Tips Hydraulic and Arbor Press Safety - Maintenance Cruz
KaPow? What was that? Something broke in the press.
I think it is pretty clear that all tools can be a great help, but also have the capacity for injury. I don't how many smashed fingers I have seen from hammers or pinch wounds from pliers, a lot. Everything in the maintenance shop has some potential to cause injuries, especially if misused. Managers worry about this potential and always have a lump in their throats worrying that even their most experienced personnel may get hurt.
You see accidents and injuries from experienced and non experienced techs all the time and it is not necessarily operator error. Tools are an amplifier of our own power allowing us to accomplish things we otherwise could not. Even a wrench magnifies our strength and brings very high forces into play, just ask anyone who has had a wrench slip and what happened to their hand. Then you progress to power tools and you are really playing with fire.
One of the most dangerous pieces of equipment in your shop is the press and in all its forms. The "H" frame press is where I will begin due to the highly dangerous nature of this equipment. The "H" frame is design to supply extremely high press power and with that comes inherit dangers. If used improperly your company would easily have a very serious injury or fatality on it's hands. I have first hand knowledge of several serious accidents and many close calls.
I personally was injured while using a hydraulic press, but my injuries were limited due to some safety measures. I wish I had a picture of the ace shield I was wearing when the bearing exploded in my face. I was pressing off a bearing, something I had done a hundred times before, when I hit a stubborn spot. I did what anyone else would do and added more pressure to overcome the sticking point. A loud pop and the bearing shifted, good it is moving, so I continued to pump the press.
I immediately hit another sticking point so I repeated the procedure from before, but this time the bearing exploded. When something made out of hardened steel shatters, it does so in a violent way sending razor sharp shrapnel in all directions. The debris hit my face shield with such force it knocked it off my head smashing me in the nose on the way. The remaining shrapnel embedded in my arm, torso, and the wall behind the press. I was bleeding but not hurt badly, but better yet my face and eyes did not get injured at all. I can say how thankful I am that I was wearing a face shield at the time.
I have repeated that story to ever tech I have ever worked with to scare them into using the safety equipment. My face shield had a serious impact mark right where my eye would have been and I have no doubt that I would have lost my eye. I rendered first aid to a tech who shattered a broaching tool, also extremely hard steel, which shattered in his face, he was extremely lucky. He had six or seven cut on his cheeks and around his eyes with one right at the corner of his eye, he was in shock. He said it just exploded like a bomb in his face and had sent him falling back.
I have seen more and had some tense moments with presses, but I think you get the idea of how dangerous this equipment can be. A misconception is that an arbor press (a hand operated press with a lever) is not dangerous or much less dangerous than a hydraulic press. A general shop "H" frame press is generally ten to twenty tons while arbor press are generally one to three ton, of course there much smaller and much bigger equipment out there. One ton of power is more than enough to create a dangerous scenario where projectiles can fly with enough force to injure or kill someone, the tech who shattered the broach was using a one ton press.
I maindate in my shops that all will wear eye protection plus face shield as well as a curtain shield when pressing. I personally wear welding leathers as an added precaution and suggest it to the techs, but I don't require it. I also have seen full cages built around presses with lexan sheets as a barrier. I think it is a great idea and would recommend it for any shop as the inconvenience outweighs the potential for injury.
There are a lot of simple things that can be done to help avoid some seriously nasty surprises. The first rule of thumb is that when it should have moved already but hasn't stop. Investigate why the parts are not moving and evaluate if maybe some heating is required. It always amazes tech when I grab a simple propane torch and free some parts that they have been fighting for hours or a little vibration helps to free the parts. I helped remove a king pin that had been hammered on with sledge hammers for three days in under an hour by just evaluating the situation. Condition one: the king pin is finished and can not be saved condition two: the pin will never slip through as it has been mushroomed by hammering. I burned a one inch hole through the pin with an air arc then cooled the pin with water. I was surrounded by sceptics until I shoved the shrunken pin out by hand. I have also shrunken steel by just welding some beads in strategic places, these are some good tips.
One the easiest ways you can help pressing operations is simple lubrication like assembly lube or liquid wrench. Anti Seize is also a good way to prevent issues in the future. I always inspect the materials I plan to put into the press carefully for condition and situations that may cause issues, like gouges or ridges on shafts. The last best tip is to take extra time and make sure that everything under the press is flat, square, and centered with the press. The number one bad situation I come across is the use of multiple press block or rods stacked on top of each other, this is a recipe for disaster as the pressure is looking for the path of least resistance.
Having a clean press in perfect working order with zero damage is an absolute requirement, that means that if a corner bolt is lost do not just replace it with anything but use original spec bolts. When the table leveling rod disappears do not replace it with a piece of pipe, ordered a new pin and lock out the equipment until it arrives, period. I always see all kinds of pipes and hand made blocks that accumulate around the press from years of rigging. Purchasing proper pressing blocks and drive rods is important and engineering has gone into this auxilary equipment.
I investigated an arbor press accident once and the culprit became clear immediately. The arbor press handle was bent and a cheater pipe lay on the floor nearby, well I guess he felt he needed more power and hurt himself and destroyed the arbor press. Hand operated machines come with handle engineered to the average person applying his weight to the handle no more, no cheater pipes allowed....ever.
Broaching is especially dangerous due to the nature of the cutting tools being under pressure. For those who do not know what broaching is I will explain. Certain machining processes are had or difficult to make on a metal cutting machine like a milling machine Items like internal keyways are made with special tool called broach, gun barrel riflings are also made with a special broach. A keyway broaching kit comes with different size cylinders with slots cut down their length to accommodate a long straight cutting tool You chose a cylinder that it the bore you wish to key and then the broach that fits, they come in sets. The broach is made to the width of the key way, but the depth is created by each tooth of the broach taking a small bite and peeling off a curl of steel.
The broach must be long to get a lot of teeth set on a very slight expanding angle, meaning the broach is thinner at the bottom than the top. As you start a broach you start taking material immediately so you incur pressure immediately. When you have a long hardened brittle cutter under pressure deflection is your enemy. I do not allow my techs to use the broaching equipment until I have trained them properly and told them my harrowing stories. You must use plenty of cutting fluid to help relieve some of the pressure by controlling friction and you must press and relieve regularly. In other words, press a little and relax and allow the broach freedom to recenter before gently applying slow pressure while watching closely with all your safety gear on.
Just look around your shop at all the hydraulic equipment you have, like bottle jacks. Bottle jacks have a lot of power and can be used in some very unsafe ways. I was taught to never trust hydraulic jacks as they can fail at anytime and that is true. I have seen them used for lifting, spreading, compressing, and metal forming. The have a nasty habit of slipping off when they are used incorrectly and set up for a bad situation.
It is imperative that the personnel in your shop realize that anytime they are multiplying their strength through the use of tools they are bringing high pressures into play.