Please look away now if you work in health and safety, but there is a homemade engineering product that is often used on sites as a get-out-of-jail tool. If there is a last minute spec change on site, after the job is finished (sound at all familar?) then holes for the fixing bolts may well need some modification (see here why would I want to enlarge a hole that has already been drilled )
Of course there are many trusted ways of re-engineering a hole on site, normally using a magnet drill, but there are many applications where size or access problems prevent access to the hole. (for example if there is a whole section of rivets or bolts close together)
The homemade version that has been around for decades is to take a bridge reamer, find a nut that fits fairly snugly onto the shank, and weld them together
There are several disadvantages to this method -
1. Accuracy- these are often welded up under site conditions without proper clamping tools, and using the MMA stick welding process. The nut is never an exact fit onto the tapered shank of the reamer, so it will only touch at one small point. This means the accuracy is compromised and they will not run true, resulting in a larger hole size than anticipated. This can lead to tolerance problems with the fixings, and it is very difficult indeed to reduce the size of a hole....
2. Shattering/Safety Issues. A bridge reamer is designed to be used in a morse taper shank rotary drill, like a large magetic drill or pillar drill. As they are not designed for use under impact conditions, users will testify to the fact these home-made site reamers can often actually shatter in use. This can cause serious HSE issues, especially because an unauthorised modification has been made, so the user is liable.
3. Geometry/Cutting Life - as above, a bridge reamer is designed to be used by a controlled rotary action with specific speed and feeds. The cutting flutes are deep and optimised for this method. As the impact cutting action works in a different way, the bridge reamer will not perform effectively nor cut many holes. This then leads to the risk of shattering (see above)
4. Price/Value - A bridge reamer will cost anywhere from £60-150 plus the time and effort it takes to take the nut and weld it up. ImpactaCut Reamers are better priced as well as performing much better, for a far lower risk.