The Owad Laboratory

Rebuilding a Porter Cable 18V battery

I have a large collection of 18V Porter Cable tools. The oldest are from 2010, and the batteries are starting to fail. I've heard that Harbor Freight's 18V battery uses the same cells. A new Porter Cable battery is about $40, whereas the Harbor Freight battery, with the ubiquitous 20% off coupon, is just $10.40.

Both batteries open by just removing a few screws. The Porter Cable battery is better packaged, but the layout of the cells is identical:

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Unboxing the Laser Cutter

The Chinese 40W laser cutter, sometimes called the K40, has been around several years now, and prices have finally dropped below $400. After waiting for discounts to line up, I was finally able to purchase one last week for about $360 shipped. How bad (or how good?) is a $360 laser cutter?

The unit is larger than I pictured it, given the cutting size. The box is 37"x25"x16". With its weight and bulk, it was too large for me to get my arms around, so I slid it in the front door and unboxed it.

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Raspberry Pi Zero and NTC CHIP size comparison

CHIP is on the left, Pi is on the right.

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CHIPbag - Customizable Case for NTC's C.H.I.P.

CHIPbag is a customizeable case for Next Thing Co's C.H.I.P..

Options in Customizer, or by downloading the attached OpenSCAD file, include:

Standard or Low-Profile design
Openings for headers
Opening for battery connector
Screw mounts added to sides
Bitbeam added to sides or back
Building bricks added to sides or back

I'm making a lot of tweaks yet, but wanted to share.

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C.H.I.P. is here!

My alpha version of Next Thing Co's new $9 computer, C.H.I.P. arrived today, straight from Hong Kong. The fun begins!

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Grizzly’s PA Moving Sale and New Benchtop Bandsaw for 2016

Grizzly announced this month that they’ll be closing their Muncy, PA showroom and warehouse at the end of October. I visited on Saturday, for what normally would have been the fall tent sale, but was a moving sale instead. As of this writing, all new in-stock merchandise is 10% off and floor models are 15% off. Demo Shop units are advertised as 25% off, but there’s essentially none left.

If you’re in driving distance of Muncy, it’s worth stopping in. For a $1,495 cabinet saw like the G0690, you’re not only saving $150 off the retail price, but you also avoid the $150 freight charge. A particularly good value is the G0771 hybrid saw. It’s currently on sale for $675, which, after the discount, brings the price to $607.50. When the sales are over, the price with shipping will be $895. (I use these examples because they’re the two saws I was torn between buying.)

Grizzly’s flier says that “all items must go”, but one employee told me that five tractor trailers of tools and equipment leave daily for Missouri. Granted, those tools are leaving, but if there’s something you need, I would suggest getting it now rather than hoping that the discount will eventually drop.

Grizzly has several tent sales each year, where they sell damaged and returned merchandise. There were tent sale items are for sale in the warehouse, but far fewer than at a typical Grizzly sale. There are no table saws left, and probably not enough woodworking equipment in general to warrant a trip, if tent sale tools is all you’re looking for. Metal working machines were more prolific, and there are quire a few small lathes left in particular.

I ended up purchasing a 7x14 Mini-Lathe and two cute little Shop Fox Micro Mills. The new lathe will hopefully replace my Shop Fox Micro Lathe from an earlier sale. It’s a brand new unit, but the control box was damaged in shipment. A new control box was included and it looks like all the parts are present. We’ll find out soon. As for the mills, one is missing the x-y table and the other is supposed to have a bad motor. (The bigger problem is that I don’t actually need another milling machine.)

The best deals at a Grizzly Tent Sale are in the first minutes after the doors open and a few hours later, when they’re ready to negotiate on price. I made all my purchases later on, so I had a good bit of time to wonder around and talk to people.

One person I was excited to get a chance to speak with was Shabir Balolia, Corporate Manager and son of founder Shiraz Balolia. We talked about the closing of the Muncy location, which he said essentially came down to two causes: First, the cost difference between shipping from the Missouri and Pennsylvania locations to the east coast is negligible, with Missouri sometimes even being cheaper. Second, visits to the showroom have declined significantly, while internet orders have skyrocketed. Speaking personally, I’ve often stopped at Grizzly’s immense showroom and been the only person there, so I can understand the reasoning.

Shabir also spoke with me about his plans for a new benchtop bandsaw. It will be the first benchtop bandsaw to feature a carry handle and upper/lower ball bearing blade guides, as well as other innovations. Shabir was excited to talk about it and clearly expects it to be the highest quality benchtop bandsaw on the market. Look for it in the 2016 catalog or on Grizzly’s website, come January. Shabir asked that I not share any other specifics, but definitely keep an eye on Grizzly if you’re planning a small home workshop.

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Setting up Cura and OctoPrint for the Mini Fabrikator (Tiny Boy)

I recently bought a Mini Fabrikator (TinyBoy) on the advice of Ex-parrot.

The instructions describe how to set the printer up with Repetier-Host. Ex-parrot uses Octoprint. Print time can take hours, so I decided to use Octoprint as well, installed on a Raspberry Pi, so that my MacBook won't be tied down while printing.

I'm using the latest version of Octoprint (1.2.5). I tried installing the latest version of Cura (15.06.03), but the option for non-Ultimaker printers seems to have been removed, so downgraded to 15.04.2, which is working well.

Below are screenshots of the settings which Ex-parrot recommended to me. I've done about a half dozen prints so far and haven't felt the need to make any changes. Comments with suggested tweaks are welcome.

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How to check the milk truck's schedule using perl and Alfred


I buy milk from the dairy farm next door. They milk twice a day, at about 5 AM and 5 PM. The milk truck picks up the milk every other day, not long after the morning milking. On days the milk truck comes, I can only get milk after the evening milking. On days it doesn't come, I can get milk any time.

This is the line of perl I use to check when I can get milk:

print int((time()-14400)/86400) % 2 ? "After 5:00." : "Any time."

time() returns the number of seconds since the Unix Epoch (January 1, 1970). Next, I subtracted 14,400 seconds (four hours), my offset from Coordinated Universal Time. Then I divided by 86,400 seconds (one day) and converted to an integer, which gives me the number of days since the epoch. The modulo operation finds the remainder after dividing by two, telling me whether this is an even or odd day, and printing the appropriate message accordingly.

A workflow to execute this perl script via Alfred is attached.

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How to build a third hand

When I’m working on a circuit board, I typically hold it in a clamp, but I’ve found that sometimes I need a third hand for holding a wire in place. This design uses only three parts:

A suction cup ($3), coolant hose ($7 for six), and an alligator clip ($3 for 28). You’ll also need a drill, a 1/2” bit, a 3/16” bit, and super glue.

To mount the alligator clip on the end of the coolant hose, I enlarged the hole on the end of the hose to about 3/16”. At 3/16”, the clip didn’t quite fit in, so I moved the spinning drill bit around in the hole, gently enlarging it, until the clip could squeeze in. It fits very nicely. It’s quite snug, but can still be easily turned. It seems most people use much more complex methods of mounting the alligator clips. I couldn’t be happier with the fit, and and this point I see no reason to do anything more complex. I’ll follow up in a few months with a note on whether or not the connection remains tight in the long term.

Next, drill a 1/2” hole in the base of the suction cup, being careful not to go to deep. Affix the coolant hose using super glue. I like to use the kind that can be brushed on.

That’s all there is to it. The techniques are basic, but the result is sturdy.

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A Digital Readout (DRO) for Shopsmith

The Shopsmith's extension tables and varying height make it difficult to attach a rip scale. The newest model uses a removable magnetic strip. Unfortunately, Shopsmith changed the front rails to accommodate the rip scale, so to purchase the option for mine would cost $200.

Instead, I bought this digital readout from iGaging. At this writing, the price is $45. The readout can display in millimeters, decimal inches, or fractional inches to 1/64. I really like the 1/64 display for woodworking.

It's important that the DRO can be quickly removed, so that the Shopsmith can be converted to other uses. I have it attached with a clamp on the right and a magnet on the left. On the right, I'm using the included right angle bracket to clamp the encoder in place. The encoder is stationary and the scale slides with the fence. There's some flex in the bracket, but the magnet on the far end is capable of holding the scale square. I'd like to make a more rigid bracket that would clamp square to the table and provide a place to attach the display.

The only custom part in this setup is the bracket below. It connects to the fence's t track and provides the magnet for attaching the scale.

The magnet is attached with two nails, as screw heads would have protruded past the magnet. On the back is a homemade t-slot nut: a piece of aluminum with two holes tapped in it. I cut the nails off flush to the back of the MDF, but I was afraid they'd still scratch the fence, so I cut about an 1/8" off to make a gap between the bracket and the fence.


To calibrate the scale, I move the fence until it's just touching the blade, then zero it. I think a preferable method would be to move the fence an inch or two away from the blade, cut a board, measure it with the calipers, and then set the gauge to that value. I've seen a few discussions about using this DRO with an arduino, so I suspect it would be possible to build an interface with this feature.

With the current setup, my test cuts tend to be off by about .004" That's plenty accurate for everything I'm doing, and I suspect the imprecision has more to do with my abilities than with the DRO.

Update, 12/5/14: I've switched to using a floating table, for most work. With the floating table, I can do cuts up to 16" from the blade, and it's a lot more convenient to adjust height, since the floating table moves with the main table.

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