Spark plug threads

[jakesmodela]

I need to clean up the spark plug threads and I found a tap that is 7/8-18 NS.... Which i believe stands for national special. Is that the correct thread type? Thanks for your help in advance!

[hardtimes]

Originally Posted by jakesmodela

I need to clean up the spark plug threads and I found a tap that is 7/8-18 NS.... Which i believe stands for national special. Is that the correct thread type? Thanks for your help in advance!

Hey Jake,
I've heard/own/used NF and NC, but not NS You are correct in doing your research where fords threads are concerned ! I'm aware of correct tools necessary to 'chase' threads, however , just any tool sold and claiming to do such job correctly..is not true..in most cases. If you 'chase'/ incorrectly 'clean up' plug threads and / or block threads..you've caused more head aches than you've cured.

[James Rogers]

Originally Posted by jakesmodela

I need to clean up the spark plug threads and I found a tap that is 7/8-18 NS.... Which i believe stands for national special. Is that the correct thread type? Thanks for your help in advance!

I just went down and checked mine and yours is correct. I believe NS stands for National Standard.

[rocket1]

you don't want to use that tap,you need a thread chaser,it's a different animal,try Summit Racing.

[C26Pinelake]

are you attempting to use a spark plug that was not meant for a Model A ?how could the threads get damaged enough to have to recut or chase ? At 3 or 4 bucks a plug I would be chucking those plugs and buying new ones.
Wayne

[machine girl]

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do not use the tap the dreamer says, rocket 1 is right. a machinerys handbook#24 can help.

[BILL WILLIAMSON]

An old plug, with 3 or 4 grooves ground in it, makes a good thread "chaser"!----Bill W.

[Bill in SoCal]

Originally Posted by BILL WILLIAMSON

. . .with 3 or 4 grooves ground in it, makes a good thread "chaser"!----Bill W.

Good for Bill. Ground or filed - that's a good way to make any thread chaser. Bill

[Tom Wesenberg]

Originally Posted by BILL WILLIAMSON

An old plug, with 3 or 4 grooves ground in it, makes a good thread "chaser"!----Bill W.

I use my Dremel with a thin cutoff wheel to slice 4 grooves into old bolts and spark plugs. This makes good thread cleaners/chasers.