Mike's Journal

electronics, engineering, entrepreneurship

McMaster-Carr's amazing same-day ground shipping

This past Monday at about 2am (up late as usual), I ordered about $150 of parts across 24 different items (screws, bolts, nuts, drill bits, taps, etc.) from McMaster-Carr.  I selected "Ground" shipping instead of "Next Day Air" or pick-up. As usual with McMaster-Carr, I didn't know the actual shipping cost I'd be charged.  That usually makes me hesitant, and on most websites stops me from getting through the checkout process at all, but I'd ordered them from them in the past and had seen them charge roughly the actual rates for UPS Ground.

Monday at 10:30am, my order was tagged as shipped on their website.

And after dealing with processing a near-record volume of orders to ship ourselves, literally as we were walking out from the NerdKits office to hop in the car and go out for a late lunch around 3pm, there was a delivery truck in the driveway with my parts!

Same-day delivery from their LA warehouse to San Diego, even when I selected "Ground".  I probably would have been waiting longer if I had selected "Next Day Air"!

And the shipping charge?  Less than $7, for ~8 lbs and a fairly large box, same day delivery.  It would have cost me much more than that in gas just to drive to their warehouse.

That's an incredible customer experience.  It makes me much more likely to order from them in the future -- even though I will try not to expect same-day delivery again.

How to mount an air conditioner in a horizontally-sliding window

1. Buy window air conditioner unit and milling machine.

2. Outfit milling machine with z-axis DRO.

3. Design bottom-side brackets from 1.500" x 0.375" aluminum bar stock to take the weight of the A/C and also the torque generated by the weight hanging out the window, and to fit around and transfer that weight and torque to the window frame/sill.  Make two on the milling machine.

(download)

4. Use 1.5"x1.5"x0.125" aluminum right-angle stock to form a top crossbar to handle the torque that's now trying to pull the air conditioner out of the window, as to spread that force to the verticals of the window frame.  Screw into the horizontal crossbar of the air conditioner with two #6-32 screws. (Caution: make sure your window frame verticals can handle this force.  Mine could without any issue, but yours might not!)

(download)

5. Use a piece of filler material (cardboard, plywood, acrylic, whatever) to fill in the space above the A/C unit.  Hold it in with two small right-angle brackets, one of which is attached to the top crossbar (shown above), and the other is screwed into the top of the window frame.

6. Enjoy!

It's November 17th, and it's finally time to remove my window A/C (but still sunny and a high of 71 today here in San Diego), so I was finally able to grab these photos.

DIY Bottle Opener

I recently made this bottle opener on the milling machine from some aluminum bar stock. As you can see from the photos, it has changed a bit since my original CAD sketch, but I've decided to include the drawing anyway.

It's very strong and light. If I were to do it again, I'd probably make it thinner than the current 0.200" thickness, and would reduce the length of the thin extended arm and increase the length of the part before the "hook" to give the user a slightly longer lever arm.

Humberto had the idea of having the step in the thin extended arm to allow it to better deform the metal bottle cap (contacting roughly at its center) instead of simply prying it off (contacting at the far edge of the bottle cap as per the CAD sketch). Any opinions on which is better?

Two photos and a sketch:

(download)

Adjustable (slotted) arm on the quill collar

We took a piece of aluminum bar and made an arm that comes out radially
from the quill collar.

It's inset so the bottom of it is flush with the bottom of the collar.
All that protrudes is the two screws. This was important to make sure
the arm wouldn't interfere with our work when milling.

It's distance is adjustable radially via the slotted path for two hex
cap screws.

We used a dial indicator and measured a deflection of about 0.002" at
the end of the arm under a heavy hand-applied force (maybe 50 pounds or
so). Hopefully this means the deflection under the drag of the slide
will be negligible!

The end is threaded radially, which is where the digital caliper will
attach.

(download)

Quill collar for 1220XL

We've been working on making a new collar to fit around the mill quill on our Smithy CB1220XL. We started with a 4" diameter by 3/4" long piece of 6061 aluminum. After a bunch of facing / turning / boring / milling / drilling / tapping / sawing operations, we've successfully made the part. We had great results with lathe accuracy, able to get diameters finished to within roughly +/- 0.002" of target.

The outer diameter is arbitrary. The larger bore diameter must fit snugly around the quill collar for a press-fit -- it is then tightened with the two hex-cap screws as shown. The smaller bore through the piece must clear the rotating spindle, but must remain close so as to provide a chip shield for the thrust bearings just within the collar.

We ran into lots of issues with work planning, some of which were due to the reduced work volume of the machine, but most of which were simply due to our original paper design taking insufficient consideration of things like obstruction by the drill chuck, tool cutting lengths, etc.

But it works! It goes on snug and is quickly tightened via the two screws. This replaces a plastic cap included with the machine. However, this version gives us the opportunity to add a Z-axis digital read out (DRO)... stay tuned!

(download)

We're making chips on the lathe and mill!

We've been busy getting tooling, and finally have been able to do some
basic lathe and mill work!

The backlash is pretty terrible (perhaps 0.020 inches), specifically for
use as a mill, so we have to move toward DRO very soon.

(download)

Two Mechanical Successes

First, we successfully changed my brake pads on my front disc brakes.
Back when I did the oil change, it ended up taking much longer than I
expected, however the brake pad replacement took much less time than I
expected! Perhaps more importantly, the amount of money saved versus paying a
mechanic to do it is tremendous in the brake case, and not so much (or
even negative if time is included) for the oil change. I was further pleasantly surprised by the AutoZone lifetime warranty for
the brake pads, where they'll replace them free for life as long as you
don't wear them down to the bare metal. In any case, it's one thing to take a bunch of mechanical engineering
classes, and another thing entirely to get your hands dirty and figure
out how various car systems are really put together.

Pair of jack stands at Harbor Freight:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38846
$20 (were on sale), but have provided hours of entertainment, education,
and lots of savings already just by doing the oil change and front brake
pads myself!

Second, NerdKits did end up buying the Smithy CB-1220XL lathe/mill combo
machine I took pictures of in this earlier post:
http://blog.compumike.com/lathemilldrill-combo-what-do-you-think
We've got a lot of work to do to dig in, clean it up, and get some
tooling so that we can be useful, but this opens up an exciting new.
Quite an adventure in Fred's new (old) pickup truck to move the thing!