Published:2026-09-28 12:00:00
MC / MGD / MGS / NH NUT BRACKET SELECTION
The same screw diameter does not guarantee a matching bracket
Start with the open or closed structure, then check the nut envelope, flange holes, centre height and table interface. Passing the screw through the bracket or fitting a few bolts does not establish compatibility.
01 / FOUR SERIES
Distinguish the nut bracket from the support unit and locknut
A nut bracket joins the ball nut to the table and moves with them. A screw support unit normally sits at a shaft end and supports that end of the screw. A locknut secures the relevant shaft-end components axially. These parts serve different purposes: nut bracket selection starts with the ball nut mounting interface, not the diameter of the screw bearing journal.
HZMotion MC brackets are open type; MGD, MGS and NH are closed type. The opening is a feature of the body surrounding the nut, not an adjustable slit for setting preload. A closed body is not a sealed assembly and does not establish a water or dust protection rating.
| Series | Structure and selection starting point | Checks that deserve attention |
|---|---|---|
| MC | Open type. Start with the nut envelope and flange connection. | Opening width and direction, D1, hole pattern and final model digits. |
| MGD | Closed type. Use the matching information and dimensions in its series table. | Hole arrangement, threads, centre height and table mounting holes. |
| MGS | Short closed type. Include it when comparing layouts with limited axial space. | A short body must still provide flange contact, adequate thread engagement and lubrication access. |
| NH | Closed type. Multiple connection layouts extend the available size coverage. | The A/B/C and other classification letters after the diameter code, and the complete hole layout. |
A series narrows the search; it is not an interchangeability guarantee. An open body does not necessarily allow sideways removal past the nut flange. A closed body is not automatically rated for a higher load. Check the assembly path, loads and deflection for the specific size and machine.
02 / SIX INTERFACES
Check the nut side and the table side together
Collect the complete ball nut drawing, bracket drawing and table mounting drawing. Agree on units, orientation and datums before comparing dimensions. Symbols refer to the relevant series drawing; a letter used by one series may not mean the same thing in another.
| Interface | What to check | What is insufficient |
|---|---|---|
| 1. Nut bore and envelope | Bracket bore D1, nut outside diameter and length, steps, recirculation features and orientation. Follow the specified clearance or fit. | Screw nominal diameter is not D1. Insertion alone does not prove correct location. |
| 2. Flange seating face | Flange shape and thickness, locating features, contact area and clearance for radii or projections. | Bolts entering their threads do not prove full flange contact. |
| 3. Flange connection holes | Pitch circle, hole count, angular positions, hole size or thread, usable depth and bolt-head space. | The same hole count can have a different pitch circle; the same pitch circle can have different threads. |
| 4. Centre height and datums | Nut axis to table mounting face, plus the dimension chain through the screw supports, guide carriages and table plate. | Two dimensions called centre height may start at different surfaces and cannot be compared directly. |
| 5. Table connection | Body width and length, hole spacing, tapped or through holes, counterbores, dowels and available adjustment. | A matching nut interface does not mean the existing table holes can be retained. |
| 6. Lubrication and clearance | Oil ports, grease nipples, fittings, hose bends, tool paths and clearance to guides and covers across the full stroke. | Clearance at mid-stroke does not establish clearance at the ends or during maintenance. |
The geometric relationship between the nut flange face and the table mounting face affects the assembled nut loading. Do not use bolt tightening to pull incompatible faces together. Read dimensional and geometric tolerances separately: IT6 is a dimensional tolerance grade, not a substitute for specified flatness, perpendicularity or parallelism values and their datums.
03 / MODEL EXAMPLE
MC2020-1 and MC2020-2: the same envelope, different connection holes
| Check | MC2020-1 | MC2020-2 | Assembly implication |
|---|---|---|---|
| B × L | 86 × 40 mm | 86 × 40 mm | The same overall width and length. |
| Centre height H | 28 mm | 28 mm | The same nominal height from the corresponding datum. |
| Nut bore D1 | 39.4 mm | 39.4 mm | The bore size matches; the full nut envelope still needs checking. |
| Connection pitch circle D4 | 59 mm | 50 mm | Different flange hole positions. |
| Connection holes n, m | 4 × M6 | 4 × M5 | The same count but different threads. |
A purchase order that says only “MC2020 nut bracket” omits the suffix that distinguishes these hole patterns. The envelope, centre height and bore may all fit while the flange still cannot be connected. Retain the full model and compare each nut hole and thread with the bracket drawing.
D1 is the bracket bore that accommodates the nut, not the screw diameter. It does not establish an interference fit for the ball nut. This table compares easily confused interfaces; it does not claim identical machine performance for the two models.
04 / INSTALLATION SPACE
Confirm insertion, tightening and lubrication access
Assembly path: establish how the body and nut come together and whether the flange, shaft-end supports, return tube or table plate blocks that path. An opening does not clear every projection. Do not remove the ball nut from its screw simply to pass it through a bracket.
Bolts and tools: distinguish the nut flange bolts from the table mounting bolts. Check clamped thickness, effective engagement, blind-hole bottom clearance and tool access. A bolt bottoming in a hole can reach the specified tightening torque without clamping the mating faces properly.
Lubrication and stroke: retain space for fitting removal and hose movement after installing the nipple. Check hoses, covers, guide carriages and limit hardware throughout the stroke. Do not block the intended lubrication port or leave a hose sharply bent to make the bracket fit.
Loads and mounting: confirm travel orientation, axial force, acceleration and table connection stiffness. If load capacity or stiffness determines the choice, use calculations, drawings and validation for the selected configuration. “Open” and “closed” are not load ratings.
05 / SELECTION AND PURCHASING
Select from complete interface data, then inspect the assembly
- Identify the ball nutRecord its full model, screw diameter and lead. Supply the envelope and connection drawing and state whether this is a new design or a replacement.
- Shortlist the bracket seriesUse opening direction, axial space and hole layout to identify MC, MGD, MGS or NH candidates. Keep every suffix.
- Check all six interfacesCompare bore, seating face, flange holes, centre height, table connection and lubrication access. Mark mismatches on the drawings.
- Agree on assembly and inspectionSpecify locating datums, permitted adjustment, tightening requirements and acceptance checks. State dimensional and geometric requirements separately.
- Confirm the purchasing packageAgree on the complete model, drawing revision, quantity, surface treatment and special requirements before ordering or machining.
- Inspect after assemblyCheck final seating, full-stroke motion in both directions and lubrication access. If tightening increases rotational resistance, use the linked troubleshooting guide to find the step that introduced the constraint.
| Information for purchasing or HZMotion | Details to provide |
|---|---|
| Nut and bracket | Full nut and candidate bracket models, plus both drawing revisions. |
| Mounting interfaces | Nut envelope, flange holes and threads, centre height, table drawing and datums. |
| Operating conditions | Stroke, speed, acceleration, axial load, orientation and environment. |
| Supply scope | Quantity, surface treatment, special accuracy requirements and whether bolts or lubrication fittings are included. |
| Replacement constraints | Table, holes, shaft-end supports, lubrication lines and installation space that must be retained. |
Continue with troubleshooting increased ball screw rotational resistance after nut bracket tightening to connect interface selection with assembly acceptance.
06 / FAQ
Frequently asked questions
Can all 20 mm ball screws use the same nut bracket?
No. Nuts for the same screw diameter may differ in outside diameter, flange, recirculation structure and connection holes. The table interface also has to match. Supply complete nut and bracket drawings.
Can the MC opening be tightened like a clamp?
Do not treat the opening as an adjustment mechanism. Assemble through the specified connections; do not narrow the opening or deform the bracket to adjust nut preload.
Is a closed bracket always stiffer and waterproof?
The name does not establish either property. Stiffness depends on the section, material, connections and loading. A closed body alone does not provide a waterproof rating.
Can the letter after an NH diameter code be omitted?
No. It distinguishes connection layouts under the same diameter code and must match the full drawing and order requirements.
If all bolts line up, is selection complete?
Also verify flange contact, centre height and datums, thread engagement, lubrication and full-stroke clearance. Recheck motion after final tightening.