Drilling out the end of a rod help

[wing_nut]

Is there a fool proof technique, or tool, of marking the center of the end of a rod or gun barrel to drill it out?

[dupes]

No.

Although even if you're off a hair initially with your first poke, you can usually adjust a bit once you start drilling (lean to one side with your blade or bit). In the frickin' wee scales you deal with, though, you may not have that sort of leeway!

[John Everett]

There's an old machinist's trick. Try clamping the bit in a vice and turning the barrel in the drill. The idea is that the the barrel will find its own center as it rotates against a fixed cutting tool.

If you work slowly, it generally works pretty well. If you have a junk barrel in the Spares Box, try it with that one first.

For marking the spot where you will place the pilot hole..........what's the diameter of the barrel? There's another trick where you put the corner of a 90 degree square along the edge of the circle and then mark the places where the edges of the square meet the edge of the circle.......It's easy if you can see some pictures. But it's only practical in circles of 1/4" or larger. Smaller than that and things become inaccurate pretty quickly.

[TRM]

There are a couple ways to pinpoint the center of the circle. On barrels...small ones in like 1/350 and 1/700, typically just drawing and 'X' will get you close enough to the center.

More accurately is similar to way John was mentioning. Take a 90^o angle and place it on the edge where two points of the square touch the outside of the circle. If you come off the vertex with a 45^o angle it will give you a line that will give you a diameter line crossing the center of the circle. Spin the angles and cross the line.

Micro Mark sells a small tool...which is easy to build yourself...



There was another trick I read about for drilling the center of solid rob....with various size tubing...one that fits to the O.D. of the rod with another that fits inside and a drill bit that fits the inside of the inner rod will do the trick and keep the drill bit from drifting.

Good Luck

[wing_nut]

Thanks for the responses guys. All that stuff for larger diameter rods and dowels I knew about but the max would be 1/8" and the majority way smaller than that.

T... The tube that fits the rod is the kinda of thing I was looking for. In fact i seem to recall that tip from waaaaay long ago.

Surfing around on-line I came across one that sounds good but i think it would be tricky even at 1/8 and no way smaller. A guy fits the rod/dowel into a hole in a hole template, marks the 4 side from the alignment hashes and then make the lines across to mark the center. But that tube thing some like ta goody.

[TRM]

Tube thing sounded like a good choice after I saw it a while back...I will keep looking myself. Probably Fakebook is where I seen it. LOL! I know you get the concept with the inner tube aligning the bit and held in place with the outer tube...guessing it makes more sense said that way! Agreed on the 1/8 possibly being the smallest. I have some 1/16 tubing and bits to go in it...but honestly, a black dot would work at that scale unless it was for parts assembly! If I find the post on my end, I will pop it up!

[wbill76]

You could also take a sharpie and blacken the surface you're drilling out, then mark the surface with the tip of a #11 blade and/or the drill bit. The exposed contrast will tell you pretty quickly if you're off center or not. It isn't as high-tech or mathematical/geometrical as the other methods but seems to work reasonably well for me when I've tried it. Even under the Optivisor!

[TomN]

There is a way, it's an old trick I saw on You-Tube, can't find it at the moment so I'll try to explain.

Take a piece of bar stock, maybe like 1/8" thick.

Drill a hole all the way through, the diameter you want in the end of the rod.

Using the small hole as a pilot, drill a hole the diameter of the rod halfway through the bar stock. 

Stick the rod in the large hole, turn the bar stock over and drill through the small hole.

Hope that makes sense.

Tom

[wing_nut]

OOPS sorta forgot this one. Bill, Tom. Thanks or the responses.

Bill, the contract idea is also a good one. I am also thinking that i need to use something with a long, thin, taped, sharp point... 4 adjectives is enough, right?... so I thought of trying an old AB needle. It helped.

[wbill76]

Nov 16, 2015 7:56:10 GMT -5 wing_nut said:

OOPS sorta forgot this one. Bill, Tom. Thanks or the responses.

Bill, the contract idea is also a good one. I am also thinking that i need to use something with a long, thin, taped, sharp point... 4 adjectives is enough, right?... so I thought of trying an old AB needle. It helped.

Just goes to show you that if you use enough adjectives, a solution will present itself.

[BJ]

For material smaller then 1/8th I use one of my collets from a pinvise I slip it in one side where it's tite then find a bit that just fits through the other side without slipping through the side slot, Then I will just twist it a few times to give me my center point indention the pull it out and drill it the size I want.
Ghetto center punch.

(Added) As long as you have a good Pinvise.. I have seen some of the cheap ones that are so out of alignment its not even funny.

Also an old drill chuck will do the same thing just for making a center punch mark.