Click here for a PRINTABLE PDF version of the above blueprint.
I have two depth gauges that I use all the time. The first one is my DIY laser depth gauge.
See above drawing. I use the laser to show the depth of the inside bottom on the outside. Am I deep
enough? Can I go deeper? Have I gone to deep?
My laser depth gauge works good on vases, hollow forms and bowls that are mounted in a chuck or on a faceplate with a tenon. When the bottom has NOT been turned yet. The tenon blocks my access to the bottom of the piece. Thus, I can not easily use my "Martel 4 Way Caliper".
The second depth gauge that I use all the time is my "Martel 4 Way Caliper". I use it when I
have already turned a recess in the bottom of shallow bowls and plates. The Martel gauge is more
accurate when there is no room to spare. It works better on shallow things. See my "Martel 4 Way
Caliper" blog entry for more info.
Note: This is another blog append for my students. They can make there own version of what they use in my studio.
Here are some usage examples.
Beware! You MUST hold the gauge level to get an accurate reading. Thus, there is a little laser bubble built into the top of the gauge.
It works great for finding the inside bottom of vases or hollow forms.
You can use it:
- After drilling a hole before hollowing. Is the hole deep enough?
- While hollowing.
- After you are done hollowing. Where should I part the vase off at?
It works great on live edge (bark on the edge) bowls. Where other methods don't work as well.
The web is full of other good cheap ways. For example, a dowel extended thru a board that
contacts the edges.
The dowel method works ok on cut edge bowls or vases but requires sighting by eye the equivalent of the laser line. My laser is easier.
The dowel method does NOT work well on live edge (bark on the edge) bowls. The rough edge tends to muddy the waters when you try to sight down the line. My laser works a lot better.
Make Your Own
You can make your own out of copper or PVC pipe for roughly $25 in parts plus the cost of the pipe. The $25 for parts will actually make two of them.
You can make the laser depth gauge out of 1/2" copper or 3/4" PVC pipe. 1/2" PVC pipe is to
You can get pipe from local hardware store. You need roughly 30" of it. You also need two 90 degree elbows.
Cut the pipe with a pipe cutter. You need the following:
1 of 11" Long (Top)
1 of 8" Long (Side)
1 of 10" Long (Bottom)
I prefer 1/2" copper pipe. It is smaller than PVC and makes a rugged and classy gauge.
I used scrap 1/2" copper pipe. I cleaned it up by chucking it up in my 4 jaw chuck, like a chuck screw. Then I ran the lathe and cleaned it up with synthetic steel wool (scotch bright pad).
You MUST DE-BURR the inside of the cut pipe ends BEFORE inserting wooden pointer dowel and laser mount. DO IT NOW, before you turn the pieces to fit into the pipe. You can use a de-burring tool or a round file. See photo.
You only need to deburr one end of the 10" and 11" long pipes. I marked these with masking tape. See photo. You do not need to deburr the ends that will be buried in 90 degree elbows.
If you are using PVC pipe then you can just glue it together. Everything will end up square
If you are using Copper pipe then you need to use a simple jig to line things up and make everything square and parallel. Copper pipe fittings are NOT a tight fit. There is a little slop to allow room for solder. You need to use a jig if you are soldering the pipe or epoxying the pipe.
My jig is just a scrap of 3/4" plywood that is 8" wide. See photo. I spread epoxy on the pipe and inside of the elbow fittings and then slip the plywood in place. Then I put it down on a flat surface (my table saw table) to dry. See photo. I clean off any excess epoxy with lacquer thinner on a paper towel.
You can use any epoxy you like. 5 minute epoxy from local hardware store will do the job. But, it may eventually fail.
I like to use good quality West System G/Flex 650 Epoxy . It is designed for an application like this. Designed for bonding metals and things that may need to flex a bit. G/Flex is thick like 5 minute epoxy so you don't have to deal with thin epoxy running all over the place. It sets up in 75 minutes. Cures in 3 hours. Two 4 oz bottles (4 oz of resin + 4 oz of hardener) of G/Flex cost around $20 on 12/4/2022.
If you want to solder the pipes together then you DEFINITELY need to use a jig. You need to clamp the pipes to the jig. Let the elbows hand off the table in thin air and solder them while they are IN THE JIG.
This photo shows the rest of the parts that you need.
The wooden parts where turned as per my blueprint drawing. Also see photos below.
See next photo for Laser, Battery Box, and Bubble Level info.
This photo show what you need to purchase from local hardware store or order from Amazon.
Its roughly $25 of parts. Plus $20 if you want to get some good G/Flex epoxy. Or you can use local hardware store 5 min epoxy.
The most important thing is the laser. Two of them for $8 is a great price. I purchased a
couple of spares for other projects.
I chose a laser that has an "Adjustable Focal Length". This means you can turn the little lens on the end of the laser to focus it. The lens is the knurled part on the end of the laser.
I like lasers that are a line, rather than just a dot. Easier to find and see. In this case I had to settle for a laser that is a cross. Because, I could not find one that is just a line at a reasonable price. I just ignore the extra line that I don't care about. See usage photos above.
Note: I know about Laser Presentation Pointers, Laser Cat Toys and the Laser Marker sold by Harbor Freight. They are to big and bulky. They have little buttons that are a pain in the back side and fail. I have learned the hard way that I STRONGLY PREFER a laser diode with a separate battery box with a good slide switch. I deal with the pain of having to solder the laser to the battery box, once and then live happy every after.
The laser needs 3 volts DC. Thus, a single 3 volt CR2032 battery is the way to go. CR2032
batteries are very common. Thus cheap and easy to find at local stores.
I looked for a CR2032 battery box with a GOOD easy to use slide switch. I found one that is ok. Good switch, but a little smaller than I would like.
I attach the battery box to my laser gauge with electrical tape. Keep it simple! I replace the tape when/if I need to change the battery.
Measure the outside diameter of your laser diode module with a drill gauge. My laser fits in a
31/64" diameter hole.
Turn the laser adapter out of any wood you have. I started with a 1" x 1" x 4" square chunk of hard maple. See my blueprint drawing.
I drilled the 31/64" hole for laser in the blank while it was still SQUARE. This made drilling the hole on center easy.
Note: 31/64" is a little less than 1/2". You could make due with a 1/2" drill and a little more epoxy.
If you don't have a drill gauge then just drill some test holes in a scrap of wood and test fit things.
Turn the Laser Adapter between centers. Test fit it in your pipe as your go. A nice snug fit
is desirable. However, epoxy can fix most sins.
My finished adapter was 7/8" diameter by 2-1/2". See my blueprint drawing.
I recommend using a CR2032 3 volt battery and battery box. You need to solder the laser to the
I cut off the leads on the laser and battery box, I make each of them roughly 1-1/2" long. Thus, total distance between laser and battery box is roughly 3".
I joint the wires end to end. This makes a nice clean joint. See photo. Stripping and twisting the small wires together with my big fingers is a bit of a pain, but doable.
Put some small shrink tubing on the wires BEFORE stripping them. The blue stuff in photo. See green arrow in photo.
Then strip the wires and twist them together and solder. I recommend doing ONE joint at a time. Use rosin core electronics solder. See red arrow in photo.
Wait for the solder to cool. Then slip the shrink tubing over the join and shrink with a heat gun or soldering iron.
5 minute epoxy or super glue the laser in the Laser Adapter you turned. See photo.
Then install the Laser Adapter in pipe with 5 minute epoxy.
Turn the pointer dowel between centers out of scrap wood.
The finished pointer needs to be roughly 3" long and fit snugly INSIDE of the pipe. You should be able to slide the dowel in/out of the pipe to line it up with laser.
Turn a nice blunt point on the end of the dowel that will not scratch your work.
Install the pointer with some electrical tape. It almost never needs to be adjusted. Thus replacing the tape if you need to adjust is no big deal.
5 minute epoxy the bubble level to the top of the laser pipe. Use masking tape to temporarily
hold it in place while the glue dries.
This is a simple rather than elegant solution.
Note: You MUST hold the gauge level to get an accurate reading. Thus, there is a little laser bubble built into the top of the gauge.
Adjust the laser focus by turning the lens (the knurled part on the bottom). Then lock in
place with a few drops of Blue Loctite.
If you do not Loctite the lens than you will probably run into trouble. When things get shaken up the lens will need to be adjusted again and again. The lens fits a little loser than I would like. But, it is acceptable if you Loctite it. A simple solution.
Note: Blue Loctite is "removable". Thus you can adjust the laser focus at a later date by just turning it. "Red" lock is "permanent". I recommend you use blue.