drilling cast iron?

[neil1967]

I need to add a rudder sensor for my new autopilot. The autopilot ram connects to a cast iron 'stub' or arm on the rudder stock. Is it OK to drill a small hole in the cast iron to attach the arm of the sensor? I know the sensor will not exert any noticable force on the stub, but I am concerned about weakening the stub. Is this likely to be a problem?

 

[Yellow Ballad]

I wouldn't have thought you would have a problem, cast iron gets drilled to "stitch" cracks back together.

But I'm no expert on it.

 

[Lon nan Gruagach]

I need to add a rudder sensor for my new autopilot. The autopilot ram connects to a cast iron 'stub' or arm on the rudder stock. Is it OK to drill a small hole in the cast iron to attach the arm of the sensor? I know the sensor will not exert any noticable force on the stub, but I am concerned about weakening the stub. Is this likely to be a problem?

really souldnt be a problem, but if you are concerned then fix something to the arm with a jubille clip.

 

[Topcat47]

Sharp drill and slow speed. Tapping the holes isn't recommended though.

 

[maby]

You should be ok with a small hole provided it is not close to the edge of the workpiece. Remember that cast iron is brittle and the crystal structure is often very coarse - any thin piece is going to be fragile. What is going in the hole? A through bolt should be ok, but a self tapping screw is likely to be problematic.

 

[NormanB]

You can drill and thread cast iron and as has been said, slower speed not too much pressure and let the sharp drill do the work. If you have to thread, then use a coarse rather than fine thread. Better though if you can 'through bolt' and clamp (conventional nut and bolt) because cast iron prefers compressive load.

 

[neil1967]

Thanks all - yes, small holes and nut and bolt attachment.

 

[vyv_cox]

You are certain it is cast iron? Seems an unusual material choice for a lever arm.

 

[Norman_E]

You are certain it is cast iron? Seems an unusual material choice for a lever arm.

Not just unusual but poor because cast iron is strong in compression but weak in tension or torsion and repeated reversals of thrust are likely to result in fracture. The most common type of cast iron is called flake cast iron because it contains flakes of carbon which weaken the structure, spheroidal graphite iron is better but it is to be hoped that it is actually a steel forging, or at least cast steel. If it is iron it will produce powder drillings, steel will produce spiral ones.

 

[neil1967]

I had assumed cast iron due to the amount of heavy surface corrosion. I guess it could be steel? It clamps on to the rudder stock and has a woodruff (?) key to prevent it slipping.

 

[Tranona]

I had assumed cast iron due to the amount of heavy surface corrosion. I guess it could be steel? It clamps on to the rudder stock and has a woodruff (?) key to prevent it slipping.

Likely to be a steel forging if it has any shape such as reinforcing ribs or machined out of solid if flat. Rusts just the same as cast iron! Quite normal to drill.