Gear 30 vs Gear 40 Teeth: Choosing eitech Gear Ratios
By eitech Metallbaukasten | Published: 2026-10-15
Category: Comparisons
Compare eitech's 30-tooth and 40-tooth module 1 gears on tooth count, bushing, and socket fit, and learn which gear ratio to choose for your model.
Quick answer
Choose the eitech Gear 30 teeth module 1 hexagon socket when you need to mount the gear directly onto a hex shaft and want a slightly smaller, faster-turning gear. Choose the eitech Gear 40 teeth with bushing module M1 when you need a larger gear that spins on a bushing and produces a slower, more torque-friendly output. Both are module 1, so they mesh with each other, and the right pick depends on your shaft type and the speed or force you want at the axle.
How module and tooth count set the ratio
Module is the sizing standard that lets gears of the same module mesh correctly. Because both the 30-tooth and 40-tooth eitech gears are module 1, they can work together in one gear train. Tooth count then sets the ratio: a 30-tooth gear driving a 40-tooth gear turns the 40-tooth gear slower, while a 40-tooth gear driving a 30-tooth gear speeds the output up. That single pair gives you a 4:3 ratio in either direction, which is a small but useful change for model mechanisms.
Mounting differences that decide the build
The two gears are not interchangeable at the shaft. The 30-tooth gear uses a hexagon socket, so it keys directly onto a hex axle and turns with it. The 40-tooth gear is supplied with a bushing, so it is intended to rotate on a shaft rather than lock to it. In practice, that means the 30-tooth gear is often the driver on a hex axle, while the 40-tooth gear works as a free-spinning or idler gear on a round shaft. Check your axle type before ordering, because the socket or bushing determines whether the gear drives or idles.
What the catalog does not tell you
The supplied listings do not state pitch diameter, face width, or load ratings for either gear. Those dimensions matter if you are designing a custom gear train from scratch, so treat the catalog facts as a starting point and confirm fit against your existing eitech parts. If you need a specific center distance between two shafts, measure your current setup before assuming a 30-tooth and 40-tooth pair will drop in.
Practical ratio choices for common builds
For a small speed reduction in a vehicle or crane mechanism, pairing the 30-tooth and 40-tooth module 1 gears is the simplest option because both are module 1 and will mesh. Use the 30-tooth hexagon socket gear as the input on a hex axle and the 40-tooth bushing gear as the output on a round shaft. If you need a larger ratio, you will need to combine more gears or add a different tooth count, since these two parts alone only give a 4:3 change. For most hobby builds, that is enough to alter the feel of a drive without redesigning the whole mechanism.
Trade-offs at a glance
- 30-tooth hexagon socket gear: Smaller gear that locks onto a hex axle and turns with it. It gives a faster output when used as the driver and needs no separate bushing. Pick this when your shaft is hex and you want a direct drive.
- 40-tooth bushing gear: Larger gear supplied with a bushing so it can rotate on a shaft. It slows the output and can act as an idler or driven gear. Pick this when you need a free-spinning gear or a slower, more forceful output.
- Mixing both in one train: Both are module 1, so they mesh. A 30-tooth driver and 40-tooth output gives a 4:3 ratio, which is a modest speed or torque change. Use this pair for simple ratio adjustments, not for large reductions.
Product facts
- Gear 30 teeth module 1 hexagon socket: eitech Gear 30 teeth module 1 hexagon socket, SKU 01805, Standard configuration, Manufaktur tag. The hexagon socket means this gear mounts directly on a hex axle and turns with it, making it a natural driver gear in a model gear train.
- Gear 40 teeth with bushing module M1: eitech Gear 40 teeth with bushing module M1, SKU 01476, Standard variant. The bushing lets this gear rotate on a shaft instead of locking to it, so it suits idler or output positions where you want the gear to spin freely.
- Tire Ø 52 mm: eitech Tire Ø 52 mm, SKU 01423, Standard configuration, Manufaktur tag. If your gear train drives a wheel, this tire size is a known eitech component you can pair with your axle and gear setup.
Which gear fits your build
Best for
- Builders using hex axles who want a direct-mount driver gear
- Modelers who need a small speed or torque change from a simple two-gear train
- Anyone adding a free-spinning idler or output gear on a round shaft
Not for
- Builds that need a large gear reduction, which requires more gears or different tooth counts
- Applications where you need published load ratings or precise pitch diameters, since those are not stated in the catalog
- Shafts that do not match the hexagon socket or bushing mounting type
