Description
The HexSizer High Heat Heavy Hex Gauge measures a heavy hex nut from one flat and tells you the standard nut size, which is also your wrench or socket size. Inch is on the front and metric is on the back. The inch side reads ASME heavy hex nuts from 1-1/16" to 6-1/8" and studs from 5/8" to 4". The metric side reads nuts from 32 mm to 165 mm and studs from M22 to M100. It works on installed nuts, where the stud is in the way of a caliper or an across-the-flats measurement.
Saw one on a buddy's lanyard? This is it: the navy blue HexSizer Heavy Hex Gauge.
Know the wrench size before you leave the shop
On a job walk through the plant, you need the nut size on that flange, heat exchanger or turbine so you can bring the right hydraulic torque wrench, socket or tensioner. On an installed nut, though, the stud is in the way, so you can't measure across the flats. A caliper reads in thousandths and leaves you guessing which standard size you're looking at. Old drawings aren't always right. Guess wrong and the crew stands around while somebody drives back to the shop. Some contractors rent the size above and below "just in case," which triples the rental cost.
The HexSizer fixes that. The nut side of the gauge is one flat wide, and it's marked with the across-the-flats size of the nut. That's the same number you use to pick the wrench or socket. Set the nut into the corner, read the size from one flat, and you're done. Only standard sizes are marked: ASME heavy hex on the inch side, DIN 934 on the metric side. There are no extra tick marks to sort through.
The stud side reads like a ruler. Put the stud end into the corner and read the stud size. Each size is matched to its nut, so you can go from stud to nut or from nut to stud.
Inch on the front, metric on the back. Both sides measure, and both edges work, so you can check a size from whichever side you can reach.
Made for hot units. The gauge is 6061 aluminum, anodized and laser engraved, and holds up to a little over 1000°F (538°C). It won't melt when you're working hot units or live steam lines.
Who uses it: millwrights, bolting technicians, pipefitters and steamfitters. It's also used in the tool crib for sorting nuts, studs and stud-bolts.
Where it's used: refineries, power plants (including nuclear), chemical plants, pipelines, oil and gas, wind and gas turbines, bridges and structural steel. It works on anything with heavy hex fasteners, including flanges, valves, pressure vessels, heat exchangers, pumps and compressors.
When it's used: job walks before a shutdown, turnaround or outage, emergency and planned maintenance, and hot bolting. Use it any time you need to confirm a size before you order, rent or ship bolting tools.
Why size it before you rent: The wrong size stops the job. I've seen a plant that couldn't wait for the right tool have welders burn the nuts off instead. That meant pulling welders off their scope, issuing hot permits, posting a fire watch and blinding off the area. They put an ignition source in a refinery because nobody had the right size. Knowing the size up front avoids that.
Size: 2" W x 4-1/2" H x 0.040" thick. It fits in a shirt pocket and won't fall out. Most bolting techs wear it on the lanyard with their plant badge.
In the package: one High Heat Heavy Hex Gauge (inch front, metric back), a detachable tether, and a fitted vinyl sheath.
Over 100,000 HexSizer gauges sold. Made in the USA. U.S. Patent 10,288,400. Designed by Wes Johnson, who has nearly 30 years of experience bolting in refineries, power plants, chemical plants, wind farms, offshore platforms and bridges.
Heavy hex stud and nut size chart (inch)
The wrench or socket size is the nut size across the flats.
| Stud size | Heavy hex nut size (wrench / socket) |
|---|---|
| 5/8" | 1-1/16" |
| 3/4" | 1-1/4" |
| 7/8" | 1-7/16" |
| 1" | 1-5/8" |
| 1-1/8" | 1-13/16" |
| 1-1/4" | 2" |
| 1-3/8" | 2-3/16" |
| 1-1/2" | 2-3/8" |
| 1-5/8" | 2-9/16" |
| 1-3/4" | 2-3/4" |
| 1-7/8" | 2-15/16" |
| 2" | 3-1/8" |
| 2-1/4" | 3-1/2" |
| 2-1/2" | 3-7/8" |
| 2-3/4" | 4-1/4" |
| 3" | 4-5/8" |
| 3-1/4" | 5" |
| 3-1/2" | 5-3/8" |
| 3-3/4" | 5-3/4" |
| 4" | 6-1/8" |
Nominal sizes per ASME B18.2.2 heavy hex nuts.
Metric stud and nut size chart (back of the gauge)
| Stud size | Nut size (wrench / socket) |
|---|---|
| M22 | 32 mm |
| M24 | 36 mm |
| M27 | 41 mm |
| M30 | 46 mm |
| M33 | 50 mm |
| M36 | 55 mm |
| M39 | 60 mm |
| M42 | 65 mm |
| M45 | 70 mm |
| M48 | 75 mm |
| M52 | 80 mm |
| M56 | 85 mm |
| M60 | 90 mm |
| M64 | 95 mm |
| M68 | 100 mm |
| M72 | 105 mm |
| M76 | 110 mm |
| M80 | 115 mm |
| M85 | 120 mm |
| M90 | 130 mm |
| M95 | 135 mm |
| M100 | 145 mm |
The nut side also reads 150, 155 and 165 mm nuts. Their studs are larger than the stud side goes.
Metric wrench sizes per DIN 934 plain hex nuts, the sizes hydraulic torque wrenches and stud tensioners are made for. These are not ASME metric heavy hex sizes, which run larger.
Specifications
| Front (inch) | Nuts 1-1/16" to 6-1/8" (20 standard sizes), studs 5/8" to 4" |
| Back (metric) | Nuts 32 mm to 165 mm (25 sizes), studs M22 to M100 (22 sizes) |
| Standards | Inch side: ASME B18.2.2 heavy hex. Metric side: DIN 934 |
| How it measures | Nuts from one flat; studs from the stud end, like a ruler |
| Works on installed nuts | Yes |
| Material | 6061 aluminum, anodized, laser engraved |
| Heat rating | A little over 1000°F / 538°C |
| Color | Navy blue |
| Dimensions | 2" W x 4-1/2" H x 0.040" thick |
| Included | Gauge, detachable tether, vinyl sheath |
| Made in | USA |
| Patent | U.S. 10,288,400 |
Frequently asked questions
How do you measure a heavy hex nut that's already installed?
Set the nut into the corner of the gauge and read the size from one flat. You don't have to reach across the flats, so the stud isn't in the way.
What size wrench or socket do I need for a heavy hex nut?
The wrench or socket size is the nut's width across the flats. The gauge's nut side is marked in that size, so the number you read is the tool you need. The chart above also shows the matching stud size.
Why does my caliper read smaller than the nut's listed size?
Nut sizes are nominal, not exact. ASME B18.2.2 gives each heavy hex nut a minimum and a maximum width across the flats. The maximum is the nominal size, the size you call it. Nuts are made to fall inside that range, so they come in at or under the size you call it, and a wrench or socket of that size always fits. A new 2H nut can measure a few thousandths under its listed size on a caliper, and that's normal. It still takes the standard wrench.
This throws people off in the field. A bolting tech reads the caliper, gets a number between sizes, and decides it "must be metric" or "must be a custom build" when it isn't. Or he's sure he needs a 3" socket when the nut is really 2-15/16". The HexSizer only marks the standard sizes, so you read the size the nut was made to, not the thousandths.
What if the nut lands between two tick lines?
Go with the larger size. If the nut goes past the smaller size's tick line, the larger tick line is your size. Nuts are made at or under their nominal size, never over, so a nut that's past the smaller mark is the bigger nut. The same rule applies to the WrenchSizer, which measures from corner to corner instead of from one flat.
Is it inch or metric?
Both. Inch is on the front and metric is on the back.
Why does one chart say an M24 takes a 36 mm wrench and another says 41 mm?
They're two different nut standards. DIN 934 plain hex nuts put an M24 at 36 mm. That's what you'll find on flanges, wind towers, pumps and compressors built overseas, and it's what hydraulic torque wrench and tensioner sockets are sized to. ASME metric heavy hex nuts run larger, so an M24 takes 41 mm. Those show up mostly in structural steel. The HexSizer metric side reads DIN 934. If you're working a metric joint, measure the nut rather than trusting the stud size, because the same M24 stud can carry either nut.
Can I use it on hot equipment?
Yes. It's anodized, laser-engraved aluminum rated to a little over 1000°F (538°C).
Will it fit in my pocket?
Yes. At 2" x 4-1/2" it fits a shirt pocket. If you want one that fits in a wallet, the 2" x 3-3/8" version reads nuts up to 4-5/8".
What color is it?
Navy blue. That's the standard HexSizer, the one you've most likely seen on the job. Black, red and gold are also in stock. Other anodize colors are made on private-label runs of 1,000 pieces.
Can I put my company logo on it?
Yes. HexSizer makes private-label gauges for tool companies and manufacturer reps. Your logo stays in the millwright's pocket and gets seen right when he's picking tools.
