3/4 inch vs 19 mm

[MikeF2316]

I don't know why I remember this after all these years, but JC Whitney used to sell a 20.8mm spark plug socket for VW's. Obviously a 13/16" socket but I guess since everything else on the VW was metric they decided to label it this way.

How about this one? Nobody I've shown it to has ever seen one like it. I found it somewhere, and I don't even remember where.

Can you imagine? "Hey Joe, this 6.3 is a little tight, hand me the 6.4!"

 

[north]

That is cool. Any brand name or COO on it?

 

[wafrederick]

15/32=15mm,Tried this once with a 15mm sized nut in a 15/32 wrench.12mm=13/32

 

[djb2]

Reviving a year old thread that went off the tracks immediately.

The question was if the tool was exactly the same, not what the size equivalent was.

Nor if there were tools marked with dual sizes (fair common when metric was "new" in the U.S."

There is solid evidence that some tool makers do use exactly the same forge and broach for near-matching sizes. I think I recall a thread here where people had pictures of 19mm and 3/4" wrenches that clearly came from the same broach. The brand and size stamping is done as a separate step, just before the finish (e.g. plating or oxide), so it's easy enough for a tool maker to do.

 

[jmm]

I have an allen wrench that is marked 19 mm - 3/4". Fits just as well as another I have just marked plain 19 mm. Never tried to measure the two, though.

 

[MikeF2316]

That is cool. Any brand name or COO on it?

I never really looked at it closely before. It's obviously a "metric" socket for driving 1/4" bits. It's an Ultrapro. Yup, not exotic at all, from NAPA. I just found it in their catalog.

 

[MikeF2316]

15/32=15mm,Tried this once with a 15mm sized nut in a 15/32 wrench.12mm=13/32

Your conversions are a little off. Exact conversions:

15/32 = 11.90625 mm

13/32 = 10.31875 mm

15 mm = 18.8976378/32

12 mm = 15.11811024/32

 

[rlitman]

60 seconds in Excel gave me this:

edit: ****, I can't get a text table to look nice, ok, image it will be

 

[bubinga]

It depends on the manufacturer. Some make separate sizes, others don't. For sockets specifically impact version, I find that many manufacturers share blanks between sizes. Take Armstrong 15-16mm sockets for example. the 15 will have thicker walls while the 16 will be thinner because they share the same blank size. Just at a set from the top down and you'll see what I mean.

I wonder if Tekton's 19mm is really a 3/4" socket. My 19mm Tekton is sloppy on my 01's Grand Prix's lug nuts and they get stuck in the socket a little bit. I'm going to try a different socket next time l pull a wheel. If course it could be my lug nuts worn a little bit too.

 

[bubinga]

I have a snap on 3/4 impact socket that is also stamped with 19mm on the opposite side.

Wow! That's crazy

 

[bubinga]

That's older than dirt. Those were available for a little while. My set also has a dual marked 7/8"-22MM and a 15/16"-24MM I think. Sixties or early seventies era. Also, many 3/4" drive sockets were marked with both, as well as striking wrenches and the like.

For some reason, 19MM wrenches are always a little bit longer than 3/4"..........

Never ran across that
I see there are a few of those 19mm/3/4 in on eBay

 

[bubinga]

Converstion SAE to metric:
1/4 - 6.35 mm
5/16 - 7.94 mm
11/32 - 8.73 mm
3/8 - 9.52 mm
7/16 - 11.11 mm
1/2 - 12.7 mm
9/16 - 14.29 mm
5/8 - 15.88 mm
11/16 - 17.46 mm
3/4 - 19.05 mm
13/16 - 20.64 mm
7/8 - 22.23 mm
15/16 - 23.81 mm
1 - 25.4 mm

This conversation is made by myself. Here in Europe I didn"t use SAE wrenches yet. Looking on this my guess is that
5/16 - 7.94 mm can be used as 8 mm,
7/16 - 11.11 mm can be used as 11 mm,
5/8 - 15.88 mm can be used as 16 mm,
3/4 - 19.05 mm can be used as 19 mm,
15/16 - 23.81 mm can be used as 24 mm.

What are your experiences about that fit and do you have any other info to add?
most of the time, yes, but not always IME!

 

[bubinga]

When I lost my 19mm impact socket, I used my 3/4 for months, and it works perfectly, but I think 3/4 is just a tiny bit smaller, it feels tighter on the lug nuts.

3/4" is a tad bigger. 19mm = 0.748 so 3/4" is 2 thou over.

 

[dnschmidt]

5/16"- 8mm, 7/16" - 11mm and 3/4" - 19mm are so close that they are entirely interchangeable. For the rest I use whatever is called for. This was a particular pain in the *** on my 1998 Pontiac Grand Prix which was half metric and half SAE. You could never tell when they would slip an SAE bolt in there.

 

[NoahG]

I do the 7/32”-5.5mm and the 9/32”-7mm interchange quite often.

 

[bubinga]

It was sort of funny I worked at a foreign car garage circa late 80s, the owner was from Czechoslovakia I guess he was totally used to metric only.
Well we had another follow there from South Africa good mechanic nice fellow anyways,
We were sort of ripping on the boss a little bit one day because the follow from South Africa was imitating the boss when he had run into a mini hose clamp that usually takes a quarter inch.
So in a whiny voice the fellow from South Africa was saying 6.5 6.5 I need a 6.5 socket but there is no such thing..
Whiny voice off........
Rough loud voice on......
JAN IT'S A QUARTER INCH!
Too bad I didn't know about that 6.3 mm socket I could have got him that specialty socket

 

[johninct]

19/32" is about 15mm.

 

[VolvoRyan]

I have a snap on 3/4 impact socket that is also stamped with 19mm on the opposite side.

I was about to say that I have the same!

-Ryan

 

[beelsr]

I don't know if I posted this before, but maybe 10-15 years ago, I made up a chart of equivalences for SAE, metric and whitworth. i have a few of these printed out and laminated and then stuck with a magnet to the toolbox lids, at the workbench, etc...

I used a 1% difference as the cutoff for exchangeability. there are two versions, SAE-Metrique and SAE-Metrique-Whitworthless. Each is two pages so you don't have to squint to see the numbers if you're also afflicted with OME (ole man's eyes)...

 

[Dave455]

You guys are making it sound like bolts are always true to size.

If a 13mm bolt was EXACTLY 13mm, and you had a 13mm wrench that was EXACTLY 13mm, you would have one hell of a time mating the two.

Tolerances are sloppy for a reason.

There is no reason why a bolt head shouldn’t be exactly to size. The way most standards work, it’s assumed that the bolt head will be to size, and the wrench head is a bit oversize so it fits. This is “clearance” rather than ”tolerance”.

Taking ISO Metric as an example, a 13mm wrench must measure between 13.04 mm and 13.24 mm. I don’t have the bolt head limits to hand, but if 13.00 mm is the maximum bolt head size, there will always be at least .04 mm clearance.

The manufacturing tolerance is the .20 mm between 13.04 and 13.24.

Taking the 19 mm, the wrench must be between 19.06 and 19.36. The tolerance for the 3/4” is actually slightly tighter, and the wrench must be (in mm) between 19.18 and 19.38.

So, if a manufacturer can consistently make a wrench or socket between 19.18 and 19.36 it can legitimately be marked as 19mm or 3/4”!

All these manufacturing tolerances are defined around what’s feasible. Over the years, as manufacturing processes have improved, it’s feasible to make tools to tighter tolerances (i.e. towards the lower end of the permitted clearance) and I have no doubt that many manufacturers do this, but only Snap On and KoKen advertise the fact.

 

[no704]

But what size does discount tire use to destroy lug nuts?

 

[honcho]

I have a snap on 3/4 impact socket that is also stamped with 19mm on the opposite side.

I can't recall if my snap on marked both 3/4" and 19mm is an impact socket or not, but it is marked with both.

 

[Wrench97]

But what size does discount tire use to destroy lug nuts?

Worn out Snap On impacts.......................

 

[Kent_B]

I can't recall if my snap on marked both 3/4" and 19mm is an impact socket or not, but it is marked with both.

I have one in 1/2" drive deep impact like that. I always thought it was a fluke. Seems I'm not alone.

 

[bubinga]

There is no reason why a bolt head shouldn’t be exactly to size. The way most standards work, it’s assumed that the bolt head will be to size, and the wrench head is a bit oversize so it fits. This is “clearance” rather than ”tolerance”.

Taking ISO Metric as an example, a 13mm wrench must measure between 13.04 mm and 13.24 mm. I don’t have the bolt head limits to hand, but if 13.00 mm is the maximum bolt head size, there will always be at least .04 mm clearance.

The manufacturing tolerance is the .20 mm between 13.04 and 13.24.

Taking the 19 mm, the wrench must be between 19.06 and 19.36. The tolerance for the 3/4” is actually slightly tighter, and the wrench must be (in mm) between 19.18 and 19.38.

So, if a manufacturer can consistently make a wrench or socket between 19.18 and 19.36 it can legitimately be marked as 19mm or 3/4”!

All these manufacturing tolerances are defined around what’s feasible. Over the years, as manufacturing processes have improved, it’s feasible to make tools to tighter tolerances (i.e. towards the lower end of the permitted clearance) and I have no doubt that many manufacturers do this, but only Snap On and KoKen advertise the fact.

Not bashing Tekton, but l have a set of Tekton tools 1/2" drive deep impacts, not used enough to be worn, and on my 01 Grand Prix's lug nuts, the lug-nuts always stick a little in the Tekton's 19mm and I have to thread it a few threads back on the stud, and pry down on the stud/lug-nut with my Impact.
Just tried the new Sunex 19mm lug-nut socket I got, and buzzed a lug-nut off, and the lug-nut fell right out of the socket. Now the car is 20+ years old, so the lug-nuts could be a bit worn too.

 

[dchawk81]

A decent quality 1/2" wrench does not fit onto a decent quality M8 bolt.

I guess Mack doesn't use decent quality bolts and Snap on doesn't make decent quality wrenches then.

 

[dchawk81]

Not bashing Tekton, but l have a set of Tekton tools 1/2" drive deep impacts, not used enough to be worn, and on my 01 Grand Prix's lug nuts, the lug-nuts always stick a little in the Tekton's 19mm and I have to thread it a few threads back on the stud, and pry down on the stud/lug-nut with my Impact.
Just tried the new Sunex 19mm lug-nut socket I got, and buzzed a lug-nut off, and the lug-nut fell right out of the socket. Now the car is 20+ years old, so the lug-nuts could be a bit worn too.

I am bashing Tekton when I say I have two sets of their flare nut wrenches and every single piece ***** ***.

 

[bubinga]

I am bashing Tekton when I say I have two sets of their flare nut wrenches and every single piece ***** ***.

I'll have to try a few more of my 19 mm impacts on my lug nuts, and see what l get.

 

[dchawk81]

I'll have to try a few more of my 19 mm impacts on my lug nuts, and see what l get.

I have other Tekton stuff that isn't so bad but I was naive when I bought these flare nut wrenches. They were cheap, but they're so sloppy they're still not a bargain.

Always cringed when I had to use them.

 

[oldschoolcraft]

What is the acceptable tolerance of a wrench or socket? Is it 0.001” or 0.005” or 0.010”?

It’s not possible to make a socket that’s within 0.00000001” you’d be down at the atomic level. So there’s obviously some kind of tolerance that’s considered acceptable. And it must apply to both the wrench itself and the coating/finish.

So the wrench itself might be 0.002” plus or minus the desired size. And the satin or chrome polish adds a bit of thickness and might be off by another 0.001” I’d bet, plus or minus.

theres also an issue of standard deviation and acceptable tolerances. Maybe 90% are within 0.002” and 5% are within 0.003” and the rest are 0.004” to O.010 off and those 5% get scrapped.

Anyone in tool manufacturing know for sure? Curious what the acceptable tolerance range is.

 

[dchawk81]

What is the acceptable tolerance of a wrench or socket? Is it 0.001” or 0.005” or 0.010”?

It’s not possible to make a socket that’s within 0.00000001” you’d be down at the atomic level. So there’s obviously some kind of tolerance that’s considered acceptable. And it must apply to both the wrench itself and the coating/finish.

So the wrench itself might be 0.002” plus or minus the desired size. And the satin or chrome polish adds a bit of thickness and might be off by another 0.001” I’d bet, plus or minus.

theres also an issue of standard deviation and acceptable tolerances. Maybe 90% are within 0.002” and 5% are within 0.003” and the rest are 0.004” to O.010 off and those 5% get scrapped.

Anyone in tool manufacturing know for sure? Curious what the acceptable tolerance range is.

Google ANSI/ASME/ASTM standards for fasteners and their tools.

 

[bubinga]

I have other Tekton stuff that isn't so bad but I was naive when I bought these flare nut wrenches. They were cheap, but they're so sloppy they're still not a bargain.

Always cringed when I had to use them.

$nap On is about the best bet for line wrenches.

 

[dchawk81]

$nap On is about the best bet for line wrenches.

Yeah that's what I bought very recently.

It's not really fair to compare the two because the entire 6 wrench Tekton set new was less than a single used Snap-on, but when they fit so sloppy they aren't a bargain at any price.

IMHO Tekton needs to do better and charge more. $100 for the same set with usefully tight tolerances would be acceptable to me.

Out of curiosity I started playing around with the old fitting, and interestingly enough the 22mm fits the 7/8 fitting extremely nicely while the 7/8 is loosey goosey enough that it gets scarily close to the corners. The old fitting isn't rounded off in any way. I tried the same on a new one and it's the same deal.

 

[bubinga]

Yeah that's what I bought very recently. !!!!!

It's not really fair to compare the two because the entire 6 wrench Tekton set new was less than a single used Snap-on, but when they fit so sloppy they aren't a bargain at any price.
I hear that!!

IMHO Tekton needs to do better and charge more. $100 for the same set with usefully tight tolerances would be acceptable to me. Yeppers!!!!!

Out of curiosity I started playing around with the old fitting, and interestingly enough the 22mm fits the 7/8 fitting extremely nicely while the 7/8 is loosey goosey enough that it gets scarily close to the corners. The old fitting isn't rounded off in any way. I tried the same on a new one and it's the same deal.

^^^^^^^^^^^^^^^^^^^^ LOL need to re-stamp the 22.........LOL
l have well gave them to my brother, but he has/had good luck with them, like IIRC a 8mm-22-mm wrench set. Got it circa 2018 before the price tripled!
OTOH l got A 14" adjustable wrench from them, jaws out of parallel enough to be a PITA in use,
They sent me a new one right away, but it's the same way. The 24" 1/2" drive ratchet l have is nice, and the 24" l think maybe 30" pry bar is nice too.
I've had the metric $nap on smaller line wrenches forever, their great, and l got smaller sizes set of SAE $nap ON line wrenches used off this site.

 

[dchawk81]

^^^^^^^^^^^^^^^^^^^^ LOL need to re-stamp the 22.........LOL
l have well gave them to my brother, but he has/had good luck with them, like IIRC a 8mm-22-mm wrench set. Got it circa 2018 before the price tripled!
OTOH l got A 14" adjustable wrench from them, jaws out of parallel enough to be a PITA in use,
They sent me a new one right away, but it's the same way. The 24" 1/2" drive ratchet l have is nice, and the 24" l think maybe 30" pry bar is nice too.
I've had the metric $nap on smaller line wrenches forever, their great, and l got smaller sizes set of SAE $nap ON line wrenches used off this site.

Lol yep. I was like damn if I knew about that 22 ahead of time I could have saved myself $400.

It never occurred to me before this that a metric Tekton would fit better on an SAE fitting than the SAE Tekton that was supposed to have been made for it.

I'm probably out of luck if I need a 22mm for a 22mm fitting. I guess I could use the 3/4. It's probably sloppy enough.

 

[rust in the eye]

Since my only job today is to monitor a brisket on my smoker I decided to make a useful contribution to the topic.
Given the difference between 19mm(.748) and 3/4" is only .002" to begin with I decided to measure a few of my wrenches. The results here:
19mm(.748")
Milwaukee Max Bite .759"
Vintage Craftsman VA .760"
Vintage Craftsman V .759"
KD tools USA .756"
Popular Mechanics .758"
Pittsburgh .761"
Vintage Sears .757"


3/4" (.750") Blackhawk USA .755"
Vintage Craftsman VA .760"
Vintage Craftsman VA .754"
TrueCraft (Palmera) Spain .756"
Stanley .758"
Vintage Sears .759"
Vintage Sears .761"

So, 14 wrenches of various brands, vintage and quality having a deviation of .007" over both sizes. Some 19mm being larger than their 3/4" brothers and two of my 3/4" are actually smaller than all of the 19mm wrenches!
Draw your own conclusions.
I'll let someone else go measure bolt heads

 

[dchawk81]

Since my only job today is to monitor a brisket on my smoker I decided to make a useful contribution to the topic.
Given the difference between 19mm(.748) and 3/4" is only .002" to begin with I decided to measure a few of my wrenches. The results here:
19mm(.748")
Milwaukee Max Bite .759"
Vintage Craftsman VA .760"
Vintage Craftsman V .759"
KD tools USA .756"
Popular Mechanics .758"
Pittsburgh .761"
Vintage Sears .757"


3/4" (.750") Blackhawk USA .755"
Vintage Craftsman VA .760"
Vintage Craftsman VA .754"
TrueCraft (Palmera) Spain .756"
Stanley .758"
Vintage Sears .759"
Vintage Sears .761"

So, 14 wrenches of various brands, vintage and quality having a variation of .006" over both sizes. Some 19mm being larger than their 3/4" brothers and two 3/4" are smaller than all of the 19mm!
Draw your own conclusions.

You have too many 3/4 and 19mms.

 

[bubinga]

Lol yep. I was like damn if I knew about that 22 ahead of time I could have saved myself $400.

It never occurred to me before this that a metric Tekton would fit better on an SAE fitting than the SAE Tekton that was supposed to have been made for it.

I'm probably out of luck if I need a 22mm for a 22mm fitting. I guess I could use the 3/4. It's probably sloppy enough.

Grind or file the 19 a bit maybe? SMDH!

 

[dchawk81]

Grind or file the 19 a bit maybe? SMDH!

That would ruin my 19 for when I need a 5/8 tho.

 

[whateg01]

I have a snap on 3/4 impact socket that is also stamped with 19mm on the opposite side.

You should post that in the messed up for lug nuts/ discount tire rant!