QCTP mounted drill for my ORAC

[DICKEYBIRD]

I cobbled up this widget recently from stuff I had lying around. I posted it on another forum but thought maybe someone here might be interested as well.

I built it to save time when making model airplane engine venturis for a friend/customer. The venturis have 4, #58 holes in them and I’d been drilling them in the mill using a square ER32 collet block. It worked fine but my mill’s top speed is a bit slow for the little drill and it required tedious setup for each one.

With the part still chucked in the lathe and this hang-on QC drill’s offsets stored in Mach, it’s now easy to drill the holes right on the money. I just mark the 4 positions on the chuck flange with a magic marker and use a simple wire pointer to index the holes. Their positioning isn’t super critical and there’s not enough torque generated from the little drill bit to move the lathe spindle around while drilling.

The motor is a Pittman 24VDC 3450 rpm given to me by forum member Jim Glass, thanks Jim! I run it with a cheap ebay KB speed controller. It came with a Peco add-on board that runs off 36VAC so I used an old 36V transformer to power it. With a few tweaks I got the motor running at a bit under 5000 rpm. Still slow but it’s twice as fast as the mill & zips through aluminum like butter. I tested it with drills up to 3/16” dia and they work great.

I made an ER16 chuck for it and was going to just press it on the motor shaft but my .3115” reamer somehow made an oversize hole. I drilled & tapped it for 4 setscrews finally got the runout down to .0002”.

The last pic shows a test run of 8, #60 holes in a piece of scrap aluminum. The macro lense setting makes the holes look huge but trust me, they’re pretty small!

 

[petertha]

What a brilliant setup. I love that U shape bracket idea that integrates into the toolholder slot. I've been eyeing some ebay VFD/spindle packages for micro grinding & this opens up new ideas for high rpm micro-drilling on the same type assembly. Couple questions

- re the tapered nose shank part held in the collet, how are you fixing the drill bits into that? (or maybe I'm misunderstanding & its a dedicated cutter?)

- if you wanted your tool to hold a progressive range of micro bits, are there ER-type collet systems that go down that small? Or would the ER collet hold a micro chuck which holds the bit? This is where I get stumped. Gripping a drill it is one thing but having it accurately centered & spin-able at high rpm is another. My only experience is with those Dremel like pin chuck thingy's

- what is the do-dad with the spring immediately behind the work piece in the lathe, or is it just coincidental background?

 

[DICKEYBIRD]

Thanks Peter; glad you like it!

The tapered drill adapter was made back when I had to drill the parts held in the mill in an ER32 square collet block I'd made 6 parts & parted them off without remembering to drill the holes. (Stoopid!) There was no clearance for the ER16 chuck to get in there so I made the extension from a bit of 10mm "printer rod". It was drilled #58 & the drill loctited in place. I tried all my pin vises but their runout was terrible, The extension got the drill in there, is plenty rigid and has little runout.

Now that I'm drilling with the part still in the lathe with more "stickout", the ER16 chuck has enough clearance without the extension. My smallest ER16 collet will grip all the way down to a #77 (.018") if needed and the biggest is 10mm. ER11 is more compact than ER16 but I didn't want to buy yet another set of collets. As far as I can tell, ER16 will do everything I need in this application.

The widget with the spring on it is my homemade Z-axis homing probe. I use it to home the Z-axis instead of other mechanical methods like fag papers, shims, eyeballs or whatever. I have all my tools' Z offsets ref'd from Z home in Mach3. I slap the part in the chuck, jog the probe into position, hit "set Home Z" and Mach automagically moves the probe slowly into the part until the probe shaft trips an opto and backs off a bit. The opto is far more accurate and repeatable than anything else I've tried.

My homemade X-axis homing is done by a mechanical switch that kicks in before the slide bottoms out & switches in an opto that reads a slotted disc on the stepper motor. This gets me a super accurate home position to set my tool offsets accurately. I have 15 different tools that have had all their offsets dialed in & saved in Mach. After homing both axes, I can slap any of the tools on the QCTP, enter the tool number into Mach and cut away with a reasonable expectation that it will produce a part that's accurate within a thou or 2. On a new part, I dial in some "negative tool wear" in the tool table, cut the part, measure it and adjust as needed to get it spot on. After doing that it'll be good to go time after time unless I screw up.