Since Yamaha is a Japanese company, their synths were likely made (or at least designed) in Japan which uses the metric system?of measurement and construction for everything, including screws, nuts, bolts, etc.

At some better hardware stores (not always the big box hardware stores) there are metal or plastic rectangle thing you can hold in your hand, called a “screw checker" that have different size screw holes in them that you can gentle try out any kind and size screw in to find out what that the type and thread of the screw is.?

America is the only country in the entire world that has a non-metric older different screw-thread system called the "American Standard” system, and complicating things even worse if that there's?two of those kinds of screws within the American Standard system?also: ?"Course” thread and “fine” thread. ?

But the influx of foreign made items sold to America has been increasing since the 1960s, and so more and more stuff now common to us is metric instead of American Standard.

So there’s a metric screw-checker for testing metric screws and a separate screw-checker for testing American Standard screws. ?Both are worth buying and keeping for situations like these. ?

Once you've got those, it's likely your DX7 is metric, so get out your metric screw-checker and unscrew one screw from your DX7 that’s closest to the missing screw holes and then test it on the metric screw checker to figure out what the thread is and write that info down. ?Then measure the length of the screw with any American ruler. ?Let's say for the sake of discussion that the screw is ?half an inch long. ?Write that down also.

Now, try that screw in each of the other holes that don't have screws and see if it tightens up properly. ?If not, you now know you need a longer screw for those holes.

But if it tightens up, now you know what length of screw to get, and that it's metric, and what metric-thread you need.

Put that screw back into the hole you got it out of and head back to that same better hardware store and tell them the exact kind of screws you want and they might have then and then back home screw them into your DX7 and you're in business. ?

Also note that these kinds of screws are called "machine screws” as opposed to “wood screws" or “sheet metal screws" or "specialized screws” of which there are many kinds.

Does this help any?

Catch ya later. ?Bye for now.

Dan Fiebiger.

Portland, Oregon

(Still using my first generation DX7)

?

?

Ethan et al,

Those screw checkers are for *tapped* holes.? That DIN standard is for a *self-tapping* screw.? The first thing is to figure out which type was used.? Here is a tapped style for comparison --



Frankly, I would be surprised if Yamaha used self-tapping screws on the DX7.? They certainly didn't? on my TX802.? These screws are used in applications where it's unlikely that removal is required.? Putting them back in without stripping the holes is tricky; even with care, they can't be removed more than a few times before loosening the hole.

Most Japanese MI gear uses M3, M3.5, M4 or M5 tapped screws with 'standard' threads for just about everything.? (Metric screws also have fine-pitch variations, but their use is extremely rare.)? That "4x16mm" sounds like a reasonable starting point:? it's commonly referred to as an 'M4 x 16', or more properly, an M4-0.7 x 16mm.? You should be able to test an M4 in a screw checker per Dan's suggestion.? Then measure the distance from the bottom of the screw head to figure out the length.? Common lengths are 6mm, 8mm, 12mm, 16mm, and 20mm.? (Actually, 16mm sounds a bit long for a case screw.)

Most quality hardware stores will have something in this size, although black oxide coating may be harder to find than galvanized or stainless steel.? But an online hardware site like MSC or McMaster-Carr will definitely have them.? Or try eBay.

________
Jan's comment about JIS is a good point:? a Philips screwdriver will work, if the user is careful.? McMaster has JIS screws, but not black-oxide ones.

Since Yamaha is a Japanese company, their synths were likely made (or at least designed) in Japan which uses the metric system?of measurement and construction for everything, including screws, nuts, bolts, etc.

?

At some better hardware stores (not always the big box hardware stores) there are metal or plastic rectangle thing you can hold in your hand, called a “screw checker" that have different size screw holes in them that you can gentle try out any kind and size screw in to find out what that the type and thread of the screw is.?

?

America is the only country in the entire world that has a non-metric older different screw-thread system called the "American Standard” system, and complicating things even worse if that there's?two of those kinds of screws within the American Standard system?also: ?"Course” thread and “fine” thread. ?

?

But the influx of foreign made items sold to America has been increasing since the 1960s, and so more and more stuff now common to us is metric instead of American Standard.

?

So there’s a metric screw-checker for testing metric screws and a separate screw-checker for testing American Standard screws. ?Both are worth buying and keeping for situations like these. ?

?

Once you've got those, it's likely your DX7 is metric, so get out your metric screw-checker and unscrew one screw from your DX7 that’s closest to the missing screw holes and then test it on the metric screw checker to figure out what the thread is and write that info down. ?Then measure the length of the screw with any American ruler. ?Let's say for the sake of discussion that the screw is ?half an inch long. ?Write that down also.

?

Now, try that screw in each of the other holes that don't have screws and see if it tightens up properly. ?If not, you now know you need a longer screw for those holes.

?

But if it tightens up, now you know what length of screw to get, and that it's metric, and what metric-thread you need.

?

Put that screw back into the hole you got it out of and head back to that same better hardware store and tell them the exact kind of screws you want and they might have then and then back home screw them into your DX7 and you're in business. ?

?

Also note that these kinds of screws are called "machine screws” as opposed to “wood screws" or “sheet metal screws" or "specialized screws” of which there are many kinds.

?

Does this help any?

?

Catch ya later. ?Bye for now.

?

Dan Fiebiger.

Portland, Oregon

?

(Still using my first generation DX7)

?

?

?

?

You're probably right.
I just remember the jet engine mechanics on the shop floor making a big deal
about it and how they had separate drivers. 
Maybe they were having fun with the Engineer - "no THAT one takes the
fillister driver".
Or maybe they actually used separate drives.

L.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of mark
audacity romberg
Sent: Wednesday, January 19, 2022 8:10 AM
To: [email protected]; ethan@...
Subject: Re: [YamahaDX] Need help identifying DX7 front panel screws (1st)

Fillister is a head shape, not a drive type. 

Well if anyone is interested in a set of
Four (4) 16mm and one (1) 13mm M4.2 Pan Phillips Tapping Steel, Zinc Plated DIN 7981-C
Let me know, had to buy a decent quantity for it to be cost effective. I also have a black oxide chemical kit I intend to use to make mine black.

As I said before, the shorter screw (on the back panel near the power) is 4 x 8mm. A 13mm screw will be too long here.

Also note, that the length of a screw is usually measured at the length of the threads, not the whole screw.

More accurate measuring reveals the thread pitch may be 1.4mm.
A hint for inserting self-tapping screws into old plastic is to first rest the screw in the hole then back the screw out slowly until you feel it drop into the thread. Then screw it in as normal and don't over-tighten.