# Locating A Part To Be Drilled On Center. ?



## WesPete66 (Jun 26, 2016)

How does one set up a piece of round bar stock when you want to drill a small cross hole, with the hole perpendicular to part's center line (like for a spring pin or cotter)?  My first attempt at locating it by eye wasn't so good, and the cotter was visibly not on center.  (.75 dia bar & .12 thru hole)
I have a basic drill press with a plain vise I can attach to the table (with no x / y movement).   I do have dial indicators & base, but I have no means of measuring movement on X / Y axis.
Also should I center drill first to keep the drill from pushing off the round stock?


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## Ed ke6bnl (Jun 26, 2016)

One good way is to lay a small scale on top of round part and lower drill bit to scale and move so scale is parallel to table


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## Ulma Doctor (Jun 26, 2016)

an easy way to do it is to make a small flat on the rod when chucked in a vice, this will locate the center.
drill on the small flat and you'll hit center everytime


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## Kernbigo (Jun 26, 2016)

both are very similar to the way i do it, put a center drill in the chuck lower it down tell you touch the piece, then move it back and forth tell there is  line on the piece, find center of the line and drill the center hole.


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## kenscabs (Jun 26, 2016)

An XY table with an edge finder would be the most accurate.  I've used this little gizmo for non critical cross holes.


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## Wreck™Wreck (Jun 26, 2016)

kenscabs said:


> An XY table with an edge finder would be the most accurate.  I've used this little gizmo for non critical cross holes.
> 
> View attachment 131431


I have one of these tools, one of the most inaccurate tools that I have ever bought, I will give it  away to the first person that wants it, shipping included.
As to the question asked  touch off one side and move on from there, simple and expedient.


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## TOOLMASTER (Jun 26, 2016)

i like to run a mill bit across the top just enough to give a bit a flat to start on, it also gives you the center


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## jtrain (Jun 26, 2016)

Interesting question and replies.  Made me think of the method to set lathe tool height by placing a 6 inch pocket ruler until it is perpendicular.  The ruler should work horizontally on the drill press.


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## kd4gij (Jun 26, 2016)

I use a V block. Center the V block under the center drill and when you lay the bar it it is centered. If you don't have a V block a piece of angle iron will work.


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## WesPete66 (Jun 26, 2016)

Thanks to all for the replies!
Actually I was looking at the v-blocks recently, the ones with the groove cut in the bottom that lets you align a drill bit to the slot.  Are those worth the money? It's gotta be better than what I have now..


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## Bob Korves (Jun 27, 2016)

WesPete66 said:


> Thanks to all for the replies!
> Actually I was looking at the v-blocks recently, the ones with the groove cut in the bottom that lets you align a drill bit to the slot.  Are those worth the money? It's gotta be better than what I have now..


kd4gij has the right idea.  If instead you put a 90 degree (45 each side) tool in your drill press spindle, you can push it down into the v-block and hold it there until the v-block is tightened to the table.  Change to a center drill, carefully peck a tiny hole and then open it to just under the diameter of the center drill tip only, no shoulder or main cutter entering the work at all.  Now change to your drill and make the hole.


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## Wreck™Wreck (Jun 27, 2016)

Bob Korves said:


> kd4gij has the right idea.  If instead you put a 90 degree (45 each side) tool in your drill press spindle, you can push it down into the v-block and hold it there until the v-block is tightened to the table.  Change to a center drill, carefully peck a tiny hole and then open it to just under the diameter of the center drill tip only, no shoulder or main cutter entering the work at all.  Now change to your drill and make the hole.


Spotting drills are 90 Deg. and designed specifically for spotting drilled holes, why would anyone change to a center drill for spotting holes? Center drills are for creating lathe centers, spotting drills are for starting holes for the twist drill to follow, these are not the same thing.


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## Bob Korves (Jun 27, 2016)

Wreck™Wreck said:


> Spotting drills are 90 Deg. and designed specifically for spotting drilled holes, why would anyone change to a center drill for spotting holes? Center drills are for creating lathe centers, spotting drills are for starting holes for the twist drill to follow, these are not the same thing.


I am assuming the main drill has a 118 degree point angle here.  The starting tip of the center drill is ground at 120 degrees.  The spotting/center drill should have a LARGER angle than the drill that follows for it to follow with proper guidance, not walking around as the cutting lips make contact with a 90 degree hole part way out on the cutting lips, which leads to chatter and poor following.  The chisel point of the larger drill should be first to contact the work in the starter hole and start cutting, with the cutting lips taking over the job from the center outward, not starting by taking notches from some random points on the cutting lips.  In this way the starter hole is truly guiding the drill.

Using the 60 degree main cutting portion of a center drill to make a starting hole for a drill is a really poor idea, even worse than the 90 degree spotting drill, but it is very commonly done.  Using the parallel bore caused by the entire tip of the center drill penetrating the work is not quite as bad, but still wrong, and is also sometimes done in error.

Again, the only way a starting drill can facilitate centering of the drill and locating where the drill should follow is for the included angle of the starting/spotting drill to be slightly larger than the drill which will follow.  That would mean a 120 degree spotting drill for a 118 degree drill to follow, and a 140 degree spotting drill for a 135 degree drill to follow.

I understand quite well that what I am posting here is not common practice.  If you disagree with it, please explain to me why it is wrong.

Specifically, in the case of starting a hole in a curved surface, which is what the OP was trying to do, the center drill is a pretty good choice because it is extremely rigid, has a 120 degree starting angle, and can leave a small, well centered starting hole if pecked lightly and carefully, avoiding the need for milling the curved surface flat first, which would be probably be best for higher precision work.  A spotting drill has a larger chisel point and is also less rigid than the center drill is, and is therefore more likely to walk off the curved surface.

Does that make sense?  It has worked well for me...


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## RJSakowski (Jun 27, 2016)

All Good Ideas!  

Here are a couple of others.  I made up some V blocks for the drill press by welding two pieces of angle to a piece of 1/4" flat plate.  You can size thwe angle to meet your needs.  The one improvement that I would make would be to make the base plate larger for more convenient clamping.

Another way to make an "emergency"  V block is to clamp two pieces of pipe together with two Vise Grips.


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## John Hasler (Jun 27, 2016)

I like the pipe idea.  It occurs to me that a couple of reasonbly precise cylinders --wrist pins, for example--- could serve as quite an accurate V-block.


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## Ulma Doctor (Jun 28, 2016)

even a pair of dowel pins could be held together and clamped or set in a vise as well, i'd imagine-


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## Paul in OKC (Jun 28, 2016)

Depending on your indicator, you can use it. Bring your part up to touch the drill bit, set indicator, tap to move part (half diameter plus half drill bit). If yu only have a 'finger' or test indicator, be a little tougher, but doable. Great ideas above as well.


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## rock_breaker (Jul 13, 2016)

One thing that doesn't get mentioned very often is to be sure the cut off tool is perpendicular to the work.  Doing this and following these  suggestions has improved my cut off  work a great deal.
Have a good day!
Ray


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## Billh50 (Jul 14, 2016)

I touch off 1 side with an edge finder then dial in center. Then center drill to diameter of the drill I am going to use. The center drill to diameter will help the drill stay on center.


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## EmilioG (Mar 14, 2017)

I'm in the middle of making cutter blocks for small diameter stock. I will use 1" hex and square stock, drill/bore and ream
for diameters dead center and use a set screw to hold stock.  Now, I can just turn the block on the flats and get my holes or flats
on the opposite side or with hex stock, at different points.  For cross holes, you can drill holes on the flats of the square stock
90 degrees opposed or any other configuration one wants.  Or, you can make bushings so one can use different size drill bits with the square or hex cutter blocks.

Cutting a small flat with end mill on round stock before drill the hole helps to keep the drill from wandering.
The idea came to me from reading Guy Lautards BSR books.


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## ghostdncr (Mar 14, 2017)

Speedy way? Chuck up a dowel pin. Lower it below the edge centerline of your round stock and hold a flashlight behind it. Ease the work piece over until you see the dowel pin touch. If you don't have DRO's, move toward center half the dowel diameter, and then continue moving half the work piece diameter. This will get you within .002 or .003" in most cases. If you do have DRO's, touch off on one side and zero the axis you're moving in. Touch off on the other side and then divide your readout number in half.

The absolute best way I've ever found for centering, short of bringing lasers into play, is the IndiCol attachment and a test indicator. You can center a hole to within .00002" if you have the correct indicator and the patience to work at that level. Choose your method based on the required tolerance of the job at hand.


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## Cadillac STS (Mar 19, 2017)

kenscabs said:


> An XY table with an edge finder would be the most accurate.  I've used this little gizmo for non critical cross holes.
> 
> View attachment 131431



I use one of those for drill press work.  Works just fine for what I need to get done.  

You did say you have a basic drill press with no X Y capability and I think the gizmo is fast and easy for that.


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