Tool steel question

[Camalot]

We spend a huge amount of time on grinding parts here. The manual machin guys bring the parts close to tolerance, send it out to heat treat and then grind it all over again.

We are planning to move a lot of these jobs into the cnc room but my experience is mainly with 6061-t6 aluminum. I'm told that A2 as well as D2 hold their tolerance very well. My question is on a flat plat .156 thick 2.25 inches dia. How much do you think it will move taking it to 50-54 RC in hardness. Is there a reason why we cant just finish it before heat treat if the tolerance in + or - .001?

On a side note. In my research I discovered that D2 is not the toughest metal. We are getting a lot of breakage on some of the punches we make for our stamping presses. Do you think d2 is too brittle when hardened to 60-62 RC for punching .125 aluminum sheet? maybe a2 is better?

 

thanks

[Kannon]

I wouldnt be afraid to check into S7..I think its a little more shock resistant especially for the this application.

[Thad]

We cut .250 thick steel panels with D2 and A2 trim steels. We have them heat treated to RC 58-60.

 

As far as things moving in HT, A2 and D2 are very stable when heat treated properly. Holes have been rumored to move .030 in heat treat when not done properly. Heat treating is a process of time and temperature. If either of these are comprimised, you'll get varying results.

 

We had a HT source that "guaranteed" a finish dowel spread of +/- .0005. We've been finishing all dowels prior to HT ever since.

 

Thad

[Moldmaker74]

I have done a lot of work with A-2.

 

If your .156 x Ø2.25 is cut from a round bar, your growth should be very predictable because the grain is uniform and runs length wise on bars.

 

We experienced .0007 +-.0001 per inch growth (on the face of a round). This may vary depending on your hardness and process. We had an oven and processed our A2 in house for proprietary products.

 

I would make a few sample pieces and test them separately in a couple of different runs or batches to prove the repeatability from your heat treating supplier.

[Kevangel]

May need to talk to heat treater you are usin and make sure they are being "vacum heat treated" also on thin A2 plates they can be "pressed" when being heat treated so they come back FLAT...not like 01 where they have to be straightened..all cost some extra. I had one .5" thick X6"X 12" A2 gage plate come back dead flat but it warped along 12" length and holes that were in line barely cleaned up in jig-grind, which SEEMS impossibal but it happened and have done several others and its never happened since. A2 is brittle compared to 01, and D2 is abrasive resistant and tough,tough, and even tougher, may want to try S7 as its shock resistant and see if that helps and it grinds easier than D2..

[Kevangel]

I made some punches out of M2 once, may want to look at that material...also try and find out what "punch manufacturers use" probably a reason why they use what they use and I have not made stamping dies in a long time..

[Kevangel]

Ok, I just looked in MSC catalog under punches and iron worker punches say shock resistant (maybe S7) and stamping punches are all A2 60-63RC or M2 which cost more, so M2 maybe the one to try..

[spork]

Camalot

1)-what material are you actually stamping?

2)-lot of breakage? once again what are you stamping? In any case check punch and die clearance, punch and die sharpness, slug draft clearance, lubrication, condition of leader pins and bushings, press alignment. Are you using a feeder? check it's progression. Are your operators any good? check them too.

[spork]

oh! you are stamping aluminum. sorry, didn't pay attention to the post. well in that case, A2 is fine. M2 and D2 aren't necessary unless you are making millions of parts per run.

[#Rekd™]

Hi,

 

Are you using any lubrication on the puches? You can finish the punch and die to size then heat treat if you like, what kind of clearance are you runing between the punch and die? You should not need any where near 62Rc for Aluminum, I would say 57 to 58. We used to use D2 to stamp 1/4" steel plate with no problems.

 

John

[jeff]

Not sure how it would hold to when used as a punch,but we do a lot of work with H-13 and it's used in extrusion dies.

Only thing is,it's not stable in HT, it will grow or shrink whenever it wants to.

[Camalot]

I'm getting very frustrated about the inability for these engineer clowns to give me a reason why they are using one metal vs another. We are using crazy hard materials for things that seem like crs should be fine. I looked back at some of the old blueprints and we are about to make something out of d2 that was previously o1? We are also using a tone of 4140 pre heat treated for die blocks. I have been doing a ton of reading on tool steels and for a punch that is piercing holes in .125 aluminum, D2 to a 60-62 Rc hardnes is to brittle. Also we are making these plates out of a2 that was previously .156 x 2.625 M2!!!!. There is a particular block we have made over 10 times in the last 6 months. It is the bottom form steel in a die that forms a channel along a length of .0325 brass. the channel is .09 wide and 3.5 inches long and draws around a .625 radius to for a U shaped channel .375 deep. We make this out of 4140 and harden it to 60 RC. And it shatters when they drop it like its made of glass. I keep asking them WTF made you decide to use that metal and they keep looking at me like who are you other than the programmer guy who talks to us like we are retarded. I would hope out there somewhere engineers choose their metal based on its properies and not just because it sounds good.

[Jack K]

Just my 2 cents......

 

Depending on anual part usage anything more than 1000/2000 pcs. I would not waste my time with A2. The price of D2 "60/62RC" is not that much more and the return is greater with less maintenace.

 

The thing about stamping alum is it like to slug pack in the die openings. Look at the consruction of the punch as well small punches might need to be guideed or strenghened up. Punch and die clearance should start at 10% per side with that material thickness.

[spork]

Are you bottoming out the form punch with the die? Don't do that. Float the strip or part and spring load the die section that makes the radius. Do you have die stops? Use them. Punch, part, and die must not act as a die stop.

Your engineers are impractical. See it all the time. Sounds like they want to re-invent the wheel and hold the company hostage until it goes down in flames. To them, functional design is a new concept. I feel your pain. Throw them to the lions.