1/8" Zerk Fitting Tab

Question

1/8" Zerk Fitting Tab

aduetto (Mechanical)

(OP)

21 Apr 20 20:23

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?

Thanks!

EdStainless (Materials) · Answer 1 · 2020-04-21 22:46:40

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.

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P.E. Metallurgy

aduetto (Mechanical) · Answer 2 · 2020-04-22 00:41:09

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".

gruntguru (Mechanical) · Answer 3 · 2020-04-22 01:21:29

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

je suis charlie

3DDave (Aerospace) · Answer 4 · 2020-04-22 01:52:11

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

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

aduetto (Mechanical) · Answer 5 · 2020-04-22 13:38:27

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.

btrueblood (Mechanical) · Answer 6 · 2020-04-22 16:09:58

"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?

aduetto (Mechanical) · Answer 7 · 2020-04-22 18:40:41

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.

btrueblood (Mechanical) · Answer 8 · 2020-04-22 18:53:54

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.

Pancholin (Automotive) · Answer 9 · 2020-04-22 22:12:25

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:)

aduetto (Mechanical) · Answer 10 · 2020-04-23 15:20:09

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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1/8" Zerk Fitting Tab