What is the purpose of the spring washer in the joint? We need to know that to understand what potential alternative solutions will work. Conical spring elements tend to have sharp outer edges that will cut into the board and traces and the wave washers have extremely low spring rates, helical...
In a case like this there are too many unknowns to be able to use calculations to really get close to an accurate answer. I would highly recommend testing to failure and then taking a % of that as your seating torque. If we try to estimate the effects of the head embedment on the aluminum...
Unless you really need the exact MIL spec coating I would try to not use that as a call out because it cuts out a lot of firms that do commercial quality black oxide but don't meet the requirements of the MIL spec. For our black oxide parts we simply call out black oxide with the appropriate...
You use the special Helicoil tap for this application prior to installing the insert. Helicoil makes oversized gages ($$$) to work with their taps if you need to gage the tapped hole prior to installing the insert. The whole system is designed to work together to give you a 3B thread after...
Wil,
I tend to agree with you about the torque test, but if you have nothing else to go by in a "commercial" quality joint, it at least get's you into the ballpark , but it doesn't tell you one bit about the achieved clamp load. In this case, I would almost take a bunch of solid rivets, a torch...
One of the issues related to ring gear applications that I have dealt with at the OEMs is lateral movement when the preload in the joint is inadequate to freeze the the ring against the carrier. This is a single shear joint that also sees a significant reversing load in service. The rivets work...
Freeze the bloody shaft with liquid nitrogen and heat the coupling at the same time. This is maintenance 101!
Get a new worker, this guy doesn't know what he is doing.
If you have no other way to determine a torque setting, take at least 10 bolts and torque them in a virgin joint with all the components that will be used until something fails in the joint (whatever that may be) and then set your seating torque at 60% of the average of the failure torque.
This...
There was an early comment about ink jet technology and I think that you should spend some time looking at that. They have very precise volumetric and directional control of extremely small volumes of material. The technology is well understood and I bet you could adopt it to your application...
Cap screws are intended to be torqued from the head side (hence the washer face) and bolts are intended to be torques from the nut side (hence the washer face on the nuts). There may be slight differences between the two, but the confidence bands will likely overlap almost completely. Other...
The railroad industry requires that bolt threads are "chisel checked or tack welded" after torquing. This is actually an AAR regulation to prevent loss of the the nut on threaded connections. Of course the chisel checking doesn't prevent initial loss of clamp load, but it makes the powers that...
I agree with Wil, the Bollhoff rivets have not been used in any air structures that I am aware of. You might want to check out some of the SAE papers that have been written about them for automotive use, there may some useful info in them.
Get a copy of Bickford's book and read it well. This is a very deep subject and there a many subtle things that can cause all sorts of unexpected results.
Is there any sort of chemical environment that may be touching the heads of these fasteners? P.C. 12.9 fasteners are very susceptible to environmental stress corrosion failures that will exhibit themselves as delayed fractures under load. The other likely root cause if there is cyclic loading...
The only users that that I have seen try to use this spec are certain U.S. government entities and they have had what appears to be limited success. My experience from the supply side is that there is not any acceptance of this as a numbering system to use for standard hardware by end users.
The film thickness under the head in the contact area is going to be negligible due to the contact pressure. I don't think that it would have any measurable effect on clamp retention. In the commercial world, there are millions of bolts installed and turned without the use of a washer- it is...
Don't count on thread lockers to be a lubricant. We have tested some that reduced the nut factor and other brands increased the friction. I would not recommend doing it for either lubrication or locking- just increasing variability.
PTFE is not a good compression material for sealing- too much creep. I would go back and try to rework the sealing surface like Moose suggested. Just plunge an end mill onto it and your good to go. Otherwise, get some new copper or aluminum washers and try those. Don't reuse, they work...
