The Leveling Foot That Compressed
We bolted a machine (a 500 kg press) on four leveling feet (article 118). On the bench, the feet held. On the floor (after a week), the feet compressed (the rubber pad flattened). The machine tilted (one foot sank 2 mm). The press wasn’t level (the parts shifted). The problem: the feet were under-sized (the load per foot was over the rating). The press is 500 kg. On four feet, that’s 125 kg per foot. The feet were rated for 100 kg each. They compressed. We upsized the feet (rated for 250 kg each). The machine stayed level. The mistake was choosing the smallest foot “to fit the frame.” The foot must carry the load.
Leveling foot load rating picks the foot for the weight. This article covers the sizing.
The Load Per Foot
A machine on four feet distributes the load. But the load isn’t equal (the machine isn’t perfectly balanced). One foot might take more (the heavy side). Size each foot for the worst case (not the average).
Load per foot = total weight / 4 × 1.5 (margin)
For a 500 kg machine: 500 / 4 = 125 kg average. With 1.5 margin: 187.5 kg per foot. Pick a foot rated for 250 kg (or more). The feet that compressed were rated for 100 kg (under the load).
The foot load rule: Load per foot = total weight / 4 × 1.5 (margin). The feet that compressed were rated 100 kg on a 500 kg machine (125 kg average). Upsize to 250 kg each. The foot must carry the load (with margin). Don’t choose the smallest foot that fits the frame.
Step 1: The Foot’s Rating
A leveling foot (article 118) has a load rating (kg, or N). The rating includes the rubber pad (which compresses under load). A cheap foot (thin rubber) compresses (the pad squashes). A heavy-duty foot (thick rubber, a steel stud) carries the load without compression. For a heavy machine (500+ kg), use a heavy-duty foot.
Step 2: The Stud (Thread)
The foot’s stud (the bolt that adjusts the level) has a thread size (M12, M16, M20). The thread must match the load (a M12 stud on a 500 kg machine is fine; a M8 stud is too small). For a heavy machine, use M16 or M20 (stronger stud). The stud also adjusts the level (article 118) — it must be long enough (to level on an uneven floor).
Step 3: The Base (Swivel)
Some feet are swivel (the base pivots to match the floor). For a sloped or uneven floor, a swivel foot contacts the floor fully. For a flat floor, a fixed foot is fine. The swivel adds a little cost but helps on uneven floors.
Step 4: Anchor (Article 162)
For a precision machine (or a vibrating one, article 162), anchor the feet to the floor (bolts in concrete). The leveling foot adjusts, then the anchor bolt holds it. For a light machine (a guard), no anchor (it just sits). For a heavy precision machine, anchor it.
| Machine Weight | Load/Foot (avg × 1.5) | Foot Rating |
|---|---|---|
| 100 kg (light) | 37.5 kg | 50 kg (M8) |
| 500 kg (medium) | 187.5 kg | 250 kg (M16) |
| 1000 kg (heavy) | 375 kg | 500 kg (M20) |
| 2000 kg (very heavy) | 750 kg | 1000 kg (M24+) |
A Foot Sizing Checklist
- What is the machine weight? (kg?)
- How many feet? (4?)
- Load per foot = weight / 4 × 1.5?
- Is the foot rated for that? (Margin?)
- Is the stud size right? (M12–M20?)
- Is the stud long enough? (Uneven floor?)
- Is the base swivel? (Uneven floor?)
- Does the foot compress? (Overloaded?)
- Does the machine stay level? (Check?)
- Is the foot anchored? (Precision? Article 162?)
The Bottom Line
Leveling foot load rating picks the foot for the weight. The feet that compressed were rated 100 kg on a 500 kg machine. Calculate load per foot = weight/4 × 1.5. Upsize the foot (and stud). For precision, anchor it. The machine that stayed level wasn’t the smallest foot — it was rated for the load.
