# Self tapping screws



## wildleg (Apr 12, 2009)

for what ? straps ? no bonding ? yes somewhere in 250


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## hardworkingstiff (Jan 22, 2007)

bgardner15 said:


> Is it a code violation to use self tapping screws in a large transformer and if so where can it be found in the code book, thanks


Where are you using them?


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## JohnR (Apr 12, 2010)

As was posted on another thread some time ago, WHICH type of self tappers are you using? There are some which may work, Most that won't.


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## Aegis (Mar 18, 2011)

For one of the phased lugs? Or for the cover? What are you doing?


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## bgardner15 (Aug 30, 2010)

Aegis said:


> For one of the phased lugs? Or for the cover? What are you doing?


 they where used to close the bottom when the transformer was put on top of 3" pipe. the connectors push the bottm up and it looked bowed so this person used the screws to close the boe and then grinded the ends off underneath the transformer so it looked like it was never done. I know they might be able to be used just wanted to know for sure before I get him for doing the wrong thing.


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## sbrn33 (Mar 15, 2007)

He is fine if it ti for something structural. Not fine if for anything electrical.Sounds like he did a quality job to me. Most people wouldn't have them ground off


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## Electron_Sam78 (Feb 26, 2010)

I believe the NEC disallows self tapping screws for bonding or grounding. I am under the impression that those are the kind with a very course thread such as threads for sheet metal or wood. A self tapping screw with fine machine threads would be acceptable IMO


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## Mshea (Jan 17, 2011)

Screws used for bonding must have 2 full threads engaged so course screws are out for sheet metal and even fine threads may require the sheet metal is flared and not drilled out.
Most covers are required to be bonded so a cover screw must engage 2 full threads too.


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