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Albert
11-25-2009, 03:02 PM
Could someone please suggest a better and/or easier way to accurately drill round pipe?

I often need to drill about 1/4" holes through the diameter of 1" SS round pipe. Most of the time, no matter how accurately I position the drill bit on the punch mark, it deviates and doesn't come out on the other side on the exact diameter. The only way I can think of preventing this from happening is to get 1" square stock, drill through that, and then use it as a guide on top of the round pipe in the drill press vice. The "problem" is that when the square stock is placed on the round pipe, positioning the punch mark in the exact center will be difficult, at best.

I know there are "V" blocks that have holes drilled in them for use as a guide to position the drill bit. I've not tried them. Would this be the best solution?

cutter
11-25-2009, 04:09 PM
Albert, here's a pretty simple guide (http://www.shopfloortalk.com/forums/showthread.php?t=9695) you can make that might do it for you.

I feel sure others will be along with their suggestions. http://www.shopfloortalk.com/forums/images/icons/icon14.gif

GWIZ
11-25-2009, 06:16 PM
I don't know how close you want it.

A square bushing is the way too go.

Also you can try, after you drill the top hole use a #3x6" center drill and drill thru the bottom hole. you may have too go with cobalt for SS.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=54&PARTPG=INLMK32

Machinist-Guide
11-25-2009, 07:07 PM
GWIZ has good advise on this one. If you don't have a long center drill you could try drill a small pilot hole first. Maybe around 1/16 or so.

Here is a link to a video on hole drilling and some helpfull drill point charts

Hole Drilling Video (http://www.machinist-guide.com/hole-drilling-tips.html)

Albert
11-25-2009, 08:18 PM
When you say, "square bushing", what exactly do you mean?

I don't know how close you want it.

A square bushing is the way too go.

Also you can try, after you drill the top hole use a #3x6" center drill and drill thru the bottom hole. you may have too go with cobalt for SS.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=54&PARTPG=INLMK32

GWIZ
11-25-2009, 08:36 PM
The only way I can think of preventing this from happening is to get 1" square stock, drill through that, and then use it as a guide on top of the round pipe in the drill press vice.

The "problem" is that when the square stock is placed on the round pipe, positioning the punch mark in the exact center will be difficult, at best.


Same thing as you stated.
It goes back to this link.
http://www.shopfloortalk.com/forums/showthread.php?t=8973


I know there are "V" blocks that have holes drilled in them for use as a guide to position the drill bit. I've not tried them. Would this be the best solution?

The problem you are having is the second surface is curved up, so the drill gets pushed around before it centers.
you have to start the second hole with a smaller drill point or prevent the drill-bit from moving with a fixed bushing.

Albert
11-25-2009, 11:52 PM
Thank you all for the suggestions. I'll try the bushing approach, combined with a long center drill for the second hole, and see how it turns out.

precisionworks
11-26-2009, 12:41 AM
On a drill press, the easiest way is to center the drill over a slot in the table, and lock the table in position. The pipe will rest on the edges of the slot, and will need to be clamped to the table. Since the drill bit is already centered in the slot, the hole will go right through the center of the pipe.

Machinist-Guide
11-26-2009, 02:23 AM
precisionworks: has good advise here also the slot will act like a v-block I use this technique on a mill it saves the time of indicating your work parallel to the table. GWIZ mentioned in post #6 about the bottom wall curving up into a concave radii. This is why I suggested using a small drill frist. The smaller drill is less ridged and will walk its self to the bottom of the tube

precisionworks
11-26-2009, 06:02 AM
The smaller drill is less rigid and will walk its self to the bottom of the tube

That is a really good idea :D

Most of the pipe I've drilled was larger, 3" and over, on a Morse Mor-Speed of WWII vintage. Typical radial drill, 48" overarm, cube table that weighed a few hundred pounds, really a nice old machine. Those T-slots were XXL in size and would easily let a 1/2" drill bit clear both sides of the slot.