I searched and came up with nothing. Does anyone happen to know the thread size for our O2 sensors? Front one, if it matters.

 

i duno exactly but it is similar to the thread on the spark plugs if that helps, its quite large

 

Thanks. Still hoping to get an exact number. Doubt I'll get it, though, it's not something most people would ever need to know.

 

so why do u need to know ?

 

On the 95 the fronts are 18mm and the post-cat is 12mm. I think.

 

18mm and 12mm still isn't a thread size. You could have 3 different thread sizes for each one of those diameters....

tatanko: can't you take one out and measure the threads to find out? Are you looking for a plug or something?

 

Yeah I suppose you're right. 12 and 18 are the socket sizes. My bad.

 

i think he's planning to drill o2 bungs

 

I need to know for the same reason ^

 

I need to take a die to a used O2 sensor I bought. The threads aren't in the best condition and I'd like to clean them up prior to installing the sensor to ensure it'll be nice and tight. How would I go about measuring it?

I'd take a picture of the threads, but none that I take seem to come out real well. The pictures make it look like it doesn't have any thread at all

 

isn't it just the distance in between threads? just count out ten threads (well eleven i guess) measure the distance that separates them then divide by ten

 

Upstream is M18x1.50 threads. Get a spark plug thread chaser.

 

...and finally the right person comes along. Thank you, sir. Thing is, though, all these "spark plug thread chasers" I seem to see are for rethreading a hole. My problem isn't the hole, it's the O2 sensor itself.

 

Good luck getting a die to do any amount of good on the O2 sensor threads, there's very little there. Die would bottom out before it really repaired a damn thing.

 

I was told it would at least help. Apparently the sensor will seal up ok as-is, I was just taking extra steps to ensure it.

 

Actually that's wrong. If you manage to get a die that is M18x1.5, it should re-thread the O2 sensor just fine. The problem is an M18x1.5 die is going to be extremely hard to find. It's not a common size.

For future reference, the M stands for "metric", the 18 stands for 18mm in diameter, which is measured from thread tip to thread tip on either side. The 1.5 means there is 1.5mm distance from thread tip to thread tip on the same side....this is also known as "thread pitch."

To measure a metric thread size, you can take a high precision steel ruler and measure how many thread there would be in one inch. For instance, if there are 38 threads within one inch, then you divide 38 by 25.4mm/inch, and this will give you a thread pitch of 1.5mm/thread.

My explanation was overkill, I know, but it comes in handy when you are trying to figure out what size things are. Thread pitch gauges are relatively cheap and can come in handy too!

 

Thank you. So you're saying I will likely need to order this die? What should I be looking for to make sure it's going to work for this specific application? What I mean is, what is going to work to fit over the tip of the O2 sensor, since the threads aren't at the very tip. Most dies I've seen are just big enough to fit over the threads and don't allow for things sticking up beyond the threads.

 

When i replaced my downstream o2 it would not catch on the thread, mind u i got it at dealership for like $120 canadian so it was the correct size and everything.

i used to work at a metal shop for 5 years (part time in the summer same place my dad works) i used to drill and tap holes for the longest time, as well as other work. I took my sensor back to the shop and ran a guide on it, im not sure what the correct terminology is in english (the factory is russian and all the parts names i learned were in russian) but u use it to make bolts with threads such as the one on the o2 that i was trying to replace.

The thread was redone and the sensor went in flush. i am puzzled by the crappy quality of the thread on the sensor tho, it seemed as if someone had tried to plug it in before they sold it to me but it was super clean (wires and head) so i duno why bosch made that thread so crappy

 

as long as everything before the threads is smaller in diameter than the smallest part of the thread itself, it should be fine. You just end up sliding the O2 sensor through the die until you get to the threads. Then re-tap the threads by spinning the die onto them. It's pretty self explanatory once see how everything goes together.

It's likely that you'd need an entire metric tap&die set. I don't think you can just buy one die by itself. You could always borrow one?

Cheapest I could find:

http://cgi.ebay.com/45-PCS-TUNGSTEN-...QQcmdZViewItem

 

Ugh, dont buy that crap, dont cheap out on machine tools. One tap from my set costs more that that whole thing. Order the die from here; http://www.mcmaster.com/ . Get the hex one, unless you have the special tool for holding round dies.

 

The ones from McMaster-Carr are over double in price what I paid for the O2 sensor to begin with Doesn't make sense to spend all that money on a single die for what will likely be a one-time use.

I'll look around. I found whole kits in a few stores around here but didn't pay attention to what sizes were in them since I didn't know what I was looking for.

 

Well thanks to the Op for tarting this thread, changed my O2's today and stripped the threads right out of each one, now i know what size tap to get tomorrow from work (machine shop), I'll take a look for you see if we got a die also (don't do a lot of die work).

PS: be nice if someone had a working link for the how to on changing O2's.

 

Then you're going broke my friend. I've had enough machine tool classes to know that you are going to end up breaking taps anyways. As for dies, they get dull after time.

$36 for one 18mm die, that's friggen rediculous.

 

I would be willing to pay shipping both ways to borrow it

 

No problem, on the way there now, another thing i can suggest is going to your local machine shop and asking them to re thread it with a die, the guy in the tool crib will usually do it for nothing (or a pack of smokes). Be back and let you know.

 

I don't believe we have anything locally

Thanks man!

 

Unfortunately i didn;t fare very well, not only did we not have an m18 1.5, but it's automotive use mainly so not even the 2 snap-on tap and die sets carried it. Went to 3 different local auto parts stores, and the largest they go is 12m 1.5

Sorry, on the good side of things i got my O2's in. Buy an extra 22mm 12 point boxend and cut a slit in it to get over the wires to put your new O2's in.

 

A handy tool to have is a thread file, ususlly available in SAE and Metric to cover all commot pitches. Its great in most every case where there is a damaged or flattened thread on a any external surface. Snap-On and most reputable tool supply palces will carry it. Cheers.

 

That sucks. Oh well, thanks for trying, I appreciate it. I'm not sure exactly what I'm going to use to put the O2 sensor on. The guy I bought it off of actually stripped the head of it a little as well, but said it came off just fine with a 7/8" wrench.
Hmm, interesting. Never heard of that. I'll look into it.

 

that's because 7/8 is incorrect, 22mm is the correct size. Oh yes a thread file... i forgot about them, yup their about 10 to 20 bucks, check for a local tool supply place.

 

Tatanko, for what it's worth, I just went out into my garage and tried to screw a NGK spark plug into my new OBX headers (which has 4 bungs) and the spark plug was WAY too small to thread in. I think the spark plugs are 14 mm, not 18mm.

 

I know 22mm is correct. I think he told me 7/8" because that was what fit correctly enough AFTER it was stripped to get it off.

As far as the files, what should I look for in reference to this specific application? Does it have to be a file for 1.5mm threads?
grey, this is all about O2 sensors I think you meant to say O2 sensors, though, and just said spark plugs because that's what you think of when you think NGK. Am I right?

 

I though someone just mentioned that the O2 sensor bungs threads were 18mm, the same as spark plugs - ?? - so I stuck a spark plug in an O2 hole, and it was too small. Way too small. Hence the Email. Reason - I was just in hardware stores earlier today, looking for bung plugs for these new OBX headers. Didn't find any.

"i duno exactly but it is similar to the thread on the spark plugs if that helps, its quite large"

I need sleep - never mind....
.

 

Ahh, I got you now. I need sleep too

 

Sorry to bring back my thread, but, I still need some things answered.

Can I re-use the gasket that's on the O2 sensor? I was told it was crush-type, and an integral part of the sensor itself, in a way.

Also, does a thread file have to be specific to this size thread or can it be a universal one?

 

A universal one is just taht, each side has thread measurements on it, it's 4 sided with 2 ends on it so you should get 8 different threads. Get the metric one or you'll have problems, or make a die the cheap way --- forgot about this, go to your local hardware store and find a 18mm 1.5 thread pitch nut, then cut 4 groves carefully the long way into the threads, boom instant cheap die.

Oh I ended up having to pick up a tap for mine, snap-on has this O2 sensor tap with sparkplug on the other side, was only $7.00

 

Not a bad idea!

 

As for a thread file, would this work?

http://cgi.ebay.com/Thread-Restore-F...QQcmdZViewItem

 

perfect, but it only works the long way not sideways, and make sure to match it up. It's really only good if you got a few nicks on the threads, if it's worn though or major bent, you'll need a die.

 

I may try the homemade die idea, then.