Ball Screw Nut Housing

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Product Introduction

Tianjin OuNaiDa Transmissions Technology Co., Ltd. is one of the leading manufacturers and suppliers of ball screw nut housing in China. If you're going to buy high quality ball screw nut housing, welcome to get more information from our factory. Also, custom service is available.

A Polish machine builder ordered twenty SFU1605 screws from us last spring and machined his own nut brackets in-house to save money. Eight weeks later he was back asking why three axes had developed a rhythmic current fluctuation on the servo. The screws were fine. His brackets were bored on a manual mill, and the bore centre sat about two tenths off the line between his bearing supports. Every revolution, the nut was being pulled sideways and then released.

The housing is the cheapest part of a ball screw axis and the one most likely to ruin it.

What the housing has to do

Three jobs, in order of how often they get botched:

Hold the nut flange square to the screw axis. Transfer thrust into the machine table without flexing. Keep the nut bore concentric with the line drawn between the two end support bearings.

The third one is the killer, because it depends on machining you did not do and cannot see once the machine is assembled.

HIWIN's own failure analysis puts it plainly: radial load exists whenever the centre line of the nut housing and the centre line of the bearing support housing are not properly aligned. The screw may bend outright if the error is large. If it is small, you get accelerated wear instead - no dramatic failure, just an axis that loses accuracy far sooner than the life calculation predicted. And the note that catches people out: the higher the preload in the nut, the tighter the alignment has to be (HIWIN Ballscrews Technical Information, Appendix A2-2).

So buying a preloaded double-nut screw and then bolting it to a rough-bored bracket actively makes things worse than a plain single nut would have been.

Aluminium BSG or steel DSG

We stock both. They are not interchangeable in the way most buyers assume.

Model	Paired screw	Bore D (mm)	Width B (mm)	Height H (mm)	Centre height h (mm)	Length L (mm)	Bolt pitch P (mm)	Mounting thread X
BSG1616	1616	32	55	40	20	27	45	M4
BSG2020	2020	39	66	47	23.5	35	56	M5
BSG2525	2525	47	80	55	27.5	34	68	M6
BSG3232	3232	58	95	66	33	55	82	M8

Aluminium BSG series. Source: OND precision transmission components catalogue, Aluminium Nut Housing BSG/DSG Series, P55.

Model	Paired screw	Bore D (mm)	Width B (mm)	Height H (mm)	Centre height h (mm)	Length L (mm)	Bolt pitch P (mm)	Mounting thread X
DSG1616	1616	32	55	40	20	27	45	M4
DSG2020	2020	39	66	47	23.5	35	56	M5
DSG2525	2525	47	80	55	27.5	34	68	M6
DSG3232	3232	58	95	66	33	55	82	M8
DSG4040	4040	73	123	90	45	60	100	M10
DSG5050	5050	90	128	104	52.5	68	110	M12

Steel DSG series. Source: OND catalogue, Steel Nut Housing DSG/DSG Series, P56.

Look at the first four rows of each table. The external envelope is identical - same bore, same width, same height, same centre height, same bolt pitch. You can swap an aluminium block for a steel one without touching your machine base. That is deliberate, and it is useful: prototype in aluminium, move to steel for the production run if the axis turns out to need the stiffness.

The differences that matter are not in the dimension table. Steel gives you roughly three times the elastic modulus, so under the same thrust the block deflects about a third as much. Aluminium gives you a third of the mass and better thermal conduction away from the nut. On a fast, lightly loaded pick-and-place axis the aluminium block is genuinely the better engineering choice, not the budget compromise.

Two things the table will not tell you. The steel range extends to 4040 and 5050 where aluminium stops at 3232 - above 32 mm screws we only offer steel, because at those thrust levels aluminium deflection stops being acceptable. And note the H suffix rows in the catalogue (DSG16H, DSG20H and so on) are the multi-lead variants: DSG20H accepts 2005, 2010 and 2020 on one housing. If you are running a mixed-lead machine, one housing part number covers three screws.

The centre height number is the one to check first

h in both tables is the distance from the mounting face to the screw centreline. BSG2020 and DSG2020 both give 23.5 mm.

That number has to match the centre height of your end support units, or the screw runs at an angle and you are back to the Polish customer's problem. Support units have their own h dimension - an AK15 sits at 40 mm, an AK20 at 47.5 mm. Pick the housing and the support units together, from the same pair of tables, at the same time. Do not pick the screw first and sort out the mounting hardware afterwards.

If the heights genuinely cannot be matched from stock, shim the support units, not the nut housing. Shimming the housing tilts the nut flange; shimming the supports moves the whole shaft line in parallel.

Where people lose money

Machining your own housing to save forty dollars. The bore needs to be concentric to the shaft line within a couple of hundredths and square to it, and that means boring it in place or boring it on a machine you trust. Most small shops do not have the fixturing.

Bolting a nut flange to a housing face that has not been faced flat. The flange conforms to whatever it is bolted against, and it drags the nut out of square with it.

Over-torquing the mounting bolts on an aluminium block. M5 in aluminium strips or distorts around the bore far more readily than the same bolt in steel. Use the lower end of the torque range.

Ordering the housing after the machine base is already drilled. The bolt pitch P and thread size are fixed by the housing, not by your CAD model.

Ordering

Give us the screw designation, including lead, and tell us whether the axis is horizontal or vertical and roughly how much thrust it sees. We will confirm aluminium or steel and check the centre height against whatever support units you are using. If you are already committed to a drilled machine base, send the hole pattern and we will tell you honestly whether it lines up.