Tapping Aluminum for Helicoil <<<what a $$$$$>>> - Off-Road Forums & Discussion Groups

TOM85CJ7 · #1 09-30-2009, 10:41 PM

What am I doing wrong? I need to install some helicoils in my TF727 tailshaft housing. This is where the D-300 mounts. The holes I need to fix are the bottom two where the tranny mount goes. I have drilled out the original threads using the bit from the Helicoil kit, I can't get the Tap from the same kit to start threading into the Aluminum. The tap starts to load up with aluminum, and then it won't cut. I have tried running the tap by hand, and also in my drill. Cutting fluid is Liquid Wrench. Please give me some tips....

Thanks,
Tom

bandhmo2 · #2 09-30-2009, 11:23 PM

One thing that really helps is to use a counter sink to flare the hole to a little bigger then the threaded size. This helps the tap get started. Also clamp the part down if not attached and make sure to apply plenty of inward force. Also make sure that in turning the tap you are not forcing it to the side. If you have the housing off and can mount it in a drill press and use a pointed piece in the chuck in the hole in the back of the tap to push it straight in, and hold it straight while you turn the tap by hand, it really helps.

It is against conventional wisdom but I have had better luck taping aluminum dry then with cutting oil, at least when hand taping. Some cutting oils such as tap-o-matic are not recommended for aluminum, I have never used liquid wrench to tap but I would think it might not be the best choice. WD40 works good when turning aluminum on a lathe and may be better then liquid wrench.

Edit:
I few other things, there are several different makes of helicoil type products. Some like the Helicoil brand are quite good and have nice sharp taps. Some of the others are complete Junk, and have poor install tools made of plastic and dull taps, and are about impossible to use.

TOM85CJ7 · #3 09-30-2009, 11:31 PM

Thanks for the tips. The parts are mounted on the Jeep, and I am having to work upside down so consistent pressure on the tap is a problem. I would agree that no cutting oil might work well. Liquid wrench is similar to WD-40, but I can try WD-40 as well. I used a uni-bit to knock the edge off the hole and it helped, but I am still having trouble. I gave up for tonight. I am actually rethinking the use of those holes all together. I may try to make a mount off the face of the D-300 similar to a clocking ring, but with a large tab pointing down. That is a lot more work than fixing these holes. Maybe tomorrow will be a better day.....

Later-

bandhmo2 · #4 10-01-2009, 02:17 AM

One other thought, what are you using for a handle on the tap? The best choice would be a regular tap handle with equal length handles to each side of the tap. If you do not have one find a box end wrench that will fit the tap, usually you can find one though it may be metric. If you are trying to turn the tap with an open end wrench, good luck but I have never had that work, I rarely could get the tap started and when I did I would wined up braking it.

Good luck I hope tomorrow goes better.

jeepnut_nh · #5 10-01-2009, 08:26 AM

wierd....i usually find aluminum to be a very easy tap.....on the bench anyways. rarely use spray oil, i have a tub of safetap paste at work...the stuff is awesome.

back to your problem, if the tap is clogging with shavings, dont forget to turn it backwards every turn or three to break off the shavings....sometimes ive had to cut a few threads, remove tap and blow it off, repeat till done, but usually just backing off a turn or so will free it up for more cutting.

Caver Dave · #6 10-01-2009, 08:45 AM

Welcome back from the "black hole" Tom!

Many years ago I worked maintenance in a paper factory and used the Heli-coils on a weekly basis. We found there were different kits... some were bare bones (coils, single bit, & tap), while others had the "bells & whistles" (same kit, but with starting *AND* bottoming taps, the threadlocker, cleaner, & release goo's, etc.)

While not likely an easy thing to source (for some sizes)... I suggest a starting tap to get everything started nice and straight. If you're really limited on space and feeling like superman, use a cordless drill (w/ clutch) to start & spin the tap... but be careful cause you'll likely only get 1 shot in the AL!

CJ7Taz · #7 10-01-2009, 09:57 AM

Quote:

Originally Posted by Caver Dave

I suggest a starting tap ...

Good call. I Was trying to figure out why he was having so much trouble with a tap.

If it’s a bottoming tap, well I won’t say never, but it will be very difficult to get started.

The tap shown at the top is a bottoming tap. You need to start with one like the middle or bottom one shown.

A bottoming tap is used to finish cutting threads all the way to the bottom of a hole that already has threads tapped using one of the other types of tap.

WILL · #8 10-01-2009, 05:23 PM

Try some of this.

Tap Magic Aluminum Cutting Fluid

Dirt Dog · #9 10-01-2009, 06:24 PM

I have to agree with the above posters about the starting bevel, and "tap magic". (I love that stuff) But I really have to add that all "kits" are not equal.

I have a lot of different kits in different sizes. Most are great and easy to use but some were cheap junk from the word go. I have had the best luck and prices with ones from Palmer Bolt & Supply, Stainless Steel Bolts, Metric Bolts & Screws, Carriage Bolts Threaded Rod,. Thats all I use now and couldn't be happier.

(PS I've never had a problem doing alum with any kit)

TeamRush · #10 10-02-2009, 01:14 AM

Ditto.

The 'Taper' is called a 'Chamfer', and you can use a much larger drill bit to do the chamfer if you don't have chamfering tools at your disposal.
Just don't go more than about half a thread width into the material or you are getting into 'Counter Sink' territory!

I LOVE my Tap Magic for Aluminum, Works GREAT!

Don't try and cut the threads all at once!
You will have to cut about 1/3 turn or so, back the tap up to break the chips curling up in the tap flutes,
Then start in again for about another 1/3 turn of cutting.

Keep breaking the chips, remove the tap frequently and clean out the chips.

No such thing as 'Too Much Lube' with aluminum...
And if you ever find yourself without actual Tapping/Cutting lube,
Use a good synthetic grease.
Much more messy, but works fine in aluminum.

'Never-Seize' works also in a pinch.

Keep the tap as centered with the hole as you possibly can,
This will ensure your threads don't get eaten out as you run the tap in and out a bunch of times.
'T' type tap handles make this MUCH easier to align the tap in the hole!

'Pilot' taps, Sometimes called 'Starting Taps', with pointed ends, will self center in a thread or two even if you start a little stupid,
And since you are using 'Heli-Coils', being a little off at start isn't a huge problem.

Then you will find 'Cutting' taps,
they have a slight taper to the end of the threads, and these are primary cutting taps used to make the largest body of the threads.
They are usually made a little different in the flutes (gaps between cutting edges) to remove the chips a little more efficiently, and they usually don't cut the threads to full depth...
Good for lesser engagement bolts... Like the common bolts you find in hardware stores with slightly rounded edges on the threads...

Then there is the 'Bottom Tap' or 'Finish Tap',
It will be virtually SQUARE on the bottom end, and won't have hardly ANY taper to get started on it's own.

This is for FINISHING the threads in a hole...
It cuts threads deeper in the hole since the bottom is square,
And it has sharper, usually longer thread cutting edges to complete the threads for full engagement bolts,
(like Aircraft bolts or high precision bolts)

Almost all automotive bolts are of the MIDDLE CLASSIFICATION...
The Taper nose tap will work fine in most cases, since automotive bolts are only about 75% of thread engaged,
You don't need the super accurate finishing taps...

But having common bottoming taps or using the finishing taps for bottoming once they get used a few times (no longer super accurate) is common practice!
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I also agree with the guys about brands of coil inserts,
Nothing beats Heli-Coil brand for common use!

Expensive compared to the knock-offs, but they work the first time, every time, and they don't get 'Soggy' like the cheap import crap/clones do!

CHEAP compared to replacing the transmission case, engine case, ect!
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Just remember to NOT drill the hole all the way through,
You want to figure out how much coil you have, and drill the hole out/tap the hole out so the coil stops in the correct place!

I've seen guys drill all the way through, then the coil wants to creep out the back side!
OR,
They drill deep in a blind hole, but the coil is only 1/2" or 3/4" long, so the coil creeps to the bottom of the hole!

You can also just oversize drill the length of the coil into the stock hole...
Leave the OLD THREADS in the bottom of the hole,
then add a coil to the top 1/2" or 3/4" or so...
That will leave the bolt to grip the stock threads, along with the Heli-coil instead of JUST the Heli-coil because you drilled the hole over sized all the way though.
(ask any Harley rider of old about that!)

The biggest screw up I see with Heli-coils is not getting the tail out of the coil when inserted!
You need a Smart, Sharp RAP on that tail to break it off,
Then you MUST get the tail out of the hole!
You simply would NOT believe how many screwed up pieces I've seen where guys tried to Heli-coil, but didn't get the tail to break clean and/or left it in the hole!

If you intend on using something like 'Never-Seize' on the bolt you are inserting into the Heli-coil...
Then use some stud locker on the threads and let it dry before you insert the bolt with Never-Seize or the coil will creep...
Doesn't always creep in aluminum, but it will ALWAYS creep in cast iron!

If you get the coil coming out with the bolt when next you disassemble...
Then just pop a new coil in!
It's no big deal, just remember to clean the hole with a cleaner that removes oil and doesn't leave residue,
The use stud locker, allow to dry before you put the bolt back in!
It WILL NOT happen again!

Heli-Coil is a pretty big step the first time for a 'Rookie',
But believe me,
Once you master this,
You will NEVER be afraid of another broken bolt again!
After this, it's just a matter if time and patience to drill the bolt/hole and pop in a Heli-Coil to repair the hole!

Same with stripping holes out!
It's just a time consuming thing that happens once you learn how to Heli-Coil properly!
Where it used to be a parts killing major event, now it's barely a blip on the radar of the day!
--------

One of the FIRST things we do is teach kids to center punch broken bolts, then drill in increasing sizes to get the bolt out...
(right hand drills if the hole is through, left hand drills if it's a blind hole)

If they get into the threads,
Then they learn about Heli-Coil first hand!

From there, you can see them get the ideas and have the courage to follow through with things instead of being scared of something going wrong!