Rounded-mandrel ground-layer pin forming jig

OR-004 / Bend a repeatable smooth U-shaped ground-layer pin around two small mandrels, keeping bend radius and leg spacing controlled instead of making sharp hand-plier corners.

Capacity and fit

One pin per cycle from annealed 1/8 in stainless wire. Target centerline straight top span 3 in, bend centerline radius 1/4 in, straight legs 6 in. Approximate outside width 3 5/8 in and height 6 5/16 in; finished tolerance 1/16 in.

Limits

Pins hold a suitable low branch near soil; they must not clamp bark. Select the crop and layering procedure separately.

No fence, anchor or lifting capacity. Do not bend spring-tempered wire, galvanized fence wire of unknown temper or wire with sharp burrs.

Hardware

Two purchased steel spacers: 1 in long, 3/8 in OD, 1/4 in bore, smooth outside

Two 1/4-20 x 2 1/2 in bolts, four washers and two locknuts

Annealed 1/8 in stainless wire, cut 15 13/16 in per pin; one pin is an output of this jig, not another counted project

Two bench clamps; two end caps or rounded covers for exposed bolt threads

Tools

Tape measure and combination square

Pencil, clamps and safety glasses

Saw with wood blade; drill/driver and piloting bits

120- and 180-grit abrasive

Wire cutters rated for the selected stainless wire

Two smooth-jaw bending pliers and a fine file

9/32 in drill bit

Fasteners

Mandrel bolts pass through 3/4 in base plus 1 in spacers; washers and locknuts complete the stack. The wire is bent around smooth spacers, not bare threads.

Cut list

Build sequence

1. Cut the base and mark its front edge. The pin legs will extend past this edge during bending; leave clear bench space below it.
2. Mark both mandrel centers at y = 4 in, x = 3 1/4 and 6 1/4 in. Their 3 in center spacing sets the straight top span.
3. Drill both 9/32 in holes perpendicular to the base. Deburr and confirm the 1/4 in bolts pass without force.
4. Insert bolts from below with washers. Fit smooth 1 in spacers above the base, then washers and locknuts; tighten without crushing the plywood.
5. Cover exposed bolt threads above the nuts. Check the working 1 in spacer height is smooth and free of burrs.
6. Clamp the base at both rear corners. Cut one 15 13/16 in length of annealed wire with rated cutters and file both ends hemispherically smooth.
7. Mark the wire midpoint and align it halfway between mandrels on their far side. Keep the wire flat against the base.
8. Bend each side around its mandrel with smooth-jaw pliers, making two approximately 90 degree corners. A 3/8 in mandrel plus 1/8 in wire gives a 1/4 in centerline bend radius.
9. Remove the pin, compare leg lengths and trim only enough to equalize them within 1/16 in. File new ends smooth and check the approximate outside dimensions.
10. Trial the pin in loose soil over a scrap dowel. Stop insertion while a clear gap remains above the dowel; then use only with an appropriate low branch and check it does not rub bark.

Acceptance checks

Mandrel centers are 3 in apart; both are vertical and cannot rotate loose under hand bending.

Pin legs are parallel, ends smooth and not pointed toward exposed footpaths.

Installed pin retains clearance over the branch and does not pinch it as the soil settles.

Use

Push by hand into prepared loose soil; do not hammer the pin or use it to pull a branch downward forcibly. Mark its location to avoid stepping on it.

Care

Remove after rooting or when no longer required, wash soil off and inspect for kinks or sharp corrosion. Retighten jig hardware as needed.

Dimensioned drawings

Sources and testing

Not performed; no load rating, animal acceptance, yield or durability performance is claimed.

How to Propagate Shrubs by Layering - Simple/tip and mound-layering context. No hormone, fertilizer or universal rooting schedule supplied.