I'm fitting a DRO to my Centec 2B. On the RHS of the body there are two unpainted nicely machined raised rectangular surfaces, each with 4 tapped holes, that were clearly intended at one time or another, to have something bolted to them.
Not wanting to drill any more holes than necessary, I have bolted the display gantry to the top surface, and am fitting part of the Z-axis scale to the other. This involves bolting on, doing some machining, and then removing it to check fit etc. Now here's the funny thing; when I remove the first bolt from the lower surface there is a noticeable puff of air from the tapped hole. It lasts only 1/4 second or so, but its very noticeable. It only happens if all the holes have been occupied and the machine used. I'm of the opinion that its trapped air that has been heated by the gearbox that is just above the top surface. Any other ideas?