Grease fittings.....

[Duff 206]

Quick question for the wrenches here, please.....

I want to put grease fittings in some pedals I will be using on my mystery build. They're probably from a mid-80's 300 or 400 series 8 speed, but these didn't have the factory grease fittings. What size drill and tap do I need? I think (?) grease fittings are normally 1/4-28 thread, but what would the correct hole size be before tapping?

Thanks very much as always!

Duff :handgestures-thumbupright:

[Martin 2,130]

i normally drill the hole just big enough to start the tap. as long as the tap will go in the hole just enough that the starting threads do the initial cutting you should be fine. if you have a drill index for your drills, that makes hole size decision easier. the hole shouldnt be any bigger than the minor diameter of the thread. see link below for sizes......

i found that 1/4-28 is ok but some zerks with so called 1/4 -28 threads were oversize and even though the thread is tapered, i still had a hard time starting the zerk in the threaded hole.

http://www.shender4....hread_chart.htm

[sorekiwi 761]

Tapping size for 1/4-28 should be a #3 (.213") if you have a number set of drills, or 7/32 (.219") if you dont.

[specialwheelhorse 174]

A 1/4 28 should have a number 3 (.213) Drill used

A 1/4 28 thread is not tapered

An 1/8 th inch pipe thread is, but a No.S drill will fill

the bill quit well, S is ( .348) Jim in Texas

[Martin 2,130]

Yes, you are right. 1/4-28 is not tapered, I was wrong. I was thinking of 1/8 npt and didn't go back after my post and proof read it. Thanks for pointing that out.

[specialwheelhorse 174]

No Big Deal !! I'm usually the one That's got my head on wrong.

Not as sharp as I used to be, Things I used to recall are no more.

Jim In Texas

[Duff 206]

Thanks very much, folks! As always, this place comes through no matter how big or small the issue!

Duff :thanks: