Needle Lag and Snag on Rotaries

In this latest installment I am elaborating on rotary stroke characteristics. What exactly is happening when the motor rotates the cam, which moves the yoke, which makes the needle go up and down. It may seem simple, but there are some characteristics to this movement which you may not realize but knowing these characteristics will help you chose a more appropriate machine and may even help you tattoo better.  Below is a diagram I drew of an offset cam. Any rotary tattoo machine that you can buy has an offset cam. It is how the motor turns rotational movement into linear movement. The offset is what the stroke is often referred to. It is how far the shaft of the motor is offset from the center of the cam.

In this diagram I have separated the cam into 4 equal parts, shown here as arrows around a circle, the circle representing the cam. I have also shaded areas in the background, blue in the middle and red on top and bottom. I will get to the shaded areas shortly. 


As the motor spins it is spinning a cam. For the sake of this explanation we can say that the motor is spinning at a constant rate all the way around it’s movement. That means that if you separate the cam’s path into 4 equal parts, as I have here, then the cam spends an equal amount of time in each of the 4 quadrants as it goes around. Let’s now look at the shaded areas in the background. The shaded areas represent the vertical movement of the cam, or the needle movement in this case. As we look at the shaded area we can see that the vertical movement is shorter in the bottom and top sections, the shorter areas are shaded red. As I said before, the needles are spending just as much time in this shorter area as the larger blue area. What does this mean? This means the needles are slowing down at the bottom and top of the stroke, and speeding through the movement around the crest of the top and bottom quadrants.

This seems like a no brainer, of course the movement has to slow down before it reverses direction right? But this isn’t just showing that the needle movement is slowing down, it shows that it is slowing down on half of the stroke. The top quarter and the bottom quarter of the stroke, together make a half.

Now that we got the complicated bit out of the way we can talk about how this translates actual tattooing. I’ve already talked about how a larger cam offset translates in to a faster needle speed in my previous posts, lets now talk about how the cam offset affects this “lag” at the top and bottom of the stroke.


As you can see in the shaded diagram the red sections are where the needles are slowing down in their up and down movement. This area of lag grows as the offset grows, and shortens as the offset shortens, but the ratios always stay the same. The needle will always be slowing down through half of the entire stroke.

This lag is beneficial on the bottom of the stroke. We want the needles to hang in the skin a bit on the down stroke, that allows our hand movement to open the skin and deposit ink in the cavity that forms behind the needle. In turn we also like the needles to speed down to the skin, that gives us the penetrating power to break the skin and deposit the ink without causing a lot of undo trauma to the skin. It is the top area of lag which is the most troublesome.  Almost all of us who have ran rotaries have experienced that sensation where the needles seem to snag in the skin. The operator, thinking the machine is running too slow, or not hard enough will put more voltage to the machine speeding it up which just makes the needles come down with too much force, and come out of the skin much too fast. Running a tattoo machine too fast, rotary or coil results in skin that is beat up and undersaturated. That snagging sensation is actually just the needles slowing down at the top of the stroke. If the stroke is too short then the needles will actually start slowing down before they retract fully in to the tube. If the needles are slowing down at the top of the stroke, but your hand isn’t, then you are going get that “snag” sensation.

I like to make sure that the stroke on my rotary machines is long enough where the whole top quarter of the cam rotation happens inside the tube. This turns this lag in to a benefit, as it slows down in the ink reservoir picking up as much ink as possible before racing down to skin. That means if you are running tube to the skin the needles are coming out of the tube at max velocity, slowing down at the bottom, and racing back up to the tube and your hand doesn’t feel the lag at all. The image at the bottom shows how this looks at the needle end. The short stroke shows the needles slowing down before retracting in to the tube. 

The longer stroke shows the needle coming back from the bottom lag and entering the tube at it’s maximum speed.


I had mentioned the needles retracting fully in to the ink reservoir and taking advantage of the top lag of the stroke. I want to explain something else that is happening while the needles are moving up and down. For this image I’ve used a shader but the concept holds true with liners as well. Most tubes have a separated ink reservoir and a flat area for the needles to ride on. The tattoo needles have a solder lug holding the individual needles together. This solder lug acts as a lid to the ink reservoir. In a longer stroke machine the needles are allowed to move up enough for ink to spill in to the needle slide area. On a shorter stroke machine the lug may never leave the top of the reservoir keeping the ink from spilling down to the skin. Many tattooers get around this by bending their needle bar, or bending the solder lug to allow the ink to flow under the needles but this is often not the best solution as the needles flatten out when tension is put on the bar from a rubber band. And bending isn’t a practical option for cartridges. A shorter stroke or a faster cycling needle will  also cause turbulence in the ink reservoir and will actually push ink away the needles and back up the tube.

So what if you prefer a smaller cam offset? Some people prefer a shorter cam offset, they feel it makes their tattoos look smoother and the movement doesn’t feel as slappy, or harsh. If we think about the needle travel on a smaller offset rotary this makes sense. The red shaded area at the top of the diagram, the area of lag, is closer to the tip of tube, and often even happening outside the tube. The needles are easing in to the skin rather than entering at their peak velocity. That makes the movement feel softer. And as the needles are coming out of the skin they are slowing down before retracting fully into the tube. As the hand is moving the needles are slowing down, usually at the top couple millimeters of the stroke, right off the tip of the tube. As the hand is moving and the needles are slowing down and scraping across the surface of the skin they are making superficial marks on the surface of the skin. The needles aren’t depositing this ink into the skin deep enough for it to stay, but it does have the appearance of “smoothing” things out. Either black and gray or color, these superficial marks give the tattoo a well blended appearance but look at the result only a year or two later and much of the color, or grays will have fallen out. Ink has to be deposited in to the layer of retention or it will fall out prematurely, there are no shortcuts to this. Going over areas multiple times doesn’t push ink further in to the skin, it only makes a more saturated superficial tattoo. Good for a photo but not for longevity.

I feel it’s important to know your tattoo machine and how it is moving. If you prefer a shorter stroke, just make sure the needles are fully in the tube the whole top quarter of the cam rotation. If you feel the snag sensation it’s best not to turn the machine up but rather be aware of what you’re actually feeling. If a longer cam offset feels too punchy or abrasive just slow it down and give it a try. When you turn a rotary down, try keeping your hand speed the same as before. You want the needles to move slightly slower than your hand, turning rotaries down, or slowing them down is actually the most efficient way to use them and often speeds the work up. I try to run my rotaries at the lowest speed possible without slowing my hand down.

Thanks again for reading, hope this adds a bit of knowledge or at least gives a bit more familiarity to you and your machine.

Rotary Liners, Shaders and Cartridge Machines

My previous posts have been describing the stroke characteristics of liners and shaders. Liners and shaders both have distinctly different ideal stroke characteristics to make them best suited for the job they are intended to do. With the liner being tuned to be snappy, strong but still respond to the skin and the shader being powerful, still responsive while having a stroke that eases in to the skin and slows down just a touch before the backstroke.

As far back as the beginning of modern electric tattooing tattooers have used two different tools for lining and shading. With the introduction of cartridges to the scene and their growing popularity I find more and more people asking me about my Method and will it line just as well as their coil machine their used to. Chances are, no it won't. It's not a downfall or a design flaw of the machine, it's just that certain compromises will be made for the convenience of one machine that you can line and shade with. Everyone is looking for the one silver bullet that is going to be capable, intuitive and dope as fuck right out the gate. Well that's an awfully tall order given the task at hand, and considering the huge variety of equipment that is available to artists now and what you are transitioning from.

The Method machine (my cartridge exclusive machine), as well as every single cartridge machine on the market has been designed to be a good all around machine. You'll find that some work better than others for lining, while others won't line at all. And you'll find that some run too fast and hard to shade with, but line real well. Every builder/engineer has a different way of approaching the problem of one machine, two distinct uses. In my opinion the Method tackles this problem very well, and shades and lines better than other cartridge machines, but if you're transitioning from coil machines I would urge you to consider this. To go from coil machines to a cartridge exclusive machine is skipping a huge step in rotary machines. The change from standard needle and tube on a coil machine to a cartridge on a rotary machine is just setting you up to be disappointed. There are too many variables that are different, it would be like having to re-learn how to tattoo all over again.

The next logical step for someone wanting to try or transition to cartridges from coils is to actually try a rotary. And not just any random middle of the road rotary on the market. As I said before liners and shaders have unique stroke characteristics, even rotaries. Go with a rotary that is built to be an ideal liner, or an ideal shader. Try my Micro-liner or a Dan Kubin Sidewinder, both built to be awesome liners without compromise. If you're setting up without a specialized tattoo machine, you will be making some compromises, period, whether that's in the form of having to tattoo slower or not have as many needle grouping options.

Having the right tool for the job isn't just important to produce a solid tattoo, it's so important to give the artist confidence to produce tattoos at the best of their abilities, starting with the design stage. Use a machine that is capable of doing any and all of the kind of tattooing you would like to do and you won't second guess or hold back on your design process, adding those little details that your machine can't do or staying away from a bolder line than the design calls for just because your machine has a hard time lining.

So to sum this up, if you use coils and love them, dope! Stick with your coils, but if you want to transition to rotaries because you have wrist strain or because you want a machine that runs the same after the 6th hour of tattooing than it did after the 1st, then try a rotary suited to your purpose. Use a rotary liner, or a rotary shader, not just some machine sold as a "rotary tattoo machine, one gun to kill em all." After that, if you're thinking of moving towards a cartridge setup then use cartridges with the rotaries that you're used to running and that you get great results with. After a while you'll come to a point when you're so comfortable with those that you'll want to experiment with cartridge exclusive machines. Cartridge machines have a lot of benefits that other machines don't have, but they have drawbacks as well. Youi have to be ready ready for that or you will be turned off of cartridges forever. Tattooing is hard enough, keep your equipment transitions small and you'll adapt quickly and a lot more easily.

Rotary Tattoo Machines

The following is a conversation I had with an artist via e-mail where we discussed many of the questions that I'm frequently asked. i asked for permission to post it here to be resource for others looking for the same answers. Please enjoy!

Hello joshua
Im a tattoo artist in France, I’ve been tattooing for 5 years and
I've always worked with coils. I've only tried a rotary neotat and a Hawk Thunder machines for a time but I dont like it, the machines dont have force to penetrate solid ,i miss the slap of coils.
I read aaron cain said that rotaries aren’t good for solid work.
I am a little confused. I see some tattooists that I like use your machines and your work looks solid, as you make both coils and rotarys can you tell your opinion please?
I like to buy one of your rotarys but im afraid that they don’t have force
Sorry my english


JB- In my opinion rotaries don't have the slap per say of a coil but they are more powerful. It's all about the stroke. Coil stroke starts off strong and then weakens as the needles move down. Which gives it that "snap" that your referring to. Rotaries carry the same force and roughly the same speed all the way through the stroke. Which makes it more powerful. Saturation is obtained by the ability to hang the needles in the skin just a touch longer so your hand movement opens up the skin a little bit more to deposit more ink with less holes. You have more ability to do this with rotaries because you have full control of needle speed, where with a coil your only controlling speed as a function of force, but mostly just adjusting force. 

So a rotary will feel less forceful than a coil when ran properly but is much more efficient. It should be avoided to turn the rotary up so far as to get the same hand feel as the coils your used to running. If you run a rotary too fast and too hard it won't open the skin at all and will just cause a lot of trauma.


S- Thank you so much for your help joshua
So maybe I guess that my mistake is that I always try to feel a rotary as a coil.
As you said we shouldn’t run a rotary so fast as a coil ,so we need a rotary with a motor with a very good torque,yes?
Because to get force in a rotary we need put more voltage,and more voltage/more speed
What the stroke you have in your machines is 4mm?
The neotat I try have 4.2mm


JB-  Every motor is different. One mistake that people make is thinking that a 4mm cam is going to react the same way on another machine as it did on the last. Every machine is built and designed differently, different motor, different offset and different frame geometry, etc. You don't need a lot of torque you just need the right amount of torque at the right speed. If the machine is too torquey at lower speeds then it will have too much torque at operating speeds and tear up the skin. If it doesn't have enough torque you will have to turn it up too much to get the torque you need to penetrate the skin, that increases the speed causing the machine to run too fast and will tear up the skin. 

There's no magic formula that works for every machine. I tune my machines to be ideal machines for tattooing because I understand tattooing, I'm less concerned with simply making a mechanism that makes a needle go up and down. Most rotaries on the market are just that, mechanisms that make a needle go up and down. By using the frame geometry, the cam offset as a lever and a couple other tricks I’ve developed I can create a stroke in the machine that slows down and responds to the skin at just the right spot in the machine stroke. This is how I tune my rotaries. 


S-  And about a direct drive rotary(circular movement) and a rotary with an up down movement ? Of course that depends of the machine. But some people defend that a direct rotary machine is better for solid tattoo, because the other rotaries with an up/down movement the needle spends more time in the down movement.
You agree?


JB-  I don't like direct drives unless your stippling with them or running cartridges.


S-  Sorry but,why is best for cartridges? Is a direct drive more powerful?


JB-  Because a direct drive can't really be tuned. There's no mechanism for modifying the stroke characteristic besides adding weight to the spindle mass, but this rarely offers any benefit to making a tattoo machine better at tattooing, it usually just adds a bit of force to the initial contact with the skin and then slows the movement down from there. Direct drives also cause a wobble in your needles since they have no mechanism for making rotational movement into linear movement. So the needles move side to side often times causing friction and rubbing on the sides of the tube. The use of cartridges with this system solves those potential problems.

These are questions a lot of people have, I would like to post this conversation to my website blog if that's ok, it would help answer a lot of questions for people.

Rotary tattoo machine stroke characteristics

I've been asked countless times what the stroke length is on my machines, if I can do custom strokes for someone who currently uses a 3.5mm and loves it and ultimately, why I don't do custom stroke lengths on my machines. In short, the stroke length on my machines are right about 4.5mm, I don't manipulate this because it is directly responsible for the tune and stroke characteristics that I've designed into my machines. Let me explain.

 Many people are mistaken that a shorter cam offset on a rotary makes for a faster machine. For example a 3-3.5mm stroke is meant for lining and anything above that is meant for shading. Because liners traditionally run faster than shaders, when not aware of the actual dynamics of the mechanism that logic may make sense. A smaller cam offset does not make the machine cycle faster however. The cam is not a gear, in that one rotation of the spindle will always equal one rotation of the cam, which will in turn one full stroke of the needle. So a machine that has a 3mm stroke running at 6v’s for instance will be running the same speed as the same machine with a 4mm stroke at the same voltage. That being said, cam offset does manipulate needle speed. This may seem confusing at first but think of it this way. A machine that is set up with a 4mm stroke running at the same voltage/ speed as a machine that is set up with a 3mm stroke the needle is cycling at the same speed as the 3mm, but traveling a greater distance in the same amount of time. So the needles are traveling faster but the machine is not cycling faster. This needle speed creates a snappy, punchy feel to the machine. A characteristic I like in my liners, and not as much in my shaders. In the same respects, a 3.5mm stroke will feel completely different on different machines. If you love your 3.5mm on your Neotat you wouldn't necessarily love a 3.5mm on my machines, There are too many factors to account for to make this generalization.

To break down stroke characteristics even further lets discuss responsiveness. Take into account that the cam is essentially a lever. The longer the lever extends from the center the harder the machine will have to work to move it against resistance. So a motor with a 3.5mm cam won’t be working as hard pushing a needle in to the skin as a machine with a 4mm cam. A DC motor unlike a coil machine however will always finish it’s stroke. Meaning it will always either go all the way around to complete a cycle or stall completely. A coil machine doesn’t have to finish a stroke. The magnets pull down on the armature bar, the needles engage the skin, when the resistance gets too great the downward motion stops and the springs pull the armature bar back up. When a coil machine is tuned and ran properly in the skin the armature bar won’t even reach the front coil on it’s cycle. The machine is being responsive to the skin, or the skin is telling the needles how deep to go, rather than vice versa. This is paramount in a well tuned machine, whether coil or rotary. This stroke characteristic allows the absolute most skin saturation, the least skin trauma and the fastest heal times. I use the coil machine example to describe a stroke characteristic that many rotary machine builders try to replicate with adjustable give. The way I allow for this with my machines is by pairing the ideal cam offset to the right motor. Every DC motor has a set torque rating at a set voltage/ speed. By pairing just the right offset cam to the right motor I manipulate the motor to slow down when meeting the resistance of the skin. By allowing the needles to slow down in the skin you allow the needles to open up the skin more. This allows for greater saturation, and a more efficient stroke with shading and lining. So without any adjustments, the machine is already set up and tuned to respond to the skin and to have the best stroke characteristics. Rotaries with a shorter cam offset often spend just as much time out of the skin as in the skin. This 50/50 stroke creates turbulence in the ink well of your tube rather than creating a nice flow of ink down to the skin.

The last topic I will discuss here is needle setup. So many artists I’ve talked to set up their machines how they were taught to do so by their mentors. A slight bend in the needle bar and adjust the tube tip to be even with the needle tip when the needles are fully retracted. This is absurd to use this as the rule of thumb for every machine you set up. Let me explain. If a machine only has a 3 or 3.5mm throw then this makes more sense, but I’ve seen so many people use this setup on a 4.5 - 4.6mm stroke machine. I only hang out the amount of needle I plan on using, I don’t care where the needles are in relation to the tube tip when retracted. Let me break this down. The further the needles are reaching out from the tube tip the further the ink has to travel to reach the skin, and the harder it is create a positive ink flow. This is even made worse when you consider that in this needle setup the solder band on the needle grouping never travels outside the tube tip, all but blocking ink flow completely. I like a longer stroke on my machines, not just because of the tuning it allows but because I can set up the tube to reveal as much needle as I want and the rest of the stroke travels in to the ink reservoir of the tube, and back out again picking up all that ink on it’s way down, creating a positive ink flow down to the skin. 


I hope this information is helpful, useful or at the very least inspires a new perspective when thinking about tattoo machines, more specifically rotary tattoo machines.