised about your cuts in Aluminum. My taig goes through it like butter. I generally use 20% of my tool diameter on a rough cut through 6061 at 5 ipm sometimes faster. Most commonly I use a 1/4 flat so that would be .05 per pass. In steel, perhaps 1/32 was optimistic.. it was just an example.. Im sure I would have found out the hard way to thin it out. YoungJim, Excellent idea regarding the investment casting. I actually thought about it but the ceramic wouldnt hold up to repeated castings of molten aluminum or brass, plus I would have to detroy the mold to remove the part. In the steel mold, I could simply unbolt the face and remove the casted part, rebolt and reuse. Andre, Thank you for the program, I already have the code to do the design I first conceived but this is a definitly Plan B. Much appreciated! Kind Regards, Michael

You can of course use a 2 flute to cut steel, but your feed rate will be half that of a 4 flute. This project already has you behind the 8 ball in terms of feeds, doubling a long job isn't pretty. To me another end mill is cheap money compared to extra hours of machine time, but everyone has their own cost threshold.

[mrscheider]

I agree. I'll shoot on over to my machine store and get a 4 flute.
Thanks everyone!