At my work I am often times called upon to restore large areas of metal; i.e. grind off the rust and repaint it etc. One particular project I received had an irregular shape to it so I chose to use a small pneumatic grinder I had never used before. I started off as usual, working from top to bottom. When I got to the bottom I sat on the ground with my legs crossed. My usual practice is to pull up some slack in the air hose and leave the excess in my lap so the grinder doesn't get obstructed. I did this but when I started the grinder again the most intense bolt of pleasure shot through my body instantly causing my dick to expand down the left pant leg of my coveralls. The grinder I was using had a very high rpm and emitted an intense frequency of vibration that I had just realized was being transferred into the air hose. I've used a good deal of air tools before, but none of them made this kind of vibration.
There wasn't anyone near me, but I was in no way hidden and I could see some people not far away. I decide to ignore the vibrations and just finish up as it was almost lunch time, but the air hose kept brushing up against my erect member making me more and more aroused. This wasn't good because it's impossible to hide an erection in coveralls and there was no way for me to move from my sitting position. I decided to see what it felt like for just a second, and then I could work on getting rid of my boner before lunch. I held the air hose up against my dick and spun up the grinder. It was indescribable, the feeling was so intense I almost came right there, but stopped myself in a desperate attempt to salvage the situation. A co-worker had just walked by, and although my pleasure was obscured by tinted safety goggles and a filter mask, I was paranoid. It didn't look like I was doing anything unusual, but what if someone asks me he help them move something, or to stand up for any reason. There was no way out, my dick was begging to cum, and I couldn't control myself. I thought I might be able to run to a toilet and finish up there but before I could finish that train of thought my hand squeezed over the lever that started the grinder. My other hand pushed the air hose hard against my dick. My last thought before cumming was 'I can't believe I'm doing this.' I came harder and longer than I ever have before. This is the one orgasm that I've had that I can say was as good as or better than my first. I let out a deep groan which was drowned out by the loud grinder. I ran it until my dick was too sensitive to continue.
Breathless, I took stock of the situation. I could feel the hot, sticky wetness of my cum on my left leg and knew I only had a minute before a wet spot developed. I was also worried that someone might be able to smell it, good thing it was lunch time. I felt dirty and embarrassed having to tell the guys that I had to run home for a minute as my still hot cum ran down my leg. I made it home to change and got back to work. I don't know how I made it out of that with nobody the wiser. I never used that tool again. I can't risk another situation like that at work even though it was the best orgasm of my life.