Supplier for off the shelf torque-to-yield (TTY) fasteners
Supplier for off the shelf torque-to-yield (TTY) fasteners
(OP)
Hi all,
I'm working on a project right now where I need a TTY fastener to attach 2 custom components together. Since the 2 members to be fastened are custom, I can still modify the design around an existing TTY fastener, to save costs on custom fastener manufacturing. Therefore, I'm looking for any suppliers which have these type of fasteners available for purchase.
I can't give out the application for obvious reasons, but the fastener should be appx. M12, fine thread, 10.9 class, preload appx. 75 ±15 kN after yield. The preload force itself isn't as important as a consistent preload - I realize 75±15 kN can likely be achieved with just torque & lubricant, but I need it to be consistent from one application to the next, hence TTY.
Any leads are appreciated, thanks!
I'm working on a project right now where I need a TTY fastener to attach 2 custom components together. Since the 2 members to be fastened are custom, I can still modify the design around an existing TTY fastener, to save costs on custom fastener manufacturing. Therefore, I'm looking for any suppliers which have these type of fasteners available for purchase.
I can't give out the application for obvious reasons, but the fastener should be appx. M12, fine thread, 10.9 class, preload appx. 75 ±15 kN after yield. The preload force itself isn't as important as a consistent preload - I realize 75±15 kN can likely be achieved with just torque & lubricant, but I need it to be consistent from one application to the next, hence TTY.
Any leads are appreciated, thanks!





RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
I guess the request for a special fastener is to ensure that there is a reduced shank which will allow for lower fastener stiffness & ensure yielding in the shoulder, rather than in the thread itself.
The goal for torque+angle is for servicability. For series production, yield point sensing equipment could be used to ensure consistent preload regardless of interface friction, but the same equipment could not be used in servicing.
To that end, do you know of suppliers which sell TTY bolts, in the sense that they have this reduced shank for yielding?
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
Thanks for the tip on modifying existing cap screws - that's an option, though I believe I'm going to have to convince the bosses to spend the development cost for the custom screw.
In case anyone else has different experience, please let know - thanks!
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
arp-bolts.com/
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
There are a few standards for waisted shank fasteners, but they are aerospace specifications like DIN 65115 or SAE AS3650. Dimensionally they are similar to reduced shank fasteners (ISO 15071 Type R), except that the shank diameter is ~ minor diameter rather than the pitch diameter. As an example, the waisted shank diameter for an M10 would be ~ 7.5 mm instead of ~ 8.9 mm. The transition for shank to thread has a radius almost as large as the thread diameter (e.g. 8 mm for M10) with a 15 degree angle. The waisted shank transitions back to the nominal body diameter under the head, with the shank at least 0.5*d away from the underhead.
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
CoryPad - ARP is an excellent recommendation, I started with them actually but they're not selling TTY bolts (at least, in their catalog). I will send an email to my contact there to be sure. The material they use is a bit stronger than a 12.9 though, which is too strong.
TVP - excellent suggestion! The waisted shank geometry would be perfect. I tried searching for suppliers, though, and couldn't find many - additionally, the publicly available information I had found on DIN 65115 suggests it's available in just standard thread (M12x1.75) but not fine thread (M12x1 would be ideal for angle to preload relationship). Do you have access to the standard to know whether it also allows for fine thread, and/or who can supply this kind of bolt in the US? I would imagine there's a better chance of finding a supplier for fasteners according to SAEAS3650, but (without having the standard) I would also imagine these are available in only UNJ thread, and I need to keep it all metric.
I tried googling for about 2 hours after the tips in this thread, but couldn't find any solid leads - hopefully I'm not leaning on you guys too much, just looking for a push in the right direction. Thanks for your help!
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
This might be a start:
http://www
RE: Supplier for off the shelf torque-to-yield (TTY) fasteners
DIN 65115 specifies MJ threads according to ISO 5855, so the thread size is MJ12x1.25. Manufacturers to consider include Alcoa Fastening Systems (UK, etc.), Johann Maier, and Ribe (Richard Bergner).
With regards to ARP, if you look at their catalog, most of the main bolts and cylinder head bolts are waisted shank designs intended for torque to yield. Under the cylinder head bolt section it even says "Most applications have undercut short bolts that can help eliminate head gasket failures through providing
more "stretch" to compensate for the additional compression of gaskets."
In my opinion, you have two options, depending upon the quantity of fasteners you need. If it is high volume automotive or similar, then you should talk to producers of high volume automotive engine fasteners that are familiar with torque-to-yield requirements. Acument and Kamax are two leaders in this area. If it anything else, then you probably should talk to suppliers of small quantities that will make what you want. Fastenal is one option here. Or perhaps contact a distributor of aerospace fasteners like Atlantic Fasteners (http://www.afaero.com/) that will have access to many manufacturers that produce reduced and waisted shank fasteners.