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If you don't have a set of calipers or a micrometer with which to gauge the thickness of the material you would like to use, you can use common household objects instead. Use chart below to get a feel for various thicknesses. You could also use any of these objects to measure existing parts.

For thicker measurements, stack several parts together. For example, 3 CDs are 3 X 1.2 mm = 3.6 mm or 0.142 inches thick.

 

 

  Inches Millimeters

Dollar bill

0.0043

0.1092

#9 Standard Razor Blade

0.009

0.2286

#12 Heavy Duty Razor Blade

0.012

0.3048

Credit Card

0.030

0.76

CD, DVD, or Blu-Ray Disc

0.047

1.2

US Dime

0.053

1.35

US Penny (Cent)

0.060

1.52

US Quarter

0.069

1.75

US Nickel

0.077

1.95

Canadian Polymer Banknote

0.004

0.091

Canadian 10 Cents

0.048

1.22

Canadian Cent

0.057

1.45

Canadian 25 Cents

0.062

1.58

Canadian Dollar

0.069

1.75

Canadian 5 Cents

0.069

1.76

 

Table : Thicknesses of common objects

 

If you're trying to find a material for your project, the options can be overwhelming. Waterjet cutting offers so many choices that it can be difficult to pick the material that fits both your design and budget.

The truth is most projects can be done with 6061 aluminum, 304 stainless, cold roll steel, or clear polycarbonate. Our customers have found that each of these four fills a unique niche.
Here's a chart that ranks the three materials against each other in terms of cost, appearance, and specific strength (also known as strength-to-weight ratio). 4 is best, 1 is worst.

  Cost Appearance Specific Strength
Aluminum 6061 2 2 4
Stainless Steel 304 1 4 2
Cold Roll Steel 3 1 3
Polycarbonate 2 3 1

 

It's worth noting that though we've ranked them against each other in terms of appearance, none of these materials look particularly bad. Stainless steel is more durable than aluminum, and thus holds its finish better. If you need a transparent material, then, of course, a metal won't work at all and you need a plastic like polycarbonate.
Cold roll steel doesn't come out on top of any of the above categories, but it's still useful. Why? It is harder (good for sliding or wearing parts), denser, and can be welded more easily than the other materials. It's also magnetic.

 

If you're considering But Need Try
Aluminum 6061 Better formability (ability to bend the material into shape) Aluminum 5052
Aluminum 6061 Better electrical conductivity Copper 110
Carbon Steel Higher strength Prehardened steel alloy 4130 or similar
Polycarbonate Lower cost PETG, Acetal, UHMW-PE or Laser cut acrylic
Stainless Steel 304 Maximum corrosion resistance (like in salt water environments) Stainless Steel 316
Stainless Steel 304 Lower cost Aluminum or one of the laser cut metallic appearance acrylics (Brushed Bright Nickel, for example)

 

Of course, there are quite a few materials which can be cut on a waterjet that don't appear on any of these charts: various kinds of wood, stone, metals, and plastics. If you're considering these, you probably already have a good idea of what you need.

One of the great advantages of waterjet cutting is that prehardened metals can be cut quite easily. Certain metals can be purchased in bulk as bar or sheet, and then cut on the waterjet. This saves the extra step of having the material heat treated for hardening after machining.

 

Cutting glass on the waterjet

Most ordinary glass will shatter when cut on the waterjet. Certain types of untempered glass can work, but will typically need to have a test cut performed on them first in order to make sure that they can be cut without breaking.

 

Medium Density Fiberboard (MDF) and plywood on the waterjet

Unfortunately, Medium Density Fiberboard (MDF) is quite sensitive to moisture. This means that when the waterjet stream starts to cut into MDF, it immediately swells up and makes a big mess.
Most quality plywood will cut on the waterjet and can be a good substitute for MDF in some projects.

 

 

Traditionally, spur gears are made using specialized tooling and setups. This means that small runs of custom gears can be expensive; much more expensive than most other types of machined parts.

However, the flexibility of a waterjet cutting machine means that gears are no more difficult to waterjet cut than any other part. At Big Blue Saw, we have made many gears for customers who needed unusual sizes of gears or gears with custom mounting holes. Other customers have wanted, for example, polycarbonate plastic or titanium alloy gears which were impossible to find off-the-shelf.

 

 

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Illustration : Steampunk costume by Chris Lee with waterjet cut aluminum gears which
actuate a set of wings http://apparitionabolishers.com/2012/09/01/steampunk-wings-mechanism-close-ups/

 

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Illustration : Steel (left) and aluminum (right) waterjet cut gears

Waterjet cutting works best with gears of 12 diametral pitch (DP) or larger (this is roughly equivalent to module 2.25 in metric gears). As you can see in the diagrams below, the waterjet cutting stream is small enough to easily machine the features of this size gear. Additionally, a geartrain of this size or larger can tolerate the roughness of the cut edge on a waterjet cut gear. With a waterjet stream diameter of 0.04 inches, however, you can make gears down to about 20 DP (module 1.25). I would only recommend this size for thinner gears in applications where there is some “slop” in the geartrain due to the surface roughness of the cut edge as well as other irregularities which can arise from waterjet cutting.

Waterjet stream of  0.04 diameter shown with a 12 DP gear

Waterjet stream of 0.04" diameter shown with a 12 DP gear

 

Waterjet stream of  0.04 diameter shown with a 16 DP gear

Waterjet stream of 0.04" diameter shown with a 16 DP gear

 

Waterjet stream of  0.04 diameter shown with a 20 DP gear

Waterjet stream of 0.04" diameter shown with a 20 DP gear

 

Waterjet stream of  0.04 diameter shown with a 24 DP gear

Waterjet stream of 0.04" diameter shown with a 24 DP gear

 

Waterjet cut gears are rough along the cut edge where the gears mesh together. This can cause a shorter gear lifetime due to wear than you might expect from a traditionally cut gear. So for applications where this might be a problem, you should consider making the gear larger, either by making it from thicker material, or decreasing the DP so that the teeth are larger.

When first using new waterjet cut gears, it is a good idea to let the gear train run continuously for a few hours without load and with a light lubricant. Then clean the gears and re-lubricate before placing the gear in service. This will even out the rough cut edges of the gears and allow the geartrain to run smoothly.

Gears above 1/8 inch (3 mm) thick should usually be cut using low-taper cutting. This allows waterjet cut gear to mesh as accurately as possible.

Some people have reported success with regular (non-low-taper) waterjet cut gears by placing two waterjet cut gears so that their tapers face the opposite directions. In other words, the top face of one gear will be on the same side as the bottom face of its matching gear.

When building or customizing robots, motorcycles, go-karts, electric vehicles, conveyor belt systems, or just about anything that moves, you will eventually run into the problem of having to tie all of the motion components together into a single system. If off the shelf components don't meet your needs, you can waterjet cut custom frames, motor mounts, and bearing blocks.

Let me show you an example from my fighting robot “Jaws”. I needed a bearing block which would give maximum support to the wheels, but would occupy a minimum amount of space and weight. The solution I came up up with was a ¾ inch thick 6061 aluminum bearing block with a bronze bushing inserted into it. Using a bronze bushing kept the size down compared to using ball bearings.

After the bearing blocks were waterjet cut, I drilled holes in the edge of the bearing blocks in order to base mount to mount them. The bearing blocks rest on their cut edge and are held in place with bolts and nuts. Below you can see a rendering of the part, and a photo showing it installed inside the robot.

 

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Illustration : Rendering of the 3/4 inch thick aluminum bearing block from Jaws.

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Illustration : The bearing block installed inside Jaws.

 

Note that if you are base mounting this type of bearing block (mounting along the cut edge),  you will want to use low-taper waterjet cutting in order to keep your driveline straight. For face mounting, you might be able to get away with using regular cutting if you can drill or ream the hole where the shaft passes through in order to give it an even diameter all the way through the material.

Now let's take a look at a different bearing block system, this one from MattyCiii of the Endless Sphere Technology forums. He needed a special bearing block for a custom electric bicycle he was building for himself. He designed a bearing block to be made in two pieces, each 0.625 inches thick. When stacked together, they are exactly the width of the 1.25 inch thick tube that they mount to. An aluminum tube fits in the large hole in the blocks, and a ball bearing fits inside that, which supports the shaft. You may notice that there is a small gap at the bottom of the bearing blocks. According to MattyCiii, this allows the bearing block to grip the aluminum tube tightly when the bearing block is clamped in place. Here is how he describes how it works:

The gripping capability is actually a combination of two things: First the gap, and second, the flat plane you see on either side of the gap is not fully flat – it’s angled in slightly. So take for example that last picture: imagine only one of the hose clamps is clamped down tight. There would be about about a 1 degree angle between the other flat part of the mount and the square tube it’s mounted on. As you tighten the second hose clamp, it pulls the piece tight against the flat and slightly shrinks the diameter of the hole. I’m not an engineer by trade, I didn’t do any calculations to find a ‘best’ angle for this purpose – but it works as designed (miraculously!)

 

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Illustration : A stacked bearing block before mounting. Photo courtesy of
MattyCiii from http://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=567 .

 

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Illustration : The bearing block from the previous photo mounted in
place on the electric bike. Photo courtesy of MattyCiii from
http://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=567 .

 

 

When building things that move using a waterjet, you're not limited to just bearing blocks. One common problem faced when building an electric vehicle is mounting the motor to an existing frame. Waterjet cutting allows you to easily make custom motor mount plates that match the bolt pattern on the motor, as well as the mounting points on the frame.

Here is a great example from Roberto Melendez of MIT. In building the Cholocycle electric motorcycle, they needed a way to mount their 25 horsepower electric motor to a Kawasaki motorcycle frame. With waterjet cutting, they were able to construct mounting plates which fit both the motor and the frame perfectly.

 

 

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Illustration : The waterjet cut motor mount attached to the front of the electric motor
for the Cholocycle. Note the rear mount disassembled in the background.
Photo courtesy of Robert Melendez http://rjmelendez.blogspot.com/ .

 

 

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Illustration : The motor installed on the Cholocycle motorcycle frame.
Photo courtesy of Robert Melendez http://rjmelendez.blogspot.com/ .


Now let's take a look at an assembly of waterjet cut parts that combines a motor mount with bearing blocks. For the LOLrioKart project, Charles Guan wanted to add a powerful electric motor to a shopping cart (yes, really). In order to do this, he needed a way to attach the motor to the frame, as well as a way to hold it in line with the driven axle. His solution was to use the waterjet to make a combination motor mount and bearing block out of ½ inch thick aluminum 6061. He used the stacking technique to make the plates thicker and thus provide a more stable attachment where the assembly rests on the cross member tube. You can see the separate pieces as well as the assembled drivetrain below.

 

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Illustration : 1/2″ 6061 aluminum plates and motor for the LOLrioKart drive
train. Photo courtesy of Charles Guan http://www.etotheipiplusone.net/

 

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Illustration : The assembled LOLrioKart drive train.
Photo courtesy of Charles Guan http://www.etotheipiplusone.net/

 

 

When making signs with lettering, it can be tedious work to generate all the necessary bridges. This is true both when the letters are positive space (solid material) or negative space (holes). Fortunately, by using the correct font, you can save time and get a result that looks good.
When the letters form positive space, one good choice is to use a script font.


In the example below from David Kaufman, the Santa Fe script font was used to design two nameplates. The right hand side of the “f” had to be modified to connect with the “m”, but the rest of the letters naturally run together with this font.

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Illustration : Nameplate signs from David Kaufman
https://www.flickr.com/photos/thevaportrail/sets/72157642700926135/

 

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Illustration : The font used in the examples above: Santa Fe LET
http://www.fonts101.com/fonts/view/Script/28879/Santa_Fe_LET


When the letters are negative space, you can use a stencil font. Below are a few examples of the varieties of stencil fonts which might be useful for your project.

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Illustration : AG Stencil http://www.dafont.com/ag-stencil.font

 

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Illustration : Bodoni Becker Stencil Bold
http://www.fonts101.com/fonts/view/Uncategorized/43971/Bodoni_Becker_Stencil_Bold

 

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Illustration : Stencilia http://www.dafont.com/stencilia.font

 

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Illustration : Tomorrow People. Note: some numbers and symbols may not
have appropriate bridges in this font. http://www.dafont.com/tomorrow-people.font

 

Below is an example logo for “thegymnasium”.

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Illustration : The original logo to be turned into a sign.


Now let's take a look at four different approaches to turning this logo into a sign. Below you will see renderings of two variations with the logo as positive space and two variations with the logo as negative space.

 

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Illustration : A rendering of the sign with the logo as negative space.
Note that the centers of the letters "e", "g", and "a" are disconnected
parts and must be mounted separately.

 

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Illustration : A sign with the logo as negative space. In this design, the centers
of the letters "e", "g", and "a" have been bridged. This makes mounting and alignment easier,
but produces a logo that is less faithful to the original.

 

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Illustration : The logo with the letters as positive space in the sign. In this variation,
the letters have been bridged with a baseline. Also note the bridge connecting
the dot above the "i". Since it is one piece, it is relatively easy to install.

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Illustration : The logo as a sign in positive space with separate pieces for each letter.
This would be the most accurate rendition of the logo when installed on a wall or other
background of contrasting color. However, it is the most difficult configuration
to install, as each letter must be aligned and mounted separately.

Signs are another popular application for waterjet cutting, as they typically convey their information in two dimensions. Logos, pictures, and lettering can all be cut using the waterjet. Most of the signs we make at Big Blue Saw are either stainless steel or aluminum. I prefer the look of stainless steel; its darker color gives the sign a more solid, serious look. Signs can be made from very thin material, but for more visual impact close up, you can go with a thicker stock.

There are generally two approaches to cutting a sign or logo:

  • Making the individual letters out of solid material and assembling them together.
  • Cutting the lettering or design from within a solid outer frame.

In other words, you must decide whether you want the design to appear as positive space (material) or negative space (holes).

The second approach can result in a sign that's easier to install. If designed correctly, you can hang up the sign as a single piece without having to worry about fastening separate letters or their alignment. In order to do this, you must be sure to join any separate islands within the design using bridges. This often comes up when adding certain letters that naturaly contain islands: A, B, D, O, etc. Note the bridging on the letters in the sign shown below.

This sign was easy to assemble, with just a few screws needed to hold the upper layer onto the lower layer, and 4 screw holes in the corners to allow the sign to be hung up.

If you want professional sign design work, you should contact RoPro Design, as they designed the sign for us shown in the picture below. At Big Blue Saw, we've worked with them on a number of projects, and they're highly professional and will do a great job.

 

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Illustration : A sign in two layers, with the logo and lettering waterjet cut from wood.

If you want the letters to be made from solid material rather than holes, you can still keep them in one piece, but you will have to come up with a scheme for joining them together. The photo below shows one possible aproach.

Note also that this sign is designed to be cut in a single pass with only one pierce of the material. This helps reduce costs (for more information, refer to our cost reduction article).

 

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Illustration : A nameplate sign with the letters as positive space and joined together.

If you want the most accurate representation of a logo, you will probably choose to have each section of the design and each letter cut out as separate pieces. This allows, for example, letters to be exactly the shapes you want them to be without having to worry about bridging. Since you don't have to worry about designing bridges or connecting elements of the logo, design can be easier. The chief downside of this kind of sign is that each piece must be hung separately. You must also take great care when installing the sign to make sure that the position and alignment of each piece is correct.

When designing a sign, you should consider how the sign is to be hung on a wall or otherwise mounted in place. If you are mounting to a wall or other flat surface, the design can include holes for mounting screws in each piece of the sign. If you don't want visible screws, you can mount the sign using adhesive or by welding attachment points to the back. Make sure that whatever attachment method you use is strong enough to hold up the sign (Big Blue Saw gives you a weight estimate for your design in the ordering process.)

 

Corner braces

Waterjet cut parts can also be used in brackets that are aligned so that the cut edge, rather than the face, connects to the part. This is accomplished using the t-nut technique. The low cost of waterjet cutting allows you to make corner braces at custom angles and with mounting points in the positions you choose. Since the cut edge is in contact with other parts, you might consider low-taper cutting for this application.

 

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Illustration : Angled inside corner brace

Flanges and brackets

One of the most common applications, and one of the simplest, is flanges and brackets. These are usually designed to hold multiple parts together, particularly parts that can't be joined with off-the-shelf brackets. These are typically rectangular, square, or round, with holes for bolts or machine screws to pass through the top and bottom faces.

 gearbox-side

Illustration : Brackets

Tabbing

Small parts must be connected, either to each other or to the sheet of material, to prevent them from falling into the waterjet tank when they are cut. This can mean that they must be broken off by working the part back and forth until it snaps off from the tab; the part is left with a vestige of the original tab. At Big Blue Saw, we offer various finishing options, like Basic Finish, to remove the tabs for you when necessary.

Below is a set of waterjet cut stainless steel parts which shows what this looks like.

 

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Illustration : Tabbed parts with US Quarter (24.26 mm/0.955 inches diameter)

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