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Author Topic: Bonding/fitting ptfe bearings  (Read 816 times)

KevinM

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Bonding/fitting ptfe bearings
« on: February 26, 2017, 07:57:00 PM »

Im wanting to make a propshaft with ptfe bearings for a long endurance voyage.


Anyway to bond them into a brass tube or maybe its best to press fit them and drill after fitting?


any thoughts guys?
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derekwarner

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Re: Bonding/fitting ptfe bearings
« Reply #1 on: February 26, 2017, 09:50:25 PM »

Kevin.......experience has shown that raw PTFE when drilled in small diameters will always drill oversize

MOs or Glass filled material is harder and the wandering of the drill is less pronounced

Reaming PTFE is near impossible as the reamer blades glide through the material, compressing and not cutting

PTFE grades also have a water adsorption of 0.015 ~~ 0.03% which will swell the material & tend to tighten it on the propeller shaft

I would not use any synesthetic material for a model propeller shaft gland bush, opting for [if space permits] a pair of Sintalite brass bushes pressed into a K&S precision brass tube, with a grease lubrication space between the bushes

The Sintalite bushes also have precision bores....... +0.0005" in sizes to 1/4" bore, the end of the bushes can be soft soldered to the K&S tube.......then reamed in one pass if necessary........if the soldering process has depleted the impregnated oil, the assembly on completion be baked in an oil bath @ 80 degrees C to re-impregnate the oil to the porous bush material 

Derek
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Derek Warner

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Illawarra Live Steamers Co-op
Australia
www.ils.org.au

KevinM

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Re: Bonding/fitting ptfe bearings
« Reply #2 on: February 26, 2017, 10:03:50 PM »

many thanks, guess I still have a lot of homework to do. The water absorbtion and swelling is certainly an issue as im looking at months in the water. I will investigate these bushs you mention thanks
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