Standard End Machining Glossary for Acme Screws, Lead Screws and Inch and Metric Ball Screws

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Nook Industries provides a complete selection of inch and metric Ball Screws, Roller Screws, Acme Screws, Lead Screws, End Bearing Supports, Precision Locknuts, Worm Gear Screw Jacks, Electric Actuators, HRC 60 Linear Shafting, Linear Bearings and Pillow Blocks to the Linear Motion Industry.

END MACHINING &
BEARING SUPPORTS

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END MACHINING GLOSSARY AND TECHNICAL DATA

Ezze-Mount
Standard Ends
Land Diameter
Root Diameter
Journal
Straightness

Annealing
End Fixity
Lock Nut Thread
Undercuts & Radii
Concentricity
Approval Drawings


	End Machining Glossary And Technical Terms PDF

END MACHINING TERMS

EZZE-MOUNT
EZZE-MOUNT™ precision bearing blocks contain anti-friction bearings and are designed to be used with lead screws. Single and double bearing base mount and flange mount versions of EZZE-MOUNT™ bearing blocks are available.

STANDARD ENDS
For each screw size, Nook Industries has designed a family of standard machined ends applicable to a variety of bearing arrangements. The use of standard machined end designs offers quick delivery.

LAND DIAMETER
The land diameter is the outside diameter of the screw. The difference between the land diameter and the bearing journal is the resulting bearing shoulder.

ROOT DIAMETER
The diameter of the screw measured at the bottom of the thread. This diameter is used for determining journal sizes. If the bearing journal diameter is larger than the root diameter, thread tracings may be visible. Generally, these tracings do not have an effect on bearing performance.

JOURNAL
A smooth diameter machined on the end of screw used as a mounting surface for bearings, couplings, pulleys, gears, etc.

STRAIGHTNESS
Although Nook Industries PowerAc™ and PowerTrac™ screws are manufactured from straight, cylindrical material, internal stresses may cause the material to bend or yield. When ordering random lengths or cut material without end machining, straightening is recommended. Handling or machining of screws can also cause the material to bend or yield. Before, during and after machining, additional straightening is required.

ANNEALING
A ball screw assembly uses rolling elements to carry a load similar to an anti-friction (ball) bearing. These elements do not wear during normal use. Therefore, ball screw life is predictable and is determined by calculating the fatigue failure of the components. Proper lubrication, regular maintenance, and operation within specified limits will allow PowerTrac™ Ball Screws to operate to the predicted life.

END FIXITY
End fixity refers to the method by which the ends of the screw are supported. The degree of end fixity is related to the amount of restraint of the ends of the screw. Examples of the three basic types of end fixity are:

FREE	No support.
SIMPLE	Shaft supported at a single point.
FIXED	Shaft rigidly restrained against axial rotation.

Simple End fixity can be provided through a single bearing support. Multiple or spaced pairs of bearings are more rigid than a “Simple” support, but because of their compliance are not truly “Fixed”. A screw can be supported with different combinations of end fixity. (SEE FIG. 1: A – D)

A: One end supported with a Double Bearing EZZE-MOUNT™, other end Free. Use Line “A” in reference to the charts shown for Column Strength and Critical Speed Charts. NOTE: Not recommended for any application other than short travels and slow speeds.

FIG. 1 A

FIG. 16 A - End Fixity A

B: One end supported with a Double Bearing EZZE-MOUNT™, other supported with a Single Bearing EZZE-MOUNT™. Use Line “B” in reference to the charts shown for Column Strength and Critical Speed Charts.

FIG. 1 B

FIG. 16 B - End Fixity B

C: Both ends supported with a Double Bearing EZZE-MOUNT™. Use Line “C” in reference to the charts shown for Column Strength and Critical Speed Charts.

FIG. 1 C

FIG. 16 C - End Fixity C

D: Both ends rigidly mounted with rotating nut or both ends mounted with a double preloaded angular contact bearing spaced apart by least 1.5 time the diameter of the mounting journal. Use Line “D” in reference to the charts shown for Column Strength and Critical Speed Charts.

FIG. 1 D

FIG. 16 D - End Fixity D

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LOCK-NUT THREAD
Lock-Nut threads are a special class of threads (defined in Machinery’s Handbook) used with Lock-Nuts to retain bearings on shafts.

UNDERCUTS AND RADII
Whenever a shaft changes diameter, an undercut or a radius is machined into the transition to minimize stress concentration. Undercuts are preferred for bearing shoulders because they allow clearance for the corner of the bearing. (SEE FIG. 2)

FIG. 2

Figure 2. Undercut

CONCENTRICITY
Concentricity refers to multiple diameters sharing the same center. For end machining, good concentricity allows all components to rotate around the same axis resulting in smooth operation and long life.

APPROVAl DRAWINGS
If custom ends or special dimensions are desired, an approval drawing can be developed once an order is placed. This drawing will show all the critical dimensions with tolerances.

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NOOK INDUSTRIES, INC. - An ISO 9001:2000 Registered Company
4950 East 49th Street | Cleveland, Ohio 44125 | phone: (216) 271-7900 or (800) 321-7800 | fax: (216) 271-7020

Nook Industries provides a complete selection of inch and metric linear, mechanical and electromechanical actuators to the Linear Motion and Power Tarnsmission Industries. Modular Linear Actuators, Precision Profile Rails, Ball Screws, Roller Screws, Acme Screws, Lead Screws, Ball Splines, End Bearing Supports, Precision Locknuts, Worm Gear Screw Jacks, Electric Cylinder Actuators, HRC 60 Linear Shafting, Linear Slides, Bearings and Pillow Blocks.
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