Adapting a drill press to an unpowered/manual tapping fixture is a
relatively easy project. The method I used doesn't require disassembly of
the DP to machine it's parts (then re-assembly).. just a fairly simple
bolt-on solution.
Step 1 for each use.. pull the power cord plug from the receptacle.. that
way, there's no need to mess with the drive belt to prevent accidental
power-up with the spindle crank in place.
A Dremel or similar rotary tool can be used to grind shallow flats on common
small taps, so they can be held securely in drill press chucks (flats don't
interfere with other holding tools).
For my inexpensive benchtop drill press, I cut a 3" diameter hole in the
belt cover above the spindle, then turned a hub to fit on the top step of
the spindle pulley on the lathe, with the recess just deep enough to accept
the top nut and the first edge of the top belt groove.
Then drilled/tapped 3 holes around the edge of the recess to accept 3
1/4"-20 screws (spaced exactly 120.0000 degrees apart so as not to adversely
affect the perfect balance of this fine piece of precision equipment).
On the top surface of the hub (approx 2-1/2" diameter x 1-1/2" thick) I
drilled 2 holes (opposite sides of the center line) to accept pins about
1/4" in diameter x 3/4" deep.
The 3 holes in the bottom side of the hub are for using 3, 1/4"-20 bolts
with washers to hold the top edge of the top pulley groove into the recess,
and the thickness/heighth of the hub just extends about 1/2" from the top of
the closed belt cover.
The crank consists of a ~12" section of 1" x 1/4" flat stock with a crank
handle on the end, and 2 pins welded to the other end, to engage the 2 top
holes in the hub.. friction holds the crank in place, no tools required.
The bar section of the crank could be double-handled or even adjustable
lengthwise, but this length works well for me.
The quill return spring housing is a cup to cover the spring with a little
tension applied (about 1/4 turn of the cup) to hold the quill in the fully
upright position (and seat belt on).
So, to do some tapping, all I gotta do, is.. Step 1 - remove the power cord
plug from the receptacle.. remove the spring cup nut and cup from the shaft
by hand, and it's ready to put the crank on top and start tapping.
Having the DP table and vise (or other holding device) makes for very simple
tapping with the absolute precision that only a fine piece of precision
equipment as this can produce (Ryobi 9" benchtop).
To convert back to a powered DP, the cup and nut can be reinstalled by hand,
holding the quill in the fully upright position, by turning the cup just a
quarter turn to apply just the right amount of quill return tension.
Attaching the hub in the manner described eliminates the top belt groove on
the spindle pulley (for the highest spindle speed) as a trade-off of being a
dual-use machine.
--
WB
..........
"Winston" wrote in message
...
I tapped (4) 3/8-16 through holes in 1/2" HRS
yesterday. I wasn't looking forward to the last
four holes, because starting the tap straight and
cutting the threads was more difficult and time -
consuming than I wanted it to be.
I decided I had a mechanical 'impedance mismatch'
between me and the tiny tap handle.
The cure was to clamp a tap handle in the wheel
for my tubing roller:
http://manuals.harborfreight.com/man...9999/99736.pdf
(See Page 6 and 7 "Turning Wheel".)
The Hanson 12002 secures perfectly in the bore of the
turning wheel once one removes the crossbar.
http://www.plumbersurplus.com/images...213-254276.jpg
The final four holes tapped quickly and easily.
I found that I could hold the tap on axis and apply
the necessary pressure to get a clean start.
The huge lever arm made the process fun!
(Yes, I was grinning at the time.)
--Winston -- A 'High - Z' guy in a 'Low - Z' world