Introduction to Live Centers
If you need extra support during your lathe application because your workpiece extends a decent distance away from the jaws holding it in place, you’ll want a live center. A live center is a tool bit placed between the headstock and tailstock of a machine tool. It is used to support a long workpiece and reduce “flex”, thus preventing chatter and a compromised surface finish.
Let’s take a look at how live centers work, the different types and how to select the right one for your application.
Why use a live center?
A word you will frequently hear when referencing a live center is concentricity. The core role of the live center, in technical terms, is to produce concentric work. Concentric means having a common axis or being coaxial. This is a fundament of geometric dimensioning and tolerancing. If you’re interested in digging a bit deeper into GD&T and its connection to live centers, check out Understanding Geometric Dimensioning and Tolerancing.
Anatomy of a Live Center
Now that we know what a live center is used for, let’s discuss its components and their functions.
The tapered end is inserted into the tailstock; the opposite end is a conical shape that connects with the workpiece. The conical head spins on the pre-loaded bearing assembly you see above. Those bearings are what allow the free rotation of the conical head.
A live center typically includes a protective ring between the conical head and the bearing base. That ring acts as a shield to protect the tool from harmful contaminants like dust and coolant, thus increasing the longevity of the bearings.
In order for the live center to be held in place, you’ll have to bore a small hole at the end of your workpiece so the live center can make, and hold contact with the workpiece.
Types of live centers and tips for selecting the right one
Live centers come in a variety of different types and shapes. Some of them are more suitable for high-precision work, such as grinding applications, while others work better with larger parts or parts with larger center holes.
In the image below, you will find examples of the different types of live centers (along with some examples of dead centers), each with specific anatomy to support various application needs. Learn more about the different live center types here.
Live centers will help you achieve higher turning speeds, tighter gripping, more force and overall a better final result, so knowing how to choose the right type is important. Here are a few things to consider when choosing a live center:
- The taper of your machine
- The weight and length of your workpiece
- The load rating of your machine tool
- The cutting force and speed you apply
- The thrust load needed to keep the workpiece seated in position (this is typically 2/3 the weight of the workpiece)
Below is a collection of live center models for general lathe and grinding work. You’ll find both medium duty options for light-to-medium sized projects and heavy-duty options for applications that require larger parts.
Medium Duty Live Centers
Morse Taper Medium Duty Live Center
This Morse taper live center is made of heat treated steel and includes case-hardened housing, hardened to 61-65 Rockwell for high speed turning. There is a washer to protect bearings from grit and dust. This center has a 60° point.
Accusize Industrial Tools MT3 Precision Medium Duty Live Center
This live center has a combination of deep groove ball bearings, thrust ball bearings and needle bearings. The anti-dust seal prevents cutting fluid and dust from entering the center bearing. The 60° rotating spindle is made from carbon alloy steel with heat treatment for high rigidity and wear resistance.
HHIP MT4 Medium Duty Live Center
The central spindle of this live center is made of hardened alloy steel and ground for high accuracy. It includes a dustproof seal on the front end. This tool can handle an accuracy load of .0003″, radial load of 1,100 lbs. and can reach 2,500 RPMs.
This live center can handle 3,000 RPMs and a load capacity of 770 lbs. It has a 60° center point and achieves 0.000197″ accuracy. The shaft is made of alloy steel through heat treatment for high rigidity and durability.
Heavy Duty Live Centers
Steelex Heavy Duty Live Center
This Triple Bearing MT3 Live Center is hardened to 61-65 Rockwell and has a unique head driving mechanism that prevents dust, chips, and coolant from entering the internal workings. Made with high quality precision bearings, this live center has an accuracy of 0.0003”.
HHIP MT4 Bull Nose Live Center
This bull nose live center has a 75° point and can support up to a 1,760-pound load rate. This live center is best used for pipe and other hollow-shaped work machining. The bull nose makes this live center great for parts with large center holes.
Live Tailstock Center, Heavy Duty MT4
This live center has double row bearings inside and supports up to 5,000-6,000 RPM. The tool bit has been heat treated for optimal durability. This model is mainly used for processing bushing parts on general lathes. With the center hole positioning, the workpiece parts are highly dimensionally accurate.
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