Need Tap/Thread Information

[damnesia]

I need to build a drag link for my truck. I got a piece of DOM and Moog ends. Now I need to determine what taps I need. The threads are 7/8-18 ( one is RH and one is LH ). Taps of this size are pricey so I want to make sure I get the correct ones. I called Moog and they couldn't answer my question. The main question is, are 7/8"-18 NS ( I see NS SP also ) taps what I need? I also see 7/8"-18 without any letters and am not sure if they are just assumed to be NS. I believe NS means non-standard but find mixed information on the web about it. Anyone know about this stuff?

 

[damnesia]

Looks like NS = American National Special Thread. I'm guessing that's just to indicate they aren't NC or NF. SP seems to indicate they are for spark plugs. Seems like I'm just looking for "7/8-18 NS"

 

[woody 73]

I must be reading things wrong because I am very confused.

The following chart lists a 7/8-9 NC.
7/8-14 NF.
7/8-20

No mention of 18 maybe I am missing something?

http://www.shender4.com/thread_chart.htm

 

[damnesia]

7/8" - 18 TPI is only common for tie rod and drag link ends as far as I know. I think they are NS because they are not standard sizes. Some spark plugs are that size as well but I think they are their own animal because all of the 7/8-18 spark plugs taps I see are indicated with "NS SP"

 

[woody 73]

Try giving the following company a phone call I am 99% percent sure they can answer your question on the phone and they can ship it fast.

https://www.grainger.com/content/catalog_Metal_Home

 

[woody 73]

These people are super nice over the phone ask for someone from their tech dept.

https://www.mscdirect.com/products/thread-taps?rdrct=taps

 

[woody 73]

https://www.zoro.com/century-drill-...52oeKgIJ3xmw9OtTi5-TLRoC2drw_wcB&gclsrc=aw.ds

Good job I think MSC is the owner of Zoro but I could be wrong as things change so fast these days.

 

[damnesia]

I'll see what they say. I called another place and they told me to call the manufacturer of the tie rod ends ( Moog ). So I called Moog and they said "We just have it listed as just 7/8"-18".

 

[yhprum]

EBay has heaps of new taps in this size.

 

[damnesia]

EBay has heaps of new taps in this size.

The problem isn't finding taps in this size, the problem is trying to determine exactly what size I need. At this point, I believe I need 7/8"-18 NS ( without the SP ) and assume if they are just listed as 7/8"-18 they are actually 7/8"-18 NS.

 

[bob15]

The -18 is 18 threads per inch. That will not change, nor will 7/8". No matter how you look at it, 7/8 is 7/8. If what you what is 7/8-18, then you need a 7/8-18 tap (ignore the letters).

 

[454ragtop]

A 7/8"-18 tap whether for spark plugs or not should be fine, just don't want a tapered pipe tap, which you aren't likely to find anyway. The only problem you might run into with a spark plug tap is it might be too short, tie rod threads tend to be very deep.

 

[MaineGuide]

Good job I think MSC is the owner of Zoro but I could be wrong as things change so fast these days.

Grainger owns Zoro, FYI. Oddly enough, I usually find it on Grainger's site first, then have to look for it on Zoro.

 

[454ragtop]

here's a source for a RHT one http://www.victornet.com//subdepartments/Special-Pitch-Taps-9-16-to-1-1-8/1270.html Unfortunately they don't offer a LHT tap that size.

 

[damnesia]

Thanks everyone. I ordered LH and RH taps. I was used to seeing NC and NF, but haven't noticed the NS or SP before. Since I now own about 90$ worth of two taps, I wanted to make sure I understood what I needed.

 

[woody 73]

Grainger owns Zoro, FYI. Oddly enough, I usually find it on Grainger's site first, then have to look for it on Zoro.

Good job darn I can never keep up anymore with who owns what they move at the speed of light.

 

[woody 73]

here's a source for a RHT one http://www.victornet.com//subdepartments/Special-Pitch-Taps-9-16-to-1-1-8/1270.html Unfortunately they don't offer a LHT tap that size.

Wow I am blown away at all the different sizes for just the 7/8.

 

[woody 73]

OP out of curiosity in the end who did you buy the taps from?

 

[b-dog]

Too bad you're not in Denver. I had to buy those taps for the TREs on my truck and I've used them once...

 

[bob15]

Grainger owns Zoro, FYI. Oddly enough, I usually find it on Grainger's site first, then have to look for it on Zoro.

What I find easiest is: open 2 tabs, one Zoro and one Grainger and once the item is found on Grainger's site, right click and copy the manufacturer model/part number and paste it into the Zoro search box. The item will come up first....no more searching the PIA search function on the Zoro site.

 

[damnesia]

I was going to try to cut the threads on my lathe, but don't trust my internal thread cutting skills enough to keep ruining DOM tubing until I got it right. My second choice was borrowing them from a friend, but no one I know had them ( now I am the one people will borrow them from now that they'll know I have them ). A new drag link was the 3rd option but I couldn't find one that would fit my custom setup on my truck. In the end I'm glad I pulled the trigger. Now I can make new drag links and tie rods to replace the super wimpy ones that come on Scout 800s.

 

[APEowner]

The -18 is 18 threads per inch. That will not change, nor will 7/8". No matter how you look at it, 7/8 is 7/8. If what you what is 7/8-18, then you need a 7/8-18 tap (ignore the letters).

There's a heck of a lot more to a thread specification than the nominal diameter and the thread pitch. Tolerance, fit and profile are all important as well. Those properties are all defined in whatever the applicable standard is for the industry and application. Fortunately, in the OP's case the applicable standard would be the SAE Standard Screw Thread which in the size he's concerned with is the same as the American Standard for Unified Screw Threads which is probably what the taps he bought are since that's more or less the default for taps in the US.

 

[larry_g]

I'm curious, What size hole is required for tapping a 7/8-18 thread?

lg
no neat sig line

 

[Cahark]

It should be .821 for 75% engagement.

53/64 is the closest match at .828


Sent from my iPhone using Tapatalk

 

[bob15]

i'm curious, what size hole is required for tapping a 7/8-18 thread?

Lg
no neat sig line

53/64"

 

[bob15]

There's a heck of a lot more to a thread specification than the nominal diameter and the thread pitch. Tolerance, fit and profile are all important as well. Those properties are all defined in whatever the applicable standard is for the industry and application. Fortunately, in the OP's case the applicable standard would be the SAE Standard Screw Thread which in the size he's concerned with is the same as the American Standard for Unified Screw Threads which is probably what the taps he bought are since that's more or less the default for taps in the US.

But that is not what the OP was asking.......

He was asking if the 7/8-18 was the same as a 7/8-18NS....which it is. Not every manufacturer or seller puts the "NS" after the size.....unfortunately.