MGN12C vs MGN12H: Which Block Length
Two blocks on one rail. MGN12C is the standard-length block, MGN12H is the extended block. They share the MGN R12 rail, the 13 mm mounting height and the 27 mm body width; what changes is the block length, the load rating and the weight. That means the choice does not affect the mounting face — only the load and the travel the block costs you.
Side by side
| Item | MGN12C (standard) | MGN12H (extended) |
|---|---|---|
| Block length L | 34.7 mm | 45.4 mm |
| Block mounting length L1 | 21.7 mm | 32.4 mm |
| Block height H | 13 mm | 13 mm |
| Block width W | 27 mm | 27 mm |
| Dynamic load C | 290 kgf (2.84 kN) | 380 kgf (3.73 kN) |
| Static load C0 | 400 kgf (3.92 kN) | 600 kgf (5.88 kN) |
| Block weight | 34 g | 54 g |
| Matching rail | MGN R12 | MGN R12 |
| Rail pitch P / end E | 25 mm / 10 mm | 25 mm / 10 mm |
| Accuracy | C / H / P | C / H / P |
| Preload | ZF / Z0 / Z1 | ZF / Z0 / Z1 |
Source: Yuantong product manual, MG series dimension table, p.68 (printed page 62). Loads are printed in kgf; kN values are converted at 1 kgf = 9.81 N. Every figure above is cross-checked against our model data at build time, and the build fails if the two disagree.
What the extra 10.7 mm buys
The H block is 10.7 mm longer: 45.4 mm against 34.7 mm. The extra length goes into the ball rows and the body, and it shows in the ratings: dynamic load rises from 2.84 to 3.73 kN (about 31% more) and static load from 3.92 to 5.88 kN (about 50% more). It also raises the permissible overturning moments, which is the number that decides a cantilevered head — we quote the moment figures for your size on the datasheet rather than printing them here, because the printed table's moment unit does not agree with its own magnitudes.
What does not change
The rail is the same MGN R12, the mounting height is the same 13 mm, the body width is the same 27 mm, and the bolt spacing B and the preload grades ZF / Z0 / Z1 are identical. Accuracy C / H / P is available on both. A machine designed for the C block can take the H block without touching the rail or the carriage plate; what it cannot do is keep the same end stops, because the block is longer.
Which one the axis needs
Take the C block when the load is centred over the rail, the carriage is symmetric and the moving mass matters: printer gantries, laser heads, dispensing axes and small inspection slides, where acceleration is usually the limiting factor rather than strength.
Take the H block when the head is cantilevered, when there is only one rail, or when the carriage sees a moment that reverses with every move. The longer body spaces the load path out along the rail, which is what a single-rail Z axis needs; the same capacity with two C blocks is possible but doubles the alignment work. If the axis already runs on two rails and the load is centred, the H block buys little and costs 20 g of moving mass plus 10.7 mm of travel.
On a fixed rail length, check the end stops: the H block is 10.7 mm longer, so the usable stroke at the stops shrinks by that much unless the rail is re-specified.
How the two are ordered
Model code plus accuracy and preload, for example MGN12H C Z1. The C and H blocks are interchangeable items on the same rail, so a machine can be built with C blocks and upgraded to H later without changing the rail — check the end stops before assuming the stroke is unaffected.
Related
Single-model pages: MGN12C and MGN12H. Block page with the full specification: MGN12C / MGN12H. Rail width rather than block length: MGN vs MGW. The whole miniature range: MGN / MGW miniature guides. What preload does to the block: preload grades.
FAQ
| Is MGN12H a heavy-load block? | No. On the MG series the H suffix means extended length. The load rises because the body is longer, not because of a different load designation. |
| Can I swap C and H on the same rail? | Yes. Both use the MGN R12 rail at the same height and width. Re-check the end stops: the H block is 10.7 mm longer. |
| Which one for a 3D printer? | Usually C, for the lower moving mass. Use H where the head is cantilevered or the carriage sees a reversing moment. |
| Where do the numbers come from? | The product manual, MG series dimension table, p.68 (printed 62), converted from kgf at 1 kgf = 9.81 N and cross-checked against our model data when the site is built. |