Utensil and tool holders give people with limited grip, hand strength, or dexterity a way to use items like eating utensils, toothbrushes, writing instruments, hand tools, and other small items. Our designer initially focused on support for eating but the program has been extended to support other objects – like food preparation utensils and workshop tools.
This design was initially inspired by a post to the ATMakers.org page on Facebook asking for a utensil holder that accommodated knifes as well as forks and spoons. The poster of that message provided a link to a 3D printable device on the MyMiniFactory website:
This design has a clever configuration for trapping the utensil and we used aspects of that configuration in our design. However, there are four issues with this design and all “universal” cuffs:
- It attempts to be “one size fits all” for attachment to the hand so it will be loose on small hands and will pinch larger hands.
- It attempts to be “one size fits all” for the utensil so there are a limited number of spoon/fork widths and thicknesses that can be held firmly.
- The utensil slot is oriented parallel a the palm so it can’t support the use of a knife without significant work and mobility requirements being placed on the user.
- Because this is a monolithic design, one cannot scale the hand mount without simultaneously and equally scaling the utensil mount.
A similar device can be found at enablemart:
This device is reasonably priced at $12 and has a three valuable features:
- It’s adjustable in size so to some degree “one size does fit all” and the size can be adjusted as the individual grows. A second smaller version is available for children.
- It can be easily laundered if needed.
- Because the design wraps the hand rather than simply clamping on the hand it offers additional stability when in use.
Unfortunately it also has several issues:
- The pocket which holds the utensil is fixed in width and therefor accommodates a small set of utensils. Based on the picture it looks like it is optimized for plastic forks and spoons.
- It’s unlikely that a knife could be inserted into the pocket and remain in a vertical orientation.
- The mounting of the utensil on top of the hand is unnatural and is likely to force the user’s hand into contact with their food.
- It will be a challenge to clean out any food that becomes caught in the pocket.
Our design incorporates the best of these two designs and goes further. The Customizable Universal Cuff Utensil Holder:
- Can be 3D-printed for just pennies using the most commonly used filaments – PLA or TPU.
- Separates the device into a palm or circular loop and a utensil/tool mount. Each can be separately sized to accommodate hands or arms of different sizes and utensils/tools of different sizes.
- The two components are joined using a common interface that can be extended for use with other objects like a pen holder or a hairbrush holder.
- The utensil mount can be sized to support both forks/spoons and knives.
- The utensil holder attaches below the hand for a natural orientation, but the palm loop can also be designed with the utensil/tool holder mount on top. The circular loop provides complete freedom regarding where the utensil holder is mounted.
- The palm loop incorporates a thumb rest/guard to protect the thumb from being injured by the utensil or dragged through the food.
First Things, First:
The program for creating your own custom universal cuff utensil/tool holder is located here on Thingiverse.
The first step will be to decide how you want to do your customization. You can use the Thingiverse Customizer but it’s really slow and clunky [Instructions for using the Thingiverse customizer can be found here.]
We recommend that you use free software called OpenSCAD, instead. [Instructions for downloading and installing OpenSCAD on your computer can be found here.] The images of the user interface shown on this page come from OpenSCAD though the user interface of the Thingiverse Customizer will be very similar.
If you decide to use the Thingiverse Customizer, just click the “Open in Customizer” button to the right of image on this page. If you’ve downloaded and installed OpenSCAD, click on the “Thing Files” tab which will take you to this page, and click on the file called “universal_cuff_utensil_holder.scad” to download the program and open it with OpenSCAD.
Depending on the shape of the utensil/tool there may be a bit of space between the mount and the utensil that can result in some wiggle of the utensil/tool. You can print a small wedge to insert into the fixture that will lock down the utensil. STL files for individual wedges and one file to print all wedges at one time are located in a file called “wedges.zip”.
Second Things Second:
You need to decide what part of your body will be used to control the utensil or tool. If you have a palm you will probably have the most control of the utensil or tool by mounting utensil and tool holders on your palm. If you hands or forearms have been amputated, you’ll probably be more effective with a circular loop and sliding it onto your forearm or upper arm.
| palm loop (with thumb rest) | circular loop |
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Palm Loop Options
The starting palm loop for holding a utensil looks like this:
The thumb side of the loop is on the left and the little finger side of the loop is on the right. A utensils holder can be mounted on the top or on the bottom of the loop.
Here’s a picture of the palm loop with a utensil holder mount on the bottom:
Here’s a picture of the palm loop with a utensil holder mount on the top:
A palm loop for holding a tool will tend to be much wider to provide greater leverage:
In addition the tool mounts will be bulkier and stronger than a utensil mount. Here’s a lower tool mount:
The mount has larger dovetail slots and they’re located closer to the center of the palm and further from the thumb for greater leverage. An alternative tool mount can be added to the little-finger end of the palm loop to provide a different orientation for controlling a tool:
You may want to consider printing your palm loop tool holder from a flexible filament like TPU to make wearing the palm loop gentler to your skin.
The next thing to consider for your utensil holder is whether the palm loop will include support for the user’s thumb. There are two options – a thumb rest or a thumb loop:
Here’s a picture of the palm loop with a thumb rest:
Here’s a picture of the palm loop with a thumb loop mount and a thumb loop in one of the six available slots:
Note that the thumb loop mount and thumb loop cannot be used with the utensil holder mount that goes on the bottom of the palm loop.
Finally, when the utensil mount is located on top of the palm loop, you can add a circular grip to the bottom of the palm loop for users who can apply pressure with their fingers. The grip can be used with thumb support mounts or without:
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You’ll need to glue the circular grip in place once you’re comfortable with it’s size.
Sizing the Palm Loop:
Note that the dimensions of a person’s left hand are often different from the dimensions of their right hand so ensure that you are measuring the specific hand of the user that they will be using to control the utensil/tool.
You’ll now need to gather measurements of your palm and determine the length of the stylus. If you plan to use a thumb loop as well, you’ll need to measure the diameter of your thumb.
The palm loop measurement tool will give you the length, height, and width measurements you’ll need. If you’ll be using the palm loop to control a tool you will probably need more leverage and will need a wider loop as pictured above.
Use the measuring rings to easily determine the diameter of your thumb.
Circular Loop Options:
As the name implies, a circular loop is circular in shape. Because it’s circular, there’s no need to choose where the utensil holder will mount to the loop. You simply rotate the loop on your arm until the utensil holder mount is positioned properly.
While your arm is not perfectly circular in shape, if you print the loop out of a flexible filament like TPU (and we recommend that you do), the loop will naturally conform to the shape of your arm. There are two ways to get a “circular loop diameter” measurement for your arm. If you have a set of calipers, take multiple measurements across the part of your arm where you would expect to place the loop and average them. If you have a tape measure (preferably one that is marked in millimeters), measure the distance around your arm (i.e., the circumference) and then divide that number by Pi (3.1416). The result will be the average diameter of your arm.
You’ll make some additional decisions about how tightly the loop will fit – adding a break in the loop for elastic or Velcro, and adding internal grips – but you should start with a simple, unbroken loop first and test the fit.
Third Things Third:
Collect measurements for the utensils/tools you’d like to use. The pictures focus on eating utensils but the concepts can easily be extended to holding tools. You may find that using a flexible filament (like TPU) gives you tighter grip on the utensil. In that case, you should slightly undersize the holder opening and let it stretch when the utensil is inserted.
You need to take two measurements of each utensil that the user wants to use. You can use a ruler to measure these dimensions but it will be much easier to use an inexpensive digital caliper like this one.
You will want to measure the width of the fork’s/spoon/screwdriver’s handle at it’s widest point (typically near the end of the handle):
In the picture the width of the fork handle is 17.94 mm.
Now measure the thickness (height) of the handle:
In the picture the height of the handle is 2.77 mm.
Round the values, up or down, to the nearest integer. In this example the height rounds to 3 mm and the width rounds to 18 mm.
Forks and spoons are normally held horizontally. Knives, on the other hand, are normally held vertically so the measurements should be taken appropriately
Measure the height and width of the knife handle at it’s widest and thickest point. Here is an example of measuring the width of a steak knife’s handle:
In this example, the width is 14.63 mm.
Next measure the height of the knife handle at it’s widest point:
In this example the height is 24.97 mm.
Rounding both measurements to the nearest integer results in a width of 15 mm and a height of 25 mm.
Some utensils/tools have circular handles. In that case, measure the widest part of the handle and record that number as the diameter of the handle:
In this case the diameter of this wooden spoon is 10.54 mm. Round this to 11 mm.
At the same time, you can specify the length of the utensil handle that will be enclosed by the utensil holder. This is a bit of an art but you can use the amount of the handle that would normally be held in someone’s hand as a starting point. Then, if you want to use a thumb rest on a utensil that would bring food to the user’s mouth, subtract the length of the rest.
For this fork, a handle length of 110 mm minus an approximately 30 mm thumb rest produces a final handle length of 80 mm.
For this knife, a handle length of 100 mm would be a good guess. In this case, the handle widens out starting at around 95 mm and including the wider part of the knife by the blade in the holder will make it more stable.
For this wooden spoon, it would be best to specify a handle length that matches the width of a typical individual’s hand – say, 75 mm. In this case, we’ll design a utensil holder that can slide to the middle of the handle for better control.
Designing Your Loop and Utensil/Tool Holders
Let’s look at how you use the program’s user interface to design and customize your universal cuff utensil/tool holder.
The customization options are organized into several categories:
The Part to Print category is where you indicate which part of the utensil/tool holder you’d like to print.
The Palm Loop Info category is where you specify the size of the palm loop, where the utensil holder mount will appear, and how/if the palm loop will support the user’s thumb.
The Circular Loop Info category is where you specify the size of the circular loop, whether you put a gap in the loop for the best fit, and whether you include internal ridges to stabilize the loop on the individual’s arm.
The Utensil Mount Info category is where you specify the length of the utensil holder mount, the distance between the dovetail slots and the size of the slots.. Finally, you can specify the angle of the slots.
The Utensil Holder Info category is where you specify the shape, height, width, and length of the utensil holder. You also specify if the holder should be closed on one side or not and whether the dovetails should be angled. The size of the dovetails and the distance between them is controlled by the choices you make in the Utensil Mount Info category.
The Thumb Rest/Loop Info category is where you provide sizing information for the thumb loop and the length of the thumb rest.
The Tool Interface Info category is where you provide sizing information for the part that will sit between the palm loop and the part that holds the tool. The tool interface allows you to hold the tool in several different locations and orientations relative to your hand.
The Tool Cup Info category is where you provide sizing information about the points of attachment to your tool that you will hold with a cylindrical-shaped mount.
The Tool Saddle Info category is where you provide sizing information about the points of attachment to your tool that you will hold with a saddle-shaped mount.
The Circular Grip Info category is where you provide sizing information about the thumb loop.
As you specify each part that you need, start at the top of the set of categories and work downward. Begin with choosing the type of part that you want to print. It will be helpful to see the part displayed in the user interface as you provide more specific details later.
Part to Print Category
The Part to Print category has a single item – a pull down list of possible parts:
You will need to print a palm loop or a circular loop and at least one utensil/tool holder. You can also, optionally, print a thumb loop and/or circular grip.
Choose palm loop or circular loop to begin the process. A default loop will be displayed. If you are using OpenSCAD to customize the loop you will see a slightly fuzzy image (the image below is for a palm loop):
The rendering process will clean up the display, but if you wait to the end to render your design, then design changes you make will be displayed very quickly. If you’re using the Thingiverse Customizer you won’t see the fuzziness because the image is automatically rendered but will take extra time to display after each change.
After you make all changes and render the loop, you’ll see a cleaner image:
As you specify your stylus more, the size and shape of the palm loop may change.
Palm Loop Info Category
Here you set three key dimensions for the palm loop. These are the same measurements that you took using the palm loop measuring tool. Here’s how they affect the size of the palm loop:
Finally, you can decide whether to provide additional support for the user’s thumb by including a thumb rest or a thumb loop mount as part of the palm loop. Explore the various options and see how they change the look and function of the palm loop. Some options cannot be used in combination with each other. Notes are provided to indicate those conflicts.
Circular Loop Info Category
The circular loop diameter (specified in millimeters) will affect how tightly the loop fits on your arm. The width of the loop will affect how stable the loop will sit on your arm. Wider equals more stable.
If you put a break in the band, you can make the loop easier to slip on your arm and then use elastic or Velcro to cinch-up the band and tighten it. If you add a break to the band, you must the specify the width of the break.
| no break | narrow break | wide break |
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You can then specify how many slots should be put in the band to attach the elastic or Velcro:
| one slot | two slots | three slots |
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Because Velcro and elastic can be found in different widths and thicknesses, you have the ability to control both aspects of the slots.
The layers of plastic created during the 3D printing process will help keep the loop from sliding up and down your arm but the loop may still spin “around” your arm more readily than you’d like. You can add some internal “grips” to the loop that will help to keep the loop from rotating around your arm as you use your utensil or tool. You can add 2, 4 or 6 internal grips:
| 2 grips | 4 grips | 6 grips |
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Finally, you can use a special type of elastic called button-hole elastic which as evenly-spaced and reinforced holes. You can take advantage of these holes to make it quick and easy to fasten the elastic. Simply add a post to one side of the break:
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Terminating the elastic, as in the picture on the right, so that it holds tight, can be confusing. This picture demonstrates how you should weave the elastic through the two slots:
Utensil Mount Info Category
You can make changes to the design of the utensil holder mount portion of the palm or circular loop that will make it easier to use the utensil or make its use more stable.
Longer utensils will benefit from longer utensil holders and those holders will benefit from longer utensil holder mounts:
| default mount length | longer mount |
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Then, if you’ve specified a longer mount, it’s probably because you wanted to space the dovetails further apart for greater stability:
| default dovetail width | wider dovetail with |
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While you can, and probably should, change the dovetail angle when you specify the utensil holder, there may be times when changing the angle of the holder mount may be more appropriate:
| -10 degree slot angle | 0 degree slot angle | +10 degree slot angle |
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Finally, you can choose whether the size of the slot should be regular or large:
| regular size slots | large size slots |
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The distance between the slots and slot size that you choose here will control the distance between and size of the dovetails that appear on your utensil holder.
Utensil Holder Info Category
Here you define whether the utensil’s handle is basically rectangular or circular. Then you specify the size of the utensil’s handle and how much of the handle should be contained inside the utensil holder.
Finally, you specify whether the holder should be open on thumb side, the little finger side or on both sides. That choice is based on whether the utensil should stick out of the holder on the thumb side, the little finger side or on both sides.
Note that the utensil holder for a circular utensil handle will have slots cut in it’s side. This allows the utensil holder to be slightly smaller in diameter than the utensil itself and grip it better.
If the circular utensil is tapered it may be necessary to create a holder with different sized circular openings. To do this, choose “yes” from the “different sized circular openings” pull down list. Then specify the diameter of the opening on the thumb side of the holder along with the diameter of the opening on the little finger side of the opening. Note that these last two options are ignored unless you first choose “yes” from the “different sized circular openings” pull down list. [These options are only possible for circular utensils.]
Here’s an example of what choosing different diameters would look like. If you set the options like this:
The holder will look like this:
Reversing the two diameter values produces a holder that looks like this:
Note that a tapered utensil must be inserted from the side with the largest opening. For that reason, the holder has to be open on both ends and the value you set for “utensil holder open on” will be ignored.
There’s and option for adding a slit in the side of the holder (pictured above) which can make the holder more springy and allow it to hold the utensil better.
Finally, you can control the angle of the dovetails. Changing the dovetail angles may provide you with better control of the utensil.
| -10 degrees | 0 degrees | +10 degrees |
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And if you print the utensil holder out of flexible filament, it will be easier for you to insert the dovetails of the utensil holder into the slots on the palm or circular loop if you don’t chamfer (angle) the ends of the dovetails. The opposite is the case if you’re printing the holder from a ridged filament.
| no chamfer | chamfer |
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Thumb Rest/Loop Info Category
The Thumb Loop Info category has two options for specifying the size of your thumb loop. In order to properly mount your thumb loop, you must have added a thumb loop mount to your palm loop in the Palm Loop Info category.
To see the thumb loop displayed, return to the “Part to Print” category and choose “thumb loop” from the “part” pull down list. You’ll see a starting image of a thumb loop:
You’ll use the measurement you took with the measuring rings to set a value for thumb diameter. The value for thumb width will depend on the amount of support required by the user.
Sliding the “thumb rest length” slider to the left, makes the thumb rest longer and sliding it to the right makes the rest longer. The middle location (zero) is the default length:
| longer rest | default length | shorter rest |
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Tool Interface Info
The tool interface part attaches to the lower tool mount of the palm loop. You can determine its width and height.
The slots in the tool interface allow you to hold manipulate your tool in several different orientations:
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Tool Cup Info
The tool cup info category is where you specify the diameter, height and thickness of the mount for holding a circular or rectangular tool. You should print this part using a flexible filament like TPU.
Tool Saddle Info
The tool saddle info category is where you specify the width, length, height, and thickness of the mount for holding the arm of a tool but not completely wrapping it. You should print this part using a flexible filament like TPU.
This part will often be used with the rotating tool interface.
Rotating Tool Interface
The rotating tool interface consists of two parts. It also requires a “608” roller-skate bearing. Note that this is not a “ratcheting” interface. It is a way to put pressure on a tool and still allow the tool to rotate freely. The rotating tool interface is sized specifically to fit the bearing so there’s no “Info” category associated with it.
The bearing is inserted into the component on the left and then the shaft of the right-hand component is inserted into the center hole in the bearing. The rotating tool interface can be used with both the tool cup and tool saddle.
The following video shows the rotating tool interface in action:
<video>
Circular Grip Info Category
The Circular Grip Info category of options has a single value and that is the preferred diameter of the circular grip. The diameter you choose will depend on how much the user can bend their fingers and how much padding you’d like to add to the grip.
To see the grip displayed, return to the “Part to Print” category and choose “circular grip” from the “part” pull down list. You’ll see a starting image of a circular grip:
The grip has a groove cut along it’s length for gluing it to the palm loop. The groove is slightly wider than the palm loop width to make attachment easy. The length of the grip is determined by the length of the palm loop. If you’d like to make the grip shorter or longer, adjust the length of the palm loop (without printing a new palm loop).
Assembling Your Cuff Utensil Holder:
The following video shows you how to assemble your customizable universal cuff utensil holder:
It’s possible that the utensil holder may be wider than the palm loop. Don’t feel obligated to attach the holder to the center of the palm loop. First check how the combined holder and palm loop fit in the user’s hand. It may be more comfortable for the user to have the utensil holder mounted further forward or further to the rear of their palm.
Using Wedges:
Because the fixture must have a slot that is wide enough to fit the widest part of the fork, spoon or knife and because most utensils are wider at the back than they are at the front, the utensil might slip a bit in the front pocket when in use. You can print a small wedge to insert into the fixture that will lock down the utensil. STL files for individual wedges and one file to print all wedges at one time are located in a file called “wedges.zip”. Because each wedge uses so little filament, it is probably easiest to just print the “all_wedges.stl” file and try them out.
Wedges look like this when printed:
The wedge is inserted into the front slot of the fixture. It can be inserted from the front of the slot:
Or from the rear (You may want to turn the wedge on it’s side depending on the amount of gap that you want to fill.):
Note that the wedges can be printed from typical filament like PLA or, better yet, printed using a flexible filament.
Keeping it Clean:
Because the hand mounts and utensil fixtures are printed using a popular filament like PLA they are temperature sensitive and cannot be put in hot environments like a dishwasher. Also, because typical 3D printers build objects one small layer at a time, there are small nooks where food can get stuck and bacteria can grow, it is important to keep these items (including wedges) clean. The plastic components should be hand washed to remove most of the food and after it is dry the surfaces should be sprayed with a mild bleach solution and rinsed with water after a few minutes. These two steps will ensure that the utensil holder stays clean and safe.
Update: 27 Jan 2021…. We printed a pair of utensil holders out of TPU filament. We put one of the pair in the dishwasher and left it there for 6 months. The dishwasher ran at least once a day (and sometimes twice a day) in sanitizer mode. At the end of the experiment, the two holders look like this:
The holder on the left was put in the dishwasher and the control is on the right. While the “sanitized” holder has lost some color, the two holders’ dimensions match exactly.
So, you may be able to sufficiently clean your utensil cuff and holder by printing them out of TPU filament and putting them in the dishwasher.
Cuffs in Action:
Here’s a short video demonstrating the use of the cuffs and the ability to do some serious cutting with the knife fixture:
In the process of making the video I decided that I’d make a new set of cuffs that were the next size smaller. The size that I printed seemed a bit large and made me want to spread out my fingers to keep them on.
Assembling and Using your Cuff Tool Holder:
The tool holder was designed around a particular ratcheting screwdriver based on the needs of a particular individual. However, every attempt was made to generalize the solution so that it could be extended to other tools.
The initial challenge was to come up with a device to allow a disabled individual with limited range of motion to use a screwdriver. The solution to the challenge started with identifying a T-handled ratcheting screwdriver:
The screwdriver can be manipulated using two palm loops, two tool interfaces and two tool cups as shown in the following video:
It’s also possible to provide gross-motor control of the direction of the ratchet by adding a ratchet wrap. By hitting the tab on the ratchet wrap (as shown in the above video), you can change the direction of the ratchet from tightening to loosening.
This part was designed specifically for the screwdriver above from Harbor Freight. You can download the STL file from Thingiverse but you may need an entirely different design for the screwdriver you purchase.
Using the the “rotating tool interface”
If you have a greater range of motion with one arm than the other, you may want to leverage that one arm and use the other to hold the screwdriver in place but not restrict the screwdriver’s movement. That’s when the rotating tool interface along with a tool saddle can be handy:
Benefits of Separate Components with a Standard Interface:
One critical aspect of this design is that the palm loop and the utensil holder are separate parts that are joined together by a pair of dove-tail joints. The joints are the same distance apart and the same size regardless of the size of the palm loop or the utensil holder. This has three benefits.
If you don’t glue your palm loop to a utensil holder, you can use the same hand mount with multiple fixtures. [Though, given that a hand mount can be printed for a few pennies there isn’t much of a downside to gluing the hand mount to the fixture and printing more hand mounts as necessary.]
Each part can be printed in a different color filament based on the personal desires of the user.
The third advantage to separating the palm loop and the utensil holder is that other mounts – for example one that holds a razor or a hair brush – can be designed that can attach to a user’s existing hand mount.
The “standard interface” between the hand mount and the utensil fixtures is the slots in the hand mount and the ridges in the fixtures. Regardless of the size of the palm loop, the slots are always the same size and in the same place:
It’s the same for the utensil holders. Every utensil holder has a standard profile:
With a standard set of dimensions:
The distance between dovetails and their size are set in the Utensil Mount Info category.
The standard interface for the tool holder is dimensioned as shown below:
