What the FAA Handbook says
| Machine | What the Handbook says | Source |
|---|---|---|
| Bar folder | For hems, flanges, seams and edges. Most have a capacity of up to 22 gauge and 42 inches. Positive stops at 45° and 90°. | Handbook pp. 4-21, 4-22 |
| Cornice brake | Sheet passes through the jaws front to rear, so the bend can be as wide as the bed. Standard capacity 12 to 22 gauge, bending lengths 3 to 12 ft; capacity depends on the thickness of the bending leaf bars. | Handbook p. 4-22 |
| Box and pan (finger) brake | No solid upper jaw: the steel fingers of varying widths come off, so boxes and pans can be formed. Finger noses have a small radius and often need custom nose-radius shims for the full bend length. | Handbook pp. 4-22, 4-23 |
| Press brake | Cornice and box-and-pan brakes are limited to about 0.090 in annealed aluminum, 0.063 in 7075-T6 or 0.063 in stainless. Thicker or more complex parts go on a press brake with punch and die. | Handbook p. 4-23 |
| Spring-back | A 90° bend on a cornice brake probably forms 87° to 88°, so set the brake to about 93°. Small radii that crack in the tempered state are formed annealed, then heat treated. | Handbook pp. 4-21, 4-22 |
Four benders, as listed
| Tool | Type | Listed spec | Where |
|---|---|---|---|
| Hand Seamer 04-44 (12-03751) | Hand seamer | Jaw 1" D × 3-1/2" W; 8" long; radius not stated | US · Aircraft Spruce |
| Hand Seamer No. 44, 44R, 793 (12-00620) | Hand seamer | 3-1/2" wide, drop-forged steel; 44R has a radius for aluminum; 793 has an adjustable depth gauge; the listing does not say which one 12-00620 is | US · Aircraft Spruce |
| Hand Seamer / 3.5 Jaw (12-00608) | Locking hand seamer | Jaws 3/16" × 1" × 3-1/2" (axes not labelled); machined radius; Vise-Grip locking; stainless jaws; for rib and bulkhead flanges | US · Aircraft Spruce |
| Tennsmith Hand Brake and Stand (12-20700) | Hand brake | Up to 48" wide; mild steel 22 ga and lighter; brake 280 lb, stand 95 lb; aluminum not listed | 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.
How to choose, per the FAA Handbook
Capacity is stated in gauge and length. The brake's width and the leaf bar set what it can bend. Check the listing for both, and for the metal it was rated on.
A brake rated for steel is not rated for 2024. The Handbook's limits are for annealed aluminum and 7075-T6; a listing in mild steel gauge is a different number.
Box-and-pan before cornice for flanged parts. The finger brake does everything the cornice brake does, plus boxes and pans, because fingers can be removed.
Radius is the aluminum question. The Handbook says material that cracks when cold-formed over small radii should be formed annealed. The minimum radius for the alloy and thickness is on the bend radius chart, and the flat-pattern length from it on the bend allowance calculator.
What the listings add
The hand seamer is not in the Handbook. It is a hand tool, not a brake; Aircraft Spruce lists one for straightening and bending rib and bulkhead flanges. The listings give jaw size.
Radius is stated on some, not all. Aircraft Spruce lists the No. 44R with a radius to prevent tearing of aluminum, and the 3.5" Jaw with a machined radius. The 04-44 does not state one.
The hand brake lists steel only. The Tennsmith is rated for mild steel in 22 gauge and lighter and bends material up to 48 in wide. The listing gives no aluminum capacity, so use the Handbook's aluminum figures with the maker.
Questions people actually ask
Hand seamer or brake for repair parts?
Aircraft Spruce lists a seamer for straightening and bending rib and bulkhead flanges. A long straight flange is the brake's and bar folder's job: the Handbook describes both as clamping the sheet along the bend line.
What thickness can a hand brake bend in aluminum?
The Handbook puts cornice and box-and-pan brakes at about 0.090 in annealed aluminum or 0.063 in 7075-T6, but a given machine's capacity is set by its maker. The Tennsmith listing states steel gauges only.
How do I allow for spring-back?
The Handbook's example: a 90° setting forms about 87° to 88°, so set about 93°. The amount depends on alloy, temper and radius; test on scrap of the same sheet.
What is a radius bar?
The Handbook does not use the term. It describes the nose radius of the finger brake's clamping fingers, which is small and may need custom shims. No radius bar or nose-bar product was found in the listings read.
Limits of this guide
A comparison of published figures and FAA guidance.
- No tool was tested. Bend quality and parallel fit are not in a listing. The site has no named technical reviewer yet, so there is no shop verdict.
- Only four tools are listed. Brakes in aluminum capacity were not found in the three shops; the table is what exists with a stated spec.
- Capacity here is not an approval. The repair data states the bend radius and the temper for the part.
- Listings change. The seller's live page is the current one.
Sources
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 4 — pp. 4-21 to 4-23: forming tools, bar folder, cornice brake, box and pan brake, press brake, spring-back.
- Aircraft Spruce listings — every figure in the table, via the linked product pages on aircraftspruce.com, read 28 October 2026.