# Cross drilling intersecting holes



## EmilioG (Nov 8, 2014)

I have a project that requires cross drilled holes or close crossed holes.
I have these 1/2" square 1018 and 3/4" square 1018 steel parts that are
2" and 3" long respectively. I need to drill holes about 1 1/2" and 2" apart
on each side. The holes are 8 mm and 10mm, 8 on the 1/2" part, 10 on the 3/4"
square part.

I've calculated the holes but they will slightly intersect.  How can I drill these holes
without the bits grabbing when it encounters the other hole. This is almost like a manifold
or 1 2 3 block.  Thanks


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## Brain Coral (Nov 8, 2014)

After drilling one set of holes, push a piece of ground rod (8mm or 10mm) into the drilled holes before drilling the next set.

Brian


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## Bill C. (Nov 8, 2014)

I have drilled holes that did intersect.  I found it easier when drilling the second hole, when the bit breaks through the wall of the first hole to gently feed it slowly to the other side so it doesn't wander off center.  How do you plan on removing any internal burrs?

The first shop I worked in as a machine operator they made their own manifolds for some of the special machines they built.  Sure looks better than a set of "T"s screwed together.


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## EmilioG (Nov 9, 2014)

Thank you for your replies.
I did think about putting pins or rods in the holes, my concern was that they may get "jammed" in the holes.
For deburring, I've made a small pin with a slot that holds emory cloth, I then use an electric drill to deburr.
I did look at those expensive hones for holes. Don't know if they make them that small, (3/8" or 10 mm)?
Thanks


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## kd4gij (Nov 9, 2014)

One trick is to grind a small flat on the outer edge of the bit  it won't grab that way and ease up just before it breaks through. I do this alot in 4140.


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## EmilioG (Nov 13, 2014)

kd4gij said:


> One trick is to grind a small flat on the outer edge of the bit  it won't grab that way and ease up just before it breaks through. I do this alot in 4140.



Good idea. Just like with brass.  I did manage to do the drilling with good spacing so only one hole slightly nipped open
the corresponding cross hole by about an 1/8". No problems, but I would like to try intersecting the holes a bit more, not so
they are all exposed like a 1 2 3 block.  I'll try a reamer as well. What size drill do I use if I want to ream a 25/64" hole?

Thank you.


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## EmilioG (Nov 17, 2014)

I;ve managed to drill my cross holes with no trouble.
I didn't even have to use any rods to fill the corresponding hole temporarily!
I punch marked the holes, used a spot to start the hole then used the final size
letter O stub length drill bit and it went right through with no grabbing or deflecting.
The burrs were minimal. I was able to use threaded rod to ream them by hand to clean
them out.  This was on 1/2" thick square 1018 steel. Slow steady feed and and about 1000 rpm.

Next, I'll drill my 3/4" square parts. (cross holes on a few as well).

Btw, I used a Bridgeport mill with a 16n Jacobs/R8.






Thanks


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