Mill Workholding

The science behind work holding in the shop is fairly basic. Hold on to the part to be machined, in a repeatable location with sufficient grip and support to allow the machining processes to be performed reliably.


Vises are one of the most common choice for workholding. 
Available in single and dual station configurations. 
Allows for a large rage of part sizes.
Machinable soft jaws are available to clamp parts that are not a rectangular shape.

Clamping Your Part 
• Keep the part down in the jaws as far as possible.
o The higher up in the jaws you hold a part, the more jaw deflection you will experience.
• Keep your parts centered on the stationary jaw face.
o This will apply uniform force across the face of the stationary jaw.
o Keeping the part to one side of the stationary jaw face will cock the jaw, creating misalignment.
• If you wish to clamp two smaller parts at the same time, place one on each side.
o Do not clamp more than two parts at the same time without special jaws to account for any part size variation.

It is good practice to become familiar with your vise's clamping forces.
• Too much clamping force could damage parts with thin wall sections.
• Repeatable clamping pressures will help you achieve better accuracy.
• Never use a cheater bar or hammer to strike the handle.
o This excessive pressure can cause damage to the vise's internal parts.
o The handle of your vise is properly designed to allow for adequate clamping pressure.

Magnetic Chuck

 Properly applied magnets will hold work pieces as well or better than mechanical clamps.
 Instantaneous clamping force of 12 tons per square foot is generated on some of these Magnets.
 The attraction or “pull” of the magnet becomes stronger as the gap between the work piece and the magnet closes. Smooth surfaced work pieces are more tightly held than rough surfaced.
 The strength of the magnetic attraction is a function of how much magnetic flux can be induced into the work piece.

There are three different types of magnetic chucks
 Electro Permanent Magnetic Chucks – requires an electric charge to turn on and off the magnet. Once turned on no more electricity is needed to keep the magnetic holding force.
 Electro Magnetic Chucks – requires a constant electric charge to keep the magnetic holding force. If power is lost the magnet will lose its holding force.
 Permanent Magnetic Chucks – uses manual switch or lever to engage the magnet.

Vacuum Tables, Chucks and Fixtures

 Because a tight air seal is essential to the holding power of a vacuum workholding, application of these devices is limited to work pieces that incorporate flat, non-porous surfaces.
 A vacuum work holding system can be expanded to accommodate very large work pieces. For example, vacuum chucks have been used successfully for gantry-type machines with table surfaces as large as 12 feet by 40 feet.
 A vacuum chuck is suitable for holding non-ferrous metals or any other flat, non-porous material.
 Its maximum holding power is approximately 13 pounds per square inch, which equates to nearly a ton of holding force per square foot of the workpiece.

Manual Fixtures

 Common workholding for castings and forgings
 Made from an array of clamps, grippers, locators and work supports.
 Uses manual labor to clamp/unclamp part

Hydraulic and Pneumatic Fixtures

 Common workholding for castings and forgings
 Constant clamping
 Limited or no manual labor to clamp/unclamp parts
 Can be used in robotically loaded machining cells
 Typically detected to one part or a family of similar parts.


 Tombstones are a popular choice on HMC’s and rotary applications.
 Can be used to hold a small qty of large parts or a large qty of small parts
 Can be combined with other workholding types, eg vise, manual fixture, Hydraulic fixture…

Alloy Clamping Technology

 Suitable for manufacturing work pieces, which cannot be clamped conventionally because support surfaces are lacking.
 The milled hollows are filled with a low melting alloy, which hardens into a plane parallel surface. The work piece is then flipped and clamped securely.
 The finished workpiece is placed into hot water at 115-338°F in order to melt the alloy attached to it.
 The alloy does not mix with water and can be collected, remelted and used again.
 Low melting point alloys containing metals such as Cadmium, Tin, Lead and Bismuth can be used.
 Commonly used in 5-axis manufacturing.


Use work supports in your manual and hydraulic fixtures to keep the unsupported areas of the part from deflecting during the machining process

Clamps, Grippers and Locators

There is a wide variety of clamps, grippers and locators available off the shelf from various manufactures to fit your application. However, you are not limited to what you can buy, many times custom or modified clamps, grippers and locators are used in workholding.

Dovetail Fixtures

• Dovetail workholding uses a dovetail feature with a locating slot on the workpeice to clamp into the fixture.
• This creates a solid positive lock that is very rigid and accurate.
• These fixtures also allow access to machine 5 sides of the part.
• This is a common workholding solution in 4 & 5 axis manufacturing.

Collet Chucks

• Common in 4 axis applications
• Each collet has a size range
• Square, Hex and other shaped stock can be held with the appropriate collet
• Capable of both ID and OD clamping

Be aware: Many service and repair procedures should be done only by authorized personnel. The service technicians at your Haas Factory Outlet (HFO) have the training, experience, and are certified to do these tasks safely and correctly. You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes.

Danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not completely understand. Contact your Haas Factory Outlet (HFO) and schedule a service technician visit if you have any doubts about doing a procedure.