Sump bolts

[A G Wood]

Another thing you may find handy MM, (particularly if you're trying to place a helicoil/V coil in situ above your head)  is to grab your drill press and make up a two-hole guide block with one hole drilled to minimal clearance on the o.d. of the helicoil/V coil drill and the other hole drilled for minimum clearance on the o.d. of the helicoil/V coil tap. I use scrap 50mm lengths of 30 x 10 merchant flat bar, you can either clamp the bar or hold it in your other hand depending on the job.
Invaluable if  you [like me] wear glasses, have a full beard and dislike being externally lubricated while you are trying to drill/tap squarely!