A few years ago, I wrote an article for the Pingame Journal on a head rebuild I did. I have cut and pasted the test from that below. The slideshow (including many additional pictures) is here:
This is my first time contributing to The Pingame Journal. Depending on how it works out and the feedback I get, I'll either be a one hit wonder, like The Honeycombs or I'll kick out a few more articles. My intent is to do a deep dive on a particular restoration technique, rather than an overview of the entire process. I'm thinking along the lines of "Pinrepair 530 – Techniques Not for the Feint of Heart." These would be major tear ups to machines, probably more appropriate for basket cases (when you have nothing to lose anyway) than decent pins. I hope to be a regular contributor.
Like most of you, pinball machine collecting is not my first or only hobby. My other hobbies include or have included: auto/motorcycle restoration and body work and wood working/cabinet making. I have noticed a lot of overlap between these hobbies and my intent was to try to bring some of the skills and techniques used elsewhere into pinball restoration. For instance in auto body repair, if a panel is rusted or badly dented, you have a few choices: Bang out the damage and fill it, or cut out the damage and replace the panel. Generally, with rust or any major damage, it is considered best practice to replace the panel. Likewise in furniture repair, it is often better to cut back to good wood and replace a larger piece of wood, rather than try to fill and repair damaged wood. This article will look at similar techniques used to restore the head of a Gottlieb Wedgehead.
History of the Machine:
The machine I repaired was a Gottlieb Pop-a-Card. Shortly after I finished that head, I did the same thing for a local collector on his Gottlieb Sweethearts, so the process is well tested. My Pop-a-Card machine was an EBay "prize." I already owned one and was looking to upgrade the playfield and backglass when this one showed up on EBay. I entered a bid on eSnipe with the intent of reevaluating the whole thing prior to the end of the auction. Then I went on vacation with my family and by the time I came home, I was the proud owner of an "EBay accident." The machine was in Green Bay, Wisconsin and I live in Ann Arbor, Michigan, so that was going to be a bit of a hike. I grew up in the shadow of Lambeau Field, so I am a bit partial to AABs. Also, I still have a lot of family in Green Bay, so the trip could also double as a visit to Mom and Dad. Plus, to top the whole thing off, it turns out the seller was a guy I went to high school with, proving once again, it is a very small world indeed.
The machine was a mess. It had been repainted "bathroom yellow" to simulate aged white. Whoever repainted the machine didn't bother with webbing and had also painted over cabinet defects. The machine had seen water and the bottom was a stinky mess. The head had a bit of damage as well. The face was broken in three corners. I believe this is typical of the damage you get when the head is dropped on a corner. Additionally, the top back of the head was broken out. It looked like somebody had tried to pry their way into the locked head and broke out the wood in the process. My original intent was to save the playfield and backglass and part out the rest. Emotions overcame reason and I decided to save the entire machine. The first task was to fix the head.
Fixing the Area by the Back Door
To fix the damage from some prior owner or crook prying the back door off, my plan was to cut back to solid wood and replace the missing wood with new wood. I wanted to minimize the use of fillers and keep the back of the head solid wood. The tools I used to accomplish this were a plunge router, a shop made router table and a 3/4" straight cutting bit. A guide fence or even a guide attached to the router could have been a reasonable substitute for the router table. I like the stability safety the router table affords. Also, I don't like to trust my skill as a woodworker if I can get the job done relying less on skill and more on jigs and setup. I set the depth of the router bit to form a natural ledge and cut back about another 3/4" past most of the damage to give me some solid wood to attach the new piece of wood. Since the router bit is only ¾", this operation required two passes. I cleaned up the corner where the router bit couldn't reach with a chisel. At this point I was left with a clean, solid, and straight groove to glue a new piece of wood to.
To make the new piece of wood, I used #2 pine. I picked out a clear part of the board and cut it a little longer than required. Next I ripped it to the exact width using a table saw. After the wood was ripped to width, it went to the portable planer for the proper thicknesses. I like to sneak up on this dimension, taking off about 0.05" per cut after I get close, until I hit it exactly. Keep trying it over and over until it is right. The last step in making the replacement wood was to cut it to length, using a power miter saw. If you are skillful and careful, you could probably make the whole piece using just a table saw, but I have "Norm envy," so I used all the tools at my disposal.
The final step in repairing the area by the back door was gluing and clamping the new wood into place. You really cannot ever have too many clamps in place on a glue up. I use three maple wooden handscrews along with two Bessey K Clamps. The Bessey K clamps are about the best you can get. They retain the alignment of the parts you are gluing an offer a large clamping area. Good money spent on good tools is never wasted.
Replacing the Front Panel
To me, replacing the front panel was really the fun part of the project. Initially, I had considered filling it with bondo and sanding it smooth. After some reconsideration, I felt that since the front face was structural to the box and since it was damaged in three of the four corners, I would be best off replacing it. I also felt it would end up being less work and look better as well. The challenges in replacing the front piece were to cut it to the exact size required on both the cutout for the glass and around the perimeter of the cabinet. It may be possible to carefully mark out, cut, and sand the interior hole (the cutout for the glass) to the correct shape, but it is impossible to cut the outside to exactly the correct size and then install it. It needs to be trimmed to fit after the installation. To do this, I cut the front face to a rough approximation of the final size and then trimmed it to the exact size on both the inside and the outside with a router and a bit known as a pattern cutting or flush cutting bit.
A pattern cutting bit is just a straight bit with a guide bearing on either the top or the bottom. The bearing is exactly the same diameter as the cutter, so you put your pattern above or below the piece you are cutting. The location of the pattern is dictated by the location of the bearing, so if you have a bottom bearing, the pattern needs to be on the bottom. In this instance, since the head itself will be used as one of the patterns, I used a bit with the bearing on the bottom.
I used a sheet of ¼" birch plywood to make the new face from. I laid the old piece on top of the new plywood and traced both the inside and outside. For the initial cut, close counts. In fact you need to leave about ¼" on every dimension to allow for the final trimming. I cut out the outside of my Wedgehead face with a table saw and used a portable jig saw for the inside. I could have just as easily used a jigsaw for everything. Just be sure to leave a little extra on all sides.
The next step is to trim the inside or window hole to the exact size. Clamp the old piece, the pattern, underneath the new piece. Make the necessary adjustments to the router depth to make sure the bit stays piloted on the old piece, turn on the router and make the final trim on the window. There are a few things to be careful of during this step. One thing to be careful of is that you need to make sure the router is being fed in the correct direction relative to the rotation of the bit. The router spins clockwise so you need to move the router in a clockwise direction. This is done to avoid a "climb cut" where the bit rotation actually pulls the router along. This can lead to an out of control, poor cut and can even be a little dangerous. Note that the feed direction will be reversed when you are trimming the outside of the face. Be careful and make sure you are feeding it in the correct direction. The direction you move the router or the work piece should always be such that the router bit rotation opposes movement. The actual feed direction will change depending on if you are routing the inside of a frame, the outside of a frame, if you are moving the router (free hand) or the piece itself, as when using a router table. The key is that the rotation of the bit cannot "help" the movement of either the wood or the router, whichever you are moving.
The other thing you will run into is that you will need to reposition the clamps at some point. The router cannot cut where the clamps are, so you will need to add new clamps, AND THEN pull off the old ones. This will retain your alignment. Some people use two sided tape to avoid this issue, but I don't trust the stuff. So route out as much as you can, put new clamps on, remove the old clamps, and then finish routing the window where the clamps were. At this point the inside, or window is complete and the outside needs to be trimmed to size.
The next step is to attach the face plate. Apply glue to both the new plywood piece and the old Wedgehead frame. Align the lines indicating the outside of the head (These are the lines that should have about ¼" excess material still), and attach the face to the head using either small brads or an air stapler. I used a stapler, as I feel it does the best job holding thin plywood.
Now use the pattern cutting bit to cut the outside of the face to the exact dimensions of the head. Turn the router on and trim back the bottom and both sides of the face to the outside of the head. Again, be mindful of your feed direction to avoid a climb cut. Here you should be moving the router in a counter clockwise direction. You can make two passes if required. Do not trim the top back yet, or you will have a disaster on your hands.
The top needs a little extra attention due to the vent holes. If you follow the same procedure you used on the bottom and sides, the bearing will follow the outline of the top and plunge into the vent holes. This will ruin your piece and you will have to start over. To get around this, I covered the vent holes with some thin melamine edge banding prior to running the router over them. This left the top edge a little proud of the head yet, so that had to be taken back the rest of the way with a random orbital sander. If I would have had a longer bit, I may have been able to set it deep enough to go beneath the vent holes, but I was working with what I had. Also, sometimes it can be difficult to control a bit that set as deep as would have been required. Any cocking of the router would have damaged the piece.
At this point, the head was essentially rebuilt. I finished it up by sanding, filling any imperfections, priming and painting. I used a touchup gun and unthinned lacquer to do the webbing, but that has been covered before elsewhere, so I won't get into it here.
I was very happy with the end result. The head looked as good and new and was structurally sound. I got to fire up the power tools, so that is always a good day. This is just one way to get this job done. Many other tools and techniques could be substituted. For instance, if you are careful you could trim back the outside of the face using just a sander. You could maybe even use a block plane if you are real good. You will need to adapt to the tools you have or are willing to buy, but this should give you plenty of food for thought.
• 1x6 #2 pine
• ¼" Birch Plywood
• Tightbond Glue
• Melamine Edge Banding (any veneer would be fine)
• Table Saw
• Router Table (with fence)
• Air Stapler
• ¾" Straight Cutting Bit ($9.95 from MLCSwoodworking.com)
• ½" Pattern or Flush Cutting Bit ($9.00 from MLCSwoodworking.com)
• Bessey K Clamps
• Maple Handscrews
• Misc. C Clamps
One More Thing – Geometry 101
While working on these machines, I usually consider what the engineers and designers may have been thinking when they did something a certain way. In the case of rebuilding this head, I put some effort into laying out the face on my sheet of plywood in the most efficient manner. In the process, I noticed that the head, if cut from a single square, would require an area that is nominally 26 inches X 26 inches. This would be an inefficient size if it were square, but the Isosceles Trapezoid shape of the Wedgehead allows for four 26 inch x 26 inch pieces to be nested and cut from a 48 inch x 96 inch sheet of plywood as shown below. So perhaps the classic design was dictated by cost, not style.