FAQ

Centreless grinding is a precision machining process that removes material from the outer diameter of cylindrical workpieces without using centres or fixtures to hold the part in place. Unlike conventional cylindrical grinding, where the workpiece is secured between centres or in a chuck, in centreless grinding, the workpiece rests on a work blade. Two wheels guide it: a grinding wheel and a regulating wheel, also often referred to as a control wheel.

The grinding wheel rotates at high speed to remove material, while the regulating wheel rotates at a much slower speed to control the workpiece’s rotation and feed rate. Often, the regulating wheel is inclined to adjust the material feed rate.

The work blade provides support at the correct angle, creating a stable “grinding zone” for precision machining.

• Higher Productivity: Continuous loading allows for faster processing
• Improved Roundness: The method naturally produces excellent concentricity
• No Workpiece Distortion: No chuck or centre pressure means no deformation
• Versatility: Can handle long, thin parts that would deflect in centred grinding
• Consistency: Ideal for high-volume production of identical components

In traditional centred grinding (cylindrical), the workpiece is held at both ends (between centres or in a chuck) and rotates against a grinding wheel.

In centreless grinding, the workpiece is not mechanically constrained but instead rests freely between the grinding wheel, regulating wheel, and a work blade. This fundamental difference eliminates the need for centre holes or complex fixturing and work holding solutions.

Centreless grinding is suitable for virtually any material that can be ground, including:

• Various steels (carbon, stainless, tool steels)
• Superalloys including Inconel, Hastelloy, Titanium, Waspalloy, Nimonic and more.
• Aluminium and its alloys
• Brass, copper, and other non-ferrous metals
• Ceramics and composites, including carbon fibre
• Plastics

There are two primary methods:

• Through-feed grinding: The workpiece passes entirely through the wheels, ideal for straight cylindrical parts
• In-feed grinding (plunge grinding): Used for parts with complex profiles or shoulders where the regulating wheel moves inward toward the grinding wheel

Centreless grinding is renowned for its precision, typically achieving:

• Diameter tolerances: ±0.0001 to ±0.0005 inches (±0.0025 to ±0.0127 mm)
• Surface finishes: 1.0 to 16 microinches Ra (0.02 to 0.4 μm) and even lower with the correct abrasive
• Roundness: Within 0.0001 inches (0.0025 mm)

This process is vital across numerous sectors:

• Automotive: For parts like valve stems, piston rods, and transmission shafts
• Aerospace: Hydraulic components, landing gear parts, and engine components
• Medical: Implants, surgical instruments, and diagnostic equipment parts
• Hydraulics & Pneumatics: Cylinder rods, piston pins, and valve spools
• Fastener Industry: Bolts, pins, and precision shafts

• While versatile, the process has some constraints:
• Not suitable for parts with multiple diameters or complex geometries in a single setup
• Requires consistent workpiece straightness for through-feed grinding
• Establishing the initial setup can be time-consuming for short production runs
• Cannot easily grind faces or shoulders except with specialised in-feed setups

Size control is achieved through precise machine setup and the relationship between three key elements: the grinding wheel, regulating wheel, and work blade. As material is removed, the workpiece settles lower on the work blade, changing its relationship to the wheels. Experienced operators use this principle, along with proper wheel dressing and feed rates, to maintain consistent sizing.

This is the self-correcting mechanism that makes centreless grinding so effective at producing round parts. If a workpiece has a high spot, that spot will contact the grinding wheel more aggressively, removing more material from that area. As the part rotates, this corrective action continues until optimal roundness is achieved.

Absolutely. Modern centreless grinders often incorporate automation for loading, unloading, sizing control, and wheel dressing. This makes them ideal for high-volume production environments where consistency and minimal operator intervention are priorities.

Today, NC and CNC machines along with automation solutions allow for a modern and clean machining process.

Consider centreless grinding if your project involves:

• Not always limited to, but has significant advantages with high volumes of cylindrical components
• Strict requirements for roundness and surface finish
• Long, slender parts that might deflect in chucking
• Parts that would be expensive or difficult to centre
• Applications where production speed is critical
• Applications where the workpiece has an infinite length

There are many different options for bandsaws, depending on materials and sizes being cut.

• Vertical Bandsaws - These range from benchtop machines for the hobbyist (generally cutting wood or plastics) right up to huge machines to cut metals ( ferrous and non ferrous). The basic design is the same where a single vertical bandsaw blade is tensioned across 2, 3 or 4 band wheels giving a maximum height under the guides, and a maximum depth from the frame to the blade ( throat).
• Horizontal Bandsaws - again these come in a small portable format for site work, right through to machine you can park a car under and saw it in half! The process is the same with machine operation coming in a manual (pull down saw), Gravity feed (saw frame descends by itself and the rate is controlled via a valve on the hydraulic circuit), semi automatic (hydraulic down feed of the saw frame and hydraulic operated vice) and fully automatic (same as the semi automatic machines but with the addition of bar feeding to allow batch cutting operations. These can also be full enclosed CNC controlled bandsaws. Horizantal bandsaws can also do mitre cuts to allow for cutting angles on sections or beams.

NO. Many factors come into play such as structure, blade size, blade speeds and coolants.

• Structure - Lighter duty machines running hi speed bandsaw blades will be ideal for woods, plastics and some non-ferrous metals
• Blade size - Trying to cut a heavy piece of material with a 13mm wide blade just doesn't work. The wider the blade the stronger it is (beam strength).
• Blade Speeds - Hi speed machines cut soft materials but when you start cutting mild steel, stainless steels or other exotic metals, then the blade speed has to be slow ( say 15 -70 m/min). These machine also need torque ( power) to drive the blade through the material.
• Coolants - a vital item needed to cut anything that generates heat or is abrasive.  Anything metal will need flood coolant or a mist lubrication system.

Depends on the daily work really. If you do lots of one offs, and quick cutting jobs ( like box sections or tube), then its quick and easy to use a pull down saw. If your cut time is longer, like heavy wall sections or solids, then let the bandsaw do the sawing whilst you go do something else!

Gravity feed machines are straight cutting or mitre capability ( swivel head), as are semi automatic bandsaws. So the fundamental design is all the same. However the key difference on a semi automatic bandsaw is the hydraulic operation of the vice and the saw frame.

Operation:

Gravity feed bandsaw - you lift the saw frame up to clear the work area, then place your work in the saw and manually clamp the vice. Press the start button to run the blade and coolant, then open the needle valve to gently descend through the job stopping the blade and coolant automatically once its hit the bottom.

Semi-automatic bandsaw - the saw frame is powered to the raised position ready for the work piece to be loaded. Once ready, you press the start button and the blade starts, vices will clamp (hydraulically) and the saw frame will descend through the workpiece. Once the cut is complete. the saw frame will raise back upto a preset position ready to start another cut, and the vice will unclamp. These controls can be changed to suit different jobs.

Another thing to consider is the size of saw needed. If your cutting larger products then the actual saw frame will be much bigger and difficult to handle. So the need for hydraulic lifting becomes vital.

Semi automatic saws operate as follows:

Horizontal machines can still be made with a 2 speed motor giving simple operation if you were doing say mild steel and stainless steels. They are typically somewhere around 40 and 80 M/min.

Better speed options give better results and longer blade life on more varied materials. A typical speed option in the modern day is to use a frequency inverter to control motor speed. This might allow speeds from 15 -90 M/min giving great results on the harder metals.

Vertical bandsaws can have invertors or mechanical variators and even gearboxes to allow for high and low ranges. Again, speeds are crucial to the material your cutting. If only ferrous metals, then slower speed ranges will be needed. If your cutting woods, metals and plastics you'll need a full speed range from 20 - 1200 m/min. These are available and would have invertors and gearboxes to give speed and torque control.

Industrial circular saws come in 2 main types. Ferrous and non-ferrous. Each range then has the option of manual, semi automatic or fully automatic.

Metal saws for steels - These are generally available with a blade range of 250 -350mm diameter and run slower speeds for mild or stainless steels. Typical 2 speed machines run a 20 / 40 rpm and would have a flood coolant system. Commonly known as chop saws, these use solid HSS circular blades and have the tooth pitch cut into them. The blades can be supplied with many different coatings depending on the materials they need to cut.

Circular saws for non-ferrous / plastics - These machine are normally single speed and run at a much higher speed. Normally @ 3000 rpm depending on blade diameter. The suitable blades for this type of machine would be TCT (Tungsten Carbide Tipped) and would be quite course in pitch. TCT blades are used for wood, aluminium and plastics with the tooth form on the blade being different for each application. TCT blade can cut dry or a simple venturi mist spray can be used to assist with lubrication.

Both types of circular saw blade can be sharpened, with the HSS slow speed blades being able to be re-cut if damaged or severely worn.

A couple of reasons really, the main being they are quick and can potentially give a better finish.

• Non ferrous circular saws are much quicker than a bandsaw and give a better cut, but they are limited to capacity. If you have a large section to cut the bandsaw might be needed.
• High end circular saws can be expensive to purchase, so make sure you can justify the limited capacity.
• Smaller chop saws for steel are just a common way to saw smaller box section, angle and tube and take up less floor space than a bigger bandsaw.