I got an Enco hand tapper recently. First thing I noticed was that the
little ball/spring setup on the lower end of the shaft didn't work. I sent
one back and got another, same problem. I figured I'd try to fix it. First
try I figured I'd drill it out with a No. 7 drill and tap it 1/4-20 for a
set screw. No dice, it's too hard. So I dug out the riffler files and got
out a roundish one and started easing the bottom of the hole where the
3/16" ball sits, so it sat deeper. That worked, but then the spring didn't
bear on the ball anymore. So I cut out a little rectangle of thin cardboard
(from a box a bearing came in) and forced the spring over the shim so the
spring pushed on the shim and the shim pushed on the ball. After that,
the tap holders clicked in pretty well.

Next thing I noticed was that the 1/4" tap wouldn't go into the 1/4" tap
holder. I figured it was just a burr and gently drove one in using a chunk
of lead as a hammer. It went in fine and had to be pushed back out, and was
noticeably easier to get in the second time. I think the problem will work
out in time as the burr from broaching wears down. I went through all of
the tap holders and noticed that there isn't one for 9/16", sigh. They
all took their tap without driving, though, except the No. 6, which was
tight but not as tight as the 1/4" had been. All the tap holders worked
with the ball/spring until the very last one I did, the No. 6. It just
drops out. I measured the distance between the flats and most of them
are over 0.450" e.g. 0.452, 0.457" like that, but the No. 6 was 0.442"
so it was just machined too skinny. I figure 8 out of 9 isn't bad, but
I wish I could send just the one tap adapter back to Enco. The finish on
the ground surfaces is real nice, and this one had no rust anywhere.

For $79.95 with free shipping, this tool appears to be a good value.

GWE