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1/8" Zerk Fitting Tab

1/8" Zerk Fitting Tab

1/8" Zerk Fitting Tab

I have some threaded 1/8" zerk fitting that I want to use, thread is 1/8-27 npt. A 1/8-27 npt tap is larger than my zerk, so it needs to be smaller. I checked my 25th edition of Machinery's Handbook but didn't find an answer. I did seen a tap on the Grainger site (https://www.grainger.com/product/IRWIN-HANSON-Tap-...) that looks like it be correct, but I haven't called them yet. Anyone know of a tap, or if this one is what I'm looking for? And what drill would be appropriate?


RE: 1/8" Zerk Fitting Tab

Where on your tap is larger? What about at the first full thread?
I recall fittings that require you to just barely tap the thread.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

RE: 1/8" Zerk Fitting Tab

A 1/8-27 npt tap is probably close to twice the diameter of this zerk fitting. The fitting is a standard one with threads that came in a pack I got from an auto parts shop a few years ago. The od of the threads is ~0.140".

RE: 1/8" Zerk Fitting Tab

In that case your fitting is not 1/8".
Perhaps it is 1/16" NPT?

je suis charlie

RE: 1/8" Zerk Fitting Tab

I think 1/16th NPT is larger than 0.140.

What size is the hexagon on the body of the fitting?

RE: 1/8" Zerk Fitting Tab

Maybe zerk fitting just have a history and story of their own!

The hex is ~0.315", thread od is ~0.238 (not the 0.140 above), the thread length is ~0.185". The package came with several shapes to the zerk (straight, angled, right a.) and 2 thread sizes. They are listed as 1/8-27 or 1/4-28, some straight thread some npt. I was surprised I couldn't find much in MA, specifically as to the tap(s) needed. Some also come as push-in, but not in my pack.

Funny how a sideline to a project can be so challenging. I do see online a 4-way tool to extract, chase threads, etc., but at a couple of bucks I don't think it will thread in steel.

RE: 1/8" Zerk Fitting Tab

"They are listed as 1/8-27 or 1/4-28, some straight thread some npt."

If you measure the male thread o.d. at .238, you have something close to a 1/16 NPT it sounds like. What is the thread pitch? What are you using the zerk for, i.e. a pressurized space or just to squirt grease into a bearing pocket?

RE: 1/8" Zerk Fitting Tab

The zerk was to squirt grease into a mower spindle. Not a critical project, just something I thought of doing (since I'm sort of confined to the house). I do see 1/16 NPT taps, I guess I'll just order one.

RE: 1/8" Zerk Fitting Tab

Stick a pair of calipers on the threads and measure to see if they are 27 tpi before you spend money. Or take the fitting down to a hardware store and compare to fittings on the shelf.

RE: 1/8" Zerk Fitting Tab

NPT is National Pipe Thread as compared to SAE or Metric threads. Needless to say they are different so the hole must fit the fitting. Or the reverse:)

RE: 1/8" Zerk Fitting Tab

I had checked the threads against my thread gage earlier, and it confirmed 27tpi. I remember also checking the 1/4-28 and it was 28tpi.

So thanks for the help, it's time to pick up a tap. Looks like I'll have plenty of time to play since Virginia has a 6/10 date for lifting the stay-at-home policy.

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