Skip to main content

tap and CRY

well this tap and die stuff is much more complicated than i imagined.  i went to the hardware store yesterday to get another bit for a different sized hole to drill and they said you want to use a small drill bit for whatever size tap you are making.  i realized that i had just guess with the last one.  i just grabbed a bit and drilled and it was okay but in hindsight it was very hard to turn the tap bit to make the threads and i always felt like i was going to just snap it in half.  so i googled it and this is what i found.  DOES ANYONE HONESTLY THINK I UNDERSTAND ANY OF THIS?  ps the hardware store people didnt know what size i needed. on the tap bit package it said use size F.  they only had sizes in numbers not the alphabet. 
  • Measure the overall diameter of the tap with the micrometer. In this particular instance, we want a drill bit for a ¼ - 20 tap. The ¼ is the diameter and the 20 is the thread pitch or threads per inch. The overall measurement of the taps diameter from the micrometer is 0.252 inches.
  • 2
    Use the following formula for finding the correct drill bit size: Dh = Dbm -- 0.0130 (percentage of the full thread desired/ Ni). Dh is equal to the drilled hole size in inches. Dbm is the basic major diameter of the thread, in our case 0.252 inches. The "percent" of full thread desired is your choice, but a good number is 70 percent to 85 percent depending on the material being used. "Ni" is the number of threads per inch, again, in our case, this is 20.
  • 3
    Apply the numbers to the formula using an 84 percent thread depth. The formula would be:
    Dh = 0.252 -- 0.0130 (84/20) = 0.0130 (4.2) = 0.252 -- 0.0546 = 0.1974 inches.
  • 4
    Find the nearest drill bit size in 1/16ths of an inch. Multiply 0.1974 times 16 and the answer is 3.15. This corresponds to a 3/16-inch drill bit; however, this is too small.
  • 5
    Determine the drill bit size in 32nds of an inch. The answer is 6.31, so a 7/32-inch drill bit can be used for this tap. In fact, if you look to a chart, a 7/32-drill bit is recommended.

Tips & Warnings

  • The metric formula is generally the same, it reads as: Dh = Dbm -- (percentage of full thread desired/ 76.98). Note the thread pitch is a constant and there is no deduction constant as in the inch formula.


Tod said…
One of the best blog post titles I have ever seen. Well played . . . well played.
paula said…
ha. glad i could entertain yhou

Popular posts from this blog

now i remember another reason i stopped blogging...i have been dickering around with trying to upload 2 photos with links and captions for longer than i should.  much easier to just do it elsewhere.
lets try again....

semi drone

for anyone who wonders...i'm hopping back on the min wage work thing.  went back to the house remodel job and trying to make enough money to subsist while sales are slow during 'back to school' time.  its good.  i reckon.  its hard, its fucking hot.  i'm just trying to work with my self and being present and taking it one day at a time.

New Art Find: Louis Pons

Louis Pons, 1991 Dock Assemblage
Louis Pons, 1981 Fils à papa Assemblage
 Louis Pons, 1974 Trésor no. II Relief 
 Louis Pons, 1972 Safari bleu Relief 
 Louis Pons, 2003 The Recluse Mixed Technique 
Friday New Art Finds.  ha.  I'm posting it early because my blog needs something on it other than ME.   I present to you Louis Pons.  Born in Marseilles, France in 1927 and apparently still going strong.  I have little to no information on this artist, he appears to be elusive on the net.  I recently watched a strange little movie called 'The Gleaners and I' by Agnus Varda.  She had a blip on him and I set to searching for images or information online only to come up with a small wikipedia blip and a few sites containing his work.
No matter, it's enough just to see his work.  This site if you translate it, appears to have the most information of any:
Primary studies at Marseilles, school of the Carthusian monks.
School of the Trades, Endoume, Marseilles. He learns the trade from fitter bu…