How to drill a small straight hole in 3/16 steel rod?

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dansawyer

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The project is replacing a 3/16 steel rod to fit into a 5/16 brass sleeve. A final assembly is a 1/16 hole is drilled through the brass sleeve and the rod to hold them in position; a small pin is then pressed into the hole to hold the rod and the sleeve in position. I am replacing the steel rod. The project is to drill a new hole in the rod that matches the hole already in the brass sleeve.
My first attempt failed miserably. I ended up with a hole 30 degrees off vertical and a new hole out the other side if the brass sleeve.
I have an RF-31 mill drill. I very carefully placed the assembly in a vise, carefully ensured the holes in the brass sleeve were vertical. I aligned the drill to the hole as best as I could. I then proceeded to miss drill a hole about 30 degrees off.
I understand when a drilling into a rod the drill will wonder. I was hoping the brass sleeve would hold it in place.
The only thing I can thing to do is mill a small flat in the rod and then start the hole with a center drill.
Is there a simpler way?
 
Yes milling a flat & spot drilling would help greatly, in fact I would have done that no matter what.

Is it possible to just make a new sleeve also? Problem with trying to match the alignment of the hole in the sleeve is that you don't know how accurately that hole was drilled to begin with. So even if you get your hole drilled accurately there's a chance it still may not line up on the other end. Given the small size of your parts makes the task more difficult to match.

And it's a drilling operation, even if set up as accurately as you can, as you know a drill can wander, a number of things can effect how straight the drill bit will drill, sharpeness of the drill, how evenly the flutes are ground, the hole that the drill first contacts to start drilling, runout, etc.

So if you could make a new sleeve, drill one hole through both parts & you won't have to worry about alignment. Of course still possible to to get it to work with what you're doing now just saying it might be easier to just make a new sleeve. But I don't know what that sleeve part consists of & if it's an option.

But who knows, it may just work fine, try milling a flat & spot drilling first. Hopefully it works out.
 
One method that I use with the drill press is to start the hole and observe the alignment from the end of the shaft. It is fairly easy to see if you are going off side. I rotate the work in the vise to correct any misalignment. This usually gets very close to center.

Another method is to use a vee block. Center the drill in the bottom of the vee then clamp the shaft in the vee and drill. Starting with a center drill will help to keep the drill properly centered. Also drilling with a carbide drill helps because of the extra stiffness of the carbide.
 
Another way when you are trying to match the holes in a sleeve is to drill about half way through and slide the sleeve into place. Then place a short pin in the hole in the sleeve and the shaft. . Rotate 180º and drill the other side. The two holes may not intersect perfectly but if you run the drill through the shaft ,you will end up with a through hole that matches the holes in the sleeve.,

This method works when the holes in the sleeve are not perfectly on center.
 
Thank you all for your advice. I did try the flat and center hole method. The result was much better. The assembly is held together by a hollow spring split drift pin. (I am not sure what these are called. This result is almost good enough that the pin will go all the way through. I think I will rotate the assembly 90 degrees and create a new hole through both the sleeve and the rod.
Thanks again. Dan
 
Glad you got it done. If faced with this again, consider making a simple jig.
This worked for me to drill tiny holes through small rods (this was about an 0.030 hole crossways through a 0.100 shaft.)
1. Use a piece of scrap, maybe some 3/8" or 1/2" square stock. Carefully layout the hole centers for the 3/16 rod and at right angles through the hole center line, a drill 1/16" hole as a drill guide.
2. Stick your rod into the jig and drill through the jig and the rod.
 
I intend to test this again. It is a good exercise for alignment. My last test was to mill a small flat and then use an edge finder to calculate the center of the rod. The first pass did not find the center accurately. I am not sure if the reason was improper use of the edge finder or if I did not account for backlash correctly. Another opportunity to learn.
 
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