What’s the consensus or suggestions for when to use #6 or #8 screws for bottom coil assemblies on new playfields?

Standard design on most pins 80s/90s era I've worked on seems to be #8 for mechs/solenoids, #6 for everything else (lamps, switches, etc ). Seems logical to use heavier screws for stuff that vibrates and such, but I suppose I'm not convinced it's necessary either.

Thank you sir. Much appreciated.

Drilling out clear keeps coming up. A lot of people are worrying over it, but I’ve lost count of how many playfields I have restored or swapped out, and here’s what works for me:

Get a small countersink, the kind that looks like a plumb bob. Doesn’t really matter if it’s a small medium or large, you’re host gonna use it to slice the clear away from the 3/32” holes you drill for post screws primarily.
https://images.thdstatic.com/productImages/e0ac7e7f-9157-435f-aa3d-aa818d41861c/svn/general-tools-countersink-bits-195st-64_600.jpg

Use the countersink pretty much everywhere you’re going to be putting a screw. You don’t really need to worry about it on machine threaded screws, but I’m you won’t hurt anything by doing holes that didn’t need it. It’s probably wider to err on the side of caution.

After many playfields, I feel that there is an excess of caution around pop bumper nails. Slicing all of the clear away from the head is a somewhat high risk maneuver that just isn’t necessary. The clear should be pliable enough to yield to the nail head as it sets from gently being tightened. If it’s not, there is either too much clear or someone has used an accelerant, making the clear more brittle than you want it to be.

I hate #8 screws in playfields. Hate them.
I’ve had old playfields where the threads were torn out from age or from people over tightening, or removing and replacing brackets without turning the screw backward to “find the thread” first. Whatever the cause, a torn out #8 screw hole gives you no recourse except to glue a tapered (preferably hardwood) dowel in the hole and re-drill, unless you have the option to pivot the bracket (sometimes a possibility with flippers.)

When I’m populating new playfields, I *always* use #6 for all coil brackets. The Williams sys7-WPC machines I have worked on used #6 exclusively and without issue. Older Stern and Bally machines used #8 on flippers and drop banks, but on repro playfields I mount them with #6.

My reasoning is: there’s no inherent greater performance using #8 screws (or, more to the point , no tendency to failure from #6) that I have seen. Down the line, if for *whatever reason* a #6 screw gets stripped out, it can be replaced with a #8 since the prior screw has effectively pre-drilled the hole for you. And the #8 should then have good purchase for a long time.

I keep both screws in my inventory. When repopulating a restored playfield I often have no choice, but increasingly I will just plug the old #8 holes with wood dowels and start over using #6 screws. If for whatever reason a #6 tears out, I can move to the #8 without having to stop what I’m doing and glue in a dowel. If the old #8 hole is solid, I will reuse it, but more and more I don’t trust those big cavities in 40 year old plywood to hold the screws securely over time.

How many screws do you come across that have sheared off though? Posts do it all the time, but screws should really never shear off under these conditions. Stripping and backing out? All the time.

So does that mean a #6 is sufficient for all under playfield assemblies in fresh new playfield holes?

I am populating a new DE Star Wars CPR playfield and I am at the point of installing the larger wire guides. For the small ones, I followed Vid's instructions (2 step drilling, barbs filed) and I am quite pleased with the results. However, the CPR pre-drilled holes for the larger wire guides are already slightly bigger than the diameter of the guide. So I think filing the barb wires would not allow me to install the guides tightly. And I am afraid that installing them as-is would damage the clear. What would be the best strategy in this case ? I am tempted to enlarge the hole at the barb locations only to guarantee that they will not touch the clear when inserted but would appreciate some advice. Thanks !!!

Jack

wire rail (resized).jpg

I have done the epoxy before. Mask off the area around the hole and add via a toothpick. Works great.

Bally has a part number for screws that have a wax coating. I guess you can have hardware
made with special coatings that I never really new.

Thans for the tips, I had not considered epoxy and it seems like an easy solution. Glad I asked.

Squirt wood glue in the hole and line it with round toothpicks. Clip them off flush. Insert screw in the center gap. We've used this technique on arcade pins for 20+ years, with lasting results.

I’m guessing that’s because they don’t pre-drill when they assembled these things in the factory.

Sure, but I’ve also restored machines where this fix has not held. I take small strips of hardwood and chuck them in the drill press, then sand them down to a snug tapered dowel.
If toothpicks work for you, great, I’m not gonna argue to point; I’m from a cabinetry background and am anal retentive.

I'm using bamboo skewers now for thread/hole repairs.

Much better than basswood toothpicks and similar to a hardwood dowel plug as far as durability, maybe better.

I have a bottomless supply of European beech in the shop.
When I make cabinet doors and face frames, there’s the initial phase of milling down the rough sawn parts. I often end up with thin strips from that process; these get sliced to short lengths and bundled, as they are very good dowel stock for such repairs, as well as good glue spreaders or mixing sticks - or, world-class kindling. If I were an outdoorsman I would toss a packet of this stuff in my bag for getting a campfire started.

Interesting about bamboo - since it is technically a grass, its fibers may in fact be better than any wood, since wood grain has direction and using any dowel for a hole repair means going into end grain.

It may be a purely academic distinction, though, since really you’re removing most of the material you put in there once you pre-drill and drive the screw. But, I’m a lunatic who spends way too much time in the shop pondering over process, so take my observances with that grain of salt