Machine v Self-Tapping Screws

[William_H]

Always tap by hand.Using a drill is not the way to go.You need to feel the tap cutting and will need to back it to clear the swarf.

The advantage of the battery drill on low speed is that you can easily hold the tap (and drill) at the correct perpendicular angle to the material with steady down pressure. Hence less chance of hand wobble that results in poor thread. The battery drill is easily reversed to clear swarf.
Of course it all depends on having the right sized hole drilled in the first place. Be careful you don't snap the tap off.
For tapping stainless steel the electric drill is not powerful enough. I have often used the drill press as the mount for the tap. This ensures precise perpendicular location of the tap. No I don't power up the drill but rather turn the chuck by hand and use the large down pressure available to help the tap start. I certainly have trouble holding a tap holder in my hand straight and steady while turning.
I would reiterate to OP that a tap in a battery electric drill (one with 2 speed via a gear box) and using the correct drill size would be the way to do the job up the mast. Anyway he can try it on the deck level screws for starters. If it is too hard to get the tap in then use a slightly larger drill size. Or try rivnuts. What suits him will become obvious. good luck olewill

 

[Graham_Wright]

The advantage of the battery drill on low speed is that you can easily hold the tap (and drill) at the correct perpendicular angle to the material with steady down pressure. Hence less chance of hand wobble that results in poor thread. The battery drill is easily reversed to clear swarf.
Of course it all depends on having the right sized hole drilled in the first place. Be careful you don't snap the tap off.
For tapping stainless steel the electric drill is not powerful enough. I have often used the drill press as the mount for the tap. This ensures precise perpendicular location of the tap. No I don't power up the drill but rather turn the chuck by hand and use the large down pressure available to help the tap start. I certainly have trouble holding a tap holder in my hand straight and steady while turning.
I would reiterate to OP that a tap in a battery electric drill (one with 2 speed via a gear box) and using the correct drill size would be the way to do the job up the mast. Anyway he can try it on the deck level screws for starters. If it is too hard to get the tap in then use a slightly larger drill size. Or try rivnuts. What suits him will become obvious. good luck olewill

+3! Tapping by hand is fraught with misalignment. Use a low torque setting and reverse frequently if the job fights back.

 

[Ian_Rob]

Thanks for the replies. All really helpful as usual.