Jay Fisher - Fine Custom Knives
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"Nunavut"
Jay Fisher - Fine Custom Knives |
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New to the website? Start Here |
"Nunavut" |
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I was asked in March 2020 to help make some face shields for Emergency Room staff during the early part of the Covid-19 pandemic. The staff couldn't find any available anywhere, which was happening all over the country during the early stages of the pandemic. I had the materials for a utilitarian design, and below are the steps that I took. Within a few days, the team had their shields.
I had to use what was immediately available in my studio, since getting shipments during at that time would have forced these critical care professionals to wait. At that time, PPE and the supplies to make the equipment were many weeks away, or completely unavailable.
Please feel free to use my design for these shields, just don't forget where they came from and please support our professionals on the front lines of health emergencies!
I happen to have a roll of PETG, a thermal forming plastic that is food contact safe and able to be sterilized. While this isn't an impact resistant material, it is a clean material, and during the pandemic, we were all limited by what we had on hand.
I had this on hand because it was acquired as surplus from a facility by my son-in-law, James Beauchamp (Thanks, James!). When you have an industrial background, you are always on the lookout for good surplus. This roll had evidently been caught in a miss-fed operation; there were some scratches and scuffs on some of the surface. While it couldn't be used by the industry for their operation, I was happy to have it available. Ordinarily, I use it to line the inside of my sandblaster window. A sacrificial panel of the PETG is cut and fitted to the inside of the glass window of the sandblaster, that way it gets blasted and replaced and the glass remains clean.
PETG (Polyethylene terephthalate glycol) is great stuff; it's thermoforming (can be formed with heat) and it takes great pressure without cracking. It can be vacuum-formed and is used to make plastic food containers and bottles for drinks. PETG is 100 percent recyclable, biodegradable, and non-gaseous.
It turned out to be a great plastic for this application.
In the photo, I'm moving the heavy roll into a position with my gantry crane so I can roll off sections to cut into the face shields.
I had already built a couple prototypes and knew what I needed in size and shape. So I used some basic layout tools to create a cardboard template for the PETG plastic shields.
I made these 10" (25 cm) tall, and 12.5" (32 cm) wide. The PETG sheet is .040" (1mm) thick.
Simple layout with a permanent marker and a large scissors to cut out the plastic. This is some tough stuff, takes a big scissors to trim it out.
The scissors leaves a jagged edge, so a quick pass on the belt grinder with a 180 grit belt and a 3" contact wheel rounds and smooths them over nicely. The belt grinder isn't just for steel! Running at a very high speed helps, a light touch and a sharp belt means the plastic won't melt and smear.
A special note about PETG: this is a thermoforming plastic, but scratches pretty easily. This is probably why it's rarely used for this application, but I had to use what I had on hand. If it has light scratches or fogging, it's worth a try to remove them. With PETG, the first thing to try is a cleaning, followed by heating the scratched surface with an electric "flameless torch." This is a heat gun sold in hardware stores to remove paint. It will flat-out melt plastic in a hurry, so a low temperature setting and lots of movement helps. Some fine scratches will simply disappear when the PETG is heated, some will not.
It's worth it to try to save some of this limited material if you can.
Most plastic can be polished, but it's a long process with specialized buffs and compounds. It takes a lot of time and steps, and really isn't worth it in this application if a quick pass of the heat gun works without distorting the plastic.
I went for a simple frame, with the material I had on hand. There are two parts to the face shield frame: the part that mounts on the head, and the part that holds the shield.
I made these from some older printed kydex that I had on hand. It's not the typical kydex that you see on most holsters or other knifemakers' sheaths, it's twice as thick (1/8"). So it's pretty durable stuff.
It takes two pieces of double-thick kydex per shield. The head frame is 1" x 12" (2.5 cm x 30.5 cm), and the shield frame is 1" x 14" (2.5 cm x 35.5 cm ).
I cut these on a table saw, using a high count, fine blade used just for plastic.
I piled them in one of my tempering ovens and set the temperature at 220°F (104°C). This leaves the kydex pliable but not so plastic that it can't be handled. It only takes a few minutes to heat these up.
While the kydex was heating, I filled a 1 gallon discarded vinegar bottle with water. This turns out to be just the right size for most forehead shapes.
I set it on a granite block and put some light leather gloves on. Each strip of kydex was removed from the oven and formed around the base of the bottle as shown. I held it there for a minute or so, just enough for it to cool and harden.
Notice that the very ends of the strips are left straight. This area will accommodate the screws (later).
Back to the grinder to round over the ends.
Find and mark the center of shield frames, at 7"
Find and mark the center of the shields at 6.25"
Align the center marks of the shield frame and the shield. Notice I'm just holding these with my fingertips, against a board clamped in a vise.
This is because I then drill a clearance hole for the rivets through both pieces at 3/16". Since these are plastics, they drill pretty easily. and the board allows you to hold the pieces easier than laying them on a drill press.
I use an aluminum 3/16" pop rivet on the center hole. Then I pull the shield around, and, keeping it square and aligned with the top edge of the frame, I drill a rivet hole at each end, and mount those with a pop rivet.
Notice that there is a bit of kydex sticking out past the side of the shield; this is necessary for the pivot screw.
Here's a stack of completed shields and frames in the photo on the right.
Remember that I had to use what was immediately available, so I chose tool drawer liner for the forehead padding. It would have been nice to use thick, cushy foam, but that would have taken many weeks to acquire. Knowing that most of the staff would be wearing a skull cap, do-rag, scarf, cloth, scrub hat, or operating room cap, there would already be some padding. Plus, I wanted to keep the weight down.
Because I wear headpieces every day in my work (magnifiers, respirators, shields, helmets) I'm familiar with a heavier apparatus pulling down on the forehead area, and in my case, a do-rag helps keep everything stable.
So I went for padded tool drawer liner. It's readily accessible, easy to work with, extremely durable and washable.
The size of each piece laid out worked out to be 4.5" x 7.375" (11,4 cm x 18.7 cm). It's simply cut out with a big scissors.
In the photo at the right, you can see how the tube is arranged. I'll have a double thickness layer against the forehead and a single thickness layer around the head frame.
I'm using my Sailrite® Ultrafeed LSZ-1. This is a great machine for webbing and heavy fabrics. It's a walking foot machine, meaning that the feed of the textile or material being sewn is held between the foot and the feed dogs while both move (or walk) forward. Most sewing machines only use a feed dog. In any case, it's a sturdy, heavy machine that will easily handle this type of job.
I'm using a 135X17-20 needle and T90 polyester thread to stitch these tubes. This is a very heavy thread for this type of job, but I wanted the tubes to be strong, since they will support the head straps.
I stitch a double row near one edge only and terminate with reverse threads, stitching through three layers of the foam padding.
I had to use what I had available, and thankfully it was sufficient. Most people building face shields, masks, and PPE at those early days of the pandemic were using full elastic straps for their mounts, and this is hugely wasteful. You might get four times as many straps using a shorter length of elastic, and long runs of elastic were simply not necessary. The reason is that elastic weakens and fails, and the longer the stretch is, the easier it becomes too loose to hold.
Another problem was that elastic, just after a few weeks into the pandemic was impossible to find. There wasn't any to be purchased in what few stores were open (most were forced to close), and online ordering was either sold out or predicted a three month delivery! Of Elastic!
In order to conserve, I chose to use short strips of elastic, just enough for the necessary stretch, and segments of 1" nylon strap. I also chose to use 1" Velcro® (Hook and Loop) fastener with a wide adjustment range for various head sizes. This way, if the elastic was too tight, the Velcro could be simply attached with more slack. If the elastic was too loose, the Velcro could be moved up tighter. The only drawback to this was that it required more stitching on my part, but it wasn't too big of a deal.
Note the layout sheet. This is a steel sheet metal plate, and I mark it with frequent sizes used for my military and tactical counterterrorism gear, when cutting these synthetics with a hot knife. Only the Velcro has to be cut with a scissors.
I start out with a 20" (51 cm) length of nylon web. I cut a 6" piece of elastic, and fold it over the end of the webbing.
I'm using a heavy zigzag stitch, with three passes over itself for strength and durability. It won't come off. This is where the LSZ-1 shines!
It allows me to create a double-strength two layer segment of elastic, conserving the elastic and adding strength. This is all the elastic you need; no need to waste 20 or more inches of the stuff when you only need a short length to stretch!
Next, I stitch a 3" length of nylon webbing to the end of the elastic double-row segment. Each time I add a segment, I've added a 1/2" (1.3 cm) length for the stitching overlap. This is plenty of room for the heavy zigzag stitching.
Sewing through multiple layers of the elastic gives a durable bond to the nylon webbing.
In the photo on the right, I've stitched the loop side of the hook and loop (Velcro®) to the nylon extension. This is stitched around the periphery with a straight stitch. This gives three inches of travel or play to adjust the fitting of the strap to the head.
Looking at the layout in the photo at the left, you can see the left end I previously made, with the Velcro loop and the elastic segment.
At the right end of the web, at 20½", I've made a mark. At that mark, I'll sew on a 3" length of Velcro hook. That will be what secures the strap to the head. There will be a bit of a tail of webbing beyond this Velcro hook pad, and that will help the wearer release (or tighten) the strap on the head. If I didn't have this, the wearer would have to dig his fingernail between the industrial strength Velcro to release it, which is a difficulty. I stitch these hook pads on with a a straight stitch around the periphery, just as I did with the Velcro loop pads.
In the photo at the right, the straps are done!
In the photo at the left, I'm threading the strap through the padding. This is where I find out if I've created a large enough passage in the padding! So it helps to make a few prototypes first. Also, careful attention to the placement of the Velcro hook and loop pads is necessary, so they engage each other without twisting the strap, and the threading through the pad needs to be correct so that the double layer is against the forehead and the strap Velcro engages correctly.
Once the strap is threaded through, It's time to make the first pivot. A hole is drilled through both ends of the forehead frame kydex, and through one end, I fasten with 1/4" nylon screws and nuts. These are plenty strong and very lightweight, and able to be sterilized, of course.
I thread the strap and pad over the kydex head frame piece as shown. This assures the correct orientation of the pad (double layer against the forehead) and the Velcro fastener pads.
Then, I drill and mount the second pivot, mounting the second nylon screw and nut.
Because the two kydex frame pieces are different lengths, the face shield frame extends out from the head frame (and face) just enough to clear the nose, glasses, or mask. Also, the nylon screws and nuts allow some adjustment, but the pivot action is clean and the face shield can be pivoted up out of the face without removing. This is a convenience, because once a lightweight shield is adjusted to the correct fit, it's troublesome to be constantly adjusting as it's removed.
The staff appreciated the fact that the face shield pivots up!
Here are a couple photos of the finished shields. They were made with what I had immediately available, and the process was posted on my Instagram account as I did it. I've since cancelled my Instagram account, as the platform became too political, and I didn't sign up for Instagram to participate in fake news and politics. Too bad, really.
If you like the design, you may freely copy it; I'd appreciate you mentioning where it came from, and that is is a complete donation from my studio to others who may need it.
These are great shields, they are tough and durable and lightweight, and can easily be sterilized in non-heat sterilizers, as many of these professionals are using for their daily PPE wear.
It was a huge honor to make and donate these face shields for the emergency room staff of a critical hospital. Personal Protective Equipment is a crucial need for those on the front lines of the Covid-19 pandemic, and these professionals have my deepest respect.
Hopefully, this shortage of PPE won't happen again, but if it does, I'll be ready to help make and supply those who may need it.
