5 Must-Have Features in a Collet Size Chart

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Oct. 21, 2024

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Machine Collet 101: How To Choose The Right Collet

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What is a collet and what is a collet used for? Our tech expert Kurt Repsher introduces you to the most popular collet types in this video, and explains the differences between R8 Collets, ER Collets, 5C Collets, and more. Subscribe to our YouTube Channel and be the first to see more awesome videos like this one!

What Is A Collet & what Are Collets Used for?

A collet is a form of chuck that forms a collar around a tool, like an end mill or drill for example, and exerts a strong clamping force on the object when it is tightened. It may also be used to hold a workpiece. Collets reliably allow fast chucking (tool changes), strong and steady clamping, and precise self-centering that makes them critical for repetitive work. Collets provide accurate alignment and static friction, making their use essential for a variety of machining applications.

Common metalworking industry-standard designs are R8 (internally threaded for mills) and 5C (usually externally threaded for lathes). The most common type of collet grips a round bar or tool, but there are collets for square, hexagonal, and other shapes. Customizable, easily machined collets include emergency collets (e-collets) or soft collets (available in an unhardened state allowing them to readily be machined as needed). Step collets are also available, and those 'step up' to a larger diameter from the spindle, allowing larger workpieces to be held.

R8 collets are designed for use in milling machines. Unusually, R8 collets fit into the machine taper itself (there is no separate chuck), and tools with integral R8 taper can also be directly fitted. The R8 was developed to allow rapid tool changes and requires an exact match between the collet and tool shank diameter. R8 collets have a keyway to prevent rotation when fitting or removing, but it is the compressed taper and not the keyway that provides the driving force. Collets are compressed by a drawbar from above, they are self releasing and tool changes can be automated.

ER collets are the most widely used clamping system. The standard series are: ER-8, ER-11, ER-16, ER-20, ER-25, ER-32, ER-40, and ER-50. ER collets collapse to hold parts up to 1mm smaller than the nominal collet internal size in most of the series (up to 2mm smaller in ER-50, and 0.5mm in smaller sizes) and are available in 1mm or 0.5mm steps. Thus, a given collet holds any diameter ranging from its nominal size to its 1mm-smaller collapsed size, and an ER collet set provides a wide range of versatility. With an ER fixture chuck, ER collets may also serve as workholding fixtures for small parts, in addition to their usual application as toolholders with spindle chucks.

5C collets are designed for work holding. 5C collets have an external thread at the rear for drawing the collet closed, allowing workpieces to pass right through the center of the collet and chuck (5C collets often also have an internal thread for locating a workpiece against the inserted work stop). Variations of these collets are also available to hold square and hex stock. 5C collets have a limited closing range, requiring shank and collet diameters be a close match. 5C collet sets offer a variety of sizes, allowing you to have the 5C collet you need readily available.

Emergency collets have a machinable face that allows you to bore an opening to exactly the size and shape you need. All have external and internal threads, and allow you to readily machine and customize as needed.

A step collet features a wide head that can be machined to hold large workpieces that wouldn't otherwise fit in a standard collet. Step collets have external threads.

The Do's & Don'ts Of Collets

DO: DON'T:

Do Always Use The Right Size Collet For The Tool Or Workpiece Being Held: c

ollet should be held securely, with no 'give'. Don't T
ry To Tighten A Tool Or Workpiece Into A Collet That Is Not Intended For That Size:
doing so can damage the tool or workpiece and increases the risk of an accident or downtime. Do Ensure Most Of The Tool Shank Is Securely Held In The Collet:

doing this increases the collet's ability to securely hold your tool, reduces the risk of failure and injury, and stabilizes the tool, resulting in a better cut and finish on your workpiece.

Don't O

verextend A Tool Held By A Collet To Allow It To Reach Further: doing this decreases the collet's ability to securely hold your tool, increases the risk of failure and injury, and creates chatter that can impact workpiece finish.

Do Regularly Clean Your Collets Between Usage:

simply blowing off chips and debris from the collet's surface extends the collet's life, ensuring its ability to properly secure tools.

Don't Leave Chips & Debris on The Surface Of Your Collet:

without regular cleaning, the outside of the collet and inside of the toolholder will become worn and less effective.

Travers Tool offers a wide range of metalworking collets with expanding, flex and quick-change designs. Choose individual collets or collet sets, and accessories from quality brands including Lyndex-Nikken, Parlec, ETM, Shark Tools, and more. Shop our website for our complete line of machine collets. Request technical support should you require additional assistance selecting the right collet for your machine or application.

Quickly & easily Identify the right collet

Download our free collet dimension & specification chart! Find comprehensive reference tables that list the dimensions and specifications of the most popular collet styles including:

R8 Collets
5C Collets
ER Collets
DA (Double Angle) Collets
SA75, PG75, or TG75 Collets

COLLETS 101 | Centaur Precision Tools

Collets 101: The Definitive Guide

Overview

Collets 101: The Definitive Guide covers five popular collet series: ER collets, TG collets, DA collets, AF collets, and RDO collets. In each section, you will find: recommended uses for each type of collet, along with accuracy metrics (T.I.R.), and tips for how to care for each collet system. If you are new to all of this, please refer to the FAQ & Glossary at the end of this guide for some answers to common beginner questions.

5 Collet Types & Recommended Applications

RDG/TG Collet RDO Collet RD/ER Collet RDF/AF Collet RDA/DA Collet Milling
Drilling
Rigid Tapping
Coolant Through Woodworking Routers
European Systems Drilling
Milling
Rigid Tapping
Tapping (with Length Compensation)
Reaming
Boring
Coolant Through
External Coolant Through
High Precision Grinding Drilling
Milling
Coolant Through
(in 50, 75 & 100 series) Drilling

ER Collets: The Best Toolholding Collet System

The RD/ER Collet System is the most versatile Toolholding System for any operation utilizing a round shank cutting tool in a machining or turning center. This includes drilling, milling, tapping, reaming and boring. RD/ER Collets are commonly known in the industry as ER, ESX, DR, BR, and VSAC Collets.

RECOMMENDED USES OF ER COLLETS

ER collets are recommended for Drilling, Milling, Rigid Tapping, Tapping (with Length Compensation), Reaming, Boring, Coolant Through, External Coolant Through, and High Precision Grinding.

RD/ER Collets are available in the following series ranges to maximize efficiency in most applications:

Series

RD 8
RD 11
RD 12
RD 16
RD 20
RD 25
RD 32 Inch Capacity

1/32-3/16
1/16-1/4
1/32-1/4
1/16-13/32
1/16-1/2
1/16-5/8
3/32-3/4 Metric Capacity

.25mm-5.0mm
.25mm-7.0mm
.5mm-7.0mm
.25mm-10.0mm
.5mm-13mm
.5mm-16mm
.2mm-20mm

HIGHEST ACCURACY: RD/ER COLLET CONCENTRICITY &#; PER DIN

METRIC Clamping Range D L Maximum T.I.R. Precision
DIN High
Precision
DIN Min Max 1.0 1.6 6 0.015 0.008 1.6 3.0 10 3.0 6.0 16 6.0 10.0 25 10.0 18.0 40 0.020 0.010 18.0 26.0 50 26.0 34.0 60 0.025 INCHES Clamping Range D L Maximum T.I.R. Precision
DIN High
Precision
DIN Min Max 0.039 0.063 0.236 0. 0. 0.063 0.118 0.394 0.118 0.236 0.630 0.236 0.394 . . 0.709 1.575 0. 0. . 1.024 1.969 1.024 1.339 2.362 0.

ACCURACY OF ER COLLETS

The RD / ER collet system is the only popular Toolholding system in which all components (ER chucks, ER collets and ER clamping nuts) are standardized by DIN . Most Toolholding Collet systems state the collet is . or .001 T.I.R. but, that does not mean that this is the accuracy one will achieve on the cutting tool when mounted into the chuck. The accuracy of the RD/ER assembly is guaranteed to conform to the DIN Table.

ER collet systems are truly interchangeable. All manufacturers of the ER collet system should conform to the DIN standard. This becomes important to users that may have toolholding systems from different Toolholding System Manufacturers. As tools are taken out of the tool crib and reassembled for different jobs, if all the RD/ER system components are in good condition, and are from Quality Toolholding System Manufacturers, the collet and tool should achieve the DIN accuracy.

Mixing components of Toolholding Systems other than RD/ER can have varying results. While other Toolholding systems may be &#;interchangeable&#;, none of the Toolholding Systems Manufacturers know the tolerances and specifications others are using for all of the components.

HOW TO USE ENDMILLS

When using endmills or any round shank cutting tool, collets and collet chucks centralize the cutting tool, unlike conventional sidelock endmill holders that push the tool to the side of the bore of the holder with a set screw. This method creates a small contact area on the cutting tool and shifts the cutting tool from the true centerline of the Machine spindle. With the cutting tool off-center, the cutting tool edges have an uneven load and will wear out prematurely. Collets and Collet Chucks centralizing the cutting tool will result in increased tool life, higher feed rates, better workpiece accuracy and enhanced workpiece finish. Carbide endmills are usually not supplied with a weldon or locking flat for side lock endmill holders. This is because they are not designed to be used in side lock endmill holders. Many Machinists hand grind a locking flat on to the shank of the carbide end mills to use them in side lock holders, perhaps it would be better to use them in the type of tool that they are designed to be used in.

METHOD OF INSERTION & RELEASE FOR RD/ER COLLETS

INSERTING

Insert collet into nut at angle as shown to engage extraction
tongue in groove of collet.
Screw nut onto collet holder with collet securely in nut.
Insert tool to be gripped and lock nut.IMPORTANT: Never screw nut onto collet unless collet is properly seated in nut.

RELEASING

Hold nut in vertical position and remove nut at an angle. Collet is automatically withdrawn from chuck by excentric ring of nut when unscrewed.

CARE AND USE OF ER COLLET SYSTEMS

The ER chuck, ER collet and ER nut must be thoroughly cleaned before assembling to maintain accuracy. Use a benchtop ultrasonic cleaner to dislodge fine chips and debris. You can also use a bottle-type brush to clean the inner diameter of the collet and a toothbrush-style brush to clean the exterior.

Once assembled, a normal machining environment will not affect the ER toolholding assembly. The ER collet must be installed into the nut (see assembly instructions) before engagement with the collet chuck to ensure the ER collet is seated into the 30 degree concave angle of the nut. Putting the ER collet into the chuck and then installing the nut will result in a condition that the eccentric ring of nut will engage only one side of the collet and produce poor results such as runout and drastically reduced holding strength.

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If you are looking for more details, kindly visit Collet Size Chart.

Never try to install a cutting tool with a larger shank than the maximum or nominal diameter of the collet to expand the collet. Most ER Collets are designed to collapse 1mm or .039. For example: If the cutting tool shank is 4.2mm a 4-3mm is not suitable. A 4.5-3.5mm collet would be required.

Sealed ER Collets for coolant through applications do not have a collapse range, and must be used at exact size. The radius of the collet must exactly match the radius of the cutting tool shank in order to maintain a complete seal. If companies claim that they have sealed collets with a collapse range please keep in mind that if the radius does not match exactly coolant canals will be created by the mismatched radius of an improperly sized collet.

RD/ER Collets must be tightened correctly. Many machinists have been trained that nothing is ever too tight. This is particularly not true with collets and collet chucks. Overtightening a collet chuck will distort the collet and actually diminish the holding strength and accuracy. Maximum tightening torque for RD/ER Systems is as follows:

Series Size
RD/ER 11
RD/ER 16
RD/ER 20
RD/ER 25
RD/ER 32
RD/ER 40 Max. Tightening Torque (ft. lbs.)
20
40
60
70
80
90

Cutting tools should be inserted into the collet the full length of the bore wherever possible. Failure to insert the cutting tool into at least 2/3 of the bore may distort the collet. Collets should be cleaned and oiled prior to storage.

BENEFITS OF ER COLLETS

ER Collets are also very economical when compared with other popular collet systems. Collets work best when used at nominal or full diameter but when the economy is desired this system compares very favorably with other systems. If a user would like to cover a range of 1/8-1&#; with a toolholding system please consider that with the RD/ER System this only requires 23 collets. With a TG system of the same capacity it takes 59 collets to cover the same range. When compared with DA collets with a capacity of 1/16-3/4&#; the RD/ER system only requires 18 collets while the DA needs 45 collets to cover the same range. This represents a significant cost saving while improving accuracy, and versatility.

THE CENTAUR &#;GREEN ZONE&#;

BENEFITS OF CENTAUR &#;GREEN ZONE&#; ER COLLETS

Centaur manufactures the widest variety of exact size collets in the industry to ensure you get the most out of your cutting tools, to reduce downtime and tooling costs.

Centaur offer RD/ER collets in full millimeter sizes, .5mm sizes and true inch size collets in 1/32&#; increments from inventory.

Centaur also offers Sealed High Precision Collets for coolant through applications.

Centaur Sealed ER collets are available with internal flow for oil hole tools or, with external flow (coolant canals through the collet) for use with cutting tools with or without oil holes. The external flow collets are especially beneficial for applications where there is coolant through the spindle but lower cost solid cutting tools are desired or applications where oil hole tools are used in through holes.

Centaur external flow ER collets are also extremely beneficial for through holes with oil hole cutting tools, as this will ensure that the cutting is properly cooled completely throughout the entire cycle. In many applications as the cutting tool is passing through or breaking through the workpiece the coolant may be just passing through the hole, with an external flow sealed collet one can be assured the complete cutting edge and lands of the drill are cooled throughout the complete cycle.

Centaur offers the most extensive program for ER tapping collets in the industry. ER Tapping collets will allow users to convert collet chucks used for many purposes into tapping chucks.

Centaur&#;s ER rigid tapping collets with square drive are available in inch or metric sizes, standard or sealed for internal or external coolant flow.

Centaur also offers RDT/ER tapping collets. These collets will inexpensively convert a standard collet chuck into a length compensating, Quick-change tapping chuck with square drive.

Centaur manufactures each collet from high-grade spring steel and are hardened and fully ground for absolute precision. Each Centaur collet is 100% inspected for the highest possible accuracy.

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TG Collets

RDG/TG collets achieve higher accuracy and greater gripping strength than DA collets and some other popular collet systems. This system will perform well in applications up to 10,000 RPM. RDG/TG collets are also known in the industry as DF, BG, VDF, and PG collets.

RECOMMENDED USES OF TG COLLETS

RDG/TG Collets are used for Milling, Drilling and Rigid Tapping. RDG/TG collets are available sealed for coolant through applications. RDG/TG collets. RDG/TG in 1/64&#; Increments or .5mm increments for metric sized tools.

ACCURACY OF TG COLLETS

RDG/TG Collets are within . T.I.R. The collet chucks are within . T.I.R. from the cone to the collet seat bore. The nuts are designed to float to allow for centering of the collet. RDG/TG systems when properly cleaned and assembled can achieve approximately .001 T.I.R. on a cutting tool shank in the assembly at a checking point length of about 2-3 times the diameter of the cutting tool. The collapse range of the RDG/TG Collets are 1/64&#;. As with all Collets it is recommended that the collet be used at the nominal or largest diameter. Sealed Collets do not have a collapse range and must be used at the exact size.

CARE AND USE OF TG COLLET SYSTEM

The TG chuck, TG collet and TG nut must be thoroughly cleaned before assembling to maintain accuracy. A benchtop ultrasonic cleaner will dislodge fine chips and debris or, a bottle type brush can be used for cleaning the inner diameter of the collet and a toothbrush style can be used to clean the exterior. Once assembled a normal machining environment will not affect the toolholding assembly.

The RDG/TG Collets must be snapped into the Clamping Nut prior to installing onto the Collet Chuck. Collets can be removed from the clamping nut by holding the small end of the collet and tilting the collet angularly until it is removed from the nut. Do not attempt to remove the collet from the clamping nut by forcing the collet out from the front of the collet nut using a punch or screwdriver as this will damage the collet and clamping nut. For maximum accuracy and holding strength RDG/TG Collets must be tightened correctly, maximum tightening torque is as follows:

RDG/TG 75
RDG/TG 100
RDG/TG 150 80 ft.lbs.
90 ft.lbs.
110 ft.lbs.

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DA Collets

RDA/DA Collets are recommended for drilling. RDA/DA Collets were originally designed to clamp well on slightly uneven surfaces such as jobbers or taper length type drills. RDA/DA Collets are available in 1/64 increments and in .5mm increments for metric sizes. RDA/DA collets are also known in the industry as DA and VDA collets.

RECOMMENDED USES FOR DA COLLETS

RDA/DA collets are recommended for drilling only.

ACCURACY OF DA COLLETS

RDA/DA Collets are manufactured to within . T.I.R. outer diameter to inner diameter. The length of parrallelism between the two female contacting angles in the chuck controls the accuracy of the system and is held to within plus or minus .. The clamping nut floats slightly to allow the chuck to center the collet. Normal accuracy is approximately .001 T.I.R at the face of the collet chuck.

CARE AND USE OF DA COLLETS

The DA chuck, DA collet and DA nut must be thoroughly cleaned before assembling to maintain accuracy. A benchtop ultrasonic cleaner will dislodge fine chips and debris or, a bottle type brush can be used for cleaning the inner diameter of the collet and a toothbrush style can be used to clean the exterior. Once assembled a normal machining environment will not affect the toolholding assembly.

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AF Collets

This highly accurate Acura-Flex collet system (AF collet system) was originated by Universal Engineering. RDF/AF Collets are recommended for drilling, milling and boring applications. RDF/AF collets are also known in the industry as BF collets.

AF collets are available in 1/64&#; increments and limited metrics sizes. RDF collets are designed to collapse 1/64. Size ranges are as follows:

Series
RDF 25
RDF 38
RDF 50
RDF 75
RDF 100 Inch Range
1/32-1/4
1/16-3/8
7/64-1/2
7/64-25/32
13/64-1&#;

*RDF/AF Collets in the 50, 75 and 100 series are available sealed for Coolant through applications.

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RDO Collets DIN Style

The high gripping strength RDO collet system was originated in Europe and are sometimes known as Ortlieb style collets or Full Grip Collets. Many machines designed for woodworking also use this system. This system is recommended for milling, drilling and boring applications. Many high production routing systems manufacturers have standardized on this system. Size Ranges are as follows:

Series
RDO 16 (form A style)
RDO 20
RDO 25
RDO 35
RDO 44 Inch Range
1/8 &#; 3/8
1/8 &#; 1/2
1/16 &#; 5/8
1/8 &#; 1&#;
1/8 &#; 1&#; Metric Range
&#;
2mm &#; 13mm
2mm &#; 16mm
2mm &#; 25mm
4mm &#; 32mm

*RDO 25, 35 and 44 series collets are available sealed for coolant through applications.

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Contact us to discuss your requirements of Collet Sizes Explained. Our experienced sales team can help you identify the options that best suit your needs.

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