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Tapping Aluminum


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#1 MH81 ONLINE  

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Posted December 07, 2011 - 07:01 PM

I have a pulley on a Midland Wards that has loosened up on the shaft. I have decided it needs 3 setscrews on each end to center it and (in the case of 2 of them) put pressure on the key. It's not terrible, but needs dealt with to keep it from getting worse.

The setscrews will go thru the buttom of the pullies, thru the sleeve, and against the shaft. Now for the questions: I know how hard aluminum can be to tap properly, does anyone have any tips or tricks to keep from damaging the threads or overheating and sticking the tap? Any special fluids?

#2 olcowhand OFFLINE  

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Posted December 07, 2011 - 07:10 PM

I just use PB Blaster. The main thing is not to try to tap the whole way through at one lick. Go a turn, then back out & clean the chips. Aluminum wants to gum up the tap. So 1 turn in, back out/clean, 2 turns in, back out to clean, & so forth. Keeping a lube on it helps prevent the aluminum from sticking to the tap. Try very hard to keep the tap dead on straight, as even a slight wobble while tapping will hog the threads out larger in the soft aluminum.
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#3 Cvans ONLINE  

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Posted December 07, 2011 - 07:19 PM

I have had good luck over the years using Tap Magic. But like Daniel said, keep the tap clean and clear chips from the hole often.
Good luck.
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#4 IamSherwood OFFLINE  

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Posted December 07, 2011 - 07:24 PM

From what I recall from my younger days in the family machine shop business, we just used cutting oil.
And as Dan said, keep it straight. A longer lead in point ground on the tap will help with that.
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#5 caseguy OFFLINE  

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Posted December 07, 2011 - 07:25 PM

I have had good luck over the years using Tap Magic. But like Daniel said, keep the tap clean and clear chips from the hole often...


I love Tap Magic for most things. There are different formulations of it for different metals though. There is at least one of them that specifically says "not for use on Aluminum". Be sure to read the label before you start! In most cases any oil that you can use for drilling will be fine. Just take your time and be sure to clean the threads.
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#6 Billygoat OFFLINE  

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Posted December 07, 2011 - 07:39 PM

I used Tap Magic when i worked in a machine shop. As was stated before, there are some that say don't use on aluminum. I was also taught that diesel fuel is one of the best cutting fluids ever made for aluminum.
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#7 Alc ONLINE  

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Posted December 07, 2011 - 08:00 PM

Will you be using a tap from a mutli size set or ones like these ? Plastic Pouched Sets, Taper, Bottoming & Plug - Tools - IRWIN TOOLS
It makes it easier to use a taper tap if your having problems keeping it center ( wobbling ) Al
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#8 olcowhand OFFLINE  

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Posted December 07, 2011 - 08:27 PM

Definitely use a taper tap. Bottom taps are near impossible to start without setting up in a jig in a drill press or lathe.
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#9 MH81 ONLINE  

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Posted December 07, 2011 - 09:14 PM

Will you be using a tap from a mutli size set or ones like these ? Plastic Pouched Sets, Taper, Bottoming & Plug - Tools - IRWIN TOOLS
It makes it easier to use a taper tap if your having problems keeping it center ( wobbling ) Al


I have a multi - set and all 3 vs of the most common smaller sizes. (1/4, 5/16, 3/8 I think)

I would use the long start taps for this as I'm coming out into a 1 inch hole where the shaft will be.

#10 HALFSCALE OFFLINE  

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Posted December 07, 2011 - 11:59 PM

I never use aluminum threads, I always thread for and install a HELICOIL, it makes your threaded area twice as much and it won't beat out like the aluminum does

#11 skyrydr2 ONLINE  

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Posted December 08, 2011 - 04:55 AM

Sharp tap, and cutting fluid and coarse threads , if tapping a cast aluminum (powdery kind if chip) use lard, if it is stringy , the use cutting fluid (any good oil) and make sure the tap is Sharp!
A "gun" tap works best in most cases, unless bottoming is needed then finish with a bottoming tap.
Also if the tap is cutting well and doesn't feel springy when turning, don't back up, keep the chip forming, its when you back up that you jam up the aluminum. So keep it lubed and a Sharp tap and it will go just fine.

Nothing taps as bad as stainless !

#12 Big John OFFLINE  

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Posted December 09, 2011 - 03:39 PM

Anything thin & oily works for tap lube on aluminum,, WD-40, diesel fuel, No stick cooking spray, or penetrating oil. Use a taper tap if U have trouble keeping tap straight. If I drilled hole in my milling machine, I will tap it there too. I use industrial
taps made for machining centers, they don't break as easy as cheaper taps.




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