Here we go again . . . MK4

[Neale]

I cheated a couple of days ago when I needed to tap some M8 holes in a slab of Ecocast I had just drilled. I held the M8 spiral-point tap directly in the drill chuck, and took off the drive belt on the mill (Warco VMC with multi-speed belt drive so easy to do). I could then turn the drive pulley by hand. Light down pressure on downfeed handle, and this was enough to get a good thread started, finished by hand later. For small taps, I have lightly guided them in the chuck jaws and tightened a tap wrench on to the shank (not square) of the tap to turn them. Especially with these easily-driven spiral-point taps, this works ok to get a thread started. But I'll have to have a look at the RDG tap holder the next time I see them at an exhibition - thanks.

[routercnc]

Hi Neale,

Yes, done something similar to that by slackening the motor / belt tension levers on the drill press. But even with the belt slack there is still quite alot of friction and it still tries to turn the motor.

To remove the belt on my Warco pillar drill completely takes a bit of time and involves a ladder, a screwdriver to open the lid, and releasing the motor bolts and is not very efficient. It's not much fun for long due to the effort of turning the chuck & motor.

The method above is quick to set up (just a quick adjustment on the chuck jaws) and is then very easy to turn.

One thing I will note is that the tap slipped occasionally, even though I tightened it as much as I could. I don't know if they do a keyed chuck version but that might be better. Maybe a bit of degrease on the inside of the chuck jaws would help. Next time I'll also try a tap handle on the round part of the tap shank as you did.

[routercnc]

Bit more progress. One of the gantry end plates was cut out over the weekend:


Tonight I drilled and tapped all the various holes. Couldn't resist a trial fit of a couple of the previous parts:
OUTER VIEW

(Note the tabs on each end still need facing off. I'll wait for the other one to be machined then do them in the same session.)

INNER VIEW


With the side plates offered up:






Another reminder of what the end sections should look like . ..



I used the tapping chuck again which made light work of the threads. Also discovered I was holding the tap wrong. I had been putting the tap right into the chuck and it gripped on the round shank - liable to slip. Looking at the 3 jaws of the chuck I noticed that it has ridges in the centre of each jaw. If you put the square part of the tap into the chuck these grip the 4 sides nicely, with 2 jaws on the flats and 1 jaw (with the ridge) on one of the chamfers of the square. Hard to describe but just put the square shank of the tap into the 3 jaw chuck and it will not rotate.