Since we can only have 10 photos, understandably, I will submit two tools today so please also look at the Bee Mite Vaporizer tool that I built this tap for. Long story short I needed a 10x1MM tap for a Glow Plug in an aluminum block for a Varroa Mite vaporizer that I was building. Here is how I did it when now could be found close by. I bought 2 10x1x40MM Hex headed bolts when the Hardware Store did not have the tap I needed. I used an old trick to make a single flute tap from a bolt
Quickly setting the bolt in the Mill/drill vise, I cut a groove down right hand side, The raised letters on the head were causing me trouble so I went to the lathe and machined the head flat and while there also tapered the thread end.
Back to the mill and deepened the groove, changing the angle so that I had more than a 90 degree opening for a flute.
I filed off the secondary edge of the groove and then using a 17MM ratchet wrench started the thread. It took a mild blow on the tap head with a mallet for the tap to catch well enough to start the thread. We went right down the whole 5/8 of an inch that I needed. The threads looked and worked well. This is an easy way out of a bind that can stop a project. Grade 8 bolts can be used for a couple of threaded holes in mild steel.
Hope this will help some of you get your project done.