I have a mastercraft nailer/stapler ..... the driving pin does not reset after the first staple ..... is there a spring perhaps, in side the housing that has come off? ... can't think what else it might be .... at this point the pin just slides back and forth with no way for it to reset above the next staple in the loading chamber
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Re: driving pin won't reset
The check valve is what causes the pin/driver to return to top of cylinder. To check if it is in place, remove the cylinder from the gun and look for an oring/band installed on a groove. This groove should have vent holes drilled thru the cyl. Holes should be clean. Any oring or rubber band can be used here. Just tight enough to stay in place. Other things to check:
Pin/driver should fit snuglly enough to hold it's own weight in cylinder. If your gun uses a plastic ring, it may be replaced with a rubber oring. Just make sure that the piston travels freely but holds its wieght.
There should be a bumper and a washer in the lower part of the gun. The bumper should not have any cuts or missing pieces and the washer should fit snuggly around the driver blade to prevent air from leaking down thru bottom of gun. If air is leaking down thru bottom, there is less pressure to push driver up. Email if you have more questions, good luck with your repair.
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The Bostitch SX150 pneumatic brad nailer/stapler uses air to both drive the brad or staple and to return the driver/piston assembly to the top of the gun for the next firing. There is no spring that goes into the sleeve or under the piston. If your driver is not returning to the top of the gun you may have put an o-ring or seal in the wrong place or left one out. The o-rings and check seal on the bottom half of the driver sleeve are what control the air that returns the piston to the top so check those first.
You didn't list the make and model of your stapler but if it's not driving the staples flush with the surface here are some possible causes: 1. The wood; If you are driving long staples into hardwood or knotty lumber you may have to use shorter staples to see how they set. 2. Stapler settings; Turning the air pressure up isn't the answer to driving staples deeper, it is only harder on the stapler. Most staplers work in the 90 to 120 psi range. The lower pressure you use the longer your stapler will last. Check/adjust the depth of drive control on the stapler to determine where the top of the staple is driven to. 3. Broke stapler; If it's not driving them to the proper depth but the level they are driven to is consistant, you may have a damaged piston o-ring/seal or the end of the driver is broken off. You'll have to go into the gun or take it to a service center to check these things.
Sometimes a gun will double fire, quickly fires twice and is caused by worn trigger valve or safety foot. However, two staples driven with one shot indicates that the staples could be the wrong gauge for the gun or the driver is damaged. The driver of a nailer has a taper on one side of the blade to prevent the driver from hitting two staples. The taper will push the remaining staples back into the rails. Make sure that the taper is facing the staples and that the staples are correct for the gun.
I have rebuilt many older Duofast staplers and have seen the problem that you describe. Duofast staplers have twice as many orings as other brands of nailers. Some people say that the nailers are over-engineered. I say that they were built to last a lifetime and need extra care when working on them. Duofast relies on various springs to reset functions or operations. For example there is a spring within the trigger valve that you do not see when you are rebuilding that may be weak and cant overcome the friction of the new orings. That spring resets the trigger after firing. If you replaced all the orings but did not replace any of the springs within the gun, it will take a while for the gun to get back to normal. I use new springs and lube all the parts with silicone lube instead of oil. Silicone lube is sold at Lowes in the plumbing department. It is used to lube orings in faucets. Instead of taking the gun apart, try using a little extra nailer oil in the gun and cycle the gun with-out nails dozens of times to work-in the new orings. If the problem does not go away, take a look at a breakdown and try streaching all the springs just a bit, or make sure that all the springs are in place. Also make sure that the head gasket is in good shape or the oring that seals the headvalve port to the body. Good Luck with your repair and email if you have other questions.