I am a machinist also, so I can add another two cents. I think
MSC is a good place to buy drills or any other metal cutting tool you want. They have the better imported stuff to very good quality. I would recommend to anyone to get their catalog. It is free and very useful. This year's catalog is 4,480 pages. I don't recommend the CD.
Anyway, sure there are better brands than others, but you must consider what you are doing with them. Take for instance a single 1/2" Guhring series 622, it is $69. 06 This is not the drill for the handyman! As far as what I would recommend, well I guess I would agree NO imports. It is probably OK if it is made in the USA. Chicago-Latrobe makes a good drill. So does Precision twist drill. Cleveland drills are also very good but they are pricey. Here are some prices for you on a 29 piece production grade set 1/16" - 1/2".
Import - $20. 54
USA - $54. 02
Chicago-Latrobe - $89. 12
Precision - $93. 58
Cleveland - $111. 22
If you are using these drills in a hand drill, I wouldn't suggest to get cobalt. Cobalt tends to chip when exiting the hole when hand drilling due to the lack of control. They do however work excellent in a drill press or any machine tool. I would suggest to just get 118 degree points. 135 degree points generally have thicker webs and require split pointing to reduce tool pressure. This adds difficulty to resharpening, particularly if you are going to hand sharpen. The greater web thickness and flatter point angle also promotes walking and out of round holes. 118 degree points are pretty much standard and work well for most applications.
As far as being able to buy replacements, MSC sells drills individually, but you would almost need to be buying something along with it to justify the shipping cost. Typically, if you have a good bit to start with, breakage only comes from misuse. If you need to get another drill in a hurry you can always go to the local hardware store.
In response to the little resharpening machines, I have never used the Darex drill doctor either. There was a
thread about it at the Ford site not too long ago. I also used the $1100 dollar model sharpener and if I were only using it at home, I would definitely agree that it kicks butt. I however used to resharpen drills for work and most of our work was for Rockwell International. They are relatively fussy about the sizes of their drilled holes. For example, if I recall correctly, a 1/4" hole was allowed to be -. 001" to +. 003" giving a range of . 249" to . 253" The Darex sharpener would not resharpen drills to hold these sizes. The sharpener we had was used quite a bit before we had Rockwell work so it did have a fair amount of wear on it. I guess you could conclusively say that it did apparently work well at one time
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You can always sharpen drills by hand, but it is an acquired skill.
If you decide to sharpen by hand, buy a
drill point gauge. With this you can check to see that your angles are equal and the flutes are the same length. Basically as long as the drill has clearance it will cut, but it has to be sharpened on center and have equal angles for it to cut to size and not walk. Don't let this paragraph scare you, it's not that hard.
Just as a tip, since you may not always have a tap-drill chart handy, here is an easy way to calculate tap drill sizes.
Take the threads per inch, divide it into 1 and subtract that from the major diameter. Two examples for you:
3/8"-16 Take the 16, divide it into one, this equals . 0625 now subtract that from the 3/8", this equals . 3125" or 5/16" That is your tap drill size.
1/2"-13 Take the 13, divide it into one, this equals approximately . 077" now subtract that from the 1/2", this equals . 423" or approximately 27/64" That is your tap drill size.
This also works on metric threads, but it is less involved due to how metric threads are declared. English threads are stated as threads per inch while metric threads are stated as the distance between threads. For example, a M8 x 1. 25 is calculated by simply subtracting the 1. 25 from 8 giving a tap drill size of 6. 75 mm
Another example, M24 x 3 is 24 - 3 giving a tap drill size of 21 mm
Another tip, to calculate the desired speed for your drill use this formula.
CS stands for cutting speed. A mediocre speed for steel and iron is 70 surface feet.
RPM = CS X 3. 82 / Diameter
By substitution for a 1/2" drill
70 X 3. 82 / . 5 = 535 RPM
So if you are using a drill press, try to find the closest speed to that. It is generally better to go slower than faster.
Hope this helps.
Bryan
P. S. Sorry for the long windedness.
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