What type of “plastic” rod machines best?

[Martin WParticipant @martinw]

Chris

 

Just a quickie, have you heard how Mr Schro’s cat is doing ?? Also when our scientists get their Qbits stable there will be a real impact and, with apologies to Star Trek, one might hear the immortal words ‘Its computing Jim but not as we know it!!’

 

If you are into this then a browse of http://physicsworld.com/cws/home is worth a look.

 

Best regards

 

 

Martin W

[chris stephensParticipant @chrisstephens63393]

Hi Martin,

Last I heard one of them disappeared in a puff of sub atomic particles down the nearest black hole, or did it? Closely followed by Mr Spock shouting “illogical, Jim” as he went. You flatter me if you think I would understand Physicsworld, do they do a version for “dummies” or do I have to wait to watch it on “Horizon”

Now to show an equal bias, It could be that PTFE works better than Delrin in some situations due to two of its properties, namely very low friction and its soft consistency. If it deforms due water absorption or due to the release of internal stress after machining, it will simply squeeze itself to conform to confines and due to low friction it will slip whatever happens. You will, I hope, forgive the simplistic approach, I find more people can understand it. If I am guilty of turning “PTFE” into “Hoover” please forgive me, I am thinking of the relatively soft white engineering grade stuff, not the hard grey stuff found in a frying pan. I am sure some smart Alec will point out there are “Heinz” different varieties, but I only use three, tape, string and big lumps, you could make that four if you count cooking.

It is nice to know that our ammunition now fires straight , shame we cannot afford any. 

Just to go back to materials and their properties in earlier posts, and our perspectives of same. Think of a child’s balloon, to a child it is a big round object that holds air and can be played with for hours, to an adult it disappointingly goes flat after a few days and has to be blown up again to keep young Jimmy happy, but to a physicist it is as porous as a sieve.

It’s all down to Perspective. And with that in mind, I shall disappear into the vanishing point.

chriStephens

[chris stephensParticipant @chrisstephens63393]

Hi Martin,

Last I heard one of them disappeared in a puff of sub atomic particles down the nearest black hole, or did it? Closely followed by Mr Spock shouting “illogical, Jim” as he went. You flatter me if you think I would understand Physicsworld, do they do a version for “dummies” or do I have to wait to watch it on “Horizon”

Now to show an equal bias, It could be that PTFE works better than Delrin in some situations due to two of its properties, namely very low friction and its soft consistency. If it deforms due water absorption or due to the release of internal stress after machining, it will simply squeeze itself to conform to confines and due to low friction it will slip whatever happens. You will, I hope, forgive the simplistic approach, I find more people can understand it. If I am guilty of turning “PTFE” into “Hoover” please forgive me, I am thinking of the relatively soft white engineering grade stuff, not the hard grey stuff found in a frying pan. I am sure some smart Alec will point out there are “Heinz” different varieties, but I only use three, tape, string and big lumps, you could make that four if you count cooking.

It is nice to know that our ammunition now fires straight , shame we cannot afford any. 

Just to go back to materials and their properties in earlier posts, and our perspectives of same. Think of a child’s balloon, to a child it is a big round object that holds air and can be played with for hours, to an adult it disappointingly goes flat after a few days and has to be blown up again to keep young Jimmy happy, but to a physicist it is as porous as a sieve.

It’s all down to Perspective. And with that in mind, I shall disappear into the vanishing point.

chriStephens

[chris stephensParticipant @chrisstephens63393]

Hi Martin,

Last I heard one of them disappeared in a puff of sub atomic particles down the nearest black hole, or did it? Closely followed by Mr Spock shouting “illogical, Jim” as he went. You flatter me if you think I would understand Physicsworld, do they do a version for “dummies” or do I have to wait to watch it on “Horizon”

Now to show an equal bias, It could be that PTFE works better than Delrin in some situations due to two of its properties, namely very low friction and its soft consistency. If it deforms due water absorption or due to the release of internal stress after machining, it will simply squeeze itself to conform to confines and due to low friction it will slip whatever happens. You will, I hope, forgive the simplistic approach, I find more people can understand it. If I am guilty of turning “PTFE” into “Hoover” please forgive me, I am thinking of the relatively soft white engineering grade stuff, not the hard grey stuff found in a frying pan. I am sure some smart Alec will point out there are “Heinz” different varieties, but I only use three, tape, string and big lumps, you could make that four if you count cooking.

It is nice to know that our ammunition now fires straight , shame we cannot afford any. 

Just to go back to materials and their properties in earlier posts, and our perspectives of same. Think of a child’s balloon, to a child it is a big round object that holds air and can be played with for hours, to an adult it disappointingly goes flat after a few days and has to be blown up again to keep young Jimmy happy, but to a physicist it is as porous as a sieve.

It’s all down to your Perspective. And with that in mind, I shall disappear into the vanishing point.

chriStephens

[V8EngParticipant @v8eng]

 

There is a chapter on plastics in the book ‘Workshop Materials’ by Alex Weiss.

 

 

[Gordon WParticipant @gordonw]

If we want to use any matl. of unknown provenance it can be tested first. weigh, and measure the sample, put it in water,oil, brake fluid, or whatever, leave for some time, then remeasure. I know this is not to industry standards but we are not industry. This is especially useful for plastics, esp. “O” rings.

[Ian S CParticipant @iansc]

Had one wee problem with carbon impregnated PTFE.Its a bearing through the piston of one of my hot air engines.I had the engine stripped down to replace a worn out crankshaft,and the PTFE bush sat for a month or so without anything in it,when I went to put things back together I found thatthe shaft would not fit through the bush.In its working life it had got oil on it and it swelled,after reaming it out everything was/and still is OK 15yrs later.Ian S C

[Chris TriceParticipant @christrice43267]

For what it’s worth, I’ve never had a problem with Acetal. I use the glass filled version where I can. I work in the film industry building animatronic and mechanical rigs and have used these materials a lot. Nylon on the other hand is another matter. I generally avoid it. BTW, the correct term for the less wise armchair experts is ‘hygroscopic’ with a ‘g’. I know it’s counter-intuitive given that we’re discussing water being absorbed but it’s NOT ‘hydroscopic’. Occasionally we have rigs that need to be submersed in water for long periods and nylon is generally avoided.

[KWILParticipant @kwil]

To add another bit of useless information for Martin W, when we had finished pumping to a low vacuum, we switched on an ion pump and buried the gases again, to achieve an even lower vacuum.

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