Grade 8 · Grade 9
Plow Bolt
UNC plow bolts with a countersunk head and square neck in grade 8 (3/8 to 1/2 inch) and grade 9 (5/8 to 1-3/8 inch), plus a grade 9 long shoulder plow bolt, supplied plain.
About the Plow Bolt
Plow bolts hold the cutting edges and end bits onto grader, dozer and loader blades, and points and shares onto tillage gear: the countersunk head sits flush and the square neck stops it turning. They are UNC and supplied plain, in grade 8 (3/8, 7/16 and 1/2 inch) and grade 9 (5/8 to 1-3/8 inch), plus a grade 9 long shoulder plow bolt in 1 x 3-3/4 inch, from 1 to 7 inches long. Choose the grade, diameter and length above; the guide below covers thread pitch, plow nuts and tightening torques.
Also called plough bolts or cutting edge bolts.
Features
- Square-neck plow bolt
- Grade 8, with grade 9 stepped-neck option
- Plain finish
- Flush countersunk head
- UNC coarse thread
Applications
- Cutting edges and end bits on grader, dozer and loader blades
- Bucket edges on earthmoving gear
- Plough shares, points and tillage tools
Plow bolts for cutting edges and blades
A plow bolt has a countersunk head and a square neck. The head sits flush in the countersunk hole of a cutting edge and the square neck stops the bolt turning while you tighten the nut from behind. Hobson lists them for securing the cutting edges of earthmoving blades; they are the usual bolt for grader, dozer and loader cutting edges and end bits, bucket edges, and plough shares and points (hence plough bolt).
Our plow bolts have UNC (coarse) threads and are supplied plain. For track shoes, use track bolts. Hobson's plow nuts are grade 8 UNC, in every diameter we carry; Hobson's grade 9 torque sheet does not state a nut grade, so follow the edge maker's nut specification for grade 9 bolts.
Plow bolt sizes and thread pitch
Match the diameter, length and grade of the bolt the edge was made for. Select a row to open that size in the selector, then pick the length.
Every plow bolt on this page, by grade and diameter. Diameter and lengths in inches; TPI = threads per inch (UNC), from Hobson's plow bolt Did You Know sheet (20182261DYK). Pack is the minimum order. The long shoulder plow bolt is Hobson's CBLG9PC range. Tap a number to show it in the selector above.
| Type | Diameter | TPI | Lengths (inches) | Pack |
|---|---|---|---|---|
| Grade 8, square neck | ||||
| Grade 8, square neck | 3/8" | 16 | 1, 1-1/4, 1-1/2, 1-3/4, 2, 2-1/4, 2-1/2, 3 | 100 to 200 |
| Grade 8, square neck | 7/16" | 14 | 1, 1-1/4, 1-1/2, 1-3/4, 2, 2-1/4, 2-1/2, 3, 3-1/2 | 50 to 100 |
| Grade 8, square neck | 1/2" | 13 | 1-1/4, 1-1/2, 1-3/4, 2, 2-1/4, 2-1/2, 3, 3-1/2, 4 | 25 to 75 |
| Grade 9, square neck | ||||
| Grade 9, square neck | 5/8" | 11 | 1-1/2, 1-3/4, 2, 2-1/4, 2-1/2, 2-3/4, 3, 3-1/2, 4, 4-1/2, 5 | 60 to 115 |
| Grade 9, square neck | 3/4" | 10 | 2, 2-1/4, 2-1/2, 2-3/4, 3, 3-1/8, 3-1/4, 3-1/2, 3-3/4, 4, 4-1/2, 5 | 35 to 80 |
| Grade 9, square neck | 7/8" | 9 | 2-1/4, 2-1/2, 2-3/4, 3, 3-1/4, 3-1/2, 4, 4-1/4, 5 | 30 to 50 |
| Grade 9, square neck | 1" | 8 | 2-3/4, 3, 3-1/4, 3-1/2, 4, 4-1/2, 5, 5-1/2 | 20 to 30 |
| Grade 9, square neck | 1-1/4" | 7 | 3-3/4, 3-7/8, 4, 4-1/8, 4-1/2, 5, 5-1/4, 6, 6-1/2, 7 | 8 to 15 |
| Grade 9, square neck | 1-3/8" | 6 | 4-1/2, 5-1/2, 6 | 8 to 10 |
| Grade 9, long shoulder | ||||
| Grade 9, long shoulder | 1" | 8 | 3-3/4 | 30 |
Grade 8 or grade 9 plow bolts?
In our range the grade follows the diameter: grade 8 for 3/8 to 1/2 inch and grade 9 from 5/8 to 1-3/8 inch, plus the 1 inch grade 9 long shoulder bolt. Hobson's plow bolt sheet gives grade 9 a minimum tensile stress of 170,000 lbf/in². The documents Hobson publishes for this page give no strength or torque figures for the grade 8 plow bolts, so replace like with like and follow the blade or edge maker's bolt specification.
Grade 9 plow bolt tightening torque
These are Hobson's guide torques for grade 9 plow bolts only. They assume plain, burr-free threads with a light oil coating, so a different thread condition or lubricant changes the result, and they apply to the first tightening of single assemblies in isolation. Where the machine or edge maker gives a torque, use theirs.
Grade 9 plow bolts, from Hobson's Plow Bolts Tensile and Torque sheet (1810201D). Torque is calculated with a k factor of 0.2 for an induced load of 75% of proof load stress; a guide only. Nm is our conversion (1 lbf.ft = 1.3558 Nm, rounded). The 1-1/8 inch size on the sheet is not in our range. Not for grade 8 plow bolts. Tap a number to show it in the selector above.
| Size | TPI | Stress area (in²) | Min. tensile stress (lbf/in²) | Torque (lbf.ft) | Torque (Nm, approx.) |
|---|---|---|---|---|---|
| 5/8" UNC | 11 | 0.226 | 170,000 | 238.4 | 323 |
| 3/4" UNC | 10 | 0.334 | 170,000 | 422.7 | 573 |
| 7/8" UNC | 9 | 0.462 | 170,000 | 682.2 | 925 |
| 1" UNC | 8 | 0.606 | 170,000 | 1,022.6 | 1,386 |
| 1-1/4" UNC | 7 | 0.969 | 170,000 | 2,044.0 | 2,771 |
| 1-3/8" UNC | 6 | 1.155 | 170,000 | 2,670.2 | 3,620 |
Fitting plow bolts to a cutting edge
- Clean the countersunk holes in the edge and the mounting holes in the blade, and line them up.
- Push each bolt through from the wearing face so the head sits in the countersink and the square neck locates in the square hole.
- Fit a nut of the same thread size on the back: a grade 8 plow nut on the grade 8 bolts, and for grade 9 bolts the nut the edge maker specifies (Hobson's plow nuts are grade 8).
- Tighten to the edge maker's torque, or for grade 9 bolts Hobson's guide torque above.
Plain finish
Hobson supplies plow bolts plain: no coating, lightly oiled to inhibit rust in the packaging and assist installation. The tightening torques above assume that light oil finish. None of our plow bolts is galvanised or stainless.
Plow bolts in Adelaide
Allmat supplies plow bolts, plow nuts and track bolts to earthmoving contractors, plant operators, farmers and fitters across Adelaide and South Australia. Add them to a quote with the rest of your list, and we will price the lot.
Plow bolts for your blades and buckets
Plow bolts, plow nuts and track bolts are available to order from Allmat for earthmoving contractors, plant operators, farmers, fitters and trade across Adelaide and South Australia. Order through Allmat, we pick and pack it, then click and collect from the Allmat yard or have it delivered to site.
Goes with
Questions
What is a plow bolt?
A bolt with a countersunk head and a square neck, used to hold cutting edges onto earthmoving blades and buckets. The head sits flush in the edge and the square neck stops it turning while the nut is tightened.
Is a plough bolt the same as a plow bolt?
Yes. Plough is the Australian and British spelling, plow the American one. The bolts are the same.
What thread is on a plow bolt?
Ours are UNC: 16 TPI on 3/8, 14 on 7/16, 13 on 1/2, 11 on 5/8, 10 on 3/4, 9 on 7/8, 8 on 1 inch, 7 on 1-1/4 and 6 on 1-3/8 inch.
What torque for a 3/4 inch grade 9 plow bolt?
Hobson's guide is 422.7 lbf.ft (about 573Nm), for plain, burr-free, lightly oiled threads on a first tightening, at 75% of proof load stress. Use the edge or machine maker's figure where they give one.
Do you have nuts for plow bolts?
Yes. Hobson's plow nuts are grade 8 UNC, in every diameter of plow bolt we carry, from 3/8 to 1-3/8 inch. Hobson's grade 9 torque sheet does not state a nut grade, so for grade 9 bolts follow the edge maker's nut specification.
What is the difference between grade 8 and grade 9 plow bolts?
Hobson gives grade 9 plow bolts a minimum tensile stress of 170,000 lbf/in²; its documents give no strength figure for the grade 8 plow bolts. In our range, grade 8 covers 3/8 to 1/2 inch and grade 9 covers 5/8 to 1-3/8 inch.
Where can I buy plow bolts in Adelaide?
Order through Allmat. Order ahead by phone on 1300 03 03 63 or send your list for a quote, then click and collect from 25 Kapara Road, Gillman, or have them delivered to site.
Plow Bolt: sizes and finishes we supply
80 lines by type and finish. Pick one above for its product code and pack sizes.
| Type | Finish | Sizes | Lengths | Lines |
|---|---|---|---|---|
| Plow (countersunk) | Steel | 3/8, 7/16, 1/2, 5/8, 3/4, 7/8, 1, 1-1/4, 1-3/8 | 1 to 7 inch (24 lengths) | 79 |
| Plow long shoulder | Steel | 1 | 3-3/4 inch | 1 |
Data sheets and documents
The documents for the product you choose are listed with the selector above. Here is every Plow Bolt document from Hobson Engineering.
All Plow Bolt documents (6)
Data sheets and technical data (4)
Did You Know flyers (1)
Guides and articles (1)
Need them in bulk?
Add the sizes you need to your quote, or send us your list and we’ll price the lot and supply it with the rest of your order.
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