# Drilling small cross holes



## deverett (Dec 5, 2013)

Recently, I had to drill a 42 thou cross hole in 2 x 1/8" diameter bars.  There have been numerous cross hole jigs described, but this is a simple foolproof way to cross drill small holes, ideal for those one offs or small batches.

Take any small lump of steel from the scrap bin and square it up, dimensions are not important, mine ended up at about 1-1/8" x 3/4" x 1/2".






Drill a hole through the length of the block for the bar to be cross drilled.  It pays to tap one end for a stop screw, particularly if there is more than one rod  to drill.  Mark the block with a felt tip pen to show which side is against the fixed jaw of the vice.





Now, turn the block so that it is lying flat in the vice, with the same side against the fixed jaw.  This is important, hence the pen mark.





You will see 2 holes.  The right hand hole is tapped in any convenient place for a clamp screw, brass in my case so that it did not mark the bar.  The left hand hole has a dimple started with a small centre drill and followed up by the 42 thou drill, right through the block.  This ensures that the long hole for the bar, the clamp screw hole and the cross hole are all in perfect alignment.

Mount up the bar to be drilled in the block and drill through the cross hole in the block.





I stamped the distance the cross hole is from the end of the block for future reference.  It helps determine where the cross hole will end up in the job.  

In this case, the bar is 1.438" long.  The cross hole needed to be 0.094" from the end.  The jig hole is 0.600" from the end (not .700 as first marked !).  So to get the correct amount of bar sticking out:  1.438 - (0.094 + 0.600) = 0.744".  The stop screw is adjusted accordingly.

Job's a good 'un.





Took me about 30 minutes, most of which was squaring up the block.

Dave
The Emerald Isle


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## crueby (Dec 5, 2013)

Nice idea - another type of jig that can save much more time and aggravation than it took to make!


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## kiwi2 (Dec 6, 2013)

Can you explain more fully why it's important to always have the same side against the fixed jaw in the vice?


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## deverett (Dec 6, 2013)

Kiwi2

Using any squared up piece of steel, you can drill the long hole anywhere, it does not have to be on the centreline.

As an extreme example:  supposing your piece of steel is 3/4" wide and you drill the long hole 1/2" from one side, it will be 1/4" from the other.  Now, turn the block so that the unmarked side is against the fixed jaw.  Your cross holes will miss by 1/4".

I did not do any marking out or measuring, except by the mark 1 eyeball.  It just so happened that the long hole appears to be near the centreline, which made the pen mark more important - otherwise sod's law and all that.

Dave
The Emerald Isle


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## kuhncw (Dec 6, 2013)

Nice fixture, Dave.  I especially like the adjustable stop.

Regards.

Chuck


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## kvom (Dec 6, 2013)

kiwi2 said:


> Can you explain more fully why it's important to always have the same side against the fixed jaw in the vice?



The centerline of the hole is a known distance from the reference side.  Since you want to drill the cross hole in the center of the rod, set the reference side against the fixed jaw and move the spindle to the known Y position.


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## Nerdz (Dec 6, 2013)

Ive been wondering how to accurately drill through the center of a rod lately. Looks like this can even be made on a 4 jaw chuck! Now I dont have to spend $40 on Vee Blocks to drill through rod


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## kvom (Dec 6, 2013)

My usual way to do it is to hold the rod in a 5C collet block and use an edge finder to center the spindle.  Start the hole with a very rigid spot drill before drilling though.  This is faster for 1 or 2 holes than the fixture, but for more than that this fixture is a good design.  Might be improved by drilling several different sizes of through holes in the fixture for future use.


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## deverett (Dec 6, 2013)

kvom said:


> ...  Might be improved by drilling several different sizes of through holes in the fixture for future use.



I thought of that afterwards.  All that would be required is to drill each set of holes well well away from the others.

Would save metal for those that don't have a large scrap box!

Dave
The Emerald Isle


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## kiwi2 (Dec 8, 2013)

Hi Dave,
           I'm still not quite sure why it's important to know the orientation of the block in the vice. Is it to aid in drilling the transverse hole in the block, or to ensure the drill is in line with the transverse hole when drilling a cross-hole in a rod? Is your vice in a fixed position under the drill?
I use a similar system. In order to get the transverse hole in the middle of the longitudinal hole I mount the bar in a vice such that it is parallel to the x axis of the mill table and put a drill in the mill chuck. I then lower the drill past the longitudinal hole and bring it flush with the end of the bar. I then center the drill with respect to the longitudinal hole using the y axis of the mill table by eyeballing it. The drill is then raised and the mill table is moved along the x axis till it is above the bar and the transverse hole is drilled.
To get the transverse hole centered for drilling a cross-hole, I clamp the bar loosely onto the mill table and fit a center into the mill. The center is then lowered into the transverse hole and the bar will move to center the hole. The bar is then clamped down hard while still depressing the center. The center is then replaced with the required drill, the rod is clamped into the bar and the cross-hole drilled. It seems to work OK as I have drilled about 20 cross-holes without any wear showing up on the transverse hole in the bar.

Regards,
Alan C.


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## Omnimill (Dec 8, 2013)

I have a rod drilling jig Dave but I like your approach on this, especially the no measure block flipping idea. Must try to remember this!
It's a no brainier really, just takes someone else to point it out to you!


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