Author Topic: Plugging holes in gunmetal  (Read 1097 times)

Offline AOG

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Plugging holes in gunmetal
« on: February 15, 2017, 03:22:18 AM »
I have a problem and I need some help. I just messed up the hole placement on a gunmetal casting. I need to plug the holes and redrill. The question is what do I plug them with? Being in the states gunmetal isn't readily available. What would be an acceptable substitute?

Tony


Offline crueby

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Re: Plugging holes in gunmetal
« Reply #1 on: February 15, 2017, 03:29:54 AM »
Will the redrilled holes overlap the misplaced holes?

Offline AOG

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Re: Plugging holes in gunmetal
« Reply #2 on: February 15, 2017, 03:35:14 AM »
Unfortunately yes

Tony

Offline crueby

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Re: Plugging holes in gunmetal
« Reply #3 on: February 15, 2017, 03:56:39 AM »
Then you need something that is close to the machining properties of the gunmetal or the drill may pull to the side.
I think that bearing bronze, C932, would be close and is readily available. I've never tried that combination, so will defer to others with more castings experience.
One other possibility, is there another chunk or sprue of a casting that you could turn down into a plug?

Offline Zephyrin

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Re: Plugging holes in gunmetal
« Reply #4 on: February 15, 2017, 07:16:35 AM »
Quote
One other possibility, is there another chunk or sprue of a casting that you could turn down into a plug?

this is the best,  I would bet that foundries making castings for modelengineers are melting gun-metal scrap (mainly large plumbing and steam fittings) rather than certified ingot.

Bronze ; Gunmetal ; Brass.
Cu,Sn  ; Cu,Sn,Zn  ; Cu,Zn

Offline Jasonb

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Re: Plugging holes in gunmetal
« Reply #5 on: February 15, 2017, 07:55:18 AM »
The other alternative is to set up on the mill with the correct hole position under the spindle and use a 2-flute cutter to plunge cut a larger hole and then you can put a piece of brass or bronze into the hole and drill that without risk of the hole wandering due to different hardnesses of metal overlapping.

If you drilland tap the insert on the lathe then it can just be put straight into the hole.

GM is quite a bit softer than the bronzes that we have here so ther can be a tendancy for a drill to wander if cutting in two different materials.

Offline AOG

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Re: Plugging holes in gunmetal
« Reply #6 on: February 15, 2017, 02:00:04 PM »
Thanks for all the help. I have a cylinder head casting with a chucking lug yet to be made. I think I'll work on that next and try to reuse the lug for a plug.

Tony