Searching for a type of bolt; machining terminology

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nkg

Sr Member
RPF PREMIUM MEMBER
So this is a two-part question, and I don't know where best to post it. Doesn't really fit with any of the forum categories here.

Anyway. Basically I'm looking to find a specific type of bolt or screw for a replica prop I'm working on. Specifically the HAL 9000 "brain room" sign.

1610801376443.png


I've made pretty accurate signage printed on aluminium sheet (I have some seconds in the "junkyard"), but I'm having difficulty sourcing the bolts that they used to fasten it to the door. So I have two basic questions here.

1) What is the machining terminology for the lathed/turned finish whereby you have ultrafine concentric rings engraved into a flat surface? I believe it's generally known as "facing" on lathed parts.

The upshot of the finish is that a flat cylinder, for example, will have a bunch of radial wedge-like shapes, bright and dark, reflected off the surface, crossing through the centre of the object. This is one of these things that's harder to describe than to show. Like this:

1610799173498.png


So. I'm looking for bolts with this finish on their flat cylindrical outer surface. Is there a name for this? It's not the same as a brushed finish. Apple used a lot of steel screws with this type of finish on their G4 and G5 computers.

2) How can I find a bolt with a head that looks like this? I don't care about the specific type of bolt - I'll cut off the head to fit the sign anyway. It's just the outer surface that matters.

Specifically I'm trying to find a stainless steel bolt, faced, like this, with a perfectly flat outer surface. A tiny bit of chamfering on the outer edge is fine. Cap head ideally - no knurling and parallel sides, preferably not countersunk. Not stamped with the steel alloy type or part number. 12mm in diameter, with a roughly 4mm hole for an Allen key.

Screenshot 2021-01-16 at 12.58.28.png


There are the cylindrical standoff picture hanger/glass panel things, and those would be fine, but I'm having difficulty finding one of the correct size with a hexagonal recess in the centre. Most are featureless on the outside, since you don't want to encourage people to unscrew the glass panels you have on the side of the staircase or whatever. There are the bizarrely-named "sex bolts" or "barrel bolts/binder bolts", but I can't find the right size.

Right now I'm sort of resigned to buying steel countersunk bolts and faking up the finish. Stick them in a drill chuck, turn the bolts slowly, and use sandpaper to crudely simulate the look.

Screenshot 2021-01-16 at 13.17.20.png

(NOT what I'm looking for ideally - this is countersunk!)

Anyway. Any other ideas? :) Thanks!

- nkg
 
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parfaitelumiere

Sr Member
RPF PREMIUM MEMBER
one name is "flat mount"
other is "flat head"
The the type of screw is "hex"
Type "flat hex" on ebay and you will find it.

Then to know the exact model you have to take a look at iso-din rules.
I found a din for the metric "tête fraisée" bolt, the right for your use would me a M6, 12mm head and 4mm hex hole.
For the finish, you can put on a drill , and use a tool to make the finish, a file or a stone can be ok.

proxy-image.jpeg


 
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nkg

Sr Member
RPF PREMIUM MEMBER
one name is "flat mount"
other is "flat head"
The the type of screw is "hex"
Type "flat hex" on ebay and you will find it.

Thanks! That gets me a countersunk head, which is fine. I've been able to find those. I'm trying to find a head with parallel sides, however, not angled in like countersunk. If I can avoid it!
 

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Zombie Killer

Master Member
RPF PREMIUM MEMBER
What your describing is a "socket head allen screw". What your showing in your hal picture is a "stainless flat head allen screw" that someone put in a lathe or spinning device and either machined the top surface down or hit it with some sandpaper to give you that machined top surface look. That finish is called machined finish
 

nkg

Sr Member
RPF PREMIUM MEMBER
Thanks for the comments, folks! I'm kind of resigned to going with a countersunk screwhead and messing around to simulate the finish at this point. :) We'll see if one of the ultra-low socket heads works.

I'm just a bit surprised about the turned/machined finish. I've seen it on a number of consumer products - notably Apple, as I've mentioned above - and I would have thought that such fasteners would be readily available for sale! I wonder where the 2001 set decorators got theirs from...
 

Pyrotechnic

New Member
Something like these?
Listing does mention "Please note the image is for illustrative purposes only"

but, also describes them as "high quality bar-turned 7075 Aluminium screws"
 
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wdtenney

New Member
If you want to simulate a cap head screw using the flat head type, you could use a cup washer. (also called a countersunk washer or finish washer)
There'd be a little bit of a visible seam between the screw head and the washer, but it would get close to the look you're describing.
link: Cup Washers
 

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nkg

Sr Member
RPF PREMIUM MEMBER
1611252098423.png

Something like these?

Thanks! :) The GWR lead was a good one. These aren't quite right - they aren't exactly what a turned steel screw head looks like. But they're good enough, and easy to work since they're aluminium. I think that's a decent approximation!

They came with slight machining marks out of the bag. They're just a bit too shiny and aluminiumy.
 
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nkg

Sr Member
RPF PREMIUM MEMBER
Okay. And this is just a steel screw, chucked in a drill and sanded. Better colour than the aluminium screw.

1611766673005.png


It’s hard to find a steel screw that doesn’t have a bunch of codes stamped on its head.
 
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