Electric tool setter

I've been a bit sloppy with my terminology. Although I've been calling it a tool setter, the "startled man" fixture is actually a jig for tightening collets etc without damaging the taper tooling or myself. It's not a tool setter as such. Professional fixtures are f expensive, which is why I'm planning to make one as a test of my CNC skills. Even acquiring the right sized stock has been a challenge but now most of the pieces have fallen into place.

A electrical tool setter is simply an electrical switch that indicates when the tool tip has touched off on a surface. You really need one of these to determine the length of each tool with some accuracy, for instance if you want to populate the tool table with tool lengths. The Newker controller has a macro (M882) to do this for you but it requires an input (X25) to be grounded when the tool touches off.

In theory you could just place a metal block on an insulator, connect it to the X25 input and rely on the (grounded) tool to tell the controller when contact has been made. But that wouldn't be very clever because the machine can't stop instantly and the result would be a broken tool. So you need a spring below the touch surface and an accurate register for the touch surface to locate against in the vertical direction.

Nothing complex about it. I actually have a pukka Renishaw touch probe that could be used on the face of it but at this stage of my CNC experience, mistakes come easy and frequently. Replacement tips are not cheap! Besides, instead of a spherical touch probe tip, you really need a flat surface to touch the tool length off against, as many tools don't actually have a surface at the centre of their end face, eg a classical end mill or a face mill.

You can get cheapish probes on Aliexpress and ebay but it's clear that they aren't up to much. For now I just need something simple but reasonably repeatable.

Here's what I drew up, having identified a suitable piece of Tufnol in the scrap bin:

Simple enough concept:

• Cylindrical Tufnol body, which is conveniently electrically non conductive.
• Simple, flat-topped steel piston
• Helical spring to hold the piston against the internal register at the top of the body
• 4mm banana socket insert to provide the electrical connection to the piston (via the spring) and also to retain the spring and piston in the body.

Then out into the workshop to flash it up:

Tufnol drilled out, then bored to size.

A piece of mystery metal. Clearly steel but not exactly free cutting. Turn down the nose, chamfer, sand smooth and part off.

Face off, drill and chamfer.

Drill 5mm cross hole for banana plug insert. 4mm blind hole at the far end for the nose.

Make up a spring from a length of 1.6mm stainless steel TIG wire. It's not exactly critical so it's simply a matter of hit and hope. It seems to have come out OK.

Finished item

And said item in position on the machine. Without getting carried away, it seems pretty repeatable on the basis of a few initial tests. Certainly, I expect it will be good enough for the likes of me, for now at least.

Bottom line is - I followed the procedure I described previously for auto populating the tool table using the M882 macro and a couple of dummy tools (one shown in the photo). With the tool setter, it becomes pretty quick and easy. 

So now I can set up the tool table for the various tools needed to make the "startled man" tool fixture!

The CAM is starting to look reasonably sensible now:

1. 3D adaptive clearing with 20mm YG-1 rougher
2. 3D adaptive to clear up with 9.5mm carbide (actually 3/8")
3. Bore out the counterbores for the cap head fixings
4. Drill out the clearance holes for the cap head fixings
5. 3D contour to clean up the taper bore with BP300 indexable tool (0.8mm radius) using fine stepdown
6. 2D chamfer to clean up the top edges - where the tool can get in. 

Looking at the recent video from NYC CNC, it seems that the 3D adaptive with the 9.5mm tool may be able to do the counterbore if you "detect flat surfaces" and change the value of the plunge radius(?). If so, I may be able to get rid of the boring operation, step 3.