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Many components can be panel-mounted by drilling a hole through the panel and then fixing in place with a washer+nut. However, sometimes the datasheet does not specify what is the hole size to drill. For example, the datasheet for this panel-mounted push button includes diameters at different points in the component, but no hole size: pushbutton size data

Should the hole size just be 7mm (major diameter of an M7 thread)? Or is it recommended to make the hole slightly wider?

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Amazingly, there is actually a standard that defines what should be the hole sizes to accomodate standard threaded screws. It is ASME B18.2.8-1999: "Clearance holes for bolts, screws and studs". There is a similar ISO standard as well (for metric only): ISO 273-1979. For each thread size, they give three hole diameters (for close, normal, and loose-fit categories).

Here is a PDF containing the chart, but you can easily find them using the "hole clearance chart metric" search terms on the internet.

In your specific case, for M7, it is 7.4mm for close fit, 7.6mm for medium, and 8mm for loose fit. You choose.

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  • \$\begingroup\$ Honestly, there's nothing "amazing" with such a standard. :) \$\endgroup\$ – pipe Jul 19 '16 at 21:08
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A correctly produced M7 thread will be slightly less than 7mm across, so should fit in a dead-size 7mm hole. But it doesn't hurt to make the hole 7.5mm.

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What you show seems quite clear. The threaded body is M7 size. Make the hole diameter whatever you would normally make it to accommodate a M7 thread without interference. Surely there are references out there for the maximum diameter of a M7 thread.

It's the datasheet's job to tell you the characteristics of the product, not how to use it in your particular case. It shouldn't tell you the hole size, although it should tell you the outer diameter of the thread without you having to look it up elsewhere. Once you know that, you can come up with your own hole size, knowing the slop in your process, how much clearance you want, etc.

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  • \$\begingroup\$ You don't consider a physical diameter a characteristic of the product? \$\endgroup\$ – Marquis of Lorne Jul 20 '16 at 5:49
  • \$\begingroup\$ @EJP: As I said, "it [the datasheet] should tell you the outer diameter of the thread". \$\endgroup\$ – Olin Lathrop Jul 20 '16 at 10:27
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The answer is actually right there on your data sheet. The circles on the right are an end view of the device. The smaller of those 2 circles represents the diameter that would be going through the drilled hole you are asking about. You can see that they have indicated it as 7.4 (and i'm assuming this datasheet is in millimeters?) So, if you make a hole the same diameter as that, you are going to get a pretty snug fit.

There is a down side to that. First, its actually tricky to put it in, cause the body and the hole have to be perfect with regards to tolerance on the measurement, and if they are, you still have the issue that if the hole is not perfectly perpendicular to the surface, the top bezel may not sit flush with the surface, rather one side will have a small gap.

You can avoid both of these by going with a loose fit, and make that hole just a tiny bit bigger. The device will go into the hole easier, and will have a little wiggle room for the front to go flush when you put the nut on. On the other extreme, if you make the hole too big (in this case, 9.5) your device will fall right through the hole.

All right there on the data sheet. You could also look it up, but they are nice enough to give us that data sheet so we don't need to, cause they already did... so if everybody goes looking these things up on their own, the guy they pay to look it up looses his job. :)

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  • \$\begingroup\$ I'm sorry, this is wrong. The 7.4 mm dimension refers to the size of the barrel from which the two pins protrude (the right side of the switch, on the side view drawing). This is not related to the diameter of what goes through the hole (although coincidently very close in size). The switch is inserted in the hole from the other side (which is mentioned M7x0.75). \$\endgroup\$ – dim Oct 4 '16 at 12:53

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