Thread Strength Of Molded Plastics

[dapeake]

Greetings,

I am seeking information on the strength of threads in various plastics.

The image below shows my part. It shows a threaded zone: 5/16-18, the length of which is .377". It needs to withstand repeated, non-shock (gradually applied) loads in excess of 100 lbs in both directions.

Note: I can lengthen the threaded zone, or switch materials, but without data on the properties of the materials, I am shooting in the dark.

Any help in nailing down the thread pull strength of various molded plastics would be greatly appreciated.

Thanks,

Dan

 

[MikeHalloran]

I try not to concern myself with tool design... beyond keeping the part geometry simple and the tolerances loose.
I.e., work with them, but let the molder and the moldmaker work out the fiddly bits.

You may expend many hours trying to adapt the part to how you imagine the mold will be made... and then a molder will come up with a completely different, better, way to do it.

Don't waste your time doing something that someone else can do better.



Mike Halloran
Pembroke Pines, FL, USA

 

[CoryPad]

The reason ultrasonic or thermal insertion can produce higher strength is prevention of porosity or other solidification defects at the insert interface.

 

[patprimmer]

I don't dispute what Cory says, but I have seen some very strong moulded in inserts when the insert is designed correctly.

One such example is the drive dog on the Titan winch handle for yachts. When tested to destruction by applying load to the hand grip and the dog engaged in a locked winch, the metal itself shears. Neither the interface nor the plastic fails.

Regards
Pat
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