SFU1605, SFU2005 and SFU2505 are three common standard ball screw sizes used in CNC equipment, automation systems, positioning mechanisms and general industrial machinery. All three use a 5 mm lead, which means the nut travels 5 mm for each revolution of the screw.
The main difference is screw diameter. SFU1605 uses a 16 mm screw, SFU2005 uses 20 mm and SFU2505 uses 25 mm. As the diameter increases, the screw and nut become larger and the available load rating and axial rigidity generally increase as well.
This makes the three models suitable for different machine sizes and operating conditions. If your equipment can use a standard SFU configuration, choosing the correct standard diameter is often simpler than specifying a special ball screw design.
SFU1605, SFU2005 and SFU2505 at a Glance
The following table compares common four-circuit versions of the three models. The data is useful for understanding the relative size and capacity of each series.
| Specification | SFU1605-4 | SFU2005-4 | SFU2505-4 |
|---|---|---|---|
| Nominal screw diameter | 16 mm | 20 mm | 25 mm |
| Lead | 5 mm | 5 mm | 5 mm |
| Ball diameter | 3.175 mm | 3.175 mm | 3.175 mm |
| Nut outside diameter D | 28 mm | 36 mm | 40 mm |
| Flange outside diameter A | 48 mm | 58 mm | 63 mm |
| Nut length L | 50 mm | 51 mm | 51 mm |
| Dynamic load rating Ca | 780 kgf | 1130 kgf | 1280 kgf |
| Static load rating Coa | 1790 kgf | 2380 kgf | 3110 kgf |
| Reference stiffness K | 20 kgf/μm | 25 kgf/μm | 35 kgf/μm |
These figures show the general progression clearly. Moving from a 16 mm to a 20 mm or 25 mm screw increases the physical size of the assembly and provides greater load capacity and rigidity. However, the largest model is not automatically the best choice for every machine.
What Does 1605, 2005 or 2505 Mean?
The model number provides two of the most important specifications directly.
- SFU1605: 16 mm nominal screw diameter and 5 mm lead.
- SFU2005: 20 mm nominal screw diameter and 5 mm lead.
- SFU2505: 25 mm nominal screw diameter and 5 mm lead.
Because all three models use the same 5 mm lead, they produce the same nominal linear travel per screw revolution. The key difference is therefore not travel per revolution but the mechanical size and capacity of the screw assembly.
The suffix must also be checked. For example, SFU1605-3 and SFU1605-4 use the same nominal diameter and lead but have different numbers of ball circulation circuits, nut lengths and load ratings. A complete model designation is therefore more reliable than specifying only "1605."
When Should You Choose SFU1605?
SFU1605 is the most compact of the three sizes. Its 16 mm screw diameter and 28 mm nut body make it suitable where installation space and moving mass are important considerations.
Typical uses can include:
- compact CNC and engraving equipment;
- small automation axes;
- inspection and positioning equipment;
- light industrial linear modules;
- general machinery with moderate axial loads.
SFU1605 is often a practical starting point when the machine does not require a larger screw for load, rigidity, unsupported length or rotational-speed reasons.
Buyers looking specifically for this size can also review the DLY 1605 ball screw specifications for available nut configurations and dimension data.
When Should You Choose SFU2005?
SFU2005 is the middle size in this comparison. Increasing the nominal screw diameter from 16 mm to 20 mm provides greater axial rigidity and higher load ratings while keeping the assembly relatively compact.
It is a practical option for:
- general industrial automation;
- medium-size CNC feed mechanisms;
- packaging and handling equipment;
- positioning tables;
- machines that need more rigidity than a 16 mm screw provides.
For many general-purpose industrial axes, SFU2005 provides a useful balance between installation size and mechanical capacity. It should still be checked against actual stroke, speed, acceleration and support arrangement rather than selected by diameter alone.
When Should You Choose SFU2505?
SFU2505 uses a 25 mm nominal screw diameter and has the largest nut body and highest load ratings of the three models compared here.
It is more suitable when an axis requires:
- higher axial load capacity;
- greater axial rigidity;
- a larger and more rigid machine structure;
- better resistance to compression and buckling;
- a larger screw diameter for the required shaft length and support arrangement.
The trade-off is a larger installation envelope and greater rotating mass. For a compact mechanism with modest loading, using SFU2505 simply because it is larger may add cost and size without providing a practical advantage.
SFU1605 vs SFU2005 vs SFU2505: Which One Should You Choose?
| Selection Condition | Typical Starting Choice | Reason |
|---|---|---|
| Compact machine and moderate load | SFU1605 | Smallest screw and nut dimensions of the three. |
| General industrial axis requiring more rigidity | SFU2005 | Balanced size, rigidity and load capacity. |
| Higher load or larger machine structure | SFU2505 | Larger screw diameter and higher reference load ratings. |
This table should be used as an initial comparison rather than a final engineering calculation. Screw length, bearing supports, operating speed and orientation can change which diameter is appropriate.
Do Not Choose a Ball Screw by Load Rating Alone
A larger diameter normally provides more rigidity and capacity, but load rating is only one part of ball screw selection.
The final model should also be checked against:
- Screw length: longer shafts are more sensitive to buckling and critical speed.
- Operating speed: rotational speed must remain within a suitable range for the screw length and bearing arrangement.
- Support method: fixed and supported bearing arrangements affect shaft rigidity and allowable speed.
- Mounting direction: horizontal and vertical axes can create different axial loading conditions.
- Duty cycle: frequent operation and long operating hours affect service-life requirements.
- Available installation space: the larger nut flange and housing must fit the machine structure.
If the original machine already uses a standard SFU model, replacing it with the same complete specification is normally the simplest route. For a new machine, the operating conditions should be checked before choosing between 16, 20 and 25 mm screw diameters.
What Accuracy Is Available?
DLY standard SFU ball screws are commonly supplied as C7 cold-rolled ball screws for general CNC, automation, packaging and industrial transmission applications.
C5 ground versions are also available when an application requires higher lead accuracy. The required accuracy should be selected according to the actual positioning requirement rather than automatically specifying the highest grade.
More available sizes and lead combinations can be found in the DLY SFU ball screw range.
Standard SFU Ball Screws for Repeat Industrial Orders
For machine builders, distributors and maintenance suppliers, using common SFU sizes can simplify model confirmation, replacement and repeat purchasing.
DLY manufactures standard SFU ball screws in multiple diameters and leads, including commonly used 1605, 2005 and 2505 configurations. Standard C7 rolled assemblies are suitable for a wide range of industrial machinery, while matching ball nuts and support units can be supplied together when required.
For buyers purchasing standard models in regular quantities, keeping the complete model number, screw length and required quantity consistent between orders helps simplify specification confirmation and repeat supply.
Frequently Asked Questions
Is SFU2005 stronger than SFU1605?
In comparable four-circuit configurations, SFU2005 has a larger screw diameter and higher dynamic and static load ratings than SFU1605. It also has greater reference rigidity. The actual suitability still depends on screw length, load, speed and support conditions.
Is SFU2505 always better than SFU2005?
No. SFU2505 provides a larger diameter and higher capacity, but it also requires more installation space and has greater rotating mass. SFU2005 may be the more appropriate standard size when the load and shaft length do not require 25 mm diameter.
Do SFU1605, SFU2005 and SFU2505 have the same travel per revolution?
Yes. All three models in this comparison use a 5 mm lead, so the nominal linear travel is 5 mm per screw revolution.
Can I replace SFU1605 with SFU2005?
Not as a direct drop-in replacement. Although both have a 5 mm lead, the screw diameter, nut outside diameter, flange dimensions and required bearing supports are different. Changing from 1605 to 2005 normally requires corresponding changes to the machine mounting structure.
Which standard ball screw should I keep in stock?
This depends on the machines or customers you support. SFU1605, SFU2005 and SFU2505 are useful standard 5 mm lead sizes covering compact, medium and larger industrial axes. Distributors should select inventory based on their customers' common diameters, lengths and nut configurations rather than stocking only one size.
Need Standard SFU Ball Screws?
DLY supplies standard SFU ball screw assemblies for CNC machines, industrial automation, packaging equipment and other linear motion systems. Common diameters, leads and matching ball nut configurations are available for regular and repeat purchasing.
Send us the standard model, screw length and quantity you require, and we can confirm the corresponding specification and supply option.
