Misumi USA Engineering Blog

To extend linear ball bushing life, it is highly recommended to reapply grease or oil to them periodically unless the application reqirements prohibits all kinds of lubricants.  Lubricant prevents metal to metal contact and also minimizes retainer wear by reducing friction.  Oils are used where low friction is a primary requirement.

Grease or oil should be applied to the internal compartment of the Linear ball bushings.  The grease or oil should be periodically reapplied depending on the operating conditions.  Reapplication may be done by adding the grease directly to the internal compartment (Using grease fitting in housing if existing) or by greasing or oiling the shaft .  A Six month lubrication interval should be sufficient for most normal operationing conditions.  If the linear ball bushings works under severe conditions (high speed, high load, high reciprocating motion etc…) a three month lubrication interval is recomended.

For applications with limited access to linear ball bushings or for re-lubrication or no downtime, Misumi offers linear ball bushings with a lubrication unit MX equipped with solid lubricant which requires limited or no maitanance.

https://www.misumiusa.com/PDFViewer.aspx?Metric=true2008&Page=231 

https://www.misumiusa.com/PDFViewer.aspx?Metric=true2008&Page=233 

Most popular types of ball bearings are single-row radial also known as “deep-groove” and single-row angular contact bearing.

Both bearings are capable of taking combined radial and thrust loads, but radial bearing is not intended for pure thrust load, while for angular bearing thrust component can be large.

The performance of ball bearings is the function of many variables like bearing material, characteristic of application... To estimate the suitability of a particular bearing two factors are taken into consideration:

- bearing fatigue life

- ability to withstand static load.

For bearing fatigue life we can use ball bearing Rated life (L₁₀).

Bearing rated life is measured in millions of revolution that 90% of apparently identical bearings under same operating conditions will complete or surpass. Rated life can be calculated as

L₁₀=(C_or/P_or)³

where C_or-basic dynamic load ratings (N), listed in the bearing table for each individual bearing

P_or-equivalent dynamic radial load (N)

P_or = X*F_r + Y*F_a

where  F_r - applied radial load (N)

F_a - applied axial load (N)

X - radial load factor given in table 1.

Y - axial load factor given in table 1.

Table1¹.

Size of static equivalent load P_o (N) under combine thrust and radial loads is

P_o = X_o* F_r + Y_o* F_a

or

P_o = F_r 

which ever is greater.

where  F_r - applied radial load (N)

F_a - applied axial load (N)

X_o - radial load factor given in table 2.

Y_o - axial load factor given in table 2.

Table2¹.

1-(26^th Edition Machinery’s Handbook; Eric Oberg, Franklin D. Jones, Holbrook l. Horton, and Henry H. Ryffell; 2000 Industrial Press INC, New York)

Generally the permitted static equivalent load is limited by the basic static load (C_or) rating listed in the bearing table for each individual bearing

*Note that calculated values are for ideal operating conditions and that no correction factors (material, operating conditions) apply. Use good engineering practice when calculating bearing life for particular application.

Radial and load factors may slightly very depending on bearing manufacturers.

For Deep grove ball bearings use contact angle 0°.

For Misumi angular bearings use contact angle 30°.

One of the new materials added to the 2009 catalog is Thermoplastic Elastomer (TPE)

Characteristics of TPE include:

(1)Low-dust generating: Superior in abrasion resistance and releases less outgas. Recommended for use in clean rooms.

(2)Ozone resistant: Recommended for use near ionizers, where ozone is often generated.

(3)Low density: With density at 30% - half that of general rubbers, TPE can contribute to weight saving.

TPO, olefi nic thermoplastic elastomer, is superior in heat and chemical resistance among various TPEs.

In addition, TPE is more eco-friendly than general rubbers as it is recyclable.

Find full specs in the 2009 Metric catalog

https://www.misumiusa.com/PDFViewer.aspx?Metric=true2009&Page=1485 

Many of our customers have inquired about NAAMS style bullet nose locating pins.  MiSUMi is pleased to announce that we now offer this style of locating pin. 

The pins are slightly different from standard NAAMS pins.  For example the flange thickness is 3mm for all sizes, but both Flanged and "No Shoulder" type pins offer a very important feature- you can configure the head diameter (0.1mm increments) and head length  (1mm increments) as well as the shank length (1mm increments).

Please, follow this link to see the new catalog page:

https://www.misumiusa.com/PDFViewer.aspx?Metric=true2009&Page=927 

Simplified unit’s conversion table from Metric system (SI) to US unit system.

PROPERTIES OF PLASTIC MATERIALS

In the Misumi catalog we list roller followers as separable and solid (non-separable). With separable rollers the inners ring can be separated and with solid rollers inner rings cannot be separated:

(click picture to enlarge)

To insure that appropriate ball screw is selected, basic safety checks need to be preformed. This includes:

• Critical Speed
• Limitation of buckling load
• Life expectancy

The Misumi catalog offers examples of ball screw selection that also includes basic safety calculations. For more information please refer to Misumi metric 2008 catalog page 453.

When making a selection, various aspects of the ball screw should be examined. First step in the selection process after determining the operating condition is choosing the appropriate ball screw depending on screw accuracy grade, screw shaft diameter, lead and stroke. Accuracy of the ball screw such as axial play/clearance, cumulative lead error and fluctuation is determined by accuracy grade.

(click picture to enlarge)

For more detailed information on accuracy of ball screw see Misumi metric 2008 catalog
page 463.

Misumi also offers different combinations of ball screw shaft diameters, leads and strokes.  Detailed specifications are listed in the dimensional table for each individual ball screw.

For metric gears the gear proportions are based on the module. Modules is the ratio of the “Pitch Diameter” to the “Number of Teeth”.

m (module)= d (pitch diameter (mm)) / N (number of teeth)

When module (m) number for metric gears is getting bigger- size of the teeth is getting bigger too.

In the USA the module is not used and instead the “Diametric Pitch” or “Pitch” (p) is used.

p= N (number of teeth) / d (pitch diameter (Inch))

When pitch (p) number for inch gear is getting bigger- size of the teeth is getting smaller.

Calculation example: Having two dimensions for each gear we will try to find number of teeth (N) using above equations:

Metric gear:
Ф (pressure angle)= 20°
m (module)= 0.8
N (number of teeth)= ?
d (pitch diameter)= 16 [mm]

Inch gear:
Ф (pressure angle)= 20°
p (pitch)= 32
N (number of teeth)= ?
d (pitch diameter)= 0.625”

p= N/d ↔ N= p*d ↔ N= 32*0.625= 20

Conclusion: for both spur gears we calculated same number of teeth. Converting inch dimensions to metric (1”= 25.4mm) we can see how close these two gears are:

Knowing pitch (p) for inch gears we can simply calculate inch module:

m= (1”/32)= 0.03125

Or knowing pitch diameter (d) and number of teeth (N):

m= d/N= 0.625/20= 0.03125

Lets convert Inch module m= 0.03125 to metric using (1”= 25.4mm) converter from Inch to Metric dimensions.

0.03125 * 25.4= 0.794

Conclusion: We can see that the metric and inch spur gears are dimensionally very similar but we should not mesh them together duo to small differences developed during design and manufacturing stage.

The question is what is the torque required to properly lock the bearings?

The bearing locknuts are usually used with angular contact bearings, but in some cases are also used with regular deep groove ball bearings. When installing the bearing locknuts, you won't really find an exact torque spec for this application. All that's required is that there is a minimum pre-load on the inner race of the bearing. It can be achieved by locking the nut "just snag" on the inner race. It can even be done by hand or with very low force when you use a wrench. It is critical that the nut is not mounted to tight because it may result in locking of the bearing race.

When you order the bearing locknut (the BNG family), it will come equipped with a set screw and a small soft metal "crash pad". Once you secure the nut on the inner race of the bearing, simply drop the crash pad in the threaded hole and drive the set screw in. The set screw will deform the crash pad and prevent the nut from loosening. The advantage of using soft material crash pad is that you will not damage the shaft thread shich is much harder that the pad.

The Diamond Shape is a critical feature that helps with machining inaccuracies and smoother  locating operation. When two pins are installed onto one plate, the distance between two mounting holes must be extremely precise and even then, the work piece will not be placed on the base as easily as it would with the use of a diamond shape pin.

(click images to enlarge)

The round pin is the datum pin that is located on the base and fixed in both X and Y direction. The Diamond pin oriented properly allows minimal misalignment in the X axis, but prevents the work piece to move in the Y direction. This way you eliminate small inaccuracies in respect to mounting hole distance and even if it’s manufactured with high precision, the operation will improve since there is less work surface area.

In “Metric” catalog Misumi use in most cases British (Japanese) standard pipe threads with some NPT (American) standard pipe threads for some components.

In “Inch” catalog we provide components with NPT (American) standard pipe threads.
See below letter designations for most popular pipe threads used by Misumi.

British Standards:

• R (BSPT)- British standard taper pipe threads, External
• Rc (BSPT)- British standard taper pipe threads, Internal
• Rp or G (BSPP)- British standard pipe parallel (straight) threads

Japanese Standards:

• PT- JIS taper pipe threads. PT threads are functionally interchangeable with BSPT threads. BSPT is old designation for R and Rc.
• PS- JIS parallel (straight) internal pipe threads (to mate with PT threads)
• PF- JIS parallel (straight) pipe threads. PF threads are functionally interchangeable with BSPP threads. BSPP in old designations replaced with G.
• For more information about the Japanese standards, click here.

American standards:

• NPT American standard taper pipe thread for general use
• For more information about the American standards, click here.
  

Sometimes design and environmental conditions are such that special type of bearings is needed. Perhaps bearings need to be waterproof, heat resistant or even nonmagnetic.

Misumi is offering comparison table for bearings for special environment (table 1.) to help customer evaluate bearing performance and select bearings with appropriate characteristics (Misumi 2008FA Metric catalog page 650).

(click picture to enlarge)

Misumi products are used in wide range of fields, characterized by different environmental conditions. In order to meet the specific needs Misumi is offering different type of grease.

For more information about different grease types see page 230 in our 2008 catalog or simply click on link below:
https://www.misumiusa.com/PDFViewer.aspx?Metric=true2008&Page=229

Different grease types can be specified with following components.

We are happy to inform you about some CAD Configurator improvements that we were able to implement recently.

1. We realized that not everyone is interested in seeing the preview of the parts and would like to go directly to download. (Especially since preview generation and part download speeds averaged about 30 seconds each).
As a result, we added an additional feature to the configurator. Instead of one “Generate” button that would first take you to the preview of the part and then allow you to download it, we now have two buttons: “3D Preview” and “Download”. This allows you to go directly to download without seeing the preview first.

2. In order to improve the speed of the Misumi configurator, we decided to install dedicated servers, so we do not have to compete with other companies, who’s catalogs are served by Part Solutions.
The servers are installed and went online this week. This change resulted in very significant latency improvements. The typical download and preview speeds are now in a 10 second range.

One of other issues we heard about was that the files are now in a ZIP form. We have not addressed it yet, but we discovered that you can eliminate a few steps if you use some of the more common ZIP programs like Winzip or Winrar. Instead of saving the file and extracting it later to a directory of your choice, you can just choose to open it and drag and drop the content to your cad system window. Please, remember that if the downloaded file is a macro, you should close all parts and assemblies first.

We will continue to work on improvements in many areas and we’ll let you know about them as soon as they are implemented.

If you are checking some of the deep groove ball bearings, angular or needle bearings you probably noticed that there is no tolerance specified for inner and outer race of the bearing. Only note provided is that these bearings are Bearing Precision class 0 (JIS B 1514). This class is equal to ANSI ABEC-1 class and in technical section of Misumi Metric catalog (2008) on page 2539 you can find table tolerance for inner and outer diameter for precision class 0 ( ABEC 1).

https://www.misumiusa.com/PDFViewer.aspx?Metric=true2008&Page=2539

Q: Do the Dimensions and Tolerances in Misumi Catalog apply to parts before or after plating?

A: Dimensions shown in catalog apply to finished product.

Customers often gets confused why some linear guides (including miniature) in our catalog are described as “interchangeable”.

In the Misumi catalog word “interchangeable” is used to describe linear guides whose components can be purchased separately. The catalog page for the interchangeable linear guide will show separate part number (price and days to ship) for the guide rail and guide block . Of course when ordering parts separately, customers need to specify the same size for both parts (rail and block) if they are to fit together.

E.g. Catalog page 305/2008 catalog.

SEBZ10- Interchangeable Miniature Linear Guides with Standard Block (shipped as a set)

SEBZ10-Guide Block for SEZB10 (can be purchase separately)

STZL10-Guide Rail for SEZB10 (can be purchase separately)

If customers buy two same (size) sets (1rail+1block) but later on decides that only one rail with two blocks is needed, he/she can simply remove a block from one rail and add it to a second rail.

If the linear guide is not interchangeable then this unit can be purchased only as a set and customers should not remove block(s) from the rail and mount them on the different rail as in previous example.

If shafts with g6 tolerance are used with linear ball bushings fit vary from clerance to transition fit with dominance of clerance fit. If shafts with h5 tolerance are used fit vary from clerance to transition fit also but with dominance of transition fit (light preload fit).

Low Temperature Black Chrome plating (LTBC) is a technology which uses an electrochemical reaction below 0º C. Through the plating process, an alloy-like diffusion layer is formed at the outer margin of the part, allowing chrome particles to completely integrate the base material and create an "inseparable" bond. This means the plating can neither be peeled off nor flaked off. The surface consists of a uniform film creating an extremely resistant rust protection layer. LTBC-plated shafts and components provide service life exceeding 10 years and, in some cases, up to 20 years and beyond is possible. Components with this plating have fracture-resistant surfaces with a high level of alternate-bending strength. The tolerances of the components remain practically unaffected. These components can be used in applications specifying corrosion resistance or minimal light reflection making LTBC suitable for use in optical applications where low light reflection is required.

Misumi offers low-temp, black chrome plating on a variety of the company’s motion components, including linear shaft, linear bushings, linear guides, ball screws and others. Other Misumi hardware is also offered with this coating, including precision-class washers.

We have been asked by several customers if this service is available in the US. Unfortunately we were not able to locate any US coating companies that provide this service. All our components that we offer with LTBC Plating are manufactured and coated in Japan.

Need more information about locating pins?

Check out the below link to the MISUMI VOICE Vol5. This issue features a technical article covering the various usages for locating pins:

http://www.misumiusa.com/globalvoice/volume5/article1a.aspx

The Linear Ball type stages use an integrated Gothic Arc design which provides high rigidity and precision, but uses fewer components and thus decreases the probability of alignment errors. It requires less space, and is more cost effective. It is made of stainless steel, which does makes it slightly heavier and gives it a metallic look.

The 2008 Metric Catalog features10 pages of NEW Linear Ball type products starting on page 935. 

Click here to visit page 935 in the online catalog. 

It is understood that all stainless steel is not created equal. There is a definite difference between the various stainless steels available today. This blog will discuss the differences as they pertain to mechanical components used in factory automation.

AUSTENITIC GRADES- (300 series) are non magnetic in the annealed condition, although some may become magnetic after cold working. They can be hardened only by cold working , and not by heat treatment. Combine outstanding corrosion resistance with good mechanical properties over a wide temperature range. The most common grades are: 303, 304, 316, 321 etc…Misumi offers 303, 304 and 316 grade.

FERRITIC GRADES- are always magnetic and contain chromium but no nickel. They can be hardened to some extent by cold working, but not by heat treatment, and they combine corrosion and heat resistance with moderate mechanical properties and decorative appeal. The ferritic grades generally are restricted to a narrower range of corrosive conditions than austenitic grades. The most common grades: 405, 408, 430 (Offered by Misumi) etc… Misumi offers 430 grade.

MARTENSITIC GRADES- are magnetic and can be hardened by quenching and tempering. They contain chromium, and with two exceptions, no nickel. Some are modified to improve machinability and other have a small addition of nickel to improve the mechanical properties or their response to heat treatment. Some of them have greatly increased carbon content and are hardenable to the highest levels of all stainless steels. These are excellent for service in mild environments such as the atmosphere, freshwater, steam, and weak acids, but are not resistant to severely corrosive solutions. The most common grades: 410, 420, 440C (Offered by Misumi). Misumi offers 420 and 440C grade.

M2.6 thread size is not a catalog mistake.  This is the correct size when listed in the catalog.  If you are having trouble locating hardware, we also sell hexagonal socket head cap screws with a M2.6 thread (Misumi part numbers: CB2.6-5, CB2.6-8, CB2.6-10, CB2.6-12, and CB2.6-15, where the last number in the part number refers to the length).

Our catalog often shows surface roughness information at the upper right hand corner of the drawing. This information will show a roughness value, and one or multiple values in parentheses. Please, see the example from page 159 from FA 2008 metric catalog. "Photo 1" The value before the parentheses means: unless otherwise specified, all surfaces are 6.3 μm and all values in parentheses represent other surface roughness specified on the drawing. 

Surface finish (surface roughness) specifications is a large topic. In fact discussing this topic in length would take at least a few pages. For this blog entry I would simply like to focus on the machined components in the Misumi catalog and point out that these components have surface finish specification (symbol and value) specified in the catalog. Please note that the surface roughness average value (Ra) in the Misumi metric catalog is measured in μm (micrometer-10-6mm) while in Misumi inch catalog it is measured in μin (microinch-10-6in).

See below as the preferred values for Roughness Average (Ra) are given in following table¹.

Metric threads have a different callout then US (inch) threads. Metric threads specify the pitch while US threads specify number of threads per inch.

Example:
Metric
M6 x 1 ( 6- nominal thread diameter in mm, 1mm-distance between threads in mm)

Inch
¼-20 (1/4-nominal thread diameter in inch, 20-number of threads per inch)

Pitch from metric fasteners can be coarse, fine and extra fine. The pitch callout on coarse thread is often omitted. For example, “M6” thread by default stands for coarse thread M6 x 1. Thread call out that includes the pitch “M6x0.75” specifies non-coarse thread (in this case fine thread). Also all threads are right-hand threads unless otherwise specified.

Majority of standards (JIS, ISO, DIN) follow this convention.

For more information about Metric Coarse Threads please see pages 2568/2569 in the 2008 Misumi Metric catalog. Also, see the following links.

Table for Metric Coarse Screw Threads
Table for Metric Fine Screw Threads

When dealing with the Case Hardness of Precision Linear Shafts very often Misumi engineers are asked if our linear shafts are case hardened or through hardened. If you look at the part specification table for Misumi precision linear shafts you will notice that a majority of our shafts are induction hardened. Induction hardening is just one of the ways to achieve case (surface) hardness. Through the induction hardening process the top layer of the shaft is hardened which increases the strength and wear resistance. At the same time the shaft core remains unaffected and material ductility and other physical properties are preserved. Hardness varies with the type of material while effective hardness depth depends on shaft diameter. Values for effective hardness depth can be found in Misumi catalog. See the following links.

Effective hardness depth for metric shafts
Effective hardness depth for inch shafts

We often receive inquiries regarding unspecified tolerances of particular component dimensions in the catalog.  We always do our best to inform the customer of all tolerances right on the product page. You will notice that the Misumi catalog covers most product dimensions as well as tolerances. There is, however a rule that is not clearly explained. Unless otherwise specified on the product page, the tolerance for most of Misumi Metric machined components (i.e. washers, collars, bearing housings, locating pins etc.) is located in the technical data section of the catalog. Please follow the medium precision tolerance in "Regular Machining Dimension Tolerance" tables.

It is always best to check with Misumi Engineering Team (engineering@misumiusa.com) and verify the tolerance.

Remember that some component tolerances (like bearings, bolts etc.) are also located in the back section of the catalog and have their own, special section.

We strongly suggest sending inquiries to engineering on all other unspecified tolerances for parts that are not machined (metal casts, extruded or molded parts etc.)

Welcome to the Engineers Blog, the blog for engineers, written by engineers. Common topics for this blog will include geometric tolerances and fits, materials, surface treatments and hardness, various calculations, product selection criteria plus frequently asked questions and other topics as well. Our head of engineering, Chris Blaszczyk, will be contributing to this blog regularly and is sure to add to this list. Chris is often busy creating materials and presenting at our Configuration Tech Seminars which have proven to be a valuable resource for engineers.

This blog is dedicated to mechanical components used in automation and the machine design and build process. It is meant to be a forum of knowledge that will help the engineer quickly and easily find resourceful information for various topics. In addition we will use this blog to link to various helpful technical resources across the web. To get things started feel free to check out this section of technical reference guides by visiting: https://www.misumiusa.com/PDFViewer.aspx?Metric=true2008&Page=2526.

Lastly, feel free to comment on any of our postings to this blog. We welcome and encourage all comments and feedback. Remember this blog is here for you to use as a resource so please enjoy.