TIP of the Month
Anvil Design Sheet
Springs & Stampings
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|SITUATION: You Are The Maintenance Man|
|JOB: Anvil and Driver Alignment.|
You are the maintenance man, it's part of your job to make sure that your company's products get out the door, but you have a riveting failure. Everyone is pointing at you. All the pressure is on you to get the line up and running again. On the internet I have seen several rivet manufactures claim that one, two or even three cracks are not only acceptable, but a way of life. My question is, "acceptable to whom?" Cracks are certainly not acceptable to you or your customer, or for that matter, a product liability judge. Where do you start?
Well I can tell you from my 25 years in this business that at least 50% of the time these types of failures are not something you did or did not do. Let me explain. First of all, the rivet industry is a down and dirty business. Rivet users (that's you) have pitted one company against another until there is very little profit left. There are several major rivet manufactures in trouble as I write this (no, don't ask, they would have me in court in a heart beat). In an effort to aid their bottom line, personnel are kept to a bare minimum. Incoming and out going inspectors are the first places to suffer; they are after all overhead. Then there are the Header men: the people who setup and run the headers that make the rivets. They do not grow on trees, and they certainly are not born to be Header men. They are people who, at a minimum, take at least a year to train to the point where they can be trusted to make your rivets the way you need them.
How does this affect you? Simple. If they are not checking the wire they use for your rivets several problems can occur. First, the tensile strength could be off, making your rivet harder or softer after the heading process. The wire could have seams. Seams may cause cracked rivets. The rivets could also be out of spec: too long, too short, or the hole in the tennon (bottom of the rivet) is sized incorrectly. If the hole is too large the wall of the rivet may be too thin. Should the hole be too small, the rivet wall is too thick. Any of these problems can effect how your rivet rolls, and for the most part, are out of your control. Trust no one. Re-check all the dimensions on your problem rivet. Remember that the staff is still pointing the finger at you. The rivet looks good and it measures in spec. Now the boss is really looking at you to solve the problem.
The first thing to check would be the rivet machine alignment. Some of my maintenance friends call it the north-south / east-west. This is a lot easier than you think. First, turn the rivet machine off. If you can, unplug it. Most impact rivet machines use a mechanical clutch system, and I'll bet you know how to trip this system to get it to start the driver (punch) on it's downward motion. By hand, turn the flywheel until the driver just contacts the pin in the anvil. Next, from the front of the machine, by eye, check that the pin in the anvil looks like it is in the center of the driver (this is the east-west). If that looks good, move to the right or left of the rivet machine and check that the pin is in the center (this is the north-south alignment). If this looks good, the rivets are still bad and the boss is still standing in back of you, you have one more way to check the alignment.
The most accurate way to check the alignment is to make a tool from a rod of steel. First, remove the driver (punch) and the anvil. You will have to determine their respective sizes to make the tool. Let us assume the anvil is larger and 1/2" in diameter. We measure the driver and find that it is 7/16 " in diameter where it slides into the arm. Measure the driver where it slides into the machine. We will assume 7/16" in diameter. Next, bring the driver slide all the way down to its bottom most position. Measure the gap from the bottom of the drive slide to the anvil arm. Take this measurement and add 3 or 4 inches. This is the length of steel or hard plastic you need to make the tool. Find a rod of the larger dimension and machine half of this rod to the smaller diameter. We now have a rod of steel that on one end looks like the driver and on the other end it looks like the anvil. The next step is to insert the rod into the driver slide of the machine. Do not lock the tool into place. Start to move the slide, by the flywheel until it is about one inch away from contacting the hole in the arm. Now see if the rod will slide into the anvil armhole. If it does you are finished. If not, then you have to do one of two things.
Locate the bolts that hold the head casting to the base, loosen them and move the head unit until you can slide the pin in and out of the driver and anvil holes, lock the head unit down and test again. The second method is to shim the anvil bracket arm with shim stock to get the same effect. That is all it takes. However, if you still need some assistance, call me. If you don't have an on-sight machine shop, we can make this tool for you.
|Northeast Fastener Solutions|
|148 Ben St.
Bristol, CT 06010
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