Introduction: Tool & Die Making; Bracket Die.
My profile says I'm an old school tool & die maker so I thought it was a good time to give you a glimpse of what I do in my day job.
The process begins when the customer presents me with a drawing of the thing they want. My first question is "What is your estimated annual use?" The number of pieces required determines the type of tool I'm going to build. In this case, I am building a progressive die capable of producing better than 8,000 parts per hour! In this context, progressive means there will be some number of stations that perform different operations on the material as it "progresses" through the die in order to make the part. The next question is "What material will the parts be made from?" Sheet metal comes in a variety of forms. It comes from the mill in a giant coil weighing thousands of pounds. From there it is processed into sheets and smaller coils and can be made to very exact dimensions and properties with tight tolerances. The customer wanted to make parts from brass, steel and stainless in various quantities. This meant that the die must be able to handle both strip and coil stock.
Step 1: The Layout, or Work Requiring Thought
I don't think I ever had a "real" drawing for this part, but this is one of the sketches we sent back and forth while discussing various features and the feasibility of them. They wanted something steampunk and they wanted to do something cool with the corners as well as add some art.
The second picture is where my work begins; designing the layout of the die. This will be a three station progressive die. What this means is that it takes three strokes of the punch press to make the first part. After the third stroke, every stroke makes a part as the material progresses through the die until you get to the end of the strip. In this die each station performs an operation. Sometimes I will add extra idle stations to create space between the working stations, but it wasn't necessary on this one.
In order for this die to handle strips of material some sort of index stop must be incorporated so that the material can be moved by hand through the progressions. I'm using a "french" stop. I don't know what else it's called, but I'm sure there are a lot of names for the same thing. This type of stop cuts a step out of the material the exact length as the progression and there is a corresponding hard point for it to stop against.
Step 2: Buying Parts.
Having finished my layout, I know how big the die shoe needs to be and what kind and size of punches to order.
I use these guys,
Buying die shoes and punches fall into the category of old machinist wisdom that tells you not to build anything you can buy cheaper. Yes, I "could" make a die shoe and punches, but this place specializes in building them and therefore it is cheaper than me making one.
Step 3: Making Chips!
This set of photos show the process of adding features to the die block. Tapped holes in the corners for mounting to the die shoe. Reamed holes for dowel pins so that the die can be taken apart, serviced, and reassembled correctly. The pierce holes that create the holes in the part, and the pocket for the stamp that adds the art. Other holes are start holes for the wire EDM work that happens after heat treat.
Step 4: Heat Treating.
The most exciting part of this process is the heat treating. Exciting because of the opportunities for bodily damage!
I used A2 tool steel for this project for many reasons. The main one is that it's my favorite. In that in all my years of tool making I have NEVER broken a piece of A2 during heat treat (knock on wood). O1 is a different story, and I don't tend to use it much anymore. A2 is also more dimensionally stable through heat treat, but I consider that a bonus and not the main selling point.
Step 1; Wrap the blocks in heat treating foil. This protects the surfaces from excess oxidation.
Step 2; Pop the package in the furnace, set to 1780 degrees Fahrenheit, and wait a couple of hours.
Step 3; CAREFULLY remove package from furnace and set in a safe place.
Step 4; When it's cool enough to handle, remove the foil and put back in the furnace set to 500 degrees and leave it for a couple more hours. This is the step called "tempering".
Step 5: Send Out to Wire EDM.
Wire EDM is a specialized process that I don't have in my shop. It's
worth paying for in the time and quality that you gain. This video is a good explanation of the process, but the company that produced the video is not the one I use. No recommendation implied.
Step 6: Mounting the Die Block and Cutting Clearance Holes.
Mounting the die block to the die shoe is a straight forward process of transferring the location of the tapped holes in the die block to the die shoe. There are a number of ways to do this. I used transfer screws for this die, but sometimes I will clamp the die block to the die shoe and match drill the mounting holes.
You put one of these in each tapped hole, place the die block where you want it, smack it with a deadblow hammer.
What you have now is little punch marks on the die shoe. This is where you drill the holes for the screws.
After drilling the holes for the screws, you put some Dykem on the die shoe so you can scribe marks where you will machine the clearance holes.
Machining the clearance holes, the holes in the die shoe that the parts and slugs drop through, can be tedious. It's possible to have this done by the EDM shop, but machine time is expensive, so I usually do it in house.
Step 7: Making the Punch Holders
The punch holders are the steel blocks that hold the punches in position and allow them to be mounted to the die shoe. This is also the step where you must pay attention to the height of all your components so that things happen the way you want them to. Sometimes you might want to stagger the punches to reduce the tonnage required to make the part.
After the punches are pressed into the block and the mounting and locating holes are done, the side that mounts to the die shoe is ground flat on the surface grinder.
Step 8: Mounting the Punch Holders to the Die Shoe.
This step is probably the fussiest part of die making. This is where the punches are aligned with the die. I start by putting the blocks on the die supported by parallels. Insert transfer screws as before, put the top of the shoe on, and smack it with the deadblow hammer. Drill and countersink as before. Once everything is mounted, I carefully check the alignment of the punches to the die. I use a brass hammer to make fine adjustments. When everything is mounted up correctly, I drill and ream the dowel holes.
Somewhere in this step I made the block that holds the art stamp on the top half of the die shoe. Guess I forgot to take pictures.
Step 9: Mounting the Stripper Plate.
The stripper plate has two jobs; one is to "strip" the material off of the punches on the upstroke of the press, and two is to guide the material through the die. I clamped it to the die and drilled the screw holes through.
Step 10: Troubleshooting
Whoops! It's not going together right. Close examination reveals interference with a couple of screws. At this point, the engineers out there will be saying that this is the reason for a more detailed drawing and design. I don't disagree. As I have said before, I'm an "old school" tool & die maker, I design and then I build, but sometimes I do it at the same time. Anyway, swapping one of the offending screws with a button head solves the problem.
Step 11: Let's Run Some Parts!
Start with a sheet of .030" brass and shear it into strips that fit the channel I made in the stripper. I forgot to take pictures of the tool in the press, sorry. The third picture shows everything produced when you run this job. In the bin are the parts, the slugs, and the cutout. Across the top is what remains of the strip. If you look closely across the bottom of the strip, you may see little burrs that mark the place of the cutout.
I've added a picture of a section of strip that shows the steps of the progression. The notch in the lower right is what is left by the french stop.
Participated in the