Hatz Biplane Association

There is some risk in threading under power with a lathe that has a threaded spindle, but only when you put it in reverse to back out the tap or for left-handed threads. However, if you rotate the chuck by hand you should be ok, or at least be able to see if it starts to back off the spindle and stop yourself. I'd still give it a shot.

As for left handed threads, look over the plans where the threaded bearings are used (like a Heim or Aurora bearing). These are used on things like the push tubes for the aileron controls, elevator controls, aileron slave struts, etc. If you check the part numbers that are on the plans you'll find that left & right hand threaded bearings are required.

If you do not have a lathe - A drill press will also work, just hold some down pressure and turn the chuck by hand. Gives a perfect alignment.

Michael
N9648B

Drag / anti drag wires are left handed but that is a die not a tap. I made some temporary wires so that I could trammel the wing, the final threads will be rolled.

The only time I used a left handed thread was on the drag/anti-drag wires and that was a die and not a tap.

Jeff Moore

Gday Chaps, as an old fitter machinist here in Australia who is about to retire I hope you don't mind if I comment on this subject.Every thing that has been said up to now is all good,couple more tips,the better quality taps will have a centre drill hole in the end,so use a live or dead centre in the tail stock of the lathe and turn the tap with an adjustable spanner while you keep the pressure on with the centre in the tail stock.Now having said that remember that the chances of breaking the tap is directly proportional to size of the shifting spanner,it is all about the length of the lever.Also a small tap wrench can be substituted for the spanner.A small tip here,the smaller the tap the less digits holding the tap wrench,a really small tap means one finger and thumb on each hand ,learn to feel the action of the tap through the fingers.The same method can also be used in the milling machine or drill press, centre in the hole with live or dead centre and then lock the table,begin the tapping process keeping the weight on with centre.This will hold the tap vertical and centred,go slow and take care. Cheers Ross