tooling for tough steel

EN24 817M40 4340 ASTM A29 tough stock with a rough finish

What would you recommend, indexable tips or carbide? this is the part I need to machine, by the 100s:



6mm (0.236) thick from 8mm (0.315) stock, faced both sides

mid recess has a 3mm (0.118) rad

currently using tips but they bang alot on this tough material like it needs a keener edge, probably have stay with tips for the facing - 45mm (1.770) wide cut but thinking about carbides for the sides and recess?

cheers,



....

If tolerances allowed i would get them laser cut, with the holes in, send out for grind, then just mill the bit out. EN24 is tough, but its not normally hard to cut relatively speaking, though i have never encountered sheet parts, everything i have done has been in rod form, some bright some black.

Milling it i would go coated carbide dry with a air blast, Something like cutwell's NC mill line will eat it for breakfast unless your having it heat treated to a high hardness first,

Does laser cutting .40 carbon steel leave a hard edge?

Illinoyance said:

Does laser cutting .40 carbon steel leave a hard edge?

Click to expand...

You bet.
Should be around ~60..65HRC ie file might scratch it if you are lucky

bspear said:

EN24 817M40 4340 ASTM A29 tough stock with a rough finish

What would you recommend, indexable tips or carbide? this is the part I need to machine, by the 100s:

View attachment 244469

6mm (0.236) thick from 8mm (0.315) stock, faced both sides

mid recess has a 3mm (0.118) rad

currently using tips but they bang alot on this tough material like it needs a keener edge, probably have stay with tips for the facing - 45mm (1.770) wide cut but thinking about carbides for the sides and recess?

cheers,



....

Click to expand...

.
there is harder metal and there is abrasive metal.
.
machining annealed M2 HSS steel is more difficult cause its abrasive and tool life is shorter. just got to change tooling more often cause it gets dull faster. obviously if the get mill gets red orange yellow white hot and melts its time to change the tooling
.
just saying some alloys are more difficult. you aint going to get the same tool life as if you were milling 1018 steel. sure you can adjust the feeds and speeds and depth and width of cuts and get some better tool life but abrasive stuff going to be hard on tooling no matter what you do

Illinoyance said:

Does laser cutting .40 carbon steel leave a hard edge?

Click to expand...

My experiance, its nothing like as bad as you expect, the heat effected zone with laser is tiny, i have honestly had more issue with the nitrided like skin left as a cut edge on laser cut parts in some stainless grades, Counter sinking laser cut stainless holes is kinda one of the worst for that.

That said, for a part like this, your not machining enough of the laser cut edge for it to be a issue if the part profile gets fully cut. The radius tool your using to mill that middle bit out will not experience any difficulty in my experience.

Sure if your laser cutters running a cheap gutless laser and the heat effected zone is greater that might be a different story, but don't forget with carbon steels you have to get them over 800C to get hard, unlike gas cutting you won't see 800C for practically any distance into the cut edge with laser.

On a part like this especially if that bottom face has to remain flat, it probably is a great idea to get it annealed any rate, this also is not expensive on bulk especially compared to od milling and drill all of the parts shape. Especially when your presumably haveing to have blanks cut out of sheet any how.

If you get the parts laser cut or plasm cut, I'd suggest you get them cut with a 1/16 to 1/10" extra allowance on the profile, so that you can get the tool edge under the skin for the entire profile. You don't want the tool barely skipping along grazing the skin. Also, use the 'conventional milling' strategy for milling the skin off.

I'd use a fine pitch corncob style roughing endmill to mill the skin off. This style seems to handle the roughing better. Even with some degree of damaged flute, the damage to a corncob mill is usually just a point or two, not a large chip spanning a considerable distance along the flute. I'm usually quite surprised at how the tool will keep on cutting when it looks pretty grossly damaged.

What machine are you planning to run these on?

Or waterjet to avoid heat issues completely. At this point people will say it's more expensive and at that point I will say go get some quotes as you may be surprised. (We have a waterjet but send large sheet projects out and are seeing factors of 2 or 3 difference in price between local laser shops which is a reminder you need to get quotes regardless of proposed method!)

bspear said:

..
What would you recommend, indexable tips or carbide?
....

Click to expand...

I'm still working on this part of the question.
What are the indexable tips made of.. HSS, CBN.??
Obviously not carbide or the question becomes should I use carbide or carbide.
Bob

carbide insert cutters come in all types.
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i have seen carbide insert mills using cheap insert not last 2 minutes and other types use more expensive inserts literally perform 1000% better. carbide inserts with grooves and wavy bumps and coatings some dont appreciate how much what seems like not much can effect its performance. every carbide insert cutter holds the insert at a certain angle both radial and axially. if the insert is not made to be used at the angle of the tool insert pockets performance can be effected easily 1000% too.
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a end mill is simpler that is it is sharpened at the proper angle relief and rake for a certain material like aluminum or steel but even a end mill if its corner radius is too small its roughing performance and tool life can be effected often 1000% too. so many use a roughing end mill and a separate finishing end mill each made to be better for roughing or finishing but not both. end mills can come with coatings to help with tool life on harder and more abrasive materials too. often a end mill made for the material being machined can perform much better easily paying for the extra cost. again the cheapest end mills often perform very badly

CarbideBob said:

Obviously not carbide or the question becomes should I use carbide or carbide.
Bob

Click to expand...

I could be wrong, but I read that it WAS that question.

As-in brazed/welded/solid-carbide vs insertable.

OP needs to clarify that, as well as the machine he has to work with.

The OP bspear says rough finish and 100s in qty.
Accuracy spec is not mentioned - means as-machined.

Just hard mill them with inserts of choice.
We had our HAAS customers doing this with VMCs for years with excellent results.
Very satisfied customers and no machine issues.

Probably use air blast only.
The tooling reps will get the right inserts.

My experience with VF5+/- would do maybe 150 parts per setup.
If you have a wobbly machine a CI (alu) subplate might help with consistency and vibrations.

Like most 100s machining stuff, this is probably technically good and relevant as an option, but might not be what You want to hear or do at all.

The laser sounds good, with edge/corner/hardness caveats.
If a laser or waterjet is an option, they are probably really cheap, if a tumbler finish is good enough and acceptable otherwise.
Laser/waterjet/tumbler, and a cnc dressed grinder for critical finish could produce extremely accurate pieces.
These might cost a few $ per piece more, maybe 5-10$ delta in qty 3x100.

It is important to know 100 pcs xx 5$ each or 100 pcs gages at 100 $ each, bulk cost 20$.