Fitting a rudder safety collar

[pschauss]

I am preparing to install my new rudders and I need to drill a dimple in the shaft of each one for the set screw in the safety collar. Is this something that I can do with a normal hand-held power drill or should I take the rudders to a machine shop? The stainless steel is so hard that center punch I normally use won't make a big enough dent to keep a drill bit from wandering.

[Carl]

Easiest way I have found...

Assemble with collar in place.

If two set screws on a collar at 90 deg, snug one of them up.

Remove screw from the other and use that threaded hole as your guide to dimple the shaft.
IF only one set screw...you'll need to be a bit more careful starting as drill likes to walk.

Do not start with a smaller drill...you'll need to use the tap drill for this to work.

So if its a:
1/4 -20 thread gets a #7 drill (.201) or 13/32 (.203)
5/16-18 thread the drill should be an "F" drill (.257)...a 1/4" works in a pinch.
3/8-16 thread then use a 5/16" drill

To drill insert drill bit into hole without turning drill on...get your position- then feather the trigger for slow rev's (a couple hundred rpm)and push like hell. SS does not like tool rubbing on it creating heat which makes the SS harder and drill dull which creates more heat that makes SS even harder and tool duller creating more heat...see where this is going.
Anyway slow revs and push...you should see chips coming out shortly. Take a look, you should have a full dimple...if not, go a bit more. Do your best to follow holes angle, collar is softer bronze, easy to go crooked enlarging threaded hole, something you do not want to do.

[Rawleigh]

Carl: What about cutting oil for SS? Will high Sulfur pipe threading oil work with SS?

[Carl]

Rawleigh- just to dimple for a set screw, all that stuff will do for you is make a mess and get the chips to stick inside.

Now if you wanted to drill through the shaft, yes that pipe cutting oil works real fine...aside from it being a messy, sticky and a smoky oil. The trick to that is not to let the tool overheat...No straw and definitely no blue colored chips should be coming out when using HSS tooling. Those colors show the tip is at the temperature the tools get tempered. So its slow the tool down, extract the hot chips.

A dimple should be done before heats a factor...unless tools not being pushed.

[pschauss]

Carl,

Thanks for all of the pointers. After having no luck with conventional bits I bought a couple of cobalt alloy bits. Took less than 10 minutes to create one dimple, running the drill dead slow in 10 second pulses.

[Carl]

If wearing out the HSS bits and taking 10 minutes...you had to push harder.

Yes...I know you pushed...but I mean push. Almost impossible to push hard enough with a hand drill in a confined space.