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Tapping -- How to's and How not to's....
Powder Keg:
Over the years of hand taping I've noticed why most taps get broken. The person is simply not paying attention to the job at hand. They are looking around the shop, chatting with a buddy, Or whatever. If you are watching the tap and paying attention to what you are doing. You wont shouldn't them. I've done a bunch of 0-80 with just a hand held T-handle and never broke one. Knock on wood
Wes
Lew_Merrick_PE:
--- Quote from: Powder Keg on October 09, 2010, 12:00:27 PM ---I've done a bunch of 0-80 with just a hand held T-handle and never broke one.
--- End quote ---
Wes, you aren't trying! I was tapping holes in a missile simulator body (.7500-10UNC) when the (8500 lb) bar started to roll (after being hit by a forklift). I snapped off the tap while trying to keep the body from rolling. I did, however, succeed in getting my foot and leg out of the way...
The vast majority of the time I break a tap, I am trying to get one more hole threaded with a known dull tap. Yeah, stupid but we all reach that point. More taps are broken by bending than torsion. You have to be a weight lifter or a rock climber to break a #10 tap by hand with torsion. A 6 year-old can snap a 3/8 inch tap in bending (my grandson proved this a few years back). Paying attention is the key, but you can't always "win" that way...
Mike E.:
Reading this old thread I thought I would add my 2 cents worth about tapping aluminium. Consider using "Lacquer Thinner" as a cutting fluid. Many years ago I learned this trick from an old machinist who worked at Lockheed Aircraft. I've tapped holes as small as 2-56 with excellent results.
sparky961:
--- Quote from: Mike E. on May 24, 2017, 01:34:14 PM ---Reading this old thread I thought I would add my 2 cents worth about tapping aluminium. Consider using "Lacquer Thinner" as a cutting fluid. Many years ago I learned this trick from an old machinist who worked at Lockheed Aircraft. I've tapped holes as small as 2-56 with excellent results.
--- End quote ---
What's the logic in this? Maybe it stays liquid in a really small hole but for any "normal" size it will have evaporated long before having the chance to be helpful.
There are plenty of "old machinist's tricks" like this you hear about, but a commercial cutting oil designed for the job is often the best solution.
PekkaNF:
I may be going against the flow, but I don't constantly back off when hand tapping, certainly not the 1/4" turn routine. My reasoning is that because it is universan acepted fact the when you ream: don't back off - you chip the cutting edge. I beleive there is some extent same mechanics totapping too. I may ease a small fraction of the turn on very difficult material, just to assit swarf packing.
incidently I used some time to get boxes and organisize my tapps. The big idea is to keep one thread size (metric coarse) tools on one box: Taps, tapping size drills (by 10 each size, short), clearance hole drill, countersunk bit and recess bit.
Too some time to design the apropriate sticker, nicked the graphics and all information from three sources.
Boes will stack two high, or I could nest them two rows, two high, but I'm using bigger box to accomondate reamers and their drills and one box for nonstandard taps.
M10 and biger stuff will go on bigger boxes on bigger sellf.
Pekka
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