Gallery, Projects and General > How to's
Tapping -- How to's and How not to's....
Lew_Merrick_PE:
--- Quote from: AdeV on August 05, 2010, 12:07:59 PM ---I'm looking at maybe purchasing a 50TC/DC unit. If I wanted to tap M6 in aluminium to a depth of 2", would this device do the job - and what sort of speed will it tap at? The website blurb says it has a "re-entry cushion" to prevent cross-threading; which suggests to me I can plunge multiple times (maybe with taper, 2nd & plug?) into the same hole & it will find the threads & augment them, rather than chewing a new set out of the old...
--- End quote ---
You main problem in tapping 2" (50 mm?) deep with an M6 tap will be getting a tap with that ability. You will need to use an "extended, undercut" tap to do the job. You may need to make (or buy) an adapter to allow your head to hold a reduced shank tap. I do this quite commonly with taps as small as #6.
I typically run my head for aluminum with a spindle speed of 240 rpm (this is the input speed, the head I have reduces that by 30% through the planetary gearing) for taps #10 and larger. I will slow it down to as low as 80 rpm for small taps and/or alloy steel. If you want speed of process, use a fixed head drive with a clutch release and use thread forming taps. The TapMatic is faster and more consistent than hand tapping -- and saves your wrists.
Yes, you can "re-enter" holes easily. When the tip pressure reverses the direction (to clockwise -- by lifting the planet to the "drive-in gears"), you hold the tap at the "entry height" for a couple of revolutions and the tap will "grab" the existing threads. This is handy when tapping deep holes as you can remove the tap from the hole, clean off the swarf, add another dose of tapping fluid, and continue on. As I have hit the age when aspirin is my drug of choice, I will set-up my tapping head for as few as three holes...
ven:
Just to agree with what others have said.
Try to obtain sets of imperial drills, 1mm to 6mm (?) sets in 0.1 increments, metric ones in 0.5mm increments, letter drills and number drills. The good ones aren't cheap but they will last for years if you are careful. Don't go for cheapness, no matter how tempting.
It took me years of Christmases and Fathers' Days to get all of mine, but it is really good to be able to just reach out and pick up any size drill, up to about 1/2"/12.5mm.
The next phase is to have a set or sets with the tips hand-ground slightly for work on brass, which tends to grab.
Jonny:
Theres a lot of rubbish drills out there probably made in China with German sounding names on and you may think you are getting a bargain.
I do a lot of hand tapping with aluminium 6082 T6 usually M3 and M4 in at 15 degrees. Found quality HSS tend to grab and pick up more than cheap carbon types. Now i have the last 6 months changed over to the machine taps with coloured bands ie red top, yellow top etc to suit the material. Plough straight in, no backing off.
When i need accurate tapped holes i usually use one of the mills. Lock beds up, drill hole to correct size, change to decent tap, drop speed usually lowest, oil and use same way as Tapmatic except when at bottom hit reverse. Everyone a gem from M5 to M20 too scared at anything less than M5.
Lew_Merrick_PE:
--- Quote from: ven on October 07, 2010, 04:44:52 PM ---The good ones aren't cheap but they will last for years if you are careful. Don't go for cheapness, no matter how tempting.
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My daughters (who grew up working in the shop with me) heard my swearing as I tried to find the drill set that had hidden itself on me about 20 years ago. They saved their pennies and bought me one of the ultra-cheap tri-dex (number, letter, & fractional) drill bit sets. It sat proudly on a shelf in my shop for several years before my youngest daughter asked me why I wasn't using them. I let her try to drill a hole with them. She was aghast at the results (which resulted in a lesson about measuring roundness and straightness of drill bits).
Most major manufacturing operations do not sharpen drill bits, they just scrap them when they get dull. If you can find the "surplus yard" they sell to, you can pick up otherwise very high quality (but now dull) drill bits for a fairly small fee (I paid $0.50/lb a couple of years back). Take a micrometer with you. My daughters now have their own tri-dex sets filled with good quality drill bits. It has now become a family tradition that my grandkids get a tri-dex drill set for their 12th birthday. The tri-dex cases far out-cost the bits!
I paid about $100 for my first set of cobalt-HSS drill bits (in three separate indexes) back in 1968. I still have them and they work fine. I picked up a broken Lysle drill-bit grinder shortly thereafter. (I rebuilt it and it too works fine.) I got a Darex drill-bit sharpener some years back. That is what I use for most "touch up" drill-bit sharpening and only break out the Lysle when I need to completely rebuild the point. I have made a set of wooden "bins" for dull bits and another for "sharpened, ready for service" bits so I don't have to stop and measure them when I have dulled a bit. Excepting my first set of bits, I don't think that I have paid $25 for all the bits in my shop -- which currently sits at (5) tri-dex sets (one for each major machine), (2) ground short as "screw machine" bits, (2) spare tri-dex sets (so I have one to grab when I have to work in someone else's shop), matched "drill & tap" and "drill & ream" sets each in their own wooden stand, and "spare bits" for standing ready to be pressed into service when another bit gets dull.
The "set" my daughters bought me have been recycled into scriber points and the like. My youngest daughter has the tri-dex case (now filled with good bits) she and her sister bought me for Father's Day back in the early-1990's.
cidrontmg:
Heh, Lew, I´ve done a very similar thing. I bought some time ago a drill set that goes from 1 to 10 mm in 0.1 mm steps. It actually came in 2 metal cases. I bought it not for the drills - I tried some of them, for fun, full well anticipating the result, and couldn´t decide if I should cry or laugh - but for the cases. They´re reasonably well made, the holes are quite accurate, there´s enough space for even a bit longer drill bits, etc. Since then I´ve repopulated the cases with the best quality bits I´ve been able to get. The drills in those cases are sort of a last recourse, I use them when I want a hole exactly the size. For run of the mill drilling, holes that are usual sizes for screw clearance, tapping, etc., I have a small set of also first class drills, that I buy in lots of 5 to 10 bits.
Drill sharpening is still a bit of a problem, especially below 5 mm. But for the price of a commercial drill sharpener, I can buy an awful lot of small drills, so it´s not a big deal. Sharpening milling cutters would be a far greater priority, also so far unsolved... :offtopic:
:wave:
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