Skull Crushers

Skull crushers are an excellent movement for bringing up your triceps, but as the name implies there is a chance of injury when doing this move. They hit the triceps from a unique angle, which stimulates growth, so they should be a staple in your arm routine. Follow these directions to get this move right, and develop your triceps without actually crushing your skull!
Lie on a flat bench with a barbell across your chest. Grab the bar with a shoulder width grip and press it straight upwards, as if you were doing a bench press.
Keeping your upper arms perpendicular to your body, bend your elbow and lower the weight towards your head. DO NOT DROP THE WEIGHT ON YOUR HEAD! Although this movement is called a skull crusher, do not actually crush your skull!
Stop the weight when your elbow is bent at a right angle. From this point move the weight back up to the starting position. Do not allow your upper arms to sway, or you will be using momentum, and not your muscles, to move the weight.
Do this move whenever you work your triceps. If you work triceps and chest on the same day, as with a push/pull/legs split, do this move after you do your compound chest work. That is, do this move after you bench press. If you do this before you bench press, you will wear your triceps out prematurely and this will reduce the amount of weight you can lift with your bench press.

Jaw Crusher Liners

If you are in an industry that uses them, then you no doubt understand the important nature of jaw crushers, and of the liners that are used with them. It's very important that an eye be kept on the crusher liners to ensure that they last for the longest amount of time possible.
So what can you do to make sure that you have the right liner for the right job? Well there are many, and the choice as to which one to use is totally up to you. Here's some of the type of jaw crusher liners with their advantages and disadvantages.
On the basis of Shape
Straight Jaw Crusher Liners
This type of jaw crusher die/liner has a lot of advantages, but overall they just don't last very long especially with smaller CSS (Closed Side Setting) settings. You'll find out that they wear out in just a short time. This is due to its poor wear distribution. They may even plug up frequently. But, they have the maximum feed opening, most effective nip angle, and the greatest reduction ratios. These crusher liners will suit your needs if you are running a small operation, but won't cut it if you have a full blow production facility going on.
Half-Belly Jaw Crusher Liners
These crusher dies/liners essentially are straight with a curved end. When it comes to wear distribution, they are better than the straight dies but have poor reduction ratios than the later. They have fewer issues of plugging but a disadvantage of smaller feed opening than the straight ones. These jaw crusher liners prove very useful when the feed material has a significant quantity of fines, that the bottom of the liner would wear off rapidly.
Full-Belly Jaw Crusher Liners
This particular jaw crusher liner is exactly the way it sounds, being a fully curved variant. Owing to the best wear distribution of all the three types of crusher liners, these liners will last the longest. They don't plug quite as bad, provide a decent looking product, and are capable of being used with smaller CSS settings without sustaining much wear on the ends of the die. However, due to its shape, jaw crusher loses the effective nip angle in the upper portion of the crushing box.
As they reduce the feed opening, these jaw dies are particularly used when the crusher is larger than required for the feed size being fed. With these jaw crusher liners, the largest feed size won't exceed the gap between the jaw dies just above the center of the dies in the horizontal direction.
On the basis of Surface
Flat Surfaced Jaw Crusher Liners
This type of crusher die/liner has a flat surface which exerts an even and flat pressure on the material being crushed. If you use a flat liner, you may discover that within a pulverizing material the pressure becomes even and flat, giving the rock absolutely nowhere to go. A flat liner has no way of gripping a rock, which is the area in which a corrugated die excels.
Corrugated Jaw Crusher Liners
Unlike Flat Liners, theses crusher dies/liners have a corrugated surface. It is a common sense that the ridges in a corrugated die will be able to produce a more concentrated force which enables to break rock with less effort, meaning that power requirements are extremely low. With lower power requirements, the crusher has less load to contend with. But these corrugated dies don't come without their own issues. They can be easily plugged and the feed opening can be reduced.
This piece of equipment is robust but isn't something that you can take for granted. You need to take care of it, keep an eye on it, and make sure that both you and your employees are using it as intended.