# Internal O ring groove ?



## robwilk (Nov 3, 2010)

I have two internal O ring grooves to put in a cylinder. The cylinder is 16.5 mm ID and the o'rings to be fitted are 20 x 2 mm i am just wondering how you go about machining these grooves and what sort of tooling do i need. I have been giving this a bit of thought for a couple of days and have had a few ideas but nothing i am confident with ???

Any comments are welcome 
Thank you 

Rob.......


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## MachineTom (Nov 3, 2010)

If I read you right, the bore is 16.5mm, the O-Rings are 20 x 2, if you were planning to put the rings on the end of the bore, they are to small with a 20mm OD ID would be 16, if you want to put them inside the bore they are to big.

Internal o-ring groove can be cut with various groove tools, square shape groove are used when there is a crush type fit, like two plate bolted together, a round profile groove is used then the ring is supported on 3 sides, and a slide or stationary rod is being sealed. I used micro 100 tooling always on ebay, of the usual suppliers MSC, Enco, others. There is a source of great info on orings from Parker-Hannifin, try parker.com.

To cut a internal groove with a boring mill you will need a Boring Facing head so you can advance the cutter while its turning. With a lathe just plunge advance the cutter. A 2mm groove could cause some chatter depending that you have for equitment. A narrower cutter can be used with multiple cuts, do NOT feed advance a groove cutter, each cut is a plunge cut.


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## Tin Falcon (Nov 3, 2010)

You need a full radius solid groove tool 
http://www.use-enco.com/CGI/INPDFF?PMPAGE=233&PMITEM=317-5589
the machinery handbook should give specs.
Tin


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## robwilk (Nov 4, 2010)

Thanks Tin and Tom. I will have a good look around for a radius tool. 

BTW Tom i am sorry if my explanation was not clear i do struggle to put meaning to words some times :
If you are wanting to have a look at the plans they are in the down load section under Stirling '60' drawn by J. Jonkman.
the part i am referring to is on page 7.
In fact here is a link.
http://www.homemodelenginemachinist.com/index.php?action=tpmod;dl=item270

Thank you.

Rob.....


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## Tin Falcon (Nov 4, 2010)

If you are skilled you can grind your own from a HSS bit they also make insert types but IIRC a bit pricey for the home shop.
Tin


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## robwilk (Nov 5, 2010)

Tin Falcon  said:
			
		

> If you are skilled you can grind your own from a HSS bit



I don't know if i am skilled enough to grind my own but i think i am going to have to give it a go because i am not finding many tools on the net that will fit my lathe or are in my price range. Also most i have found are abroad not in the UK which make it even more expensive.
Thanks for you time Tin .

Rob......


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