Drilled A Tapered Hole. But Did Not Mean Too.

[modela]

I took so many math classes in college that I wound up with a second major. I like math because it gives me the illusion that some of my problems have solutions...

I graduated with a degree in mathematics. When I was involved in the Mt. Pisgah Bridge project I wrote an article titled, "What Old Math Guys Do" and sent it to the University of Colorado math department. We had three retired Ph.D. mathematicians working on the project and I thought it was a little more fun than some of the other articles. They published it and the editor even made a trip out to view the bridge.

Jim

 

[joshua43214]

I graduated with a degree in mathematics. When I was involved in the Mt. Pisgah Bridge project I wrote an article titled, "What Old Math Guys Do" and sent it to the University of Colorado math department. We had three retired Ph.D. mathematicians working on the project and I thought it was a little more fun than some of the other articles. They published it and the editor even made a trip out to view the bridge.

Jim

Very cool. It is such a small world. My father did his undergrad at Colorado before getting his Ph.D. in number theory at Reed. As an "Old Math Guy," he mostly tromped around the rainforest in Washington with his medium format camera lol. We used to have fun debating the merits of proof by numerical analysis (he was having nothing to do with it). My actual degree is in Molecular Genetics. Pure math is pretty useless in my field, all bio people care about is p-values...

 

[modela]

Very cool. It is such a small world. My father did his undergrad at Colorado before getting his Ph.D. in number theory at Reed. As an "Old Math Guy," he mostly tromped around the rainforest in Washington with his medium format camera lol. We used to have fun debating the merits of proof by numerical analysis (he was having nothing to do with it). My actual degree is in Molecular Genetics. Pure math is pretty useless in my field, all bio people care about is p-values...

I started a master's degree program at CU and after a semester of classes with only young guys and all theoretical classes, I decided it was not me. I ended up getting a master's degree in operations research in Business. I have never regretted it. My daughter received a bachelor's degree at the University of Oregon and a Ph.D. in water resource management from Oregon State. She now works for an environmental consulting firm in Boulder, Colorado.

 

[extropic]

I started a master's degree program at CU and after a semester of classes with only young guys and all theoretical classes, I decided it was not me. I ended up getting a master's degree in operations research in Business. I have never regretted it. My daughter received a bachelor's degree at the University of Oregon and a Ph.D. in water resource management from Oregon State. She now works for an environmental consulting firm in Boulder, Colorado.

But can she drill a cylindrical hole?

 

[modela]

But can she drill a cylindrical hole?

When she was getting her degree we volunteered to help her dig a bunch of holes up to 80" deep. She added 1" pipe as a casing and then monitored them monthly to collect data. Someone remarked that my wife and I were given Ph.D. degrees, Post Hole Digger. Ironically, my dad was a water well driller.

 

[MAlcocer]

Just an update. I did not get a chance to drill larger holes today but I did drill 11 with a #29 (.1405) and I got good results. I used a chuck this time and the drill bit had visible runout at the tip even being only 2 inches or so long. I used a #2 center drill and made sure I drilled this larger than the final drill size. All the holes came out good but the material was thin.

I checked run out inside the taper of the spindle and it was less than .0005" (not sure if that should read +/-.00025" as the total swing of the indicator was .0005") I put a piece of 1/2" drill rod in a collet and got a hair over .0005" (+/-.0003"?) At the collet and checked 5" down. First test was .009" (+/-.0045"). I spun the rod 180° in the collet and repeated the test and got .003" (+/-.0015") so my guess is the runout 5" out would be the difference of the two tests? .006" (+/-.003") not sure what run out on w1 drill rod is.

Final question, anyway to check the runout at the tip of a drill bit. The 1/2" bit is moving visibly but with the flutes and reliefs on them I can't tell much. Also anyway to measure the tip and see if one lip is longer than the other?

I am going to pick up a spotting drill and give it a whirl. Long and the short is I am learning that drill bits are roughing operations. Thank you for all the help. Learning a lot.

 

[brino]

I checked run out inside the taper of the spindle and it was less than .0005" (not sure if that should read +/-.00025" as the total swing of the indicator was .0005")

You got it right! Most folks quote "TIR" or Total Indicator Reading to clarify.

anyway to measure the tip and see if one lip is longer than the other?

I use calipers at the bench grinder when sharpening drill bits. I don't care about the actual measurement, just use them to compare the two lips.

-brino

 

[MAlcocer]

I was attempting to figure out a way to do this but they just keep slipping off. Do you lock the calipers down and overlay them on the bit to use as a visual reference?

 

[brino]

I was attempting to figure out a way to do this but they just keep slipping off. Do you lock the calipers down and overlay them on the bit to use as a visual reference?

I just hold them up to the business end of the drill bit under a magnifier light. Set them to either the leading or trailing edge of the sort of trapezoid of one cutting lip and then compare it to the same thing on the other side. The caliper body is at the same angle as the cutting edge. Basically a visual reference.
-brino

 

[David VanNorman]

Try drilling a pilot hole all the way thru and then running the larger drills thru. the WD40 works as a lube.