Manual Automatic Tool Change

 Setting Up the Tools 

The statement “Manual Automatic Tool Change” sounds like an oxymoronic statement unto itself.  Basically what it’s a way to convince Mach 2 that you have an automatic tool changer, when in fact you do not (not yet at least).  The auto-change routine includes a pause and a prompt to ask for the proper tool.  Somewhere in there it applies the proper tool offset and then resumes the program.  When we though this up it cut the production time of our brackets from 3 hours down to 1:20 flat.  Now that’s a manufacturing improvement, more so it allows an unskilled operator to “baby sit” the mill without a bunch of training.

This “Manual Automatic Tool Change” series is broken into 3 sections:

  • Prepping the tools (this section)

  • Setting up the tool table

  • Setting up everything else and making it work

Prepping the tools.

Anytime we talk about swapping tools we need an accurate way to get them in there the same way each time.  Basically this is a way to get the drill bits the same, and maybe a few other things that might be helpful.

 
Start with a piece of solid stock, I choose brass because it solders easily, anything that will solder will work.  
Rough turn it down to the diameter + 0.010 of collet you're going to use.
Pilot hole.  A good pilot bit is self centering, so it makes things easier.  It's worth the 50 cents to pick one up.
Using the same bit that you're going to mount into it, bore a hole about "yo" deep.  At least to the depth of the flutes.
That's what "yo" deep looks like. 
Part the piece off.
Remember the vice that came with the mill, this is a perfect job for it.
Get it hot, but not red hot, enough to melt solder and maybe a pinch more.
Fill'er up with solder.

I've used both silver and regular solder successfully. 
Stick the bit in the solder and press all the way to the bottom twisting all the way.  Make sure it is clean and fluxed first.  Tinning the bit is optional but couldn't hurt.

When you press down the solder will more than likely SQUIRT OUT.  Use caution.
Let it cool and chuck it up.  BIT ONLY.

True up the first pinch of the brass, enough to get a better grip.  Take your time and make VERY small cuts, mostly with a bit this small.
Chucked up a little better.
Trued.
Test it on the actual R8 collet.
Flip it around and clean up the front.

The bit should run true and straight at this point.
Get a few shaft collars.  These are pretty cheap, about 75 cents if bought in bulk.
Shaft collar mounted.  Isn't she pretty?...Ok it's a drill bit with a 3/8 brass shank.
More of my collection.  Since I use double ended mills I paint the NOT used end with finger nail polish.  When I flip the cutter I paint the other end, milling wears the polish off in just a few minutes of operation and it's easy to determine which end to use.
Final Thoughts:

The drill bit used in the pictures is a pinch smaller than 1/8" small bits are always tough to do, larger bits are quite a bit easier and you will not need to cut the little bit to get a better grip.  I've done bits as small as 1/16.  (Not bragging, just saying you can do it too)

I use a C5 Collet closer, it's actual not necessary, a 3 jaw will work fine.

I chop off the larger diameter bits to shorten them up, then I do them.

I have some popular sizes that are done in both a 3/8" and a 1/2" shank this allows me to speed up production by not having to swap the collet.

Black oxide coated bits don't work, you'll need to remove the bottom section of coating at least.

If a bit snaps while in operation, check the solder joint by heating it up and removing the bit.  Check for solder adhesion, you might need to improve your soldering technique.
 
Notes on repeatability:

Once a cutter is setup in a specific collet don't change the collet without resetting the tool height.  More on this.

A torque wrench set to a preset value will give better results than a regular wrench and just "snugging it down"

A power drawbar (an expensive one) uses a butterfly impact gun on a regulator to get repeatable torque.