Guides / Parts / Design for Manufacture

Isolation Feet and Spikes: Threads, Materials and Finish

July 14, 2026

Feet are the last thing designed and the first thing the customer touches when they lift the box. They are also where a beautifully finished product picks up its worst reviews, because a foot that marks a shelf or a levelling screw that seizes is remembered longer than a good faceplate.

Thread selection

The thread is both the levelling mechanism and the load path.

Thread	Load capability in aluminum	Use
M4	Light only	Small DACs, headphone amps
M6	Moderate	Most source components
M8	High	Amplifiers, anything over about 10 kg
M8 x 1.25	High	The de facto standard in aftermarket hi-fi feet
1/4-20 UNC	High	North American market compatibility

Two rules that prevent the common failures:

1. Thread engagement of at least 1.5 times the diameter in aluminum, 2 times if the part gets adjusted often. A 10 mm deep M8 in a 6061 base plate is fine. A 5 mm deep one will strip the third time someone levels it.
2. Do not run an aluminum stud into an aluminum boss. Aluminum on aluminum galls, and a galled levelling foot is permanently stuck. Use a steel or a stainless stud, or fit a threaded insert.

Levelling

If the foot is adjustable, the drawing has to define the range and the locking.

• Range: 5 to 10 mm of adjustment covers almost any shelf. More than that and the foot starts looking spindly.
• Lock nut: a knurled or hex lock nut is the conventional answer and it works. Specify whether it is captive.
• Access: the user has to turn something. A knurled band on the foot itself, a flat for a spanner or a hex in the base. Decide, because an adjustable foot nobody can grip is not adjustable.
• Feel: a nylon patch or a thread locking compound keeps a foot from wandering without needing a lock nut. On a lighter component this is a cleaner solution.

Tip design

This is where the product’s claims and its materials have to agree.

Spike, meant to penetrate carpet and couple to the floor. The tip is a genuine point, typically 60 to 90 degrees included angle, and it must be hard. Stainless 303 or 304, or a hardened steel tip pressed into a decorative body. An aluminum point rounds over on the first move.

Cone, meant to present a small contact area. A small flat or a radius at the tip rather than a point, usually 1 to 3 mm. Safer on hard floors, no marking, no penetration. Aluminum or brass is fine.

Flat foot with a compliant layer. An elastomer, sorbothane or felt disc recessed into the base. The recess matters: a pad glued to a flat base peels off, a pad in a 0.5 mm deep recess stays put.

Protector disc. A separate hardened cup that sits between the spike and the floor. If your product ships spikes, ship discs with them.

Damping inserts

Many feet use a two part construction: a machined outer body with a damping element inside, typically an elastomer ring, a sorbothane puck or a small steel ball in a seat.

Manufacturing consequences:

• The insert pocket needs a tolerance that fits the element. Elastomers vary batch to batch more than metal does, so leave room.
• Assembly is a manual operation. Price it.
• If the element is visible from the side, it becomes a cosmetic feature and needs its own specification.
• If the element compresses under load, the installed height is not the machined height. State the loaded height on the drawing if it matters for the product’s overall stance.

Finish

Feet are small, handled and near the floor, which is a demanding combination.

• Black anodized aluminum is the default and is nearly always right.
• Brass, polished and lacquered, looks superb and needs the handling discipline that brass always needs.
• Stainless, bead blasted, for spikes, because it is hard and does not need coating.
• Knurled grip bands on the adjustment ring need a deburr operation. A sharp knurl on a part the customer grips is a genuine complaint.

Rack points on a small threaded part are easy: the finisher can rack through the thread. Say so on the drawing, and say the thread is masked or chased after finishing so the anodize does not tighten the fit.

The set is the part

Four feet under one component have to match: same height within a few hundredths, same colour, same texture, same knurl. A single foot that is 0.2 mm shorter makes the component rock, which is the most noticeable possible defect in a product whose whole claim is stability.

SUPPLY AS A MATCHED SET OF 4.
HEIGHT VARIATION WITHIN A SET: 0.05 mm MAX.
FINISH ALL FOUR IN ONE LOAD.
PACK AS A SET. DO NOT MIX BETWEEN BATCHES.

A drawing checklist

• Thread size, pitch, depth and material of the mating boss
• Whether the stud is separate and what it is made from
• Levelling range and lock method
• Tip geometry, including the included angle if it is a spike
• Tip material and hardness if it must bite
• Insert pocket dimensions and the element part number
• Loaded height, if the foot compresses
• Grip feature and its deburr requirement
• Base pad recess and the pad specification
• Set matching requirement and height variation limit
• Which faces are cosmetic, and that the thread is masked during finishing

Frequently asked questions

Keep reading

• How a CNC Volume Knob Is Made and What Drives Its Price
• What a Turntable Platter Needs From the Shop That Machines It
• Machining Headphone Cups and Yokes That Match Left to Right

This guide is part of Knobs, Platters, Cups and Feet, one of four sections in the guide library.