Touching down tool to work when turning

Edited By Weldsol on 12/02/2011 21:18:00

If using a QC system it shouldn't be too hard to come up with a poor boys version of the industrial tool setting system. One workable way would be to make an L shape carrier deep enough and wide enough to take the complete tool holder having closed ends sufficiently far apart to contain the maximum tool projection you anticipate using. By firmly pushing the tool holder into the channel, interposing suitable spacer block(s) between the tool holder and one closed end then sliding the tool along until it touches the other closed end before nipping up the clamping bolts it should be possible to control tool projection adequately closely. It doesn't matter exactly what the projection is so long as its repeats so a couple or three spacer blocks should do fine. I'd probably use bar stock 1/4 or 6 mm (ish) thick milled on the edges and screwed together to ensure accurate right angles.

Of course the correct way of using a QC system is to have a roughing tool and finishing tool set-up in separate holders ready to swop over at the appropriate point on the job. One reason I'm unconvinced over QC systems for hobby users, novices in particular, is that you need a decent number of holders to exploit the system. Which comes expensive, at the last count I had 16 holders! QC systems for smaller lathes really aren't large enough for optimum stability and the extra joints inevitably reduce stiffness. Small lathes are flexy enough at the best of times without adding potential problems. Much to be said for keeping the top slide for special jobs when its really needed and doing most work with a spacer block instead, ideally with a heftier tool post.

If you have a 4 way, or other type of block tool post, a U gauge in either drop over the top or push against the front format ought to be workable. Push against the front with the two channel arms against top and bottom of the post looks preferable but the job may get in the way.

If you use Armstrong tool holders and HSS bits, or any similar system which holds the tools sloping upwards, setting the tool tip to centre height after sharpening automatically sets the projection too. The optical type centre height gauge makes this easy. In my view interchanging tool bits in Armstrong holders mounted via inexpensive shop made tool blocks is a much more appropriate QC system than commercial offerings for the hobby user given the (usually) restricted financial constraints.

Clive

Had a feeling that there would be something like this for more industrial situations than our prototyping really is. I might consider trying to arrange something, along the lines that Clive suggests.

With tipped tooling I just turn the tip round to get a fresh face.

Edited By mgj on 13/02/2011 01:14:30

 Dusty, can you please explain this method a bit more detailed? Where do you tap the hand wheel? At 12 o'cl, 2 o'cl  or any time  ? in which direction? Axially or radially? Do you try to hold the wheel stationary with the left hand while you tap it (assuming you are right-handed ) ?

I would like to try that, if I would know exactly how.

I had never much luck with the color band method; I think when I see the color disappearing then the cut is often already too deep.

Greetings, Hansrudolf

Dusty, I am glad to report that your method works a treat! One learns something every day; I never saw that  in the many books I own.

Both my lathes have friction dials (no 'hand wheels'), so I tapped instead (very lightly, with a small brass rod) the center of the ball handle. Giving a light bias with the index finger in the desired direction, I could see the index lines creep forward in minuscule steps. Say about 20 taps for 1/100 mm.

I put then some cuts with a sharp HSS tool on a piece of scrap free cutting steel, and was able to reduce this several times in repeatable steps of 1/100 mm on diameter. The finish was perfect, and the  'swarf' was a bit of black powder! The tool was possibly not even the best; I think even smaller cuts would be possible with a better one.

Graham, I don't think that this qualifies as  'striking a machine tool with an implement'. Using the palm of the hand does not work. It must be a tap which gives a vibrational (or call it sonic) pulse to the leadscrew.  My interpretation, I admit. But I am absolutely sure it does no harm to the machine.

Greetings,