View Full Version : Looking for an internally threaded Allen bolt/nut

07-17-2011, 08:37 AM
I guess it is technically a nut because it has female threads. I want to bolt a plate onto a stud that is sticking out, except that the stud is kind of on the short side relative to the plate's thickness. There exists this kind of nut which is shaped like a normal Allen socket head screw, except that the body is smooth on the outside and the threads are on the inside. The plate has a hole much bigger than the stud, and gives the nut enough room to screw over the stud. Then the head of the nut catches onto the plate and that holds everything down.

Anybody know exactly what this is called, and where to get some? I need size M6x1.

07-17-2011, 08:40 AM
A hank bush?

EDIT: no, just re-read your description. What you need is similar to the nut they use to hold the exhaust manifold clamp plates on Yamaha motorcycles. You tighten them using an allen key.

07-17-2011, 08:49 AM
Here you go, M6 stainless allen-nuts


Lew Hartswick
07-17-2011, 01:26 PM
Except he needs a flange on the head. I'd make it if I only needed one
or two. Start with a large socket head cap screw remove the threads
to clear the hole (or make the hole to fit the screw) and then bore
and thread the inside to fit the stud.

07-17-2011, 01:44 PM
I saw that, but the bolts look quite thick walled so possibly thick enough to allow for machining a step. Either that or turn a step and use a washer.

Weston Bye
07-17-2011, 01:48 PM
Google the term sex bolt. No kidding:D

07-17-2011, 01:59 PM
No thanks :D

I was just thinking that this type of bolt is also used extensively in flat-packed furniture - the kind you spend all weekend trying to assemble into something Homer Simpson would be proud of :D

07-17-2011, 02:25 PM
I would get long 10mm allen bolts that have a straight part between the head and threads. Cut the threads off and drill and tap the middle for a 6mm. Even grade 8 bolts are fairly soft in the middle.

doctor demo
07-17-2011, 02:45 PM
Google the term sex bolt. No kidding:D

Yup, use a similar fastener to attach door closers to metal doors only We call them She bolts.


07-17-2011, 02:49 PM
You will also find them under "Chicago screws" and that you can get the stud longer by using a "post" extension (so you would not have to have both "halves" of a Chicago screw "set"...just extend the post and use a nut...mentioned as most that I could find were slotted heads and that in turn may not be a good choice for your application)

07-17-2011, 04:10 PM
Here's an example of the bolts I want

07-17-2011, 05:37 PM
I know you think you'll be bombarded with smut, but when I googled "sex bolt" as per Weston's suggestion I got Wiki and commercial sales entries talking about what sounds like what the OP wants.

There may have been smut further down the page, but I didn't look.

No kidding !

But I'm afraid there were no entries that explained why they're called that. Curious.

John Stevenson
07-17-2011, 06:08 PM
I know you think you'll be bombarded with smut, but when I googled "sex bolt" as per Weston's suggestion I got Wiki and commercial sales entries talking about what sounds like what the OP wants.

There may have been smut further down the page, but I didn't look.

No kidding !

But I'm afraid there were no entries that explained why they're called that. Curious.

Good job Tiffies not about, that Tiffiepedia search would have seen him off :D

07-17-2011, 06:50 PM
Sex Bolts are often a 2 part set with male and female threaded parts.

07-17-2011, 06:53 PM
I've never seen a sex bolt where you can really put down the torque.

07-17-2011, 07:38 PM
Iv seen some used on bike brakes.. but they where threaded all the way through, and the alen key shape was then pressed into the threads.. very weird. Hex ID threads (or maybe before threading)

07-17-2011, 07:52 PM
There is another type commonly used on aircraft called a Riv-nut. It is pulled in place blind like a pop rivet. They are available in both aluminum and steel.


07-17-2011, 08:43 PM
Got ya...those sex bolts or whatever other name, a not likely going to do it for your purposes (at least the ones I saw were not like your photo)...


that's a place specializing in small parts or difficult to find parts for bicycles and though they are not identical to your photo in shape (the heads are round and not inverted cone shape) they do have several options, mostly to do with length [size seems pretty standard for the use, bike brake attachment with different lengths for fork crown "thickness"]

look under "brakes" tab, items # 7, #42, #43, #54, # 57 and # 63

a bit problematic is a proper name, "recessed Allen nut/bolt" is used sometimes and you get what you want (more or less) but other times you just regular Allen/hex socket cap screws...it seems difficult to describe both the socket for the hex key but also that the bolt itself is hollow...and it gets odder as there are hollow hex head bolts (basically a regular bolt with a hole down the center) as well as ones with shoulders

"hollow clamp bolt", "hollow recessed allen bolt" or similar mostly end up back with bicycle stuff...

the only one I could find like yours (that slight taper) were ones based on the old Dura-Ace Shimano stuff

07-17-2011, 11:58 PM

07-18-2011, 12:32 AM

Try searching for 'barrel nut'. McMaster has them, but not in metric. Have a look and see if they would work for you.

07-18-2011, 03:46 AM
Russ, that's the closest I've seen so far, but I think the head on that is still too small. Next I will see if I can find any specialty motorcycle nuts and bolts sources.

07-18-2011, 03:15 PM
Is this what you are looking for?


I have a bunch of those with a cone head, they are axle bolts used on skateboards, inline skates etc.
They come in handy now and then.
Most skateboard shops should have them.

Here is a link to a flathead m6x1 set. http://www.inlinewarehouse.com/descpage-SEAK.html

You'll have to search around if you want the cone head style.

07-18-2011, 11:51 PM

I'm sort of anal once I get going on something like this but sorry, still very little luck. This one "got to me" as they have to be from somewhere...and...

The most common motorcycle issue with hollow bolts appears to be for routing wires (makes perfect sense) but the configuration is all wrong. The other motorcycle bit that comes up consistently is the use of hollow bolts in swing arms (mostly single sided?) but these tend to be quite large diameter.

Automotive will get you hits but those hollow bolts are mostly for oiling systems ("banjo" bolts...the bolts are hollow but are cross drilled to act as part of the lubrication system).

Bicycle stuff keeps coming up to but you can also get large sizes for either chainrings (problem there is they are really really short) or for attaching stem/handle bars (problem there is so many types each slightly different appearing to be mainly proprietary)

Not what you want but maybe a place to start re: motorcycle specialization

Make specialized hollow bolts but hard to say exactly what configuration as few pictures (also openly state will not do "one offs" as they need to make common enough to produce economically)

More bike stuff but variations including in titanium (more sizes, one or two with those "cone" heads not really any larger though)

again, not what you are after, exactly but almost enough meat around the head for additional machining

No offense, but I would say, unless you need a lot, rolling your own looks pretty good...related: I found it sort of funny the number of times similar requests got the suggestion of finding a local machinist and that it would only take ten minutes but you would be charged for 2+ hours of work

07-19-2011, 12:04 AM
Got the bolts, and you get a choice of exact head style...now to get the hollow part. Gotta warn you, titanium.



one "taper head", the other "button head" buy em and drill em? (;

edit: don't know what gives with those links, they are taking forever to load (first time it was fast), anyway, they have a section specific for brake parts (both off road and road race) and those look A LOT closer but since those sections don't load...

07-19-2011, 12:05 AM
Russ, thanks for looking into it. The bolt/nut doesn't have to have a hole all the way thru, if that makes searching easier. It just needs an Allen socket to engage the top, have big enough of a head/lip to grab on to the plate, and then be internally threaded the rest of the way to grab the stud. The bicycle and skateboard bolts/nuts are have the right configuration, although I don't know if they have the strength to grab onto something really good.

My guess now is that these parts aren't even uncommon, but custom for particular products. Maybe I'd have to search for them as replacement bolts for something.