How to install The Bolt Up and The Bolt Up Fixed 60° on a square tube, how tight to make the bolts, and when to re-check them.
Installed examples
What you need
| Item | Notes |
|---|---|
| Tool needed: 1/4″ Allen wrench (not included). | Standard hex size for 5/16"-18 socket head bolts. |
| Four 5/16"-18 bolts | Included. The Bolt Up: 1" (25.4 mm) for strap, belt or portable attachments; 3" (76.2 mm) for tubes up to 2" (50.8 mm); 4" (101.6 mm) for tubes 2" to 3" (50.8 to 76.2 mm), measured under the head (your chosen length). The Bolt Up Fixed 60°: 3" or 4". These are socket head bolts measured under the head (1.000", 3.000" or 4.000"). The 3" and 4" bolts are threaded for the last 1.500" (38.1 mm) at the tip; the 1" bolt is fully threaded. |
| Four flat + four split lock washers | Included with both Mounts: four flat washers and four split lock washers. On each bolt, the split lock washer goes directly under the bolt head, then the flat washer, then the Mount. Measured thickness: split lock washer 0.0895" (2.27 mm), flat washer 0.055" (1.40 mm). |
| The Bolt Up | Included. The Bolt Up, the plate the guide calls the Mount: 4.526" x 3.601", 0.313" A36 steel, gloss black powder coat, with 4 corner bolt holes and two groups of small holes for the DIY Dock. Ships in The Bolt Up kit alongside 2 nut plates (your chosen size). |
| Nut plates | Included. The Bolt Up: two separate nut plates, 2 holes each (2" or 3" option). The Bolt Up Fixed 60°: one 4-hole nut plate, 0.313" A36 steel, tapped 5/16-18. The nut plates sit on the far side of the tube and take the bolts. |
| DIY Dock | Install it on the Mount first, before installing The Bolt Up on a rack or with a strap. |
| Chafe pads | Included. They go between the steel and your tube to protect the finish. The Bolt Up: 1 large pad, 0.138" (3.5 mm), shaped like The Bolt Up, goes under the Mount, and 2 small chafe pads, 1 mm (0.039"), shaped like the nut plates, go one under each nut plate. The Bolt Up Fixed 60°: 1 large pad, 0.138" (3.5 mm), under the Mount, and 1 large chafe pad, 1 mm (0.039"), under its single large nut plate. |
| Torque wrench (recommended) | Not included. An inch-pound or small ft-lb wrench with a 1/4" hex bit makes it easy to hit the value below. |
Which bolt length to use
| Bolt length | Best for | Available on |
|---|---|---|
| 1" (25.4 mm) | For strap, belt, or portable attachments (material under 7/32" (5.5 mm) thick) | The Bolt Up only |
| 3" (76.2 mm) | Tubing up to 2" (50.8 mm) | Both |
| 4" (101.6 mm) | Tubing 2" to 3" (50.8 to 76.2 mm) | Both |
The bolts should pass fully through the nut plate threads (both plates on The Bolt Up) with the Mount clamped tight. If a bolt bottoms out before the Mount is tight, or barely reaches the nut plate, you need the other length.
How the bolt goes through
From the bolt head down, the order is:
- Bolt head (socket head, 5/16"-18)
- Split lock washer, 0.0895" (2.27 mm)
- Flat washer, 0.055" (1.40 mm)
- The Bolt Up, 0.313" (7.95 mm)
- Large chafe pad, 0.138" (3.5 mm)
- Your tube (the bolts pass outside it, on both sides)
- Small chafe pad, 1 mm (0.039")
- Nut plate, 0.313" (7.95 mm), tapped 5/16"-18 (no nut)
- Bolt tip, sticking out slightly past the nut plate
At the maximum tube size, the whole stack under the bolt head is 2.948" (74.9 mm) on a 2" tube with 3" bolts and 3.948" (100.3 mm) on a 3" tube with 4" bolts. The tip sticks out about 0.052" (1.3 mm) past the nut plate in both cases. On a smaller tube, it sticks out further.
Step-by-step installation
1Pick the spot
Choose the height and side of the tube where you want your VOLTRA I. Wipe the tube clean so the chafe pads sit flat.
2Install the DIY Dock on the Mount first
Install your DIY Dock on the Mount now, before you install The Bolt Up on a rack or with a strap. Do not mount The Bolt Up first and add the Dock afterward.
3Position the chafe pads
Hold the chafe pad against the tube where the Mount will sit, lined up with the Mount's bolt holes. The Bolt Up: use the large 3.5 mm pad here, and set the 2 small 1 mm chafe pads on the opposite side of the tube, where the nut plates will go. The Bolt Up Fixed 60°: use its large 3.5 mm pad here, and set its large 1 mm pad on the opposite side, where the nut plate will go.
4Place the Mount and nut plates
Set the Mount, with the DIY Dock already installed, over the chafe pad on one side of the tube, and the nut plates on the opposite side. The Bolt Up: place the two 2-hole nut plates, each over a small chafe pad. The Bolt Up can be rotated 90°. Turn it so the bolts sit closest to your tube. The Bolt Up Fixed 60°: place the single large nut plate over its large 1 mm pad. That plate is the same shape and size as the Mount's base plate, 0.313" thick, with 5/16"-18 threaded holes. The four bolts run along the sides of the tube, outside it, from the Mount to the nut plates.
5Start all four bolts by hand
Put a split lock washer and then a flat washer on each bolt (the split lock washer sits against the bolt head), then thread all four bolts into the nut plates by hand (two per plate on The Bolt Up, all four into the one plate on The Bolt Up Fixed 60°) a few turns each. Do not tighten any one bolt fully yet. Starting by hand prevents cross-threading.
6Snug in a cross pattern
With the 1/4" Allen wrench, snug the bolts in a cross (X) pattern: top-left, bottom-right, top-right, bottom-left. Keep the gap between the Mount and the nut plates even on both sides, and check that the Mount sits square and at the height you want.
7Torque in a cross pattern
Tighten in the same cross pattern in two or three passes, finishing at the torque below. Stop right away if the rack tube, the Mount, or the nut plates start to crush or bend, even before you reach that torque.
8Check before use
Push and pull firmly on the Mount. It should not slide or rock. Attach your VOLTRA I to the DIY Dock and start with light loads.
How tight should the bolts be?
This is a conservative value. It is the dry torque for a 5/16"-18 alloy steel socket head cap screw in Eugene Fastener's chart (about 65% of proof load). Socket screw makers list a much higher maximum seating torque for this size (415 to 425 in-lb), but that is for the bolt alone. Here the bolts clamp a hollow tube with plastic chafe pads in between, so the lower value is the safer target.
| Source | 5/16"-18 socket head cap screw | Conditions |
|---|---|---|
| Eugene Fastener | 170 in-lb (14.2 ft-lb) | Alloy steel (ASTM A574), dry, about 65% of proof load. Reduce 20–25% if lubricated or thread locker is used. |
| Holo-Krome | 415 in-lb (about 34.6 ft-lb) | Alloy steel, thermal black finish with light oil |
| Unbrako | 425 in-lb (about 35.4 ft-lb) | Alloy steel seating torque, plain screws |
Doubling with The Bolt Up Fixed 60°
The Bolt Up Fixed 60° is built for 2:1 doubling and has a doubling attachment point. Install and torque the Mount fully, and check it is solid, before you connect any doubling hardware. Doubling puts more load on the Mount, so follow the re-check schedule below closely.
Maintenance and re-check schedule
Powder coat and the chafe pads settle slightly under load, which can let bolts lose some clamp after install. Re-checking is normal good practice.
| When | What to do |
|---|---|
| After the first few sessions | Re-check all four bolts at the recommended torque, in a cross pattern. |
| About 2–3 weeks | Re-check torque and look the Mount over. |
| About 1 month | Re-check torque again. |
| After that | Check monthly, or every few months for light use. Also check any time you move the Mount. |
What to look for
- Movement: any slip down the tube, rocking or clicking under load.
- Chafe pad wear: tearing, squeezing out from the edges, or bare spots. Replace any worn pad: the 3.5 mm pad under the Mount, or the 1 mm pad(s) under the nut plate(s).
- Bolt loosening: a bolt that turns easily before reaching torque, or a gap that is uneven side to side.
- Tube damage: dents or bowing where the Mount clamps.
Sources
- Eugene Fastener, Socket Screw Torque Chart & Hex Key Size Reference (5/16"-18: 1/4" hex key, 170 in-lb dry): eugenefast.com
- Holo-Krome, Inch & Metric Fastener Chart (5/16 UNRC: 415 in-lb): holo-krome.com (PDF)
- Unbrako, Engineering Guide (5/16 UNRC seating torque: 425 in-lb): unbrako.com (PDF)
- Nord-Lock Group, bolting on painted surfaces (coating settling and preload loss): nord-lock.com
Torque values are quoted from published fastener charts as of October 2026. Voltra Mounts is not affiliated with Beyond Power or the companies listed.