graphite bushes/bearings ?

[Anthony KnightsParticipant @anthonyknights16741]

I have obtained drawings for a low temperature stirling engine, which specifies graphite to be use for certain bushes and bearings. Would carbon motor brushes be a likely source of material or is there a plastic which could be used as an alternative ? If none of the above, where could I obtain suitable pieces of graphite?

[Anthony KnightsParticipant @anthonyknights16741]

[Russell EberhardtParticipant @russelleberhardt48058]

Be careful if using motor brushes. Many of them incorporate copper powder to improve the conductivity.

You could try **LINK** for or http://www.olmec.co.uk/graphite_blocks.htm graphite rod.

Russell.

Edited By Russell Eberhardt on 21/02/2016 12:02:19

[egaParticipant @ega]

Anthony Knights:

You could consider Nylatron, graphite impregnated nylon available from eg Direct Plastics.

[JasonBModerator @jasonb]

Noggin End sell graphite in small amounts

[Roderick JenkinsParticipant @roderickjenkins93242]

Noggin End stock graphite **LINK**

Rod

[Chris Evans 6Participant @chrisevans6]

Check out the EDM (spark erosion) suppliers for graphite. Where are you based ? a few suppliers here in the Midlands.

[Ex contributorParticipant @mgnbuk]

Does it specify a grade of graphite on the drawing ?

If you post the block dimensions required & any grade info I'll see if I can find a suitable offcut at work (graphite machining specialists – many tonnes of various different grades on site !).

Nigel B.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nigel B on 21/02/2016 16:57:17:

(graphite machining specialists – many tonnes of various different grades on site !).

.

Nigel,

You could end-up as everyone's best friend !!

Seriously: It might be worth striking a deal with your employer.

MichaelG.

[AjohnwParticipant @ajohnw51620]

Looking at a commercial LTD it seems to use a grade that will more or less take a polish. I'd guess that means very dense and very fine grained but there is little information about.

It would be logical for Noggin End to stock the correct on but he mentions other uses for it.

It's about on ebay in rod form as well but no info on grade.

John

–

[jason udallParticipant @jasonudall57142]

If stuck ( or don’t have any better source).

Artists pure graphite pencils..
Ihave used these with some success.

You can even buy them in various grades.
My fav for this purpose are the hex section ones about 13 mm acros flats..these are “pure” graphite so no grade number

[Anthony KnightsParticipant @anthonyknights16741]

Thank you gentlemen. As usual, prompt and useful advice. No grade specified, but there are 3 parts to make which would probably only need 25mm of 10mm rod, which was why I asked about motor brushes. Noggin End looks good so I'll be giving them a try.

Edited By Anthony Knights on 21/02/2016 17:53:01

[Ex contributorParticipant @mgnbuk]

Seriously: It might be worth striking a deal with your employer

I would clear anything with the boss first – not worth risking the job for a bit of graphite !

In the past he has been amenable to requests for small bits / offcuts, but larger amounts of more expensive grades would most likely be chargeable. In the past also it has not been worthwhile commercially to raise invoices etc. for very small orders, but he has recently installed a credit card machine specifically to cater for small online orders of "standard" machined graphite parts like studs, nuts & bolts, so supply of smaller quanties of "raw material" should also be possible now.

As above, let me have a bit more info & I'll see what I can do.

Nigel B.

[martin perman 1Participant @martinperman1]

I managed to pick up graphite rod from large Arc Lights at a car boot sale a while back.

Martin P

[Chris Evans 6Participant @chrisevans6]

When I was running EDM machines here in the Midlands I bought off two companies. Erodex and Graphite Technologies. There are other suppliers but these where local to work.

[MWParticipant @mw27036]

Posted by ega on 21/02/2016 12:09:08:

Anthony Knights:

You could consider Nylatron, graphite impregnated nylon available from eg Direct Plastics.

I would also vouch for this, very durable

Michael W

[HopperParticipant @hopper]

http://www.graphitestore.com will have everything you need.

Also, graphite rods sold on eBay for use by jewellers stirring pots of melted gold or silver etc.

[Ian S CParticipant @iansc]

I have some graphite impregnated PTFE/ Teflon, I use it for the bushes on displacer rods in hot air engines.

One design of LTD that I'v seen uses pointed ends on the crankshaft bearing on blocks of graphite, I think the suggestion was to use motor brushes for this motor.

Are you going to use a diaphragm, or a piston, if the latter a bit of graphite for the piston would be good, and a glass cylinder, best cylinder a glass medical syringe.

Ian S C

[CirclipParticipant @circlip]

"Be careful if using motor brushes. Many of them incorporate copper powder to improve the conductivity."

So how will this affect operation in this application?

Regards Ian.

[MWParticipant @mw27036]

Posted by Circlip on 22/02/2016 09:29:08:

"Be careful if using motor brushes. Many of them incorporate copper powder to improve the conductivity."

So how will this affect operation in this application?

Regards Ian.

Well, if i might hazard a guess, best case scenario it's for a push fit bushing which sits as dead as a door nail, not harming or upsetting anything or anyone else around it. Now worst case scenario it's for a moving part like a piston that might, on the worst of all the worst days becomes a conduit for electric shock?

Other than that, it might just be a handy to know piece of info, i ne'er knew that before now, i thought a carbon brush meant exactly that.

Michael W

Edited By Michael Walters on 22/02/2016 10:08:53

[roy entwistleParticipant @royentwistle24699]

Michael W Seeing that both carbon and copper are conductors How would a moving part make any difference How would there be any chance of electric shock ?

[Danny M2ZParticipant @dannym2z]

Posted by roy entwistle on 22/02/2016 10:40:04:

Michael W Seeing that both carbon and copper are conductors How would a moving part make any difference How would there be any chance of electric shock ?

Lol, second that.

* Danny M *

Edited By Danny M2Z on 22/02/2016 10:54:37

[CirclipParticipant @circlip]

And don't forget, most Nylons are hygroscopic so clearance can be affected. Don't apply to Carbon Carbon/Copper.

Regards Ian.

[MWParticipant @mw27036]

you can mock me if you like but i know we live in a world of possibilities, no matter how unlikely it might seem. I believe coarse humour is detrimental not only to the recipient but to the mocker themselves.

Michael W

[Joe PageParticipant @joepage27051]

I bought some graphite rod from these;

**LINK**

Seems to be good quality and machines nicely, I have about 6" of it left, if your in the Sheffield area you can have half of it for free.

Otherwise I used to machine carbon or graphite impregnated PTFE, should be quite easy to get hold of. Seal manufacturers may give you some, or fluorocarbon uk make it, or GAPI uk will stock it. It's not hydroscopic, very easy to get a good finish and has little thermal expansion.

As Circlip says, do not use any nylon it will expand when the moisture hits it, normally about 1-2%.

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