Threading directly into 6061-T6
Threading directly into 6061-T6
(OP)
Rules about threading into 6061-T6.
I've got a design application that due to it's closeness to the design size envelope limits, and the part's size, force threading directly into 6061-T6 for some #4-40 SHCS.
The other choice is using Helicoils, but their larger dia takes the threaded holes to within .030" of breakout on the edge of the part.
What is the lesser of 2 evils? Using Helicoils close to the edge of the part, or using no insert and not exceeding a calculated max torque?
As a subquestion... How does "number of times cycled" change the decision? Will an aluminum thread "wear" much even if if the torque is calculated and kept under some predetermined, non-destructive limits? I've heard this before, but is there anyone that's ever tried to quentify cycles with or without a steel insert?
I've got a design application that due to it's closeness to the design size envelope limits, and the part's size, force threading directly into 6061-T6 for some #4-40 SHCS.
The other choice is using Helicoils, but their larger dia takes the threaded holes to within .030" of breakout on the edge of the part.
What is the lesser of 2 evils? Using Helicoils close to the edge of the part, or using no insert and not exceeding a calculated max torque?
As a subquestion... How does "number of times cycled" change the decision? Will an aluminum thread "wear" much even if if the torque is calculated and kept under some predetermined, non-destructive limits? I've heard this before, but is there anyone that's ever tried to quentify cycles with or without a steel insert?





RE: Threading directly into 6061-T6
I've done development work on small assemblies that had #2-56 stainless screws threaded a couple diameters into aluminum, and they survived at least dozens of cycles without trouble. The parts were clear anodized, which may have contributed a little to their durability.
Mike Halloran
Pembroke Pines, FL, USA
RE: Threading directly into 6061-T6
I've got an application that is being force in the direction of a helicoil insert but I'd rather not doe to size and cost on a producton basis...
RE: Threading directly into 6061-T6
RE: Threading directly into 6061-T6
Mike Halloran
Pembroke Pines, FL, USA
RE: Threading directly into 6061-T6
I have used hex socket capscrews into 2024-T4 for hydraulic motors for over 30 years of production with no problems.
Ted
RE: Threading directly into 6061-T6
Regards,
Cory
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RE: Threading directly into 6061-T6
I don't like seeing threads finer or smaller than roughly M6x1.0 (or 1/4-20 if you prefer) threaded into aluminum.
RE: Threading directly into 6061-T6
Install a stud once with Loctite.
RE: Threading directly into 6061-T6
RE: Threading directly into 6061-T6
A little vacuum grease on the threads helps reduce galling, and extends thread life.
RE: Threading directly into 6061-T6
Ted
RE: Threading directly into 6061-T6
Cheers
Greg Locock
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RE: Threading directly into 6061-T6
Can you tell me what form tap was used?
Thanks.
RE: Threading directly into 6061-T6
TTFN
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RE: Threading directly into 6061-T6
Ted
RE: Threading directly into 6061-T6
I have had a similar design problem to yours. In my case, I wanted the biggest possible threads into the edge of an aluminium 6061-T6 1/4" plate in an airborne system. The plate was chemical filmed, rather than anodized, so that we could control EMI/RFI. I anticipated that the structure would be assembled and then never taken apart.
I specified 8-32UNC without the helical inserts. I made the holes as deep as possible as per MikeHalloran's suggestion, above. We did use lubricating threadlocker (Loctite 242). The alternative design would be 6-32UNC with thread inserts. I think I picked the lesser of two evils.
Does your part absolutely have to be aluminium? If it is a tiny part, the weight may not be critical, and you will be able to use brass or bronze.