Funting with a Polespear

I have recently added a new hobby to my life.

The timing couldn’t be worse, really.

I already have a 2 year-old daughter, a baby boy due any day, a full time job, a wife, and a large number of unfinished projects, but now I have to accommodate the compulsive urge to kill fish with pointy objects.

I grew up in the Seattle, Washington area and always enjoyed fishing, but somehow, since moving to San Diego 10 years ago, I haven’t found to time to go fishing.

I guess the problem is that I’m pretty busy with many other areas of my life, and it’s hard to justify spending a few hours on a weekend sitting and  waiting for a fish to commit seppuku with a hook on a string.

Then I discovered spearfishing. Spearfishing is different, it’s like snorkeling with a purpose. It’s not just sitting around waiting, or even just swimming around and looking, it is hunting. Fish hunting. Funting. 

I’ve gone twice now, and I’m mildly obsessed.

As is the case with most of my hobbies, it’s not enough for me to just participate in spearfishing, I have to improve on it, customize it, make it better, or at least make it my own.

To this end I modified the tried and true polespear to add a trigger mechanism.

The polespear design is simple: it’s a spear with a rubber band attached to the base. To kill a fish with it, you hook the rubber band with your thumb, stretch the band toward the tip of the spear, and then grab the spear shaft near the tip in order to hold the band under tension. Then you point it at a fish nearby and loosen your grip, allowing the spear to lurch forward; ideally impaling the fish in the process.

The idea to modify this weapon came to me when my friend complained about his hand getting tired from swimming around holding the polespear cocked and ready to shoot. 

I decided that the polespear would be better if it had a trigger, and came up with this design:

Then I built it…

First I took a piece of stainless steel and shaped it into a snug-fitting collar that I attached near the tip of the spear with a spring pin.

Then I glued together a few pieces of wood (something like teak that I had laying around from old patio furniture), drilled a hole through it (slightly large than the spear shaft), cut it to and arbitrary shape using the bandsaw and affixed a little latch (also made from stainless steel) to hook onto the collar.

To keep the spear from traveling too far, I added a collar at the base with some soft rubber tubing to act as a cushion when the spear is stopped (I think the piece of rubber is an in-sink garbage disposal adapter).

To use the spear, I hook the rubber band through the wooden handle, and then slide the handle up the spear till it latches onto the collar at the tip.


And then I fired it at a piece of plywood.

I will hopefully get to use this to kill a fish this weekend, if my son doesn’t disrupt my plans by being born.

Update: I used this over the weekend and probably killed a few fish. I say “probably” because I didn’t actually “catch” any fish.

The rubber band I used is the standard light-duty polespear band, and the added weight/drag of the collar seems to have slowed the spear down just enough to really damage a fish but not actually skewer it. The result is that there are an number of disabled fish hobbling around the waters off the San Diego coast, if they are lucky. The unlucky ones died slowly Saturday morning, trying to figure out why I feebly stabbed them with a dull piece of metal.

The trigger itself worked beautifully, and I’ve ordered a more powerful band that should many little fish fatherless when I next enter the waters.


Lathe Boring Bar Holder

I find boring bars exciting.

I have a boring head for my milling machine, which is excellent (indispensable) for milling holes to a certain diameter in square stock. But for round stock in my lathe I’ve been messing around with various cutters with mixed results while trying to cut the inner diameter of various projects.

Boring bars are the correct tool for the job on a lathe, but I don’t have any. Even if I did, I don’t have a holder.

I decided to rectify this situation by making a holder that would accept the cutters from my boring head set.

When I made my quick-change tool post, I milled a dovetail into a large block of steel. The idea is that I can cut off chunks as needed to make various tool holders without having to mill a new dovetail.

I sliced off a chunk with my portable bandsaw, cleaned up the shavings, and then milled it down to a more appropriate size.
Boring bar holder for lathe
I drilled a starter hole  in one end and through the full length of the workpiece.

Then I used my boring head to bring the diameter to fit the boring bars’ 1/2-inch shanks snugly.
Boring bar holder for lathe
Boring bar holder for lathe

In order to check by progress while boring the hole, I had to move the workpiece out from under the cutter and fit some calipers into the hole. My DRO proved very helpful for this: I could set the axis to 0, move the table to get the workpiece to a measurable location, and then  move it back till the DRO read 0 again. It perfectly relocated the hole under the boring head every time.
Boring bar holder for lathe
Boring bar holder for lathe
Boring bar holder for lathe
Boring bar holder for lathe

Once I had bored out the hole to the proper depth and diameter,
Boring bar holder for lathe

I set the workpiece on its side and drilled 2 holes through to the 1/2-inch hole, which I then tapped out with 1/4-20  threads for set screws (i once again use the DRO to relocate the holes after changing the drill bit out for the thread tap)
IMAG1Boring bar holder for lathe069
Boring bar holder for lathe
Boring bar holder for lathe

In order to tap the threads perfectly straight, I like to lock the tap in the drill chuck, and then use my lathe chuck handle to turn the chuck manually.
Boring bar holder for lathe
Boring bar holder for lathe

I slapped the new boring bar holder on my lathe and bored out the inside of a couple of my lathe feed gears as an inaugural project. The boring bar performed perfectly in its new holder.
Boring bar holder for lathe

I win.

Cleanup Tip: Metal Shavings

If you notice the background of most of my pictures, you’re probably thinking “why would I take cleanup advice from that guy?”.

True, I don’t clean up as often as I should, but that doesn’t mean I don’t know how to do it.

I have a portable bandsaw that I got for Christmas and that I am fairly certain is the most awesome tool ever.
I use it to slice through angle iron and tubing like a hot knife through Vaseline; and through 3.5-inch thick bricks of steel like… okay, it’s not that fast with the thick metal, but it gets the job done and takes up a whole lot less space than a horizontal bandsaw.

However, as is true of all saws, it makes a mess. Which brings me to the point of this article: a neat trick to quickly clean up metal shavings.

I use this method whenever I have a fairly localized mess of shavings in an area that isn’t easy to use a broom in, such as around my vice and grinder on the workbench, or on the floor in front of the vice where I use my portable bandsaw.
What you need:

  • A strong magnet (ideally a rare earth magnet)
  • A shop cloth (I like to use pieces of old t-shirt)

Place the magnet in the cloth…

Fold the cloth around the magnet…

Wipe the area where the shavings are to collect them…

Then go over the to trash can, and unwrap the magnet and set it aside…



Now you have a handful of shavings to empty into the trash and a clean magnet.

See? I can clean if I want to.

Cheap DRO! – part 2

Continued from Part 1

With the X-axis DRO installed, I turned my attention to the Y.

The difficulty here was that there weren’t any pre-existing holes or dovetail slots to take advantage of, so it was an entirely custom installation.

The other complication was that the base of the mill flared out to a wider footprint, so the only surface to mount the DRO’s rail on was at an angle relative to the surface on the sliding table itself.

I started by taking off the handwheel on the left side if the table and moving the table all the way to the right to give me working room.

I then removed the end cap of the table to give just a little more space.

There was a flat space just under the lead screw that looked like a promising location to mount the measurement unit’s bracket, so I drilled and tapped a 1/4-20 hole in the center of it (approximately).

Just then my daughter woke up from her nap, so I put things on hold until the next day.

Since I knew I would be modifying brackets, I started working on the rail so that I would have precise references to work from.

After cutting the rail to length,

I drilled and tapped a hole near the back of the mill first. I placed it so that the mounting bracket would sit just under the line where the base began top taper outwards, this way I could use the same line near the front to visually confirm the straightness of the rail.

In order to avoid obstructing the full range of motion along the Y axis, I had to modify a couple of the mounting brackets and attach them to the front of the mill, instead of the side. The modification was essentially to attach two brackets together (using one of the spare brackets from the X-axis), so that I could reach the front of the base and still keep the rail parallel to the table.

Now that I had the rail mounted, I could get a feel for what sort of bracket I would need to fabricate to hold the measuring unit to the sliding table.

I’ll gloss over the details, since they aren’t particularly useful), but suffice it to say that I used a vice, drill, hammer, and welder to create the necessary Frankenbracket.

Since this bracket is always hidden under the table, the install looks pretty good.

The display units conveniently had magnets on the back, so while a long term setup will be a little cleaner, I was able to stick the displays on the head of the mill for immediate use.

With the installation complete, I turned my attention to re-mounting the vice on my table.
Because of the location of the travel locks and the dovetail slot, The X-axis measuring unit sits about a millimeter above the surface of the table.


I always keep my milling vice installed on the table, so I needed a way to avoid the top of the measuring unit.

I could shim up my vice, but that would introduce instability and inaccuracy.
So I marked the bottom of the vice where it crossed the edge of the table.

Then I clamped a large aluminum bar to the table, parallel to the Y-axis (front/back),

and then clamped this bar in the upside-down vice (I had to space the vice from the bar with a 3-2-1 block to clear the clamping bolts).

Then I milled out a swath 1.5 millimeters deep and 1.5 inches wide, starting from the mark I made and cutting towards the back of the vice(away from the jaws).

This was sufficient to clear the measuring unit.

I re-aligned the vice and now I’m back in business (figuratively.. I don’t actually have a machining business…)

So there you have it. $60 and 4 hours later, I have DRO on all 3 axis of my milling machine.
I’ll let you know at some later point in time if it lives up to expectations.

Cheap DRO! – part 1

Cheap DRO!

I bet you never thought you’d read THAT statement!

If you don’t know what a “DRO” is, then you must have REALLY not expected to read it.

A DRO, or Digital ReadOut, is a measurement tool and a display that attaches to each axis of a milling machine or metal lathe and clearly shows the distance traveled during milling operations.

The alternative to a DRO is to count the number of turns and markers on the hand wheel as you make your cuts, but I’m not a very good counter and longer cuts require a lot of turning the wheel (10 turns per inch on my machine). There is very little dispute around the assertion that you should use a DRO if you can.

The problem with DROs is that they are very expensive. It’s not unusual for decent DROs to cost several hundred dollars, and the nice ones are often over $2000. Now, if you’re running a production machine shop, this isn’t a lot more money to add to your capital investments; in fact, your $13000 milling machine probably already has it. But if you’re running machines in your garage as a pass time, it can be tough to justify the extra expense to your wife (unless you commit to an equivalent investment in her pass time, so really the DRO costs double the list price… plus tax).

Enter the Grizzly T23012/T23013 DRO:

T23012 12

I don’t know why it hadn’t occurred to me to look on Grizzly for a cheap DRO; I stumbled across them by accident, browsing the sale items on the Grizzly website.

I had been planning to make my own DRO by modifying a couple cheap digital calipers, but by the time I would have purchased and customize the necessary parts, I would have spent more than the cost of these new.

What’s the catch? These are basically pre-modified cheap digital calipers: they have aluminum slides, plastic housings, and an accuracy certification of +/- .004-inches per 12-inches traveled.

If you can live with this (you can live with this), then these are an amazing deal.

I bought them.

I ordered a 12-inch one for the Y axis and a 24-inch one for the X. This weekend I installed them.

My mill is the G0704, a BF20 type milling machine. I bought it almost exactly 1 year ago, and I love it.

The first thing I did after taking the DRO out of the package was to install the battery and make sure the thing worked. I started removing the screws around the housing and then realized that the battery could be opened by hand.
Right… good start.

I installed the batteries (it takes two, and comes with two spares), and turned it on:

Numbers! okay, on with the rest.

The X axis would be the easier to install, so I started there. I removed the handwheel to get it out of the way for now.

My mill has a dovetail along the length of the front of the table to set stops for left/right cuts.

I’ve never used the stops, so I re-purposed the slot to mount the brackets for the DRO’s rail and used the threaded holes from the stop itself to mount the actual measuring unit.

I had to cut the rails for the DRO to the proper length, but this was easy with a hacksaw.


I had to drill out the rail brackets to fit the screws in the dovetail, but that was also easy enough.

The difficult part here was mounting the measuring unit.

The bracket that came with it was inexplicably designed to hold the unit much further away from the mounting surface than the rail brackets.

In order to use the bracket, I had to flatten it in my vice, and then shorten it to remove the unnecessary bent metal.


As Murphy would have it, I cut the bracket too short, so I had to file a notch in it and clamp it in place using one of the extra stops from the dovetail as a sort of washer.




The washer behind the bracket is my spacer, it keeps the measuring unit perfectly aligned with the rail.

The end result looks cleaner than it is and is actually quite sturdy.


I ran a the table back and forth a few times to verify that the DRO agreed with my handwheel counting and it did.

One down, one to go…

…and now for something completely different

If you look at my history of posting topics, this one is completely uncharacteristic. However, if you think of my postings as showing off something I did that I’m proud of, this fits right in.

My sister got married last week. I was supposed to give a toast, but her other older brothers and I decided to surprise her (and the groom) with a song instead…

How to Make a Quick-Change Tool Post – Part 1

I have a metal lathe.

I’ll just let that fact sink in for a minute


It’s a relatively small Chinese lathe sold by Harbor Freight long ago and purchased by me from Craigslist a while back.

I’ve had a lot of fun learning how to use it, and now it’s time to start putting my little machine shop to work: that’s right, it’s time to start making parts and tools to use in my machine shop.

The biggest shortcoming of my lathe is the tool post (the part that holds the cutters).
Tool Post

It’s a standard design, with four sides that can each hold a cutter, and in theory you can rotate the holder to bring each of those cutters to the workpiece as needed. The problem is that cutters have different thicknesses, and they must be shimmed by various amounts to place the cutting tip at the correct height (exactly aligned with the center axis of the workpiece).

Finding and placing the shims is a pain, and I am rarely able to get the height just right.

So I decided to make a new tool post that could be quickly and easily adjusted.

I decided the best approach would be to start with the concept of a sliding/locking dovetail, and figure out the rest as I went.

First order of business: a big chunk of metal…

IMAG0269Tool Post

Tool Post

Tool Post

Then I drilled a hole through the center to accommodate the locking bolt and roughed out the cylindrical hub on the bottom.
Quick-Change Tool post

I significantly misused my boring head to bring the cylinder to its final diameter and smoothness.
Quick-Change Tool post

I marked, drilled, and bored out a hole horizontally through the block to fit a piston that would lock the dovetail.



Then I went over the the lathe to make the piston itself.

Then I drilled a smaller hole near the back of the tool holder (the opposite end from where the dovetail and piston would be). This is where I would place the cam that would move the piston and lock the dovetail.

To make the cam, I started with a shaft that fit in the newly drilled hole and marked it where it crossed the hole for the piston.

Then I placed a piece of a washer between the shaft and one of the teeth of the lathe chuck to set it off-center and turned on the lath and cut passes between the marks on the shaft until the cutter was removing material all the way around the shaft.


Now I had a shaft with a cam (a camshaft) to move the piston.
I put the camshaft into place and them set the piston in the hole.
I rotated the camshaft until the piston was at its lowest point and then scribed a line.

Then I shortened the piston to this line so that it would be flush with the surface with the cam in its low position and protruding slightly with the cam in the opposite position.



Coming soon: Part 2 – The dovetail, the tool holders, and the camshaft handle

How To Patch A Hole In The Wall

As part of my ongoing bathroom renovation activities, I’m moving the light fixture. This means I need to make a new hole in one wall and to patch the old hole in the the other wall.

It’s a little tricky to patch a wall when the hole isn’t near any studs, but it’s not too difficult with a little planning.

Here’s what I do (It’s as easy as one, two, three…, four, five, six, seven, eight, nine!):

1. Locate the hole.

Hole in the wall

2. Cut a piece of plywood that is a little narrower than the hole.
3. Put a screw near the center of the plywood and use it as a handle to put the plywood in the hole and hold it against the back side of the drywall. (Note: it is best if the screw is closer to one end of the board lengthwise, otherwise it may interfere with getting the board into the hole)

Hole in the wall

4. Pull on the screw with one hand, while you drive in screws through the drywall and into the ends of the plywood.

Hole in the wall

Hole in the wall

5. Remove the center screw from the plywood.

6. Measure the hole.
Hole in the wall

7. Cut a new piece of drywall.
Wall Patch

Wall Patch

Wall Patch

Wall Patch

8. Screw the new piece of drywall to the plywood.
No Hole in the wall

No Hole in the wall

9. Done.

Cutting Blind

I’ve been working on remodeling my master bathroom for the last week or so (in between shifts at my day job and episodes of Battlestar Galactica).

I took out my old fiberglass tub and shower surround and am replacing it with a nice porcelain enameled steel tub and a white tile surround.

I am using a concrete backer-board for the tile (as is recommended for wet areas), and I had installed the tile on two of the three walls when I got to the side with the plumbing and realized that my valve was too far forward and would not sit properly behind the tile.

This would require me to remove the backer-board and re-solder the copper pipes. But since I had already installed tile on the overlapping wall, I didn’t want to remove the whole board, and so I decided to handle things surgically.

I planned to cut an access hole in the backer-board to work on the pipes and then re-attach the cut-out by screwing pieces of plywood to the inside of the standing wall and then screwing the cut-out onto the plywood.

The only problem was figuring out how to cut the hole.

Concrete backer-board will destroy normal drywall saw blades, and the angle grinder with a diamond blade creates too much dust for indoor work. I have a jigsaw with a tile-cutting blade that would do the trick, but since I had plumbing behind the wall and I couldn’t see or remember exactly where it was, I needed to make sure it didn’t cut too deep and nick an artery.



At this moment, inspiration struck: If I put a spacer between the the wall and the jigsaw, I could limit the depth of the cut to just barely cut through the wall and leave the plumbing behind it unscathed!


I cut a couple pieces of plywood and them taped them to the bottom of the saw, put the blade through a starter hole (that I drilled with a flat-head screwdriver bit), and started cutting.


As soon as I inched the saw forward it started bouncing all over the wall making dents wherever it landed, like a pogo stick on a wet lawn (I got in trouble for that one…).

I stopped and surveyed the damage – minimal, although I bent the blade badly – and thought about what I had just done.

It is a recurring observation in my life that striking moments of inspiration are not always intelligent.

In the excitement of implementing my “solution” to the problem, I forgot that I was working with a jigsaw, not a sewing machine.

A jigsaw blade always needs to stay in the work piece, it cannot plunge in and out of the cut like a sewing machine needle because it is not designed to pierce, it is designed to cut (as are most saws).

My 3/4-inch plywood spacer allowed the blade to pull completely out of the backer-board on the up-stroke, only to nosedive into the board on the way back down.


I tore off the plywood spacers and cut the hole in the wall at full depth with devil-may-care gusto!

It worked. The plumbing was safely out of reach without any spacers needed.

I sure do over think these things sometimes.