What’s the difference? (Grinding)

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What are the benefits and downfalls when choosing between a 4” and 4-1/2” angle grinder?
Reply:Design-wise, I don't know....but, you can put a 4" wheel on a 4.5" grinder with the safety guard on, but not vice versa...at least with mine.Smithboy...if it ain't broke, you ain't tryin'.
Reply:4" wheels typically have a 1/2" arbor, I think.  It's been a long time since I used one.  I've never seen one used on a 4-1/2" grinder, but that doesn't mean it can't/doesn't happen.4-1/2" wheels typically have a 7/8" arbor, designed to work with a spacer around a 5/8" threaded shaft.  Some (same with the 4") have the threaded nut built-in to the grinding wheel.  I've used lots of different makes/models of this size, and even they vary in how the blade goes on.
Reply:I think you'll find more variety of blades in the 4-1/2" these days.  You'll get higher surface speed on a new 4-1/2" blade until it wears down to 4", assuming the grinders are the same RPM.  Blade life is significantly longer and the blades cost about the same.
Reply:Tractor supply sells a pack of 4" unthreaded wheels that fits the 4.5" grinder's arbor and HF also sell an arbor adaptor for the smaller arbor (little screw-on sleve) that lets a 4" grinder have the arbor of 4.5".  I have a dewalt 4.5 and an off brand 4 (I have no idea who made it) that I use these tractor supply wheels on.  I just never take off the arbor adapter...I totally forgot the arbors were different, but you are right...they are.Smithboy...if it ain't broke, you ain't tryin'.
Reply:Hmm, I don't think the arbors are any different between my 4" and 4 1/2" angle grinder. I use the same wheels for both. I'll have to check that one out. I did have to change my guard a bit on the 4" grinder to accept the larger wheels. It is now re-inforced and can now accept 4 1/2" wheels.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:All right...now y'all have me doubting my memory.  I thought I was right, then I thought I was wrong... That means I gonna have to spend some time in the shop tonight playing with power tools...for educational purposes, of course.  You'll hear from my wife about this...Smithboy...if it ain't broke, you ain't tryin'.
Reply:smitty'  SMITTY'  ---TIME TO COME IN  you said you'll do smithboy  we all feel your pain---jk
Reply:Smithboy , you are NOT wrong. SOME 4inch wheels only use a 3/8ths  inch arbor. I know . that's why i used to buy only Makita or Black&Decker  4 inch grinders , cause  I had a whole bunch of 4 inch cutting wheels (1/16th inch thick, 4in.Dia. W/  3/8ths hole in them . the 3/8ths is same wheels that a good air powered angle grinder uses .( like the  "ARO" brand . used to cost maybe $450-$550)Last edited by Roy Hodges; 06-06-2006 at 06:31 PM.
Reply:There is a general rule of thumb that with each step up in wheel size there is also a step up in power and also body size naturally. While that may not be true for every make and model I think you'll find that it is true more often than not. The 4"ers are pretty handy for quick light work one handed. They tend to bogg down with two hands bearing down hard for aggressive removal. The 4 1/2" inch ones can be used two handed and hold up fairly well power wise without boggin too bad, and can still be used for a one handed operation without wearing you down too much. By the time you get to the 5" ones the one handed operation is very limited but the power and increased wheel size allows you to bear down and get with it pretty good.  Take a ponder at the bulk of your work and kind of go from there. I run one 5" and two 4 1/2's. Untill I get a little whimpier the 4 1/2's are as small as I need to go for one handed work plus there is not need to switch to a bigger one if you need to lean into iy for a minute or two. I've also got a couple of air angle grinders I keep rigged up for tight spots and light work.All three grinders have the same arbor sizes (adapters) and same shaft size, so it makes inventory easy. Every wire cup, grinding wheel, cutting blade, flap disc can be moved from the 5" to the 4 1/2 when it wears down a bit.
Reply:OK...Chalk this one up to the CRS disease.  My dewalt uses 5/8 - 11...My off brand uses (I think) a 3/8 inch spindle size with an aluminum screw-on adapter to make it a 5/8 - 11...but, I think the point is kinda moot, because I just looked to see how many 4 inch grinders have the 3/8 spindle size now, and it's dern few outside pnumatic ones.  There are a few that claim to have a 1/2 inch spindle (probably with 3/8 threads), but these are few and far between.  Even the 10 dollar HF 4 inch grinders now have the same spindle size as the 4.5 inch.  I guess manufacturers decided (after I got my first 4 inch grinder) to standardize to the 5/8-11.  Even the 7-9 inch grinders use this thread size, as best as I can tell.Last edited by smithboy; 06-07-2006 at 10:48 AM.Smithboy...if it ain't broke, you ain't tryin'.