Adjustment brass screw (Hex nut replacement)

Does anyone know where I can find these types of thumbscrews, but with a hex nut? I am having a hard time tightening the knurl nut without the thumbscrew turning and loosing alignment on my mirrors.

@cprezzi helped me out finding this type of screw generally.

However, this Google search doesn’t find anything.

If I were you, I’d carefully file flats on those existing screws to match a wrench you have handy. (I would cut them on my mill since I have one, but that’s mostly for fun, brass files easily.)


I’m going to try filing the screws like you said and order some new ones from aliexpress to have as spares. 1pcs M7* Pitch 0.5mm Laser Head Machine Optical Path Adjustment Brass Screw Reflection Mirror Frame Cutting Machine Accessories - Bolts - AliExpress


It would be easier to find a hex nut to thread in place of the knurled ring. That’s how my laser is equipped and it’s easy to hold the knurled portion while using a wrench on the hex nut.

It’s the 7x0.5mm thread that’s tricky here. It’s a relatively unusual diameter/pitch.

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Yeah, my searches come up completely empty/useless. Even aliexpress has nothing of the sort. If it wasn’t for the specifics in the images, one could wonder if there’s an error, but it’s pretty clear that it’s M7-0.5.

This would be a good place for a rotary broached hex socket in the head. One can’t find M7-0.5 anything, really, although I did locate a tap and die for that via Amazon. Maybe drill out an M6 nut and re-tap?

I don’t know if there’s even a published spec for M7x0.5 to know what the drill size would be; did the tap list the associated drill size? This migh require precision fine enough to have to ream to final dimension, too!

It’s easy enough to single-point a 7mm x 0.5mm exterior thread on a lathe, but to single-point the internal thread would require something like this Micro 100 internal threading tool:

I have one of their miniature boring bars and it’s lovely, so I’d expect this one to be the same. Could use brass hex stock and knock out some nuts if you had the right drills and reamers, or I guess drill and small boring bar…

I’m on a detour right now from my plan to make my Z Live Center do dual duty as a rotary broach, but yes I agree it would be a good target for one. More fun than filing flats! :grin:


Judging from the reviews in this amazon listing, this is also a common thread form for vaping. Which… I wouldn’t have had any idea.

Here’s a fairly detailed drill size chart. It shows M7 x 1 and M7 x 0.75; reading between the lines up and down the chart it looks like for M7 x 0.5 you probably want a 6.4mm or so drill. You could probably use a good ¼" bit (6.35mm) since drills tend to go a touch oversize.

This is actually not a terrible collection of tap/drill size charts covering imperial and metric and including charts relating the two.