Bored of lame tool reviews? Meet DeWalt's 12 Amp Grinder part A

grinder and paint makes me the welder I ain't I think I should give you fair warning that this is not gonna be an overfed salesman bobblehead review where I plug it in and I grind some stuff and I tell you how great the thing is actually gonna take it apart see if the things in you can good at all welcome back to the shop gentlemen today we add a new toy to the stable the D wilt this is the makita killer or so my colleagues on the dumb end of the tape tell me as you can see the stalls are already pretty filled up I got lots of makita's there and when it comes to grinders I prefer Percherons to Arabians so we're gonna see which one this is they're probably thinking to yourself why the hell does he need so many grinders well my friends this is a high production obvi shop and the first are a lot premiered it was we have zip cut flap wheel Cup wire wire wheel regular grinder diamond and another zip cut that just happens to have a broken disk when you don't got a friggin for a change in the wheels mid-project it gives you an enormous sense of well-being and the whole thing is with grinders is their friggin awesome you can cut anything with them so this Dewalt is more or less the challenger to the world champion 5 inch grinder the makita i mean for the past 30 years probably this has been the grinder all right pay attention because we're gonna check out the marketing see if it stacks up 120 volts 12 amps 10,000 rip ohms 1837 watts in your hand that's two and a half horsepower they're saying here okay so VA p equals IV into 120 volts times 12 amps that's 144 plus is zero fourteen hundred and forty so where the hell are they get in 1837 I'll tell you where they're getting that out of thin air it's I'll get the Box open yeah it's yellow you ask at the ugly the will plug through i Skookum cord seems like though got some extras handle and a grinding wheel as well the ones that come with a grinder obviously consistently and one of these things space spanner you might as well just throw this out right away cuz you're gonna lose it anyway oh it feels real beefy it's heavy both 3.1 kgs which if I'm not mistaken is about 200 pounds and the makita the latest version of the makita is 2.6 kgs so about 10 pounds so hopefully the extra weight is actually copper windings and not lead weights it's probably too much to ask for okay one thing before we get too hung up on specs the most important thing about any grinder is how it feels to you everybody's got a different shape ahend everybody's got a different size of hand so you got to make sure that it's comfortable for you you know you're holding a horsepower and a half in your hand for hours at a time it's got to allow you to have the correct body positioning so that you're not fighting the tool all the time you're working with the tool I know I like the makita I don't know if I like the DeWalt yet it feels okay I know I hate the paddle style it's horrific horrific some guys love it I hate it so that's all we're gonna say about the makita for this bit back to the stable she goes right off the bat this is interesting quite a bit different than the makita if it weren't so much like cheating I'd go and look at the parts stack up to make sure that the spring of things and clockworks don't fly out at me but yeah bag it we got the top words of the business-end prized off and they've got some interesting stuff going on here the this shaft here is 3/4 so you think that's nice and beefy but they actually got to stuff that down because in behind here is a luxe Lu exit you can find the manufacturer so hung low Charlie brand 600 one bearing which we all know the center of is only a 12 millimeter ID so that means what you see is not what you get this actually has to get stepped down and this is a real interesting gear doesn't look or feel like there's any grease on it at all we'll get back to that in a second so here's the housing we see the pinion it looks exactly the same like there's no grease on it and how this looks for all world to me like molybdenum disulphide paste which is a super duper expensive lubricant for high pressure gear sets and disc springs and real industrial stuff and surprising to me that they would use this molybdenum disulphide because it's really expensive the last time I sourced it it was a thousand bucks for 20 liters of this stuff but then I get thinking about it and I can see that the both the gears are they look like they got no Lube on them at all and of course open gear grease or molybdenum disulphide sticks to everything it's particularly attracted to white coaches and that's why I'm not allowed to have it in the house but on closer inspection this is not that this is just a gray pasty kind of grease it might have some moly in there but you can see if you smear it it's got a it's really thin and it doesn't have much stick tivity to it and if you smear it on your finger it's almost like you can see little particles of the moly dull sulphide in the grease I could be wrong though so let's have a look in the microscope just gonna take a little smear of this and put it on a piece of puppy we'll have a look under the microscope and see what we can see okay so here's a little smear and super interesting you can see that there's actually it's not homo gene it's heterogeneous and there are particles of that gray material suspended in the grease and we can see here at the very edge of the smear yeah there's some tiny little particles of molybdenum disulphide but it's a real odd composition I've never seen anything like that before I think we can safely assume that it's been well engineered by Dewalt and they know exactly what they're doing it's just nothing I've seen before kind of interesting now having said that of course why is it that there is no grease on the gears what's happening so here's the pinion here consequently this is a spiral bevel gear set I'll show you that in a second but you can see there is no appreciable grease on the pinion itself and you can even see at the interface here where the mound of grease is sitting and the gear is going through the grease but it's not really sticking so I guess they're relying on the molybdenum disulphide particles to get crushed into the gear base itself now this is a very well made gear I would say it might even be a little bit better than the makita I remember the makita the hypoid saw anyway had some Chowdhury marks at the very edge but it could just be that this gear hasn't been used at all now let's have a look at the crown [Music] here's the top of the tooth on the crown and you can sort see there's no machining marks and it's rounded over nicely that's totally different than the makita which had very prevalent machining marks and then if we can see the root down into the root here if I can focus there we go that is a nice looking gear and you can see what looks to be those molybdenum disulphide particles now this gear face actually is pretty looking at it almost like it's been sandblasted so maybe yeah look at that so maybe that's why we don't see the machining marks on the top of the tooth because they've sandblasted them away okay so and there's the wear pattern there the initial wear in pattern of the crown against the pinion actually looking at it now this is a really rough gear surface I'm assuming that they're they're using the molybdenum disulphide to fill in all those voids and then it should polish up over time but it's actually not as nice of finish as the makita hypoid saw apples meet oranges but had to guess at this I would say this has been finished in a vibratory deburring media of some sort so at first glance it's good from far but far from good when you get up close it's all pitted I imagine that's no big deal a little we're in nicely I'm sure and it helps if you file with the right end of the file instead of the handle and that is a lot that's hardened and it's very hard it's a lot harder than the makita gear actually a lot harder the file basically the file doesn't even touch it that's pretty close to file hard there right so you can tell that this is a spiral bevel and not a hypoid because the pinion goes through the center line of the crown shaft so we have the three-quarter shaft which gets shouldered down to 12 millimeters holding on this crown gear and then it goes down to quarter inch which is six millimeters so really you got this tiny little shaft this is two and a half horsepower remember that according to the manufacturer and you got a six millimeter stub shaft here and a tiny little bearing now they need to do that in order to clear this they could redesign that so it's a little bigger but just at first glance it seems pretty anemic to me for for something you're holding in your hand that's rated for two and a half horsepower that's their rating mind you not mine I got the r2d2 helmet often I'm just going to take a second to in here myself against sticklers the difference between a greece containing molybdenum disulphide and molybdenum disulphide paste is a matter of semantics but at least in my experience paste has a much higher moly disulfide content like right around 80 plus percent whereas I think the grease has quite a bit less as you saw with the microscopic view they're just tiny little particles suspended and a really strange grease like it doesn't stick to anything with look at this pinion there's no grease on it it's very odd okay so here's the pinion it's a big pinion awesome and I also like look at this it's got a proper ole ring and then a dust seal there a white burr to keep the grinding crap oh that's awesome and if we look at this bearing behind there it's a shielded bearing so we got the double protection awesome we got the motor rotor out and here's the fan supercool it's metal incredible but then you look at it well that's not really gonna move even a tenth of the air is the squirrel cage which look at that Hey plastic underneath very very nice I'm impressed now this rotor they did a lot of work to this obviously a quality rotor check this out they potted down here by the commutator and they balanced the living out of this thing look at it they'll give us a cute it's still got the Chinese guy witness mark on here until the the Chinese handwriting I wasn't gonna take the pinyin off but I'm glad I did so we look at this here and there's a 6,200 bearing so that's makes this an eight-millimeter shaft and 30 millimeter OD but there's the pinion and there's no key so this is bizarre they're relying on the friction between the clapping of this little nut to clamp it hard enough so that it doesn't spin free on this shaft basically the torque is is going through the inner race and plot it up against this now this is interesting too it's got a labyrinth seal on there not only does it has a single lip seal it also has a labyrinth seal going on keep the grease out of the motor and the dust Oh interesting so yeah let me know what you think of that no keyway that's uh Wow yeah blows my mind that that even works that there's no key way here it boggles my mind it really does so I gotta take a second and do something that they don't teach you in school unless you're a pilot or a sailor we're gonna do some dead reckoning on this so this is an 8 millimeter shaft that means that's right around 4,000 pounds that it's clamping when it's properly torqued now this is cheese grade so we'll de-rate that we'll say it's 3000 pounds and that so remember that number 3000 pounds and the static coefficient of friction of steel on steel is 3/4 but will deer ate that so we'll go half remember that number half then because we're talking about torque we have to take the the centroid anyway so this shaft is eight millimeters that ID is 8 millimeters that boss is going to be 10 millimeters half of that is going to be 5 millimeters which is the radius 25 millimeters to the inch so that's five divided by 25 is point to remember that number 0.2 so now we're gonna go point two times three thousand times 1/2 so 1/2 of three thousand is 1,500 point two is three hundred so you need three hundred inch-pounds in order to get this to slip so three hundred divided by 12 is 25 so 25 foot-pounds oh god this thing's yeah this motor is running at 20,000 rpm it's a two and a half horsepower motor so we'll say two horsepower motor that will develop way less than say half a foot pound and we're talking about we need 25 foot-pounds to get this to slip so we're yeah we're a factor of over safety factor of over 25 so that's really incredible actually that anyone would put a key on that whatsoever there's no need to having a key so if you're lucky enough to still be in school arithmetic just simple simple arithmetic is a very powerful tool as long as you know what you're looking at so I dare say it rivals Google because we took three numbers all we needed to do is remember those three numbers and we figured out then we got more than enough wiggle room for not having a key way here look at this this is so weird this is the brush housing assembly here you take that whole cover off and you got access to all this stuff this is interesting there's a nice Skookum watch spring there and then you pull it oh oh wait you can get the motor up nice yeah nothing wrong with that brush nice big brush lots of wear but this is really odd instead of having the field windings wrapped around they got one of these little Spade connect on here so Elise I'm really surprised I wouldn't trust that because it's getting hot it's getting cold skating cause it's getting cold it's getting hot it's getting cold I don't know about that it's definitely not nearly as good as having round beefy brush holder with the broach rectangular key way and then the field winding goes around that yeah we just got a yeah I don't know oh not nearly as good I do like to see a nice heavy preload spring on these brushes now this is a big round watch spring and if you look at that that's a lot more material a lot more spring steel than in the makita so you're gonna prevent your brush from floating around like what I don't like though is the Spade connector that's totally chinzy we're getting into here now I'm just going to pull the handle off the field winding section and unfortunately instead of coming in through the back door like a like a Makita they go in with these big long ties screws I don't like long screws the longer they are the more up they are to bend however a plastic body I mean what's gonna give first right the plastic body is so no big deal but yeah secretin on the inside sorry I got ahead of myself I'm all tough to boat ain't you dead reckoning and I gotta live in the moment cuz I know some freshly minted engineer is gonna take me to task for making a mistake but be in the moment now where was I yeah we didn't have a look at the motor rotor so we get a little condom here for the back bearing and this is a little skateboard bearing yeah even smaller than a skateboard bearing it's a 607 RS and this I guess is some sort of in case it's not aligned or whatever I why can't they just put this in the plastic housing like the plastic housing isn't cheap enough they gotta add a little crappy buna and condom rubbish anyway other than that yeah the commutator bars very nice commutator bars Skookum so the magnet wire in this is a 20 gauge you'll recall in the high point saw which was 15 amps it was 18 gauge larger so this has a cross-sectional area I had to look this up 0.5 2 millimeters and we'll just say half a millimeter and we'll go 12 amps rated divided by half just the same thing as saying times 224 oh I'm off screen here 24 amps per millimeter which is not as good as the hypoid saw the makita hypoid saw a pulse again meat oranges but that was running at 18 amps per square millimeter so still not bad but the higher the average through that square millimeter of magnet wire the hotter the wires gonna get and the sooner that the insulation is going to fail now the crappy harbor freight tools that i've cut apart they're running at about 35 to 40 amps per millimeter squared so still half of what our crappy tool is and getting back to this potting this is interesting this is an epoxy resin that they'll put on there and that's great because I have seen like on the makitas the old grinders that I buy at auction some of them fail because it breaks the wire breaks right here so this this is a gonna be long term it's gonna be great to have this on there strengthening that wire bond I just picked this up and I noticed this actually isn't a fan it's a fan job because these tanks get indexed in the housing and then don't move and then this move so I was wrong on that one Mia culpa and this back bearing is sealed which is interesting because in all tools this background it's just shielded so they'll be grease in there and it's sealed up from dust the shielded there's grease in there but it's just shielded from ship flying out at big chunks not from dust and same thing with this one these are CW bearings based in Ningbo China I don't think these these small sized bearings you can even buy from Germany year like they just don't make them anywhere other than China bigger bearings of course they still do but so this is interesting here even though this bearing is sealed on both ends they still add a little hard plastic guard here to protect from the commutator brushes wearing and that carbon going into this housing now you would think that carbon lubricates quite well because it lubricates the commutator bars quite well so why would they not want that getting out or maybe it's a matter of not wanting something in although the graphite I know the graphite I use that I machine is very abrasive because it's got a clay matrix now maybe brushes are a little different compound but I'm sure they still have clay in them which would make them quite abrasive if somebody could spare a thought for that and maybe chime in with a little more expertise than I can muster I'd really appreciate that holy look at this this is something else sex on a stick EPOC seat field windings very nice spared no expense wow wow wow and we go from just incredible overkill on the field windings to gentleness on the brush housing you see the Milwaukee rather than Makita I am I get a mixed up different color the teal ones they have this big beefy round machine bronze brass and it's all the way around you know it's well ensconced in there now this is just it's just got one little bar down here that's been bonded to the plastic so what will happen it these get hot and they'll eventually loosen up that plastic can break off I yeah it's not nearly as Skookum as the makita style that's for sure plus I mean this is just and here of course we have same old crappy rear bearing housing same as every tools always plastic you just can't get away from it this is interesting how it's a gantry over top and it's not totally enclosed it seems pretty rigid to me let's see what temperature this plastic can can take we're gonna do a quick test of the thermal properties or the melting point of the case but commenter JK smith had commented and seemed legitimate he sounded like he knew what he was talking about because he didn't start his comment with i've got 30 years engineering experience in such and such in my experience when somebody starts a comment with their credentials there are goof so mr. Smith had a guest that it was PE plastic Pei plastic not the land of potatoes mind you poly ethyl mines something something but that it was glass fiber reinforced so I got a little sample that I've taken from the case we're gonna burn it and see if we could find some glass fibers been a long time since I've done how nice thank you God I'm not as dumb as it used to be well that is clearly glass we got the microscope on there and here we go glassy glass glass glass very cool well I do believe that brings us to teatime gentlemen and yes I do enjoy a good tea bag so I'm gonna do some research on that glass impregnated plastic and I'll give you gentlemen some respite I'm gonna end the video here and give you a teaser for the next video which finalizes the mechanical tear down and we get into the nuts and bolts of the electrical testing we're gonna come up with some very surprising results you will find interesting guaranteed now if I can keep your attention for a couple more seconds I have a humble request I enjoy doing these teardown reviews I haven't seen anybody else on the Internet do this you're never gonna find a slimy sales guy that's gonna take a tool apart and tell you what's wrong with it so if you like this kind of review I would really appreciate it if you would take the time to share it with your friends see what they think about it and I appreciate your comments your concerns if I made any mistakes dunderheaded lab senses and judgment what have you please share this video link is right down below thanks for watching keep your stick on the ice

Channel: AvE

Views: 1,600,835

Rating: 4.8851361 out of 5

Keywords: DeWalt (Business Operation), welding, chuck 2009, trade school, grinder, makita, milwaukee, woodworking, machining, electric motor, motorcycle, fabrication, what grinder is best, what is the best, which grinder to buy, metal, metalworking, Tool (Literature Subject), tool review, teardown, universal motor, power tool, power tool review, Review, Automobile (TV Genre), diy, repair, how to fix, How-to (Website Category), Do It Yourself (Hobby), Hobby (Interest)

Id: LWH5bfpivSU

Length: 27min 14sec (1634 seconds)

Published: Sun Jan 11 2015

Reddit Comments

[u/joshontheweb]

I just watched 60 minutes of this guy. What an interesting journey. Love it.

[u/suave_king]

This guy is amazing. Thank OP.

[u/deevil_knievel]

and he's on reddit! /u/superUnknown2

[u/Dif3r]

This guy is awesome basically the mechanical version of the guy who does EEVblog.

[u/dude142]

"Sex on a stick! Epoxied field windings!" Good old fashioned engineering porn.

[u/noslipcondition]

Wow this guy is good. Funny and he clearly knows his stuff.

Good find!

[u/THE_PUN_STOPS_HERE]

Skookum as fuck.

[u/Dif3r]

Where is that guy from? He uses BC slang (or at least slang I've only heard in the PNW) but has a weird accent almost like an Ontario accent or maybe he's from the interior?

[u/davidthefat]

Taking machine design right now; the keyless shaft on the surface seemed like a stupid idea. Turns out actually using numbers is a lot smarter while making judgement on design decisions.