Dies, Maintenance, Pelleting
Nov 15, 2015
La Meccanica
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Dies: the clamping surface

Clamping Surfaces

An important part of any die inspection is the inspection of the quill flange clamping surfaces. These areas can commonly be cause of a broken die if the proper maintenance has not been performed on the adjacent wear parts, such as clamps and wear inserts. Thus, the overall goal of examining the clamping surfaces is to gauge damage to other parts of the machine. There are four surfaces that are inspected:

  • the loose clamp surface
  • the clamp bottoming surface
  • the wear ring surface
  • the keyway

Loose Clamp Surface

The loose clamp surface is the front of the die quill flange that mates against the clamping surfaces. This surface can suffer wear for various reasons. Items that can affect the wear include undersized quill flanges, worn pellet mill quills, worn die clamps, worn wear rings, and worn keyways. Finding the cause of the wear will necessitate gauging the rest of the surfaces.

A worn quill can cause wear on the loose clamp surface and the butt surface that mates against the quill directly opposite the loose clamp surface. Wear on both of these surfaces could indicate a quill rebuild is needed. Certainly the quill should be inspected carefully and the next opportunity.

Usual wear on the loose clamp surface is the result of worn die clamps. The clamps should be checked with the appropriate wear gauge provided for that die. The condition can be observed by cleaning off any anti-seize material or rust from the surface. Wear will appear as polished metal. A good item to determine is whether the surface was ground or hard turned during manufacture. By determining the type of finish, the wear can be gauged.

Clamp Bottoming Surface

Clamp bottoming occurs when wear to the die, quill, clamps, or any combination of the three becomes so severe that the inside of the clamp rubs against the top of the quill and the top of the die quill flange (the clamp bottoming surface).

The condition can be observed by cleaning off any anti-seize material or rust from the surface. Wear will appear as polished metal. A good item to determine is whether the surface was ground or hard turned during manufacture. By determining the type of finish, the wear can be gauged.

Wear Ring Surface

The wear ring surface is commonly called the die pilot surface. This surface mate up against the wear ring insert in the quill. Again, the types of grinding and turning are similar to those previously mentioned, depending on the place of manufacture. Wear on this surface can be caused by installation with an already worn wear ring or an undersized pilot diameter.

Undersized pilots are a common occurrence. Most wear on these surfaces is caused by installation of the new die with an old wear insert. Wear on this surface indicates that wear ring inserts should be changed immediately. Wear can also indicate that a die is loose and may often be the cause of wear on other surfaces within the mill. The condition can be observed by cleaning off any anti-seize material or rust from the surface. Wear will appear as polished metal.

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Keyway

The keyway is the area recessed into the die pilot that fits the key and provides the drive for turning the die. This surface will tend to experience wear only if the die is loose or the key was undersize and worn to begin with at installation. The battering or “wallering” effect experienced by the keyway is caused by the loose key. As the key pivots in the keyway, it causes a doming effect on the sides of the keyway.

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