Drilling holes through tubing

[914pete]

I'm feeling a little stupid.  I clearly do not know the trick to drilling holes straight through tubing. I'm working on the shock struts.  I bought two V-blocks thinking that would help and clamping the tube down to them.  The V-blocks are smaller then I expected but do help with holding the tubing better.  I'm eye balling the top of the tube/drill bit on my drill press and go straight through the tube.  It seems the bottom exit hole is ALWAYS slightly off center though. Any tips/tricks?

[Dan_]

If you have a dial indicator with a magnetic base, you could chuck up a big drill bit and attach the indicator.  This will allow you to sweep the table of your drill press to check it for square to the drill bit.

Otherwise there is this: https://www.amazon.com/Aircraft-Tool-Supply-Drill-Guide/dp/B005VR3L4O

[stevejahr]

I have had challenges with this problem as well.

Have not tried this... but this (or last?) month's EAA magazine had a suggestion of balancing a steel ruler between the tube and the drill bit.  When the ruler stays horizontal with the drill bit pressing on it you are centered.

[Tom XL-7]

This subject came up in the past.
I made a jig ( or is this a tool) Out of wood. Never used it yet, just made it as an example.
Well, I searched the old yahoo forum if that is possible- not for me. Looked for the actual piece. It has been in my hands recently and obviously, I put in a " safe" place. 
Off to old thumb drives. no luck  The real thing is hidden in my attic, and a set of photos reside on an old computer that is not assembled. If you are interested I will continue my search. 
Tom XL-7

[Dan_]

This subject came up in the past.
I made a jig ( or is this a tool) Out of wood. Never used it yet, just made it as an example.
Well, I searched the old yahoo forum if that is possible- not for me. Looked for the actual piece. It has been in my hands recently and obviously, I put in a " safe" place.
Off to old thumb drives. no luck  The real thing is hidden in my attic, and a set of photos reside on an old computer that is not assembled. If you are interested I will continue my search.
Tom XL-7

Go here:  https://groups.yahoo.com/neo/groups/EaglersNests/conversations/topics/14171

Pics are attached...

[Tom XL-7]

Thanks, I just found the message and the photos don't have to post now.
Tom XL-7

[scottiniowa]

I'm feeling a little stupid.  I clearly do not know the trick to drilling holes straight through tubing. I'm working on the shock struts.  I bought two V-blocks thinking that would help and clamping the tube down to them.  The V-blocks are smaller then I expected but do help with holding the tubing better.  I'm eye balling the top of the tube/drill bit on my drill press and go straight through the tube.  It seems the bottom exit hole is ALWAYS slightly off center though. Any tips/tricks?

Pete you almost have everything you need.    On your V- block, -tig weld your drill guide on the end so that it is centered on the vee... thus when your V-block is held to your tube with it's clamp, ( I assume you have the clamping kind of V-block)  if you welded your drill guide strait and true, you will get your hole through both sides strait and true as well.  Done right, you will have this drill guide block forever and works on all sizes of tubing that might have.  you can also do two different size guides,    i.e.   .25-" and 3/16's on the other end of the block.   (center id's) 

Good luck.  
ps... done tooling steel, these guides will last a long time.    Some will clamp the v-block in mill, and make a shallow grove on the end, to assist getting the guide perfectly aligned   A little work up front has great rewards later.

[914pete]

Welp, I discovered a few things working against me.  My drill press is just an inexpensive table top Delta.  No matter how tight I tried to secure the platform, it can still move side to side ever so slightly.  While that was happening my standard drill bits were bending ever so slightly which would make the hole on the other side of the tube off center.  Can't tell you how many through holes I drilled in scrap tubing yesterday.

I'm not sure I fully understand your tip Scott but it got me thinking.  I have a simple Craftsman slide clamp which I bolted to the drill press platform and clamped the V-blocks in.  I then drilled a 1/4" and a 3/16" center hole maybe 3/16" deep in one of the V-blocks. I happened to have 3/16" dia. and 1/4" dia. rod in the warehouse so I cut a 1/2" length of each to use as removable "pins".  I also bought step drill bits at HF (no bending).  I center the bit in the hole I drilled in the V-block, place the tubing on the V-blocks, drill my first hole then place the appropriate dia. pin in the hole in the V-block flip the tube over, the pin goes through the first hole and helps hold the tube in place, drill the second hole, no measuring necessary, and you have a perfect centered through hole.  Quick and easy.  I also like the step drill bit because it puts a nice chamfer on each hole.

[scottiniowa]

excellent Pete- looks like you got it figured out...

[ultra]

I'm feeling a little stupid.  I clearly do not know the trick to drilling holes straight through tubing. I'm working on the shock struts.  I bought two V-blocks thinking that would help and clamping the tube down to them.  The V-blocks are smaller then I expected but do help with holding the tubing better.  I'm eye balling the top of the tube/drill bit on my drill press and go straight through the tube.  It seems the bottom exit hole is ALWAYS slightly off center though. Any tips/tricks?

I would strap that tube down in a V block on the mill then mill a flat about 15 thou off the top of the tube.

This way you can center punch a mark for your drill as well as keep the drill on center.