PA-012 Hand-turned exterior jar inspection cradle

Rotate a cool sealed jar gently to read its exterior label or inspect its outside without sliding the glass along a rough table.

Original bounded component build. Dimensions describe this example, not an approved structural, occupied-building or universal fit design. Unbuilt / untested. US customary dimensions control.

Before cutting

• Read the whole assembly and inspect its receiving space before cutting. Measure actual sheet thickness; nominal lumber labels do not control these joints.
• Set aside straight, clean stock and allow it to acclimate. Keep fingers clear of blades, clamp work and use tool-appropriate eye/hearing protection.
• Dry-fit moving pieces before final fastening; stop if a proposed dimensional substitution changes clearances. Purchased hardware dimensions and hole patterns below must match the actual item.

Materials and actual cuts

Hardware and tools

• 6 x #8 x 1 1/4 in wood screw. A into feet
• 6 x #8 x 1 1/2 in wood screw. Feet into cheeks
• 4 x 1/4 in x 1 1/2 in hex-head lag screw. Plain roller journals; no rated bearing claim
• 4 x 1/4 in ID nylon thrust washer,actual 1/32 in thick. Two per roller; do not substitute an unmeasured nominal stack

Tape, square, pencil; clamped saw setup appropriate to the material; drill/driver and depth stop; countersink for wood fasteners; files/sanding block; clamps. Specific additional tools are noted in the steps.

Measured assembly reference

x=left/right, y=front/rear, z=up; origin is front-left underside unless stated

Retained segments with the same part/instance belong to one machined stock piece, not additional parts. Positions and sizes below are US inches; rotations are degrees.

Numbered assembly

1. Use only cool intact cylindrical jars with body diameter 3 1/2-5 in and axial length no more than 8 in, tested empty first. Keep both hands near the jar; this cradle is not a lid-opening device.
2. Cut A 12 x 9 x 3/4 in, B two 9 x 3 x 3/4 in and D two 9 x 1 1/2 x 3/4 in feet. Cut C two 8 15/16 in lengths of 3/4 in round hardwood dowel.
3. Mark B bearing axes 1 1/2 in above its lower edge and 2 1/2 and 6 1/2 in from one 9 in end. Both cheeks must carry the same pattern.
4. Clamp B together and drill 9/32 in through-holes at all four marks. Separate, deburr and confirm that a 1/4 in bolt slides freely without enlarging the hole into a slot.
5. Drill a centered lag pilot 1 in deep in each C end using the actual lag manufacturer's root-diameter guidance for the selected hardwood; test on scrap first. Reject any split or off-center bore rather than assuming one pilot fits all wood.
6. Before placing anything on A, assemble each B/D pair with D underside accessible. Set B on D at the shown lateral offset: left B x 3/4-1 1/2 on left D x 0-1 1/2 in; right B x 10 1/2-11 1/4 on right D x 10 1/2-12 in. Drive three #8 x 1 1/2 in screws upward through each 3/4 in D into B bottom edge at y 1,4 1/2,8 in. Center these at x 1 1/8 in left and x 10 7/8 in right; the 3/4 in bite runs up the 3 in cheek height. Countersink the D underside heads flush.
7. Now place the two B/D subassemblies on A with feet at x 0-1 1/2 and 10 1/2-12 in,y 0-9 in. From beneath A fasten into D with three #8 x 1 1/4 in screws per foot at y 1,4 1/2,8 in, x 3/8 in left and 11 5/8 in right. These axes are 3/4 in from the cheek screws and clear their flush heads. Each crosses A 3/4 in and bites D 1/2 in, leaving 1/4 in below the D top. Verify 9 in between cheek inside faces before installing rollers.
8. Set each C between B at z 3 in,y 2 1/2 or 6 1/2 in, with a measured 1/32 in nylon washer at each end. The specified 8 15/16 in roller plus 1/16 in total washers fits the 9 in inside span; reject an incompatible actual stack.
9. Drive one 1/4 in x 1 1/2 in lag screw through each cheek bearing hole and washer into the roller pilot. Tighten until supported, then back off enough for free hand rotation; do not crush or split the dowel end.
10. Turn both rollers through twenty revolutions. Any wobble, rubbing or screw loosening requires correction before a jar is placed on them; these are plain bearings, not rated machinery.
11. Place an empty matching jar horizontally across both rollers with its long axis parallel to x. Roll it a small amount by hand while preventing it from leaving either end.
12. Use only for exterior label viewing on a level table. Lift jars out before carrying the cradle and keep the roller surfaces clean/dry; stop if glass can strike a cheek or the base.

Checks

• Bearing holes share z 3 in assembled height and y 2 1/2/6 1/2 in centers.
• Actual roller length includes the measured washer clearance between cheeks.
• Both rollers turn by hand without end splitting or loose lag screws.
• An empty matching 3 1/2-5 in body-diameter jar, no more than 8 in long, rests on both rollers and stays under manual control.

Use and maintenance

Exterior inspection only; not a lid-opening clamp, hot-jar carrier or food-safety test.

Keep hands on the jar. Rollers provide no automatic end restraint or load certification.

Keep the rollers dry and clean only their exterior by the actual finish/material guidance. Remove jars before checking any journal or base screw.

Inspect lag pilots for splitting and recheck free hand rotation/washer clearance. To access cheek screws, remove the base-to-foot screws first and support the B/D subassembly; do not pry a cheek off the closed base.

Measured interface notes

Order is B-to-D first, then D-to-A. Cheek screw x 1 1/8 /10 7/8 in and base screw x 3/8 /11 5/8 in remain 3/4 in apart; no inaccessible screw must be driven after the base closes the underside.

Primary context

Purdue University Extension: Wood drying: FNR-37 Source

Utah State University Extension: Food Storage in Home Source

King Plastic Corporation: Food Service sheet materials Source