What AC 43.13-1B says about torque
| Topic | What the AC says | Source |
|---|---|---|
| Why it matters | Undertorque wears nuts, bolts and the parts they secure. Overtorque can fail a bolt or nut by overstressing the threads. | AC 43.13-1B ¶7-40, p. 7-6 |
| Calibration | Calibrate the wrench at least once a year, or immediately after it has been abused or dropped. | ¶7-40a, p. 7-6 |
| Which size | Torque is for the size of the bolt shank, not the wrench size. | ¶7-40 note, p. 7-6 |
| Friction drag | Run the nut down near contact, measure the drag torque, and add it to the desired torque. The sum is the final torque, which should register on the indicator or setting for a snap-over type wrench. | ¶7-40c-d, pp. 7-6, 7-7 |
| Technique | Apply a smooth, even pull. If it chatters or jerks near final torque, back the nut off and retorque. | ¶7-40e, p. 7-7 |
| Adapters | Anything that changes the effective length of the wrench changes the reading or setting. Work it out as in Figure 7-2. | ¶7-40h, p. 7-7; Fig. 7-2, p. 7-8 |
| Default values | Table 7-1 gives torque for standard nut and bolt combinations when the manufacturer gives none. Examples for tension-type nuts (MS20365, AN310): 10-32 is 20-25 in-lb, 1/4-28 is 50-70, 5/16-24 is 100-140, 3/8-24 is 160-190. | ¶7-40i; Table 7-1, p. 7-9 |
Six torque wrenches, by the numbers
| Wrench | Type (as listed) | Drive | Range | Accuracy as listed | Where |
|---|---|---|---|---|---|
| Tekton 90-tooth dual-direction (12-06872) | Micrometer, mechanical click | 1/4" | 20-200 in-lb; 1 in-lb increment | ±3% CW and CCW | US · Aircraft Spruce |
| Micrometer Type Torque Wrench (15-05531, 97351A) | Micrometer | 3/8" ratchet | 25-250 in-lb (3.61-29.03 Nm) | ±4% right-hand, ±6% left-hand, 20-100% of capacity | US · Aircraft Spruce |
| Drive Torque Wrench With Case | Micrometer, economy | 3/8" and 1/2" | 3/8": 20-200 in-lb; 1/2": 10-150 ft-lb | Not stated; calibrated at manufacture, cannot be recalibrated | US · Aircraft Spruce |
| Dial Type, 300 lb-in (12-00531) | Dial, memory pointer | 3/8" square | 0-300 lb-in | ±2% of reading, 60-300 lb-in | US · Aircraft Spruce |
| Dial Type, 600 lb-in (12-00532) | Dial, memory pointer | 3/8" square | 0-600 lb-in and 0-50 lb-ft | ±2% of reading, 120-600 lb-in | US · Aircraft Spruce |
| Tekton 72-tooth split beam (12-06797) | Split beam, click-type | 3/8" | 20-100 ft-lb; 2 ft-lb increment | Specified on each calibration certificate | US · Aircraft Spruce |
As Aircraft Spruce lists them, no prices. Each name links to the seller's own page, read 28 October 2026. "Not stated" means the listing does not give it.
Click, dial, beam: what the AC and the listings say
The AC names two kinds of reading. It talks about the final torque registering "on the indicator" or on the "setting for a snap-over type" wrench. That is the click (snap-over) wrench, set to a value, against the wrench that shows a reading. It does not describe beam wrenches or rank any type.
Click. The Tekton 90-tooth lists "Mechanical Click" feedback with a 1 in-lb increment. A click wrench is set to the final torque, so friction drag has to be added to the setting before you start.
Dial. The two dial wrenches in the table read continuously and carry a memory pointer that holds the highest torque reached. That makes the friction-drag reading in the AC procedure a direct read-off.
Beam. No plain beam wrench in inch-pounds turned up on the Aircraft Spruce pages we read. The one listing called a beam, the Tekton 72-tooth, is a split beam click-type in foot-pounds, too coarse for small AN hardware.
Pick the range from the hardware
Match the scale to Table 7-1. The 10-32 bolt of an AN3 sits at 20-25 in-lb, the 1/4-28 of an AN4 at 50-70 and the 5/16-24 of an AN5 at 100-140. A 25-250 in-lb wrench starts at the top of the 10-32 range.
Accuracy is quoted over part of the scale. The 300 lb-in dial lists its 2% from 60 to 300; the 600 lb-in dial from 120 to 600; the 97351A micrometer from 20 to 100 percent of capacity. A target in the lower fifth of a dial sits outside the stated accuracy.
Adding friction drag raises the setting. The final torque is the target plus drag, so the setting must stay inside the wrench's range with the drag added.
Check that it can be recalibrated. The AC asks for yearly calibration. One economy wrench in the table is listed as calibrated at manufacture and not recalibratable.
Questions people actually ask
Click or dial torque wrench for aircraft work?
The AC does not choose. It describes both a wrench with an indicator and a snap-over type with a setting, and the same procedure applies to either. In the listings, a dial wrench reads the friction drag directly and keeps the highest value; a click wrench is set to the final value. Pick on the range of the hardware first.
What torque wrench range for AN bolts?
Table 7-1 puts the AN3 (10-32) at 20-25 in-lb, the AN4 (1/4-28) at 50-70 and the AN5 (5/16-24) at 100-140 for tension-type nuts, when the manufacturer gives no value. The manufacturer's value always comes first. A 20-200 in-lb wrench covers those three; larger bolts move into foot-pounds.
How often must a torque wrench be calibrated?
AC 43.13-1B ¶7-40a says at least once a year, or immediately after it has been abused or dropped. A shop's quality system may set a shorter interval.
Do I need to adjust for a crowfoot or extension?
Yes, whenever the adapter changes the effective length of the wrench. AC 43.13-1B ¶7-40h and Figure 7-2 give the correction, and the torque wrench extension calculator does the arithmetic.
Limits of this guide
A comparison of published figures and FAA guidance.
- No wrench was tested. Repeatability, click feel and durability are not in a listing. The site has no named technical reviewer yet, so there is no shop verdict.
- The Airframe Handbook, Volume 1, has no torque-wrench section. This guide draws on AC 43.13-1B Chapter 7, the FAA's own text for the procedure.
- Accuracy figures are the seller's. They are not a calibration certificate.
- Beam wrenches are not covered in the table. None in inch-pounds was found on the pages read.
- Listings change. The seller's live page is the current one. The manufacturer's manual sets the actual torque.
Sources
- FAA AC 43.13-1B CHG 1, Chapter 7, ¶7-40, Figure 7-2 and Table 7-1 — pp. 7-6 to 7-9: calibration, friction drag, technique, adapters and the default torque values.
- Aircraft Spruce listings — every wrench in the table, via the linked product pages on aircraftspruce.com, read 28 October 2026.