Comments sought on new build: A CNC Router for RC Gliders and Planes

[routercnc]

Sorry to hear about the tap! So annoying and as they are very brittle it's not easy to tell that they are about to go.

I've seen them spark eroded out, but it takes ages and I think is done underwater (?!).

I've had success with Jazz's method of pecking it out with hard tools and getting lucky until I could unscrew it. Sometimes there's enough sticking out to get a mole wrench on it, but not with yours.

If you definitely need the hole at that location and it won't budge then one option is to use the CNC machine to cut out a large through hole around the tap (say 30mm diameter) so that a nice round cylinder of aluminium is removed containing the tap. Then machine a round pocket (say 60mm diameter and 5mm deep) centred on the same hole. On the lathe turn up a part which fits the 60mm dia pocket and has a shank of ~30mm which goes right to the bottom of the hole -essentially a plug the same shape as the removed material. Drill a couple of countersunk holes (to keep the bolts flush) into the top flange of the plug, and through into the bed. Tap the bed and bolt the plug in place. Then drill and tap the centre hole again with a new tap!

Another option if you manage to get the tap out but damage the thread too much is to use a heli-coil which uses as oversized tapped hole to insert a spring shaped piece of metal which then creates the original thread diameter again.

[njhussey]

Sorry to hear about the tap! So annoying and as they are very brittle it's not easy to tell that they are about to go.

I've seen them spark eroded out, but it takes ages and I think is done underwater (?!).

I've had success with Jazz's method of pecking it out with hard tools and getting lucky until I could unscrew it. Sometimes there's enough sticking out to get a mole wrench on it, but not with yours.

If you definitely need the hole at that location and it won't budge then one option is to use the CNC machine to cut out a large through hole around the tap (say 30mm diameter) so that a nice round cylinder of aluminium is removed containing the tap. Then machine a round pocket (say 60mm diameter and 5mm deep) centred on the same hole. On the lathe turn up a part which fits the 60mm dia pocket and has a shank of ~30mm which goes right to the bottom of the hole -essentially a plug the same shape as the removed material. Drill a couple of countersunk holes (to keep the bolts flush) into the top flange of the plug, and through into the bed. Tap the bed and bolt the plug in place. Then drill and tap the centre hole again with a new tap!

Another option if you manage to get the tap out but damage the thread too much is to use a heli-coil which uses as oversized tapped hole to insert a spring shaped piece of metal which then creates the original thread diameter again.

Cheers Barry, im favouring trying the smash it out with a hard pointed punch. The annoying thing was that I was backing the tap out the hole...

I like the plug idea, ive got to surface the Ali base at some point so might turn a press fit plug.