Given that the difference between 3/4 and 19mm is what, thousandths of an inch? Do manufacturers of wrenches and sockets actually make two different sizes or are they just stamped with a different label? In other words, how tight are their tolerances?
3/4 inch vs 19 mm
- Thread starter MadeInUSA
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osborn.ozzy
Banned
Same could be said for other sizes like 8mm 11mm 16mm 19mm 21mm 22mm 24mm
Fedwrench
ALLIANCE MEMBER
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.
biscuit141
Well-known member
I have a snap on 3/4 impact socket that is also stamped with 19mm on the opposite side.
Wakefield
Well-known member
There is a chart in my Wright catalog that attempts to show which traditional and metric sizes can be used in each others place.
wreckercologist
Well-known member
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"..........
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?
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?
ajchien
Well-known member
I'm personally only comfortable with 5/16=8mm, and 3/4=19mm.
I used my "emergency road box" yesterday and used a 5/16 in substitute for an 8mm. Today, I got myself an extra 8mm to put into that road box. More OCD on my part I think.
I guess if you use 6 pt instead of 12 pt, you may get away with poor tolerances even more, but I really have no proof of that.
I used my "emergency road box" yesterday and used a 5/16 in substitute for an 8mm. Today, I got myself an extra 8mm to put into that road box. More OCD on my part I think.
I guess if you use 6 pt instead of 12 pt, you may get away with poor tolerances even more, but I really have no proof of that.
FriendOfYours
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- Feb 26, 2012
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That's because 1/2in is often too small to fit 13mm. It's a whopping .3mm off 13
purplezr2
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11/16 and 17 are usually close
Slingshot Engage
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I agree with that
Gort the giant robot
Well-known member
I have some Bridgeport open end wrenches marked with SAE sizes on one side and metric on the other.
Gort.
Gort.
shoturtle
Well-known member
The EU and Asian tools makers that double up makes them closer to the metric standard then the SAE. As Metric is expanding and sae is contracting.
It was the other way about 10 years ago, brought a US husky set for work, and they double 7/16 and did not have a 11mm.
It was the other way about 10 years ago, brought a US husky set for work, and they double 7/16 and did not have a 11mm.
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MechManiac
Well-known member
5/8" for 16 works for me as does 3/4" for 19.
MechManiac
Well-known member
the manufacturer could lie to me and I won't know if its SAE or metric in my case above. I really don't know if they do though.
The Dutchman
Well-known member
The closest pair I normally come across: 27mm & 1-1/16". Separated by only 5 ten thousandths of an inch.
Ign
Well-known member
I remember looking at some of the "Ram Tools" impact sockets from Cummins Tool (traveling tool gypsies). Some like 3/4" were stamped with both sizes.
Lone Wolf's chart is how I think of it too, but backwards. I prefer to think of it strictly in thousandths. Thus 8mm and 5/16 are only 2.5 thou apart (.315 vs .3125). That's less than a human hair. 19mm is less than 2 thou under 3/4" (.74803 vs .750)
Now, if you ever take an off-the-shelf hex fastener and measure it, you'll find it's 10 to 15 thou undersize. Now take an open end wrench and you'll find it's 10 to 15 thou oversize. So yeah, I wouldnt' worry about a couple thou between something like 8mm and 5/16.
And no, I don't believe most manufacturers are truly making different sockets for the above sizes. If they're smart they're not. No reason to not take the same socket and simply etch it with either metric or fractional, and cuts down on manufacturing costs obviously.
But I'll trade ya a 1/4" drill bit for a letter "E"!!
Lone Wolf's chart is how I think of it too, but backwards. I prefer to think of it strictly in thousandths. Thus 8mm and 5/16 are only 2.5 thou apart (.315 vs .3125). That's less than a human hair. 19mm is less than 2 thou under 3/4" (.74803 vs .750)
Now, if you ever take an off-the-shelf hex fastener and measure it, you'll find it's 10 to 15 thou undersize. Now take an open end wrench and you'll find it's 10 to 15 thou oversize. So yeah, I wouldnt' worry about a couple thou between something like 8mm and 5/16.
And no, I don't believe most manufacturers are truly making different sockets for the above sizes. If they're smart they're not. No reason to not take the same socket and simply etch it with either metric or fractional, and cuts down on manufacturing costs obviously.
But I'll trade ya a 1/4" drill bit for a letter "E"!!
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IDASHO
Well-known member
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.
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.
shoturtle
Well-known member
especially with all the flank drive out there. The is way more slop in the socket. 
dudutzu905
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or a worn 13/16 used as a 21mm
I've never seen one .. Do you have a picture of it? thanks
jvitez
Well-known member
The plastic fuel filter cap on my Dodge Ram Cummins needs a 29 mm socket. I have one, but my 1 1/8" socket fits better. The difference is .425 mm.
ajchien
Well-known member
Agreed. But I still have OCD though.
I usually check my sockets or wrenches to see how much play there is in tool to fastener fit. I keep a chart taped to the lid of my tool box that shows the differences in thousandths between SAE and Metric sizes. I will swap tools and even between SAE and Metric to find the best fit on some bolts. Sure it takes a little extra time, but I am not a paid auto mechanic so I have the extra time both when I am at work on a job or at home working on something for myself. I very rarely round off or damage fasteners. One thing I definitely check sizes on are lugnuts, especially the ones with the chrome covers. Mopar uses that style quite a bit. I have never destroyed one of those lugnuts. Although having my vehicles go through various tire shops, those guys with impact guns are almost guaranteed to destroy that type of lugnut due to sloppy fitting sockets. I once found a 13mm 12 point socket on an oil pan drain plug of a vehicle I had just purchased. It was left there because it was the wrong size! The drain plug was actually a 1/2" Maybe it's just a pet peeve of mine, but if somebody is working on something that belongs to me (ie my vehicle) I prefer they use the correct socket!
Jawn
Well-known member
True, but adding too much slop is a bad thing as well.
Some cheap 1/4"x20tpi has an undersized head so it can theoretically fit in a 7/16" or 11mm socket, but I find 7/16" too loose in this case. The difference is a bit over 1/10 of a millimeter. Doesn't sound like much, but how the socket "feels" on the head is completely different.
19mm - 3/4" is about the only one I've found that I'll use interchangeably.
The "magazine" sockets sold by Snap-On are labelled both. Theres a snap-on brand version and a blue-point version thats etched.
http://buy1.snapon.com/catalog/item...roup_ID=681315&store=snapon-store&dir=catalog
http://buy1.snapon.com/catalog/item...roup_ID=681315&store=snapon-store&dir=catalog
beelsr
Well-known member
Attached is a PDF I made up a few years ago.
SAE - Metric - Whitworth and SAE - Metric.
Differences of < 1% are in red.
Cut the page in half. If you use whitworth, you'll like the left side. If not, the right side is a bit easier to use.
Works for me...
Sneak preview:
SAE - Metric - Whitworth and SAE - Metric.
Differences of < 1% are in red.
Cut the page in half. If you use whitworth, you'll like the left side. If not, the right side is a bit easier to use.
Works for me...
Sneak preview:
Attachments
that is a 1 and an 8th...Chrysler DealerConnect says so...
N.I.
Well-known member
A decent quality 1/2" wrench does not fit onto a decent quality M8 bolt.
N.I.
Well-known member
Don't forget 1 1/16 is a perfect fit for 27mm
skulldrinker
Well-known member
When I come back to my box holding the wrong size socket I have a chart that I made to tell me what the next size up or down is. Since I came on the scene late I am not familiar yet where SAE and MM fall into place. Those industrial charts with all those columns and decimal equivalents I used at first but they had way to much info for me to sift through. So this is what I came up with. Simply socket and wrench sizes that I would come across. I have it laminated and stuck to my inside top cover with a magnet.
Attachments
I'm sure they were sold as 20.8 but I agree it does convert to 20.6