How to tap a deep hole?

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TF360

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Started tapping a hole in my aluminum slant manifold but the tap was about one inch too short. What is used to tap deeper? I need to go down about 3 1/2 inches. What do you guys use?
 
Started tapping a hole in my aluminum slant manifold but the tap was about one inch too short. What is used to tap deeper? I need to go down about 3 1/2 inches. What do you guys use?
You need a long tap or drill the hole out 1 size larger than the barrel of the tap and just thread the bottom. You will still run into a issue because tap extensions (so you can get to the bottom of the hole) are fairly large.
 
Try MSC Industrial. It might cost $50 for one. Do you have a machine shop close. A $20 bill might get it done.
 
What about thin-wall 8-point or spline-drive sockets in 1/4" drive? The OP didn't state what size tap..???
 
why not just use a bolt that is an inch shorter?
what could you possibly be attaching that needs 3 inches of engament on the bolt?
 
What about thin-wall 8-point or spline-drive sockets in 1/4" drive? The OP didn't state what size tap..???
A socket will be almost twice as big as the tap. You would have to bore a pretty large hole.
 
What size is the tap? Can you put a socket on the end of it with a long extention.
 
3/8-16 actually need to go down a hair longer than two inches
 
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Not all taps have the same size square-drive, I have a 10mm tap with a very small(.230") drive, & a 3/8" tap (dimensionally smaller threads) with a .285"square drive.
 
Sometimes you can put a 1/4” extension on the top of the tap up side down and use the a tap handle socket end of the extension.
 
Long-shank taps are out there, but....$$$, unless You look for chinesium,.....Enco maybe or????
 
3/8 - 16 the shank is bigger than the tap, looks like damraider has the fix.
 
The tap itself is to wide to go into the 5/16 hole. I'm tapping the two holes for the long bolts that go into the exhaust manifold. from the intake into the exhaust manifold
 
Slant 6 intake manifold- in the area where the kickdown linkage attaches
 
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