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Most bolts come in a Package or a Bulk Box. Shop hex, carriage, lag, tap, flange, square head and plow bolts. Inch bolts come in steel grades, 18-8 and 316 stainless; metric in Class 8.8, 10.9, A2 and A4. Filter by diameter, length, material and finish.

Choose the bolt type

Hex bolts: general-purpose hex head bolts in low carbon steel, A307 Grade A and Grade 8, plain, zinc or hot-dip galvanized, up to 2-1/2" diameter.
Carriage bolts: round head with a square neck that holds the bolt in wood or a square hole while you tighten the nut. Inch #6 to 7/8" and metric M5 to M16.
Lag bolts (lag screws): hex head with a wood thread, driven into timber with no nut. Inch and metric (M6 to M12).
Tap bolts: hex head bolts threaded the full length, used with a nut or in a tapped hole. Grade 5, Grade 8, low carbon and 18-8 stainless.
Flange bolts: hex head with a flange under the head that spreads the load like a washer, serrated or non-serrated. Inch Grade 5 and 8, metric Class 8.8 and 10.9, and stainless.
Square head bolts, plow bolts (No. 3, dome and large head), hanger bolts, elevator bolts, step bolts, timber bolts and anchor bolts.
For high-strength and structural work, see heavy hex bolts, A325 and A490 structural bolts and hex cap screws.

Material and grade

Steel bolts are listed as low carbon steel, A307 Grade A, SAE Grade 2, Grade 5 or Grade 8, or metric Class 8.8 and 10.9. Use the grade your drawing or the original part calls for. Inch stainless is 18-8 or 316. Metric stainless is A2 or A4, for example A4-70 carriage bolts. Some hex cap screws also come in silicon bronze. The material is named in each product title.

Shop by grade: Grade 5, Grade 8, Class 8.8, Class 10.9, 18-8 stainless and 316 stainless.

Thread and size callouts

Inch bolts are listed as diameter-threads per inch x length. 1/2"-13 x 3" is a 1/2" coarse thread (UNC) bolt, 3" long. 1/2"-20 would be fine thread (UNF). Metric bolts list diameter, pitch and length: M10-1.5 x 40 mm. Titles also say partial thread or full thread where it applies. Lag bolts have a wood thread, so they list diameter and length only.

Finish

Steel finishes include plain, zinc, zinc yellow, hot-dip galvanized, black oxide and black phosphate. Plain steel has no coating. Zinc plating is a thin coating, best for indoor or dry use. Hot-dip galvanizing is much thicker and suits outdoor or wet use; pair it with galvanized nuts from the same coating process. Stainless is passivated. The finish is the last item in each title. See hot-dip galvanized.

Head and drive

Hex, heavy hex, flange and square heads take a wrench or socket. Carriage and step bolts have a round head and a square neck that stops the bolt turning, so you only wrench the nut. Elevator bolts have a flat countersunk head and a square neck. Plow bolts have a countersunk head that sits flush. Hanger bolts have no head: a wood thread on one end and a machine thread on the other. For wrench sizes by bolt diameter, see the wrench size chart.

Length

Hex, square, carriage and lag bolt length is measured from under the head to the end. Countersunk heads such as plow and elevator bolts are measured overall, including the head.

Packages and bulk boxes

Most bolts come as a Package or a Bulk Box. Piece counts depend on size, for example 20 / 200 or 45 / 450. Each variant shows its count. Need volume pricing? See wholesale.

Bolt types and sizes

Type	Typical use	Materials stocked	Thread / sizes	Shop
Hex bolts	General bolting with a nut	Low carbon steel, A307 Grade A, Grade 8	Inch, up to 2-1/2"	Shop hex bolts
Carriage bolts	Wood, square holes	Low carbon, A307, Grade 5, Grade 8, 18-8, 316, A2, A4, Class 8.8	#6 to 7/8", M5 to M16	Shop carriage bolts
Lag bolts	Timber, no nut	Low carbon steel, 18-8, 316, A4	Wood thread, 1/4" to 3/4", M6 to M12	Shop lag bolts
Tap bolts	With a nut or in a tapped hole	Grade 5, Grade 8, low carbon, 18-8	Full thread, 1/4" to 1-1/4"	Shop tap bolts
Flange bolts	Flange under the head spreads load	Grade 5, Grade 8, Class 8.8, Class 10.9, 18-8, A2	1/4" to 3/4", M4 to M16	Shop flange bolts
Square head bolts	Square-head replacement	A307 Grade A, low carbon steel	1/4" to 1-1/4"	Shop square head bolts
Plow bolts	Flush countersunk head	Grade 5, Grade 8, low carbon	3/8" to 1-1/4"	Shop plow bolts
Hanger bolts	Wood to machine thread	Low carbon steel, 18-8	#6 to 1/2"	Shop hanger bolts
Heavy hex and structural	Steel connections	A325, A490, B7, A307	1/2" to 2-1/2"	Shop heavy hex bolts

Bolt FAQs

What is the difference between a bolt and a screw?

Bolts such as carriage, hex and square head bolts are usually fastened with a nut. Hex cap screws and tap bolts can also go into a tapped hole. Lag screws have a wood thread and need no nut.

What is the difference between a hex bolt and a heavy hex bolt?

A heavy hex bolt has a larger head than a standard hex bolt of the same diameter. A 1/2" hex bolt takes a 3/4" wrench; a 1/2" heavy hex bolt takes 7/8". See the wrench size chart.

When should I use a carriage bolt?

Use a carriage bolt when you can only reach the nut side. The square neck holds the bolt in wood or a square hole while you tighten the nut. Carriage bolts come in steel, 18-8, 316, A2 and A4 stainless.

How do I read a bolt size like 1/2"-13 x 3" or M10-1.5 x 40 mm?

1/2"-13 x 3" is a 1/2" diameter bolt with 13 threads per inch (coarse), 3" long. M10-1.5 x 40 mm is a 10 mm bolt with a 1.5 mm thread pitch, 40 mm long.

Which bolt finish should I use outdoors?

Hot-dip galvanized steel or stainless steel. Zinc plating is thinner and best indoors or in dry areas. Use galvanized nuts from the same coating process as the bolt.

Can I buy bolts in bulk?

Yes. Most bolts come as a Package or a Bulk Box, and each variant shows its piece count. See wholesale for volume pricing.

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