A reader wrote in with a very interesting question about adjustable vs. variable speed terminology as it pertains to power tools.
Just to warn you, this is going to be somewhat of a philosophical discussion on tool semantics. Please feel free to join the discussion and share your take in the comments section!
Milwaukee is advertising this grinder (model 2888-20) as “5-speed” AND “variable speed”. Any insight?
I looked into it, and there’s a speed control dial located at the end of the handle that sets the maximum speed.
The paddle switch and slide switch grinders are both described as variable speed tools.
Mike responded with:
I guess it’s a matter of semantics. I would call it “adjustable speed”. To me, “variable speed” is when I can vary the speed according to how far I pull the trigger.
Here’s where things get complicated.
A cordless drill with variable speed trigger allows for instantaneous speed adjustments depending on finger pressure. When you talk about a cordless drill with variable speed trigger switch, there’s a common understanding about how it works.
When you have a set-and-forget speed control dial that’s completely separate from an on/off switch, is that a variable speed dial, or adjustable speed?
When talking about drill presses, variable speed is used when speed settings can be changed electronically via dial or buttons, as opposed to having to change belts and pulleys or other such adjustable mechanisms.
Variable speed is never used when belt changes or similar are needed.
So, you can have two drill presses, one with variable speed, and the other with adjustable speed, with the difference being electronic vs. mechanical settings.
Dremel rotary tools are advertised as having variable speed, and this usually involves a rotating dial that’s separate from on/off controls.
Barrel grip jig saws are often described as having variable speed motors, similar to D-handle jig saws. D-handle jig saws often have variable speed trigger switches as well, while barrel grip jig saws have speed settings and a separate on/off switch.
Most cordless drills – except for the cheapest entry-level models – have 2 or more gears and speed ranges, with a sliding switch toggling between them. That’s not usually referred to as either a variable speed or adjustable speed feature.
Here’s a good example, at least in my opinion. On the left is a Foredom foot pedal variable speed controller, and on the right is a Foredom tabletop variable speed controller.
The foot pedal works in a similar way as a cordless drill’s trigger switch, while the tabletop controller works similar to a speed control dial on an angle grinder, rotary tool, barrel grip jig saw, or other such tools.
Wouldn’t both tools be described as variable speed controllers? One adjusts the speed based on real-time user foot pressure, while the other is more of a set-and-forget dial.
My opinion is that either can be added to a Foredom flex shaft tool to provide variable speed features.
I would generalize things, to say that if you can adjust the speed or speed range via electromechanical switch, that’s variable speed. If speed changes can only be accomplished via mechanical changes, such as by moving a drill press’s belt to a different pair of drive pulleys, that’s adjustable speed.
The reader made an excellent point, but I believe it is generally understood that variable speed need not be instantaneous by means of a pressure-sensitive switch or similar.
Can the speed or speed range settings be adjusted via electromechanical switch? Variable speed. Can the speed or speed range settings be changed via mechanical adjustments? Adjustable speed.
That’s my take on this. There’s the potential for exceptions, but I haven’t come up with any yet.
Do you agree? Disagree?
And if if you’re wondering “why is any of this important?!”, it’s not, but I found the question and topic to be interesting, and thought some of you would too.
IMHO, variable means that the operator has continuous control over the function. Drill/driver trigger has speed. Lights have a dimmer. Air suspension has ride height.
But, if there are detents or fixed points, I would call it adjustable. I’ve used rotary tools with variable speed via a dial on the handle or the motor box. I’ve also used adjustable where the dial clicked in a few positions like low/medium/high. The former is variable. The latter is adjustable. Or ‘multi-speed’.
I have corded and cordless drills that are variable speed. I have a multi-speed full-heigh drill press. It’s adjustable, not variable.
I had an SUV that had air bags on the rear suspension. It was an automatic ride height adjustment. I couldn’t select it. All it did was pump until the vehicle was level again, or hit it’s max pumpiness (if that’s a word). There are much better systems that have a variable ride height that can be dialed in by the operator or by a selectable performance profile built into the control system. I would never have called my on/off suspension ‘variable’, no matter what the marketing team tried to call it.
“Continuous” as in constant, or stepless?
Variable speed trigger switches allow for real-time adjustment, but most have steps that are functionally similar to a speed control dial with discrete settings.
If you gently squeeze a drill trigger switch, you should bear step-like changes in motor tone, corresponding to different speed settings. Rather than being continuous, there are intervals, with the number depending on the switch and programming.
In other words, if multi-speed was the differentiating factor, most variable speed tools would fit in the same bucket regardless of trigger switch vs rotary dial adjustment.
That’s where electronic controllers blur the line. Continuous…meaning I can keep moving across the speed band on demand. Steps in the band/ramp are different than the definitive low/medium/high that were set with switches or detents. To extend that metaphor, cruise control steps in 1mph increments. I’m sure that fuel supply in electronic injection has steps too, but should still be considered variable input from the gas pedal.
I would consider flight controls on a jet to be variable, even though steps exist in the fly-by-wire programming.
This is quite true, just about all variable speed triggers, you can feel the steps.
Truly variable, I guess, in the analogies offered in other posts, would be like a carburetor engine and accelerator pedal. The little arm connected to the float was truly variable.
Most anything that has a digital component is going to actually stair-step, even if the steps are too small to see.
Analog devices can truly vary continuously, but those are more and more rare. Even if the controls look analog, they’re often just changing a digital value somewhere in the computer.
An example are the fire control computers that couldn’t be replaced until quite recently because they were analog, and very continuous. https://www.youtube.com/watch?v=gwf5mAlI7Ug
I don’t think I would count on power tool companies using either description consistently to correlate to a particular type of adjustment. I expect they are more likely to use whatever sounds better to the marketing team.
On the other hand, if I think of how I interpret the words, I think my interpretation would align with Mike – e.g. “variable” sounds like the speed can change as I work (like a drill trigger), whereas “adjustable” sounds like I can make a change to a different speed (e.g. dial switch).
So for the Foredom speed controllers, you could consider the foot pedal a variable speed attachment, and the tabletop controller an adjustable speed attachment?
That’s what makes the most sense to me
Yep. I realize that in terms of the input to the tool, those are indistinguishable – yet for the user, one is speed “variable” in use, the other is adjustable.
I suppose that means I’m only looking at how the user interacts with the speed interface, not how the speed adjustment is accomplished.
I have a separate but related question – do DC motors lose power when the speed is lowered?
My old AC variable speed grinder has noticeably reduced torque when the rpms are turned down. I think that is because the motor is slowed by decreasing current and/or voltage.
Hopefully newer motors maintain full power at all speeds, but can anyone verify?
Generally speaking, DC motor speed is proportional to the applied voltage.
For a typical DC motor, the power vs. speed chart is a downwards-opening parabola, with maximum power at 50% speed.
(That’s max speed for the motor, and not necessarily max output speed for the drill.)
So, if you look at a power vs. speed curve, or at least a segment leading up to max power, power is going to be proportional to speed, albeit not linearly.
Modern tools are increasingly computer-controlled, and so motor characteristics might not indicate power tool operating characteristics.
In other words, yes, for a DC motor, lower speed = less output power.
Torque is inversely proportional to speed, though.
What you’re possibly noticing is lower power of the tool under load, and not necessarily lower torque.
Many modern tools claim to maintain speed and power under load.
Check out the Wen variable speed drill press. Uses belts but you can change speed on the fly (in fact, a sticker says you must change speed while the motor is on). Conical pulleys.
I think this comes down mainly to the idiosyncrasies of the English language.
The adjective ‘Adjustable’ is easy turned into the verb ‘Adjust’ in common conversation, which ‘Variable’ simply isn’t, limiting it’s usage and what it can be applied to.
Ex: “Hold up, I need to adjust the speed on my drill press.”
You never see triggers referred to as ‘adjustable’, as their speed control is constantly variable and won’t ‘hold’ a continuous RPM. On the other hand, a one time setting that holds it’s position, defining a specific range of speed or some other factor feels much more like an ‘adjustment’.
For me, if a control is continuously modulated by the user, like a gas pedal or trigger, that’s ‘variable’.
If it’s a setting that holds it’s value, controlled by a stationary dial, switch or buttons, that’s ‘adjustable’.
What about “vary”?
In the English language, many times two (or more) words can mean the same thing.
With either word, I know the tool can be used at different RPMs.
I need (or care) to know no more……
While inagree with your semantic take, I also known that, in the case of the grinders and say, the Super Sawzall, Impact tool, jizs, etc., there are Both on the same tool.
There is a dial that can be set to the maximum allowable speed/power that you want the tool to operate at while pulling the trigger to its maximum depth, and then the trigger itself adds or removes the power from 0% up to 100% of said dial setting. This gives you maximum control and maneuverability as well as safety of said tools.
Variable Speed should incline adjustments easily or plausible while under operation.
Adjustable speed inclines a determined setpoint before use or not intended during operation.
Like an older vehicle: The accelerator is continuously variable, the transmission is step adjustable. I’d go with that analogy, myself.
So, the key words aren’t variable or adjustable, but continuous or step.
Hmm. The problem is, in modern tools, most if not all variable speed trigger switches aren’t continuously variable in the same way as say a fuel valve. They might seem to be analog switches, but the output is often digitally stepped.
I’d consider the terms would apply to how the user perceives the interfaces to operate. Inside the case, how it’s engineered, should be invisible.
To me: Variable would that on/off is controlled by a trigger and that the harder you pull the trigger, or farther you press the pedal, there is a further increase in motor speed. Speed up and down with the trigger as needed. No further adjustment.
Adjustable would be that there is an additional control besides on/off swith or trigger, whether a sliding switch or dial, that makes something 2 speed, 3 speed, 5 speed etc or even close to variable where it may have a dial with not just a few fixed positions, but perhaps 24 or 48, 64 equivalent positions on a circular dial, where you get fine increments between the listed numbers ( on for instance some oscillating cutting tools, sanders, jigsaws, … ). But this is a set speed dial separate from your on off swith or trigger … and the dial is typically not used or accessed during operation.
I guess there could be some blurring of the lines where something like a drill is more than variable, but also has a speed control, where you set a max speed ( 1 2 3 ) and then have trigger control over the variable speed up to that limit.
I guess over time you become familiar with the terminology for different tools.
You know a drill has a trigger and without a doubt, variable is on the trigger. When I get a barrel grip jigsaw, Dremel tool, and similar, I expect the variable to be a separate dial. (much to my dismay when I bought my first barrel grip Bosch jigsaw, but got used to it and love it)
semantics indeed. I sort of see variable speed as being the tool operates as different speeds. be it select steps like a normal drill press (650/800/1200/1500) as example.
or 0-25000 rpm like a dremel 4000 – IE variable output use speed.
Adjustable I think doesn’t matter. but continuous variable speed is a different matter.
note variable speed trigger Jig saws as mentioned above as opposed to variable speed / on off jig saw like a barrel grip.
And blurring that line is my 3 spd variable trigger impact driver. 3 speed/power settings – but variable speed trigger. Issues like this is part of why I like to put hands on a tool before I consider buying one.
ON that motor question speed vs torque of a motor. Yes there is an RPMvs Torque output curve for most motors. AC, DC, etc. and it varies a bit by motor design but often with output speed torque increases to a point.
In the 80’s it became common to see variable load curves due to a feedback circuit – so you could have an AC or DC motor were it had 2 curves and a shaded area – showing that due to current thoughput the motor might provide more torque at lower RPM’s in this band. Wish I could post a picture but again small changes.
Today’s EC motors and note I didn’t say brushless as it can be applied with brushed motors. Electronic Control motors are a few steps beyond that yet where it will vary the power to the motor to meet demand and try to prop up desired RPM. Again common use of this is on a jig saw. ALL brushless motors work this way – so that’s true but that’s not to say you can’t have EC and a brushed motor. I have an RC car in the attic from 97 that has as advances an EC controller as any you buy today so it’s not new is my point.
IMO, “most” tools fall into the variable speed category. If you can move a dial and the speed is set and forget, then it is adjustable. Or, as you mentioned, move a belt from one pully to another to “adjust” the speed. None the less, it really comes down to knowing your tools before you buy and get what you want.
I can really only speak from a Linguistic point of view… yet another one of those fields of study that I find interesting, but no one else cares about.
Variable and Adjustable speeds are Synonymous. They both mean “Can Be Changed.” Where they differ is the usage tense. We all think about the Temporal Tense, as in Past, Present, Future, Etc. But Usage Tense is when you are doing something with a specific intention, or tangibility. To dumb that down, because it’s unnecessarily complicated, it has to do with whether or not you are active in touching it while it functions. If you touch it all the time, it a Tangible Positive Tense. If you Touch it, then Leave It, that’s a Tangible Negative Tense. A Switch, such as one on a wall, is another Usage Tense called Tangible Activation Tense. Positive, Negative, Activation, and one that will come up in the actual discussion, Controlled Tense.
That’s the linguistics Nerd out of the way, let’s talk Tools. What are the Variable and Adjustable functions actually controlling? I would say the mode switches on a Drill, such as speed control, or torque settings, are all Activation Tense based. When you have many Activations, that is an Adjustable Tense for the whole tool, and an Activation Tense for each of the settings. Think of these as Absolute Positions equaling Adjustability. Just like a switch on a wall, or a binary set of instructions in a digital system… something is on, or off. Even if there’s a lot of things to switch on or off, it’s still Absolute. The entire job the tool is going to perform when activated, is set up.
As to Variable controls, these are all Active Tense, or Tangible Positive Tense to be technical. The variable-speed trigger or paddle control, this is something you actively have to change to achieve the tool’s use. On a Drill, you would think, logically, it’s Adjustable versus Variable, right? And you would be right. Because the Drill may be Adjustable (Tangible Negative Tense) in a variety of ways, but it is Actively (Tangible Positive Tense) Variable. Since many of those Adjustments apply to a Range of things, rather than an absolute setting, there’s an element to them that allows the user to span the range of the settings, depending on the variation of their use of, in this Drill case, the trigger.
Then there’s bigger machines. Drill Presses, Mills, Lathes, Cars/Trucks, the list goes on. Where we are no longer talking about a single tool or entity. It is, in fact, a collection of separate tools, put together to make a whole item. The Drill Press has a Motor, and Quill (I watch way too much Tested, I know this despite never using a Drill Press or Mill myself.) which can be directly linked as a single tool. But there are other tools attached within that housing, in order to change the behaviour of the Motor and the Quill. Some, control speed, some control an amount of lubricant being regularly dispensed for normal operation, and some control the distance the Quill travels when used. This means there’s a whole variety (a word that is important here.) of different kinds of Adjustments (Both Tangible Positive and Negative Tense) that are sitting in the operation of this large-scale tool. Similarly… The engine of a vehicle has as much complication in controlling it, as setting the seat how you like it. They are separate task-performing items, held within the same entity… the vehicle. And just like a Vehicle, many more complex tools, are actually many smaller tools being used to control the main function of the device.
So… I would have to say, if you can hold it in your hand, and constantly change a setting, that is a Variable Speed tool. If it also includes an absolute setting that you don’t, or can’t, change while the tool is active, that is an Adjustable Speed tool. But, as I mentioned about the larger scale tools, if it contains items that are Tangible Negative Tense adjustments, as well as Tangible Positive Tense adjustments, then you really have to accept that Adjustable and Variable are Synonymous in the tool. They’re referring to one or two controls that a comparable model in their own line, or their competitor’s line, don’t have the ability to use in that way. You can also go further and say that the vast majority of Marketing teams are not as well versed in language as someone like myself, and they’re just winging it, like they always do. Confusing as it may be for all of us, there is some logic to Adjustable versus Variable… but there’s no guarantee the Marketing for the tools have ever read a book with syllables that exceed 3 per word, let alone compound tenses, or the Tangible Tense as a whole.
So… In Language, there’s an absolute answer to this versus question. In Marketing? You really have to remember how truly stupid the Marketing Execs are. The Smart people are the Engineers and Designers of the tools we love to use. But those same people aren’t always great at convincing people to buy things. So, the intention is often lost when handed over to the Marketing people. They don’t know the language that the Engineers and Designers do, and they certainly don’t have the passion for linguistics that I do… so maybe take the term with a grain of salt, because it could simultaneously mean something profoundly important, or nothing at all.
“Variable and Adjustable speeds are Synonymous”
Yup, ‘nough said
For most people, yeah. I’m just… well I’m a Language Nerd… so I love to go off on a full linguistic exploration of the words used.
You’re probably not as weird as me, so the short version is good enough. But where I’m weird… Language is never enough! but, I’m weird, so, that’s just me. Make no mistake though… Weirdos like me need folks like you, to translate our crazy for us! So, I appreciate your input here! (Is there a smiley face that will show on here? I’ve never found any that work…)
To add to the confusion, I have an impact driver with 3 distinct motor speed settings gs, along with a variable speed trigger. What do we call that?
Imo, in general adjustable speed means you set the speed in steps. Might be just a couple, like low/med/hi, or could be many, like a drill press, and variable speed is more or less infinitely adjustable.
Based on looking at what I have in my garage, unknown rpm which can be adjusted is variable. Adjustable rate is only on my drill dress documentation which you know what RPM you are selecting.
I think you are all arguing two different things.
Let’s take the case of a drill press with both a gearbox and electronic variable speed control. This is becoming more common but it’s more typical of a machine shop grade machine than home workshop. So in this case I want consistent speed because I tend to eat up drill bits and quality of the drilling suffers if the drill is turning too fast. The drill press motor is AC and designed to put out more or less a constant speed regardless of the load unless I just plain overload it and stall it out. On electronic speed control I can vary the speed but I have the same maximum torque…no matter what the speed is, it overloads at the same point. This is what you would get with a DC motor and controller or an AC variable frequency drive. But another much more primitive way to do it is by varying the voltage to the motor. So in this case we are essentially purposely stalling it out. It slows down as the load increases and with this type of design, we want a motor that is a lot more “mushy” and not a “stiff” response like most drill motors are. This is typical with say a 4″ grinder because I am going to routinely stall it out and need it to be forgiving of this, and where speed is far less critical. In this case variable speed control means I can vary the maximum torque but speed is not something I can truly control.
Now with either design getting back to the maximum torque the second option is with a gearbox and this is something no electronic system can do (with a small exception of some electronically commutated motors). By changing the gearing I can decrease speed but also torque goes up a lot. So if I have say a 2-3 speed handheld cordless drill I can select a speed “range” and then within those ranges the trigger just varies the torque.