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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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centering a hole with a drill press
I have a drill press, and I need to center a hole in the face of a
cylinder. I would be perfectly happy to one hundredth of an inch accuracy. An X-Y table attached to the drill press stage would do the job, but I suspect that for the level of accuracy that I need, there is a simpler solution--and I just don't know it. I've tried scribing diameters across the face, and picking where they intersect--but the results have been less than impressive. Does someone have a trick for this? Clayton E. Cramer |
#2
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In article .com,
wrote: I have a drill press, and I need to center a hole in the face of a cylinder. I would be perfectly happy to one hundredth of an inch accuracy. An X-Y table attached to the drill press stage would do the job, but I suspect that for the level of accuracy that I need, there is a simpler solution--and I just don't know it. I've tried scribing diameters across the face, and picking where they intersect--but the results have been less than impressive. Does someone have a trick for this? What did you use for positioning the diameters? A V centering head on a combination square should do a pretty good job, as long as your scribe has a very skinny point, and you angle it so the point is right along the edge of the scale. Then, you need a spotting drill and good magnification to get the hole started as close to the intersection of the lines as possible. Once that is done, you can move up to a larger bit. But 0.010" may be pushing it if you don't have experience in doing this. Better, of course, would be a lathe of sufficient size with a 4-jaw chuck, and a good indicator, and a center drill in the tailstock chuck once you get the end running true. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#3
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DoN. Nichols wrote:
In article .com, wrote: I have a drill press, and I need to center a hole in the face of a cylinder. I would be perfectly happy to one hundredth of an inch accuracy. An X-Y table attached to the drill press stage would do the job, but I suspect that for the level of accuracy that I need, there is a simpler solution--and I just don't know it. I've tried scribing diameters across the face, and picking where they intersect--but the results have been less than impressive. Does someone have a trick for this? What did you use for positioning the diameters? A V centering head on a combination square should do a pretty good job, as long as your scribe has a very skinny point, and you angle it so the point is right along the edge of the scale. Then, you need a spotting drill and good magnification to get the hole started as close to the intersection of the lines as possible. Once that is done, you can move up to a larger bit. But 0.010" may be pushing it if you don't have experience in doing this. Better, of course, would be a lathe of sufficient size with a 4-jaw chuck, and a good indicator, and a center drill in the tailstock chuck once you get the end running true. Good Luck, DoN. Here's a very simple, but surprisingly accurate method. Place a small pointed rod in the drill chuck, a countersink bit will do at a pinch as long as it comes to a point. Place the bar in position as close as you can by eye and lay a flat metal strip horizontally across it - a 12" steel rule will do nicely. Lower the drill chuck so that the pointed end of the rod gently pinches the rule between it and the bar. The chances are that this pushes the rule off the horizontal because the point is not on the highest part of the bar. Move the bar so as to get the rule as horizontal as you can get it. Replace the pointed rod with a slocome and start the hole. If you do the maths you will find that the rule being off-horizontal by 1/2 degree translates into an accuracy of approx. 0.004 x the diameter of the bar. Half a degree from horizontal is very easy to spot when you compare it to other horizontal things around, so this method can easily give an accuracy better than 2 thou on an inch diam. bar. I hope this helps. -- Regards, Gary Wooding (To reply by email, change feet to foot in my address) |
#4
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Just use a dial indicator in the chuck and indicate around the
periphery of the shaft, once it's all dialed in you will be bang on the center. Any type of dial indicator will work, just detach the post form the mag base and put it in the drill chuck, if you have a scrap one, chop it down if there is a height restriction. -S |
#5
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Wooding wrote:
DoN. Nichols wrote: In article .com, wrote: I have a drill press, and I need to center a hole in the face of a cylinder. I would be perfectly happy to one hundredth of an inch accuracy. An X-Y table attached to the drill press stage would do the job, but I suspect that for the level of accuracy that I need, there is a simpler solution--and I just don't know it. I've tried scribing diameters across the face, and picking where they intersect--but the results have been less than impressive. Does someone have a trick for this? What did you use for positioning the diameters? A V centering head on a combination square should do a pretty good job, as long as your scribe has a very skinny point, and you angle it so the point is right along the edge of the scale. Then, you need a spotting drill and good magnification to get the hole started as close to the intersection of the lines as possible. Once that is done, you can move up to a larger bit. But 0.010" may be pushing it if you don't have experience in doing this. Better, of course, would be a lathe of sufficient size with a 4-jaw chuck, and a good indicator, and a center drill in the tailstock chuck once you get the end running true. Good Luck, DoN. Here's a very simple, but surprisingly accurate method. Place a small pointed rod in the drill chuck, a countersink bit will do at a pinch as long as it comes to a point. Place the bar in position as close as you can by eye and lay a flat metal strip horizontally across it - a 12" steel rule will do nicely. Lower the drill chuck so that the pointed end of the rod gently pinches the rule between it and the bar. The chances are that this pushes the rule off the horizontal because the point is not on the highest part of the bar. Move the bar so as to get the rule as horizontal as you can get it. Replace the pointed rod with a slocome and start the hole. If you do the maths you will find that the rule being off-horizontal by 1/2 degree translates into an accuracy of approx. 0.004 x the diameter of the bar. Half a degree from horizontal is very easy to spot when you compare it to other horizontal things around, so this method can easily give an accuracy better than 2 thou on an inch diam. bar. I hope this helps. To avoid confusing the poor OP, I gotta stick my .02 in and point out that you've just given him a good way of drilling a hole through the SIDE of a round bar so that it comes out close to being exactly on a diameter of the bar. But the OP said he wanted to drill the hole in the center of a "face" on the bar, which most machinists would read as being the "round" end of the bar. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "As long as there are final exams, there will be prayer in public schools" |
#6
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Jeff Wisnia wrote:
Wooding wrote: Here's a very simple, but surprisingly accurate method. Place a small pointed rod in the drill chuck, a countersink bit will do at a pinch as long as it comes to a point. Place the bar in position as close as you can by eye and lay a flat metal strip horizontally across it - a 12" steel rule will do nicely. Lower the drill chuck so that the pointed end of the rod gently pinches the rule between it and the bar. The chances are that this pushes the rule off the horizontal because the point is not on the highest part of the bar. Move the bar so as to get the rule as horizontal as you can get it. Replace the pointed rod with a slocome and start the hole. If you do the maths you will find that the rule being off-horizontal by 1/2 degree translates into an accuracy of approx. 0.004 x the diameter of the bar. Half a degree from horizontal is very easy to spot when you compare it to other horizontal things around, so this method can easily give an accuracy better than 2 thou on an inch diam. bar. I hope this helps. To avoid confusing the poor OP, I gotta stick my .02 in and point out that you've just given him a good way of drilling a hole through the SIDE of a round bar so that it comes out close to being exactly on a diameter of the bar. But the OP said he wanted to drill the hole in the center of a "face" on the bar, which most machinists would read as being the "round" end of the bar. Jeff Whoops, mea culpa - I must learn to read posts properly. I must learn to read posts properly. I must learn to read posts properly. I must learn to read posts properly. -- Regards, Gary Wooding (To reply by email, change feet to foot in my address) |
#7
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I was a little confused by his post, to me the "face" of a cylinder is
the end of the bar, and the cylinder itself would be to put a hole through the periphery of the cylinder. Perhaps i have been machining too long for laymans terms. -S |
#8
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Depends on what tools you have available. Assuming you don't have
things as surface tables and height gages, or even a good caliper.......... I would use a divider or compass. Just set it at your best guess at half the diameter, and scribe arcs from the outside. If the arcs from opposite sides don't intersect, increase the size of the arc. If three or four arcs define an area that is too big, decrease the size of the arc. Should be able to get to your 1/100th of an inch, but not much closer. Dan |
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