The full FAA torque table for airframe bolts, transcribed and cross-checked: Table 7-1 of AC 43.13-1B gives the torque limits for installing shear-loaded bolts and the maximum allowable tightening torque for AN3 through AN20 in fine thread, plus the coarse-series companion rows — with the interpretation rules (friction drag, castle-nut alignment, clean-and-dry threads) that make the numbers usable instead of dangerous.
Regulated maintenance data — read before using this chart
Aviation maintenance is regulated work. Tightening a bolt on an aircraft is not the same act as tightening one on a trailer: the work must be performed or approved by certificated personnel (a licensed A&P mechanic or repair station), and it must follow approved data — the aircraft manufacturer’s manual first. AC 43.13-1B itself states it contains methods acceptable to the FAA only when there are no manufacturer repair or maintenance instructions, and that its data may be used as approved data only if it is appropriate to the product, directly applicable to the repair, and not contrary to the manufacturer’s data. Treat every value on this page as a study reference to the FAA source — not as installation authority for any specific aircraft.
Every cell below is a verbatim transcription of FAA AC 43.13-1B Table 7-1, Recommended Torque Values (Inch-Pounds), cross-checked against an independent reproduction of the same document. The two left-hand value columns are the torque limits recommended for installation of bolts loaded primarily in shear; the two right-hand value columns are the maximum allowable tightening torque limits. The annotations in the source header state the stress the tightening induces in the bolt: 40,000 psi (tension-type nuts, installation), 24,000 psi (shear-type nuts, installation), 90,000 psi (tension-type nuts, maximum) and 54,000 psi (shear-type nuts, maximum).
Table 7-1 is built as a maximum-allowable table, not a target-preload table. The FAA caps how far you may tighten a given bolt size because the tightening operation itself stretches the bolt — the table’s column headers literally quote the resulting stress in psi carried in the bolt. Every torque you apply on an airframe joint must also respect two additions the AC defines in par. 7-40: the friction drag torque (measured while running the nut down) is added to the desired torque to get the wrench reading, and the manufacturer’s manual value always supersedes the table when one exists. Where the two limits meet — a castellated nut whose cotter-pin hole must align — you work inside the window from the minimum to the maximum and change hardware rather than force the alignment past the ceiling.
For the actual tightening spec of a specific aircraft part, consult the aircraft maintenance manual; use this table as the FAA-source reference frame around it.
| AN bolt | Tap size | Dia (in) | Install torque (shear-loaded bolt) | Maximum allowable tightening | Lubricated max | ||
|---|---|---|---|---|---|---|---|
| Tension nutsMS20365 / AN310 · 40,000 psi | Shear nutsMS20364 / AN320 · 24,000 psi | Tension nutsMS20365 / AN310 · 90,000 psi | Shear nutsMS20364 / AN320 · 54,000 psi | ||||
| — | 8-36 | No. 8 | 12–15 | 7–9 | 20 | 12 | — |
| AN3 | 10-32 | 3/16 | 20–25 | 12–15 | 40 | 25 | — |
| AN4 | 1/4-28 | 1/4 | 50–70 | 30–40 | 100 | 60 | — |
| AN5 | 5/16-24 | 5/16 | 100–140 | 60–85 | 225 | 140 | — |
| AN6 | 3/8-24 | 3/8 | 160–190 | 95–110 | 390 | 240 | — |
| AN7 | 7/16-20 | 7/16 | 450–500 | 270–300 | 840 | 500 | — |
| AN8 | 1/2-20 | 1/2 | 480–690 | 290–410 | 1,100 | 660 | — |
| AN9 | 9/16-18 | 9/16 | 800–1,000 | 480–600 | 1,600 | 960 | — |
| AN10 | 5/8-18 | 5/8 | 1,100–1,300 | 600–780 | 2,400 | 1,400 | — |
| AN12 | 3/4-16 | 3/4 | 2,300–2,500 | 1,300–1,500 | 5,000 | 3,000 | — |
| AN14 | 7/8-14 | 7/8 | 2,500–3,000 | 1,500–1,800 | 7,000 | 4,200 | — |
| AN16 | 1-14 | 1 | 3,700–5,500 | 2,200–3,300* | 10,000 | 6,000 | — |
| AN18 | 1-1/8-12 | 1-1/8 | 5,000–7,000 | 3,000–4,200* | 15,000 | 9,000 | — |
| AN20 | 1-1/4-12 | 1-1/4 | 9,000–11,000 | 5,400–6,600* | 25,000 | 15,000 | — |
All values in inch-pounds (lb·in), exactly as published. The asterisked shear-installation values for 1-14, 1-1/8-12 and 1-1/4-12 carry the source’s own footnote “* Estimated corresponding values.” The 8-36 and 8-32 rows have no AN bolt equivalent (the smallest AN hex bolt is the AN3, No. 10); they appear because Table 7-1 prints them for smaller hardware. Source footnote reproduced from the AC: the values may be used for cadmium-plated steel nuts of the fine or coarse series that have approximately equal numbers of threads and equal face bearing areas.
The lubricated column is intentionally empty: AC 43.13-1B publishes a single set of values derived from oil-free cadmium-plated threads and defines no lubricated figures. Never convert them yourself — see the lubrication section below.
The coarse-series rows apply the same four limits to standard coarse threads from No. 8 through 7/8 inch. Standard AN airframe hex bolts are fine-thread hardware, so the AN column is empty here: these rows matter for other coarse-threaded hardware that shares the same nut families and cadmium-plated thread assumptions — and they are the values most often borrowed wrongly, because a coarse thread of the same nominal diameter delivers more clamp load per inch-pound than its fine-thread twin and therefore gets a lower ceiling.
| Tap size | Dia (in) | Install — tension nutsMS20365 / AN310 · 40,000 psi | Install — shear nutsMS20364 / AN320 · 24,000 psi | Max — tension nutsMS20365 / AN310 · 90,000 psi | Max — shear nutsMS20364 / AN320 · 54,000 psi |
|---|---|---|---|---|---|
| 8-32 | No. 8 | 12–15 | 7–9 | 20 | 12 |
| 10-24 | No. 10 | 20–25 | 12–15 | 35 | 21 |
| 1/4-20 | 1/4 | 40–50 | 25–30 | 75 | 45 |
| 5/16-18 | 5/16 | 80–90 | 48–55 | 160 | 100 |
| 3/8-16 | 3/8 | 160–185 | 95–100 | 275 | 170 |
| 7/16-14 | 7/16 | 235–255 | 140–155 | 475 | 280 |
| 1/2-13 | 1/2 | 400–480 | 240–290 | 880 | 520 |
| 9/16-12 | 9/16 | 500–700 | 300–420 | 1,100 | 650 |
| 5/8-11 | 5/8 | 700–900 | 420–540 | 1,500 | 900 |
| 3/4-10 | 3/4 | 1,150–1,600 | 700–950 | 2,500 | 1,500 |
| 7/8-9 | 7/8 | 2,200–3,000 | 1,300–1,800 | 4,600 | 2,700 |
Same source, same caution, same units — FAA AC 43.13-1B Table 7-1, coarse thread series. No lubricated variant exists in the source for these rows either.
Aviation hardware carries three overlapping families of part numbers, and reading them is the first skill you need before any torque value makes sense. AN (Army–Navy) numbers are the oldest of the three, dating to the wartime standardization that gave aviation its shared hardware language. An AN bolt number encodes its geometry in dashes: the first dash is the nominal diameter in sixteenths of an inch, so AN4 means 1/4 inch and AN20 means 1-1/4 inch; the second dash is the grip length, also in sixteenths, measured from under the head to the start of the thread shank. A trailing A marks an undrilled shank and an H prefix a drilled head for cotter-pin or safety-wire passing — which matters here because drilled-head bolts pair with castellated nuts and their min-to-max torque window.
One quirk of the dash system is worth memorizing: the AN bolt series runs AN3 through AN10 in consecutive sixteenths (3/16 through 5/8), then continues only on whole fractional diameters — AN12 is 3/4, AN14 is 7/8, AN16 is 1 inch, AN18 is 1-1/8, and AN20 is 1-1/4. There is no AN11 or AN13 hex bolt, because 11/16 and 13/16 are not airframe bolt diameters. The thread is fine series throughout: No. 10-32 on the smallest bolts, 1/4-28, 5/16-24, 3/8-24, 7/16-20, 1/2-20, 9/16-18, 5/8-18, 3/4-16, 7/8-14, 1-14, and 12-pitch threads on the largest two sizes.
NAS (National Aerospace Standard) numbers cover the close-tolerance and high-strength hardware that grew out of the AN system — internally and externally wrenching bolts, twelve-point tensile bolts, and the reamed-hole fasteners used where joints see severe load reversals and vibration. MS (Military Standard) numbers largely superseded the AN nut families: the castellated tension and shear nuts that pair with AN bolts appear in Table 7-1’s headers under both their AN and MS identities, which is why the columns read “MS20365 and AN310” or “MS20364 and AN320” rather than either name alone. AC 43.13-1B par. 7-36 adds the identification layer: head markings tell you the material (a raised dash or asterisk for steel, a single dash for corrosion-resistant steel, two dashes for aluminum alloy), a triangle marks a close-tolerance NAS bolt, and — critically — a bolt with no markings at all is low-strength hardware that does not belong in a structural joint.
| Part family | What it is | Torque guidance |
|---|---|---|
| AN3 – AN20 hex bolts | The classic general-purpose airframe bolt: cadmium-plated alloy steel (raised dash or asterisk on the head), corrosion-resistant steel (single dash), or aluminum alloy (two dashes). Fine (NF/UNF) threads throughout; the first dash number is the diameter in 1/16 inch, the second dash the grip in 1/16 inch, “A” marks an undrilled shank, “H” a drilled head. | Covered directly by the fine-thread rows of Table 7-1 on this page. |
| AN310 / MS20365 nuts (tension type) | Full-height castellated tension nuts — the AC pairs AN310 with its MS successor MS20365 in the tension columns, where the tightening stress allowed in the bolt is highest. | Read the tension-nut columns (40,000 psi installation / 90,000 psi maximum). |
| AN320 / MS20364 nuts (shear type) | Shorter castellated shear nuts. Being shallower, they cannot take the same tightening stress — the AC caps them at lower values in both the installation and maximum columns. | Read the shear-nut columns (24,000 psi installation / 54,000 psi maximum). |
| MS21250 twelve-point bolts | External-wrenching twelve-point high-tensile bolts used on commercial and military airframes, with fine and coarse thread variants and much higher strength classes than AN hardware. | No AC 43.13-1B dash-number value exists — torque comes from the aircraft SRM or the component's ICA. Table 7-1 must not be transplanted onto it. |
| MS24665 & other self-locking nuts | Prevailing-torque nuts (nylon-insert and all-metal families) that hold torque without a castle slot or cotter pin. Run-down drag counts against the wrench reading. | Final clamping torque = wrench reading minus prevailing (run-down) drag; reuse is limited by the AC's minimum prevailing-torque requirements. |
| NAS close-tolerance bolts | Per AC 43.13-1B par. 7-44: hex close-tolerance bolts (AN173–AN186), 100° countersunk close-tolerance high-strength bolts (NAS333–NAS340), and titanium close-tolerance series (NAS653–NAS658, NAS663–NAS668, NAS673–NAS678) for joints under severe load reversals and vibration. Reamed interference-fit holes; heads carry the triangle marking. | Torque per the aircraft manual; the AC's own torquing procedures (par. 7-40) apply, including warming a freezer-installed bolt to ambient temperature before torquing. |
Most torque charts the home mechanic meets are target charts: pick a value, pull the wrench, done. Aviation publishes something deliberately more cautious, and the difference is visible in Table 7-1’s own header language — maximum allowable tightening torque limits. Why would the FAA publish a ceiling rather than a number to aim for? Because on an aircraft, the torque operation itself is a load case. Every inch-pound delivered by the wrench twists the nut against friction and stretches the bolt into tension; the table’s column annotations state that residual stress outright — 90,000 psi in the bolt at the tension-nut maximum, 54,000 psi at the shear-nut maximum. The published ceiling is where the tightening-induced stress is considered acceptable for the hardware family, before any service load is added on top of it.
That is also why the table is written against nut type and thread series rather than against a job. A full-height tension nut (MS20365/AN310) tolerates more tightening stress than a shorter shear nut (MS20364/AN320), so the same AN6 bolt has two ceilings: 390 in-lb toward the tension nut and 240 in-lb toward the shear nut. And it is why the installation columns for shear-loaded bolts are separate: a bolt whose service life is spent in shear has its fatigue margin spent differently than one in tension, so the AC recommends lower, windowed installation ranges — 160–190 in-lb for that same AN6 with tension-type hardware — instead of inviting you to tighten right up to the maximum.
The second half of the philosophy is traceability of the wrench reading. Par. 7-40 of the AC builds the final torque in layers: run the nut down to near contact, measure the friction drag torque of turning it, then add the drag to the desired torque to get the “final torque” that the wrench should register. A self-locking nut’s prevailing drag subtracts in the other direction — the run-down effort is not clamping the joint, so it must come out of the reading. Add the AC’s instruction to apply torque to the nut rather than the bolt where possible, to pull smoothly (and back off and re-torque if the pull chatters), and the published number stops being a single fact and becomes a small procedure with the table as its boundary condition.
Finally, the philosophy is deliberately subordinate to the manufacturer. The AC’s own purpose statement says its methods are acceptable when there are no manufacturer maintenance instructions and not contrary to manufacturer data — and FAA AC 20-37E repeats the theme for engines: correct torquing procedures are given in the manufacturer’s service instructions. Table 7-1 is the reference frame; the airframe or engine manual is the authority. Study the table, then look up the aircraft.
Torque is a load case, not just a numberPhoto: UnsplashFAA mechanic-general tests have long asked what “torque values for aircraft bolts normally consider,” and the credited answer is that they consider the threads to be clean and dry — mirroring par. 7-40.b and the Table 7-1 caution about oil-free cadmium-plated threads. The published numbers are conditional on thread condition; that is the sentence’s whole meaning.
Ask any forum “do I reduce the torque if I oil the threads?” and you will get a confident percentage. The FAA’s published position is more careful. Table 7-1 carries a caution in capital letters: its values are derived from oil-free cadmium-plated threads — that is, clean hardware in as-plated condition, which is what par. 7-40.b means when it tells you to be sure the bolt and nut threads are clean and dry unless the manufacturer specifies otherwise. The table defines no lubricated variant. That is why the lubricated column above is a row of em dashes: the honest transcription of a value the source never published, and a deliberate speed bump against the reflex to multiply the dry figure by 0.8 and call it data.
The physics behind the caution is uncontroversial. A wrench reading splits into three sinks: thread friction, bearing-face friction, and actual bolt stretch. Lubricating the threads shrinks the two friction sinks, so the same inch-pounds convert into more bolt tension — sometimes dramatically more. A lubricated joint pulled to a dry-thread value can therefore sit near or past the very ceiling the table exists to enforce, which is the failure direction the psi annotations are guarding. The reverse error is quieter: reducing by an unverified factor and leaving the joint under-clamped, which par. 7-40 flags from the other side as undertorque that lets nuts and bolts work loose through wear.
So what is the correct procedure when a joint genuinely runs wet — engine cases, propeller attachment hardware, anything the manual calls out with lubricant? Use the manufacturer’s wet torque value, which exists precisely because the combination of bolt, nut, lubricant, and plating is a system. FAA AC 20-37E makes the generalization impossible in one sentence: the use of dry or lubricated bolt threads for torquing purposes is not standardized and may change from one engine to another using the same propeller. If the manual is silent and the hardware matches the table’s assumptions, the table’s clean-and-dry values are the FAA-recognized frame; anything beyond that belongs to approved data, not to a rule of thumb.
A calibrated wrench, a clean thread, a ceilingPhoto: UnsplashThe castle nut is where the torque chart stops being a single number and becomes a window with a mechanical ending. A castellated nut (AN310 tension, AN320 shear, or their MS equivalents) must be safetyed with a cotter pin through the bolt’s drilled shank, and the nut’s castellations must line up with that hole at the final torque. Par. 7-40.f gives the procedure: start alignment with the cotter-pin hole at the minimum recommended torque plus friction drag, then tighten within the range until a slot lines up. The note that follows is the part people get wrong: do not exceed the maximum torque plus friction drag even if the hole and castellation still refuse to align — the remedy is to change the washer or the nut and try again, because the maximum is a stress ceiling, not a suggestion with negotiation room. And once the pin is in, safetying rules apply: par. 7-38 requires all bolts and nuts to be locked or safetied (self-locking nuts excepted by design), and cotter pins and safety wire are never reused.
Self-locking nuts move the problem from alignment to drag. Because their locking feature resists rotation before the bearing face ever touches, the run-down effort — the prevailing torque — rides inside your wrench reading without clamping anything. The effective clamping torque is the wrench reading minus the prevailing drag, which is why the AC’s Table 7-1 ceiling has to be approached with that subtraction in hand and why the AC publishes separate minimum prevailing-torque requirements for re-used self-locking nuts: a nut whose locking feature has worn below the minimum no longer holds torque, and it is discarded rather than re-tightened. Par. 7-38’s exemption of self-locking nuts from cotter-pin safetying is conditional on that locking feature actually working.
Reuse rules for the bolts themselves lean on the same caution. The AC’s torquing note records that many aircraft and engine applications require stretch checks prior to reuse, “due primarily to bolt stretching caused by overtorquing” — a reminder that the ceiling in the table exists because exceeding it does permanent, measurable damage. Grip length should be re-verified on the bolt rather than trusted from a parts manual (par. 7-37’s advice to measure before ordering), washers used to make up grip are limited to 1/8 inch of combined height, and every installation should still show at least one thread protruding through the nut when finished.
Not every airframe bolt lives in a normal clearance-fit hole. Par. 7-44 of the AC describes the close-tolerance families — hex machine bolts AN173 through AN186, countersunk high-strength bolts NAS333 through NAS340, and the titanium close-tolerance series NAS653–NAS658, NAS663–668 and NAS673–678 — used where two parts bolted together face severe load reversals and vibration. These bolts are installed in reamed holes with an interference fit; the AC notes they may need light tapping to seat, and that chilling the bolt in a freezer before installation can ease the friction — with the explicit caution to let the bolt warm back to ambient temperature before torquing. The point for this page: a tight-fit joint changes the friction picture around the nut as well, so the manual’s value, not a transplanted table cell, governs the wrench.
The other half of the reliability story is the wrench itself. Par. 7-40.a requires calibration at least once a year, or immediately after the wrench has been abused or dropped — a schedule with teeth in it, because an uncalibrated clicker can be confidently wrong in the direction that over-stretches bolts. Par. 7-40.h extends the same discipline to geometry: any adapter that changes the effective length of the wrench changes the delivered torque, so the wrench indication or setting must be corrected with the adapter installed, using the calculation the AC illustrates with its figure 7-2. And the note that opens the whole torquing paragraph draws the line that keeps charts honest: be sure the torque applied is for the size of the bolt shank, not the wrench size — a reminder that threads at the shank diameter are what carry the load, and that a chart keyed to wrench sizes is already the wrong chart.
Bolt fit ties the two threads together. Par. 7-39 permits, generally, the first lettered drill size larger than the nominal bolt diameter for bolt holes — but excepts AN hex bolts in light-drive (reamed) applications and the NAS close-tolerance and clevis bolts, defines a light-drive fit as an interference of 0.0006 inch on a 5/8-inch bolt, and directs anyone considering drilling or reaming a hole in a critical structural member to consult the manufacturer’s structural repair manual, the manufacturer’s engineering department, or the FAA first. Hole condition, bolt family, and torque ceiling are one conversation.
The most common home-shop habit the AC contradicts is pulling to the chart value and stopping. Par. 7-40.c–d makes the friction drag part of the final reading for plain nuts, and par. 7-40.g repeats it when torque is applied to bolt heads or capscrews. The chart value is the desired torque; the wrench shows desired plus drag.
Four limits exist per size, and the differences are not decoration: the AN6 maximum is 390 in-lb with tension-type nuts but 240 in-lb with shear-type nuts. Choosing the wrong column is the classic lookup error — identify the nut on the joint first, then read.
The source footnote limits the values to cadmium-plated steel nuts with approximately equal threads and bearing areas — and the printed ranges themselves are not smooth (the 7/16-20 row overlaps the 1/2-20 row). Interpolating between rows, or converting dry to lubricated with a personal factor, produces numbers no authority recognizes.
Par. 7-36’s marking system is the entry gate to the table: steel, CRES, or aluminum alloy; a triangle for NAS close-tolerance bolts; and no markings at all meaning low-strength hardware. A torque ceiling only protects a bolt that is actually the bolt you think it is.
The aviation ceiling philosophy contrasts usefully with the commercial world, where torque tables publish target values by grade marking. Compare the two regimes side by side in our bolt torque spec chart (SAE grade and metric class hardware), check head and wrench sizes in the hex bolt & nut dimensions chart, or start from the calculator hub on our homepage for preload and strength work. Every guide lives on the guides index.
The lookup questions this chart gets most — answered strictly from AC 43.13-1B and companion FAA material.
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