So my coin press had been acting up sporadically over the last several months. Usually, the symptom was that it wouldn't complete the ejection cycle. After a coin is stamped, the coin will be lodged tightly in the collar. The ejection is performed when the press pushes up on the lower die to force the struck piece out of the collar. And the last action in a striking cycle is for the lower die to drop back down into the original (lower) position. When it does that, a new planchet can be inserted into the collar for the next striking. The problem was that, more and more often, the lower die would not drop back down at the end. My quick work-around for that was to remove the lower die and repeatedly strike "air" until the lower die dropped back down, But, eventually, I could not get that to work at all. I suspected that it might be related to the "Clutch Valve Failure" fault that I worked on a few weeks ago. It was time to fix the problem once and for all. My biggest challenge was not knowing entirely how some of this worked, or what would be necessary to fix it. After taking off a couple cover plates and looking into some narrow spaces using a bright flashlight, I began to theorize that something was not right in the large shaft that contacts the bottom of the lower die anvil (to push it up). There was only one way to determine for sure what was going on here. I had to remove the large orange-painted metal block (red arrow) and examine the cylinder and bore surface inside it and under it. It took every trick I had to get the large bolts loose, and use wood planks to slide the block out onto a tall cart. The piece weighs over 120 pounds. When I finally got it out, this is what I saw under it (the screws, not the coin shown for scale): One screw was bent a little, but relatively undamaged. The other screw had obviously been caught in the mechanism and destroyed. Since I got the press, I have never been into this area before. The screws were undoubtedly left there by a careless US Mint employee. I would never do that. It wasn't until recently that it managed to cause a noticeable problem. But I believe that the one screw had actually been causing damage for quite a long time. The large steel cylinder that pushes on the bottom of the anvil slides up and down in a heavy brass-lined sleeve. This cylinder also has a flange on the bottom of it that acts as a stop to the sliding. The screw fragment had apparently been smashed between the flange and the bottom end of the brass sleeve. This caused a deformity in the brass sleeve which impinged upon the sliding motion. The impingement was severe enough that I could not push the cylinder through the sleeve. I had to use a sledge hammer to pound the cylinder out of the sleeve. Then I used various sandpaper and stripping tools mounted on my hand drill to "hone" the bore (sort of like what you would do to a cylinder in an engine block. Eventually I got the cylinder to slide freely in the bore. I put things back in place (also very difficult due to the weight). Then I tried striking. I was expecting it to work perfectly. The ejection system never worked as smoothly, quietly, or effortlessly as it did now. However, there remained one big problem. The lower die still would not drop down. And at the point in the striking cycle were it was supposed to do that, there was a loud hissing sound coming from the left side of the press. Full pressure air was being vented, without restriction, into the room. Here is the left side of the press (behind the cover panels): The air control valve that I worked on a few weeks is here (orange arrow, in image below). The main lever that actuates the lower die up or down is the large red-painted metal piece (green arrow, in image below). After trying to figure this out for a day or two, I determined that the pneumatic actuator (purple arrow) is what causes the lower die to move UP to eject the struck piece. Now the question: what gizmo causes the lower die to drop back down, and why is so much air escaping ? Eventually I took both air lines off of the air control valve (orange arrow). I finally determined that, at the time when the lower die was supposed to drop down, the valve was sending air pressure OUT to the upper air line. But the same air pressure was being sent back through the lower air line, and the control valve was simply venting this out to the room. It was as if the two air lines were connected with no hindrance in the flow at all. That shouldn't be. Also, the two air lines wrapped around the red lever and disappeared behind it. What did they do behind there ? The red lever is actually constructed out of two identical and parallel steel plates with about three inches of space between them. After using a mirror and a flashlight, I found that there was another pneumatic cylinder (just like the one indicated with purple arrow) INSIDE the large red lever. The blue arrow points to it. It is mounted diagonally, parallel to the two air lines that are in front of the red lever. Now, how in the hell do I get that damn thing out of there ? The lower end has a cotter-pin type of attachment. So that was not a big problem. The upper end was a mystery - it was very difficult to see in there. Finally I noticed a 1/2-inch diameter pin in the red lever (just out of the picture but located about where the white arrow is pointing to). If I could get that pin out, the pneumatic cylinder would come right out. First I tried pounding the pin through. No matter how hard I pounded with a hammer, it wouldn't budge. But even if it had moved, I realized that there is not enough clearance behind the red lever and the bulkhead for the pin to be removed anyway. And what if the pin had a step-down diameter ? That would prevent the pin from moving forward at all. The pin did have a small threaded hole. So I concluded that, with the right screw inserted, I might be able to use that to PULL the pin out. I went to the local hardware store and "MacGyvere'd" this pun puller tool (sort of like a miniature steering wheel puller, if you know what those are). The small screw goes into the pin. The large bolts are screwed inwards to push against the surface and pull the pin. I deployed my new tool and turned the bolts as hard as I could. I only managed to bend the metal plates in my tool. The pin still did not move, not even a thousandth of an inch. So I began to think that the pin was not designed to be removed. I investigated removing the entire red lever arm, but that appeared to be basically impossible. I had no hope of fixing it unless maybe I could take the pneumatic cylinder apart while it was still in-place, and replace the guts inside it. The only chance of doing that was to remove other items that were in the way. So I took out the blue air pipe (yellow arrow, in image above) and the flywheel brake mechanism (red arrow, in image above). After taking those out, I had a little better view of the upper left end of the pneumatic cylinder. And then I saw it. A small set screw perpendicular to the pin shaft. It was hidden just around the corner behind the front plate of the red lever. Once I removed that set screw, my tool pulled the pin out like butter. The pin actually had a fairly deep groove that the set screw went into. At this point I still wasn't 100% sure, but I was pretty certain that this was the offending part: My theory is that the ejection cylinder was severely pinched in the bore (inside the large orange block). And someone turned up the air pressure to overcome that. The high air pressure eventually blew out the pneumatic cylinder. This is the inside of it. At first, it may look OK. But the rubber diaphragm is supposed to be securely fastened to the brass shaft were the groove is (red arrow). It was torn off of its mounting and also degraded to where it would let air pass right through it. The crate of spare parts that came with the press still provides gifts almost 20 years later. I have two more replacement pneumatic cylinders. Now that I have a replacement installed, when I stamp things the press works perfectly. It is quieter, smoother, and seems to stamp more effortlessly than ever before. I don't feel any vibrations in the floor, even when stamping at 300+ tons. Previously, I would. Now I can get back to doing some real work.
Thanks for sharing. Good thing you had some spare parts, and the skill to repair and replace damaged parts.
Made me miss all the hours underway shipboard down in the engine room and machine shop ... as if! I retired 27 years ago so memories are designed to fade away.
Had to go back and look at the posters name... Nice work Dan, did you Google a YouTube video or have a manual some things you just have to tear into to see if you can get it fixed.
I hope you know by opening that machine up you may have voided your valuable manufacture warranty. James
Your troubles sound frustrating to say the least! But, the accomplishment of fixing the problems makes up for that frustration, right? Right? LOL! YouTube is your friend. You can find out how to do just about anything on YouTube! This, however, I'm not sure there are many videos about. You just need loads of patience and the drive to tear it apart and figure it out! Great job!!!
That was a fascinating read, and a real exercise in problem solving! Thanks for taking the time to post it.
A few weeks ago I posted some info and pictures related to my coin press malfunctioning. After further use of the press, it became obvious that there were still some issues. Now that I know more, everything I had worked on previously was related to the ejection system. That system WAS fixed, but there were other problems lurking ... The mysterious "Clutch Valve Failure" fault seemed to be fixed when I repaired the ejection system. But the problem became more frequent and harder to get past as I used the press more. Eventually, I could not get the press to run at all. For a while, every time I had that fault, I would shut down the press and fiddle with the ejection system. Upon starting back up again, the press would work. But only for a shorter and shorter time in each instance. In every case, sooner or later, pushing the "two-hand" buttons to initiate a strike would result in the fault and the press would stop moving right in the middle of the striking. Eventually, I could net get the press to move AT ALL, no matter what I did. I began to realize that the "Clutch Valve Failure" was related to something other than the ejection system. I surmised that the reason the press would work for a short time after starting it up was that it functioned when "cold", but would fail when warmed up some. I was going to be hosting an event for one of the local coin clubs, and I had to get this thing working right or everybody would be disappointed. What is the "Clutch Valve" (the one that was failing) ? I previously thought it was the valve that controlled the ejection system, but that was not it. Finally, I started looking at the obvious. This device (orange arrow) looked like some kind of large valve. The blue pipes are high-pressure air lines. The tan cables are electrical. This seems like an electrically (solenoid) operated air valve. It diverts air through the center shaft of the flywheel to cause a clutch to engage on the inboard side of the flywheel. Engagement of that clutch is what causes the press to move (and strike) : So it was time to take that gizmo apart and see what was going on inside it. Fortunately, it was easy to get at. Upon taking it apart I found that it contained two solenoid-controlled plungers that controlled air flow. Both plungers had silicone rubber seals. The first thing I noticed was that both had chipping around the edges. These had been in use for a long time ! : The central area does not make contact with anything. The portion of these gaskets that is outside the scribe circle (pink arrow in the image above) is the area that makes contact to seal off the air. The chipping had just started to get to the circles. I believed that they were borderline functional, and that is why it was difficult to pin down the real issue. I fabricated new gaskets out of some silicone rubber I had. After I installed them, I started up the press and pushed the two-hand buttons. The press performed a normal striking motion ! Then I pushed the buttons again to perform another normal strike. I heard the normal sounds that preceded the engagement of the clutch for striking. But then NOTHING. No striking movement at all. What the hell ! I shut down the press, turned it off, then back on and started it up. The first push of the buttons resulted in a normal striking motion. The second time - nothing. I checked all the electrical connections that I could find everywhere. I investigated all sorts of things. Eventually, I got the idea to try a system reset while running. I pressed the two-hand buttons and got a normal strike. I pushed the buttons again and nothing happened. but I left the press (flywheel) running this time. Pressing the "Reset" button on the control panel did nothing because, as far as the press was concerned, there was nothing to reset. I had to give it something to reset. So I came up with the idea of triggering an over-load fault (by pushing a certain test button). Then the reset button would do something. So I did that and then when I pressed the two-hand buttons, I got a strike. Pressing the two-hand buttons again - nothing. The reset procedure allowed as many strikes in a row as I wanted. But I can't keep pushing those overload & reset buttons for every strike - that would be very inconvenient (and shouldn't be necessary). So why wasn't the press automatically resetting itself after completion of a strike cycle ? It did before I worked on the clutch valve, why not now !!? I rebuilt the clutch valve again - no difference. I thought about it for a while and inspected the timing mechanism inside the right side of the press. I found nothing there. While still thinking about the issue, I decided to take a break from that and inspect an area on the left side of the press where I had previously repaired a small oil leak. That oil leak was stopped (for the most part). But at that point I happened to notice a device (switch) that was nearby. This switch has a roller wheel that rides on a ledge. When the frame rail moves up and down (for striking), the ledge moves as well and the switch is activated. Maybe the switch was bad ? So for my next test, I started the press and did one strike. Pushing the two-hand buttons again did nothing. But at that point I went around to the roller switch and lifted it up. At that point I heard a click inside the electrical cabinet (an electrical relay had tripped). After that, pushing the two-hand buttons was successful in causing another strike. The roller switch position is adjustable by loosening the set screw. (light green arrow): I used the press for 17 years and never touched this switch. The set screw was still tight. But now that I have repaired some faulty systems on the press suddenly it needs adjustment, even though I never touched it !!? I can't explain why it needed adjustment at this time. But I set the position and everything worked ! I then proceeded with producing an order of nearly 1,000 pieces. I struck 950 of them with no press issues whatsoever. Then, suddenly, a loud sound THWAT-THWAT-THWAT-THWAT ... etc. I immediately shut down. It sounded bad. I checked the motor, flywheel belts, etc. I found nothing wrong. So I started the flywheel again. The same alarming sound started immediately. This time I left it running while I looked and listened closely (and carefully - being close to the spinning flywheel is intimidating). Soon I put my hand on the device that is mounted on the end of the motor shaft (see the GREEN arrow in the first image above). The device was vibrating badly. I was pretty sure it was the culprit. So I shut down the press and started removing the device. It is apparently an RPM speed switch. Below a certain RPM threshold, the switch is electrically closed. Above that RPM, the switch opens. One function of the switch is to prevent restarting of the motor unless the motor RPM is below a certain threshold. The actual RPM threshold is adjustable via external set screws on either side of the device. Upon removing the device from the motor shaft, a washer fell out, but I couldn't tell from where. I took the device apart and rebuilt it. I did not find anything obviously wrong. But, upon reinstalling it, I found that the rubber buffer that fits in the universal connecting joint on the shaft looked defective. It should be in the shape of an "X". But two wings of it were missing (see yellow arrows): It seemed logical that the missing rubber pieces could cause the shaft coupler to "THWAT" repeatedly. Feeling around the oil pan below the joint I came up with the two broken pieces. I had a similar (but not exactly the same) coupler that was replaced years ago on one of my engraving machines. The coupler itself wouldn't fit. But I modified the red rubber buffer from it and put it into the old coupler on the press (the blue arrows point to three of the four ends of the "X"-shaped red-rubber buffer): After that I started the flywheel and there were no unusual noises. A couple days later I hosted the coin club striking event and there were no issues with the press. A good time was had by all. Whew !
I love troubleshooting stories, and these two are up there with the best of them. One question: that screw fragment from the first post, the one that fell into the mechanism and was struck while the press was still in service - you are going to send it to PCGS to be slabbed, right?
Not like you can get on the horn and call in a mechanic to fix one of these things. Great job at tracing down the problems Daniel. And an most excellent 'read' too....
Nice stories, Dan. So, how would you remove the sheared bolt in the exhaust header on my old F250? My mechanic tried all sorts of things and didn’t succeed. There is now a broken lefthand-twist drill bit in the bolt. Truck still passes smog test, so it’s not a big deal to remove the bolt. Cal
Well, you can't drill out the bolt if it has a hardened steel drill bit embedded in it. If any part of the broken bolt is above the surface, I might try a cut-off disk to grind a slot in the end of the broken bolt and/or broken bit. Then use that slot like a slotted-head screw driver.
The bolt broke because they all had to be removed to replace the header gasket. This one was stubborn. My mechanic tried all kinds of tricks: lube, thermal shocking, gentle tapping, low force impact wrench. Finally tried a long-handled wrench, and the bolt sheared just below the surface. Then tried a lefthand twist drill bit, and it broke just below the surface. Replaced the gasket and other bolts, and there is little or no leakage. It's the only vehicle I own where folks (always men) ask if I want to sell it. It’s a 1977 F250 I inherited from my dad. Still only 130k miles, has the fancy trim, working 8-track player, bed liner, toolbox under the bed, rack and crane on the back, tow hooks on the front, 460 engine, dual fuel tanks, 1500-watt inverter. We only use it on the ranch except for service and fueling. Had a problem once where the carburetor needed work. Hard to find a mechanic that can work on auto/truck carburetors; no Ford dealer will do it. Finally, found shop 50 miles away; they did a great job. Easier to get a lawn mower or chainsaw carburetor fixed than one on an auto or truck. Now needs seals replaced on the power steering actuator. Local mechanic will give it a shot. Cal
He didn't try heating the bolt & area with a torch before attempting to back out the bolt? Sometimes that works. Too late now. If it were my truck, I'd get the header off and then remove the head and have a machine shop remove the broken bolt or just replace the head altogether with a used one from places like on ebay or the local junk yard. The older trucks are more popular because some are old enough for smog exemption while others don't have all the computer bs on them like cars do. I have a friend in Texas who is looking for a 89' or older pickup for these same reasons.
Yep, thermal shocking was used. First you freeze the area with CO2 spray, then torch it. Then try torching and CO2 spray. No joy. It's not really a serious problem. There is little or no leak. Truck does have to be smogged, but only certain types of exhaust leaks are a problem ... like ones before a cat converter. This truck is too old for a cat converter, so no problem. Cal
