Question about grinder wheels

[Jason L]

I ordered some grinder wheels last week, very late night purchase, and they came in today. What had happened wuz, I was about to go to bed and I had been looking at grinder wheels for a couple weeks and, well, I ordered the wrong size. Daytime ordering from now on. I had a set pulled up but apparently I clicked on the one NEXT to the one I actually wanted. I realized it the next day but by then it was too late, they had already shipped. 

That led me down the rabbit hole of grinder wheels and looking at lots of grinder builds, I couldn't stop myself. So it turns out, the set I ordered came with four wheels, one drive wheel, one tracking wheel and two idler wheels. As luck would have it, the drive wheel and the tracking wheel are both crowned. After having gone through many pages of builds I noticed that several people were suggesting that only one or the other be crowned since they would cancel each other out. So my idea is to now order a non crowned drive wheel and see if someone else can use the crowned one that came in the set. The problem is that the shaft size is .94" so I don't know if anyone will want it. That said, it would probably cost me an arm and a leg to return the set, then I'd have to wait for the new set to arrive, and since all the other wheels are the correct size, I figured I would keep them and just replace the drive wheel. The wheel is 4" which brings me to my main query. What is a recommended size drive wheel? Shaft size seems to be standard 5/8" but it looks like people differ on drive wheel size. Also, is there an advantage or disadvantage with rubber coated drive wheels? 

My uses are going to be random, mostly smaller stock, 3/4" or less, just general purpose.  I haven't ordered the motor yet, still saving up for that. It'll probably be after Christmas before I pull the trigger on that. 

I know Frosty weighed in on a lot of the grinder builds and I'm thinking about just going back to the 4" non crowned wheel for the drive wheel but if someone has a better suggestion, I'm all ears.

[Frosty]

That's almost like asking how much water is enough. 

The general rule of thumb is the larger the drive wheel the faster the belt travels and the lower the torque. If the motor has enough power the only concern is belt speed. If on the other hand it isn't a particularly powerful motor the larger wheel will cause it to stall more easily if you apply pressure. What does the plans you followed recommend?

I suggest you run some numbers and look at belt speed and motor torque and choose your poison.

Opinions differ. well . . . DUH!  When have you known any two blacksmiths to have fewer than 5 opinions?

Frosty The Lucky.

[Jason L]

Gee Frosty, I was hoping you wouldn't ask about which plans I'm using, I'm not using any. I've spent a long time looking at every grinder build I can find and I've noticed that there doesn't seem to be two identical grinders anywhere in the world unless they were store bought. I can't work from plans very well and I certainly can't draw them, so I build it in my head over the course of a year or two then set to work on it. 

As far as what I'm going to need, it's not very much. I mostly hand sand everything. It lets me get out of my head and go on autopilot for a while. This is more something to occupy my time and at the end I'll have something to show for it. My plan is to use a 2hp motor with a bolt on faceplate but I might use what I've got for the moment and see if I like the idea. I'm leaning towards a 4" drive wheel but my bump it up to 5". I'm thinking that will do most everything I need unless there's something I haven't come across. 

You're right about many answers from few people Frosty. I guess that's why every grinder seems to be different from every other one. Having never seen a 2 x 72 grinder in person, I'm relying on pictures, videos and the few sparse measurements I could find to come up with something that I hope will suit my needs and I feel confident that I'll be able to do something. I've never not successfully done it yet

[Buzzkill]

If you are able to use a 2 hp motor at its full potential you should be able to use either a 4" or 5" drive wheel without any problems.   A lot of electric motors in the US have stated RPM ratings around either 1800 or 3600.   If you have a lower RPM motor you'll probably want to go with the larger drive wheel.

If you can fully utilize a 2hp motor, I believe that indicates you either have high amperage 110v circuits available to you or you will be using 220v.  If it's the latter and you can afford it, I highly recommend getting a VFD (variable frequency drive) which will allow you to use a 3 phase motor and adjust the speed of the motor to your liking for a given task.

[Frosty]

DRATS! I was hoping you had a set of plans I could check out. I made most of mine at a club grinder build clinic and some parts were just too eyeballed for me, I believe in measuring and marking even when I'm winging a build. 

I work from drawings whenever possible, even if they're "sketches" on graph paper, I LOVE graph paper and use it for almost everything. It really surprises most folk how much trouble shooting you can do on paper, I rarely have more than a little grinding to trouble shoot builds. However, Dad started teaching me to read blue prints about the time I was learning to read. And drafting when I was maybe 8-9. His philosophy being you can't get a decent job if you can't read prints. That should be enough clue as to what kind of jobs he had his entire life. "Butch, as long as I'm paying for your education you'll take drafting." So, I've taken drafting for at least 12 semesters and dang I've used the skill my whole life.

Soooo, when I got my clinic built belt grinder home I did some measuring, sketching, drawing, (using scale, triangle, compass, dividers, etc.) and cleaned up the build. It still has an uncomfortable level of slop but I tweaked the adjusters and it works well enough for my purposes. 

Were I to make another I'd build it on a plate of aluminum or steel to eliminate about 95% of the headache making a telescoping tubing frame precise and free enough to work well. There are a LOT of river boat builders in Alaska so finding 3/8" & 1/2", T1 (armor plate) aluminum plate drops for scrap prices is a matter of asking around the boat shops. I already have some 2" x 2" stainless angle iron so I wouldn't even need to weld it to a base plate.

BUT the one I have is more belt grinder than I need, not being a bladesmith guy so it'll probably leave my shot at my estate sale. 

I think Buzz's advice is sound, about what I'd do were I doing it again. Except the 3 phase part I avoid 3 phase. VFDs come in single phase or IIRC convert from 3 to 1 phase and vis versa if that's what you need. I was given a couple 3 phase motors that can just sit as far as I'm concerned.

Frosty The Lucky.

[Buzzkill]

Just so you know where I was coming from there -- When I bought my 2hp motor, the 3 phase versions were less than half the cost of single phase.  A VFD/3 phase motor setup also will "soft start" (at least mine does) rather than try to instantly be at max RPM.   I don't know enough about the different motors and VFD's to know if you can effectively do variable speed with single phase without sacrificing horsepower.    I do know that I like my grinder much better now with 3 phase 2hp and variable speed than I did at single phase 1 hp and step pulleys.

[Frosty]

Yeah, my limit with wiring is the occasional wall outlet and switch if I'm feeling bold and it's not connected to anything important. When I was looking I saw soft start VFDs for 1 & 3 phase up to a few thousand volts. No simple stuff for the electrically ignorant you know.

I'll take it to my favorite electrical outfit in Anchorage and have a plug and play built for me. I don't know about my motors though, I have a couple 3hp hot tub motors I'd like to use but not necessarily in the grinder, one of the 2hps will be more poser than I need. I'll have them checked out and maybe trade all but one if they still do trades.

I need to build my grinder a dedicated stand though, I need to dig out that notebook and get back to drawing it up. My plan was to use the slip stream caused by the belt with a little help from a built in squirrel cage to make an integral dust comp and put the filter (small shop vac) under the grinder.

The downside being when I start thinking of what I'd like I start thinking about how much easier it'd be to just build a whole new belt grinder. I could make it so much simpler, more precise, adjustable and compact with my band saw and drill press. Okay, I'd need my taps and hand tools. Seriously, enclose the belt with an access door to change belts and built in dust comp. Almost no dust and grit in the shop. I've already found a small motor I can modify into a magnet for catching steel grindings under the tool rest. Give it a pulse of AC and the dust will just drop off as the iron core is demagnetized.

I'm pretty sure this is why I've never really changed the one I have beyond good enough, I can't stop thinking of tweaks and once I think of one I start designing and integrating it. Integration is usually the toughest part of all.

Frosty The Lucky.

[Jason L]

Buzzkill, I've never used a variable sped grinder, I've always just adjusted the pressure and it's worked pretty well for me. Except of course if the right song pops up on my playlist, then I get a little aggressive. VFD's sound like a good idea but it seems a bit complicated for me. Like Frosty I am electrically challenged. After thinking about it a little more, 2 HP may be more than I really need. I don't have 220 available to me and I really don't want to mess with installing an outlet only to find out it would go better over there. Maybe a single pony is all I need. Not sure what I have but I doubt it's even that. Probably no more than half a horsepower. 

Frosty, I'm fascinated by people making CAD plans, blueprints or even drawing it out on paper. It drives me nuts that people can think in two dimensions well enough to draw out something that has a third dimension perspective. I've tried to do it and just can't. When I was young, my dad was lead electrician for the power company and he would bring home these huge schematics for substations and he would tell me he needed copies. I could draw those accurately enough but it was just straight lines and symbols. I had no idea what I was drawing, I was just copying what was already there. My electrical knowledge has not improved much. Like you, my experience lies in electrical outlets, maybe replacing a pigtail on an oven or refrigerator or something. Even then I don't do it enough to retain what I've learned so I have to look it up again every time I start to make sure I'm remembering it right. 

As for someone else's drawings, I always get in a hurry and miss a step. That's why I do it in my head over and over again. That way I can see most of the mistakes and correct them before I ever lay hands on it. It's always worked for me pretty well and I always use exactly the amount of materials that I did in my head. Ok, maybe slightly more, but not much. My biggest problem is the little stuff. I usually go to get screws or washers or something and for some reason I always get half of what I actually need, so I have to go back and get more. I've never been able to get past that hump, even when I make a list and take it with me. I can convince myself that I figured wrong. It never occurs to me that having extra isn't a bad thing. I think I try to have the precise amount so that I don't have to think about it while building, I just use them till they're gone and I know I'm done. My mind doesn't work quite right I guess. 

[Frosty]

1/2 hp isn't enough, I know. It makes no sense at all to build something that does a poor job at best when doing it right is as simple as a larger motor. Plus if you decide you don't want it after all a 2hp sander will sell where a 1/2hp one won't cover materials costs not counting the motor.

Drafting isn't about making a drawing that represents a 3D view. That is a "Rendering" and in all my years at a table I never made a rendering outside a classroom that is. Drafting is drawing each dimension individually in 3 views. Plan view, (straight down) Front elevation and side elevation. Elevations would be looking at the front or side standing on the ground.

3D rendering on a computer is not CAD. Renderings are for the marketing guys to sell a thing. Nobody building things, builds from a rendering they use blue prints. Three view prints if they're building a 3D object like a French Provincial Cottage.

Frosty The Lucky.

[Buzzkill]

If you go down to 1hp or lower with a 2 x 72 belt grinder you are going to have to sacrifice speed or you'll bog it down easily.  My original configuration was with a 1hp single phase motor and step pulleys opposite each other like you might see on a drill press for changing speeds.   On the fastest belt speed configuration I could easily stall the motor with only moderate pressure on the belt. 

I don't want to discourage you.  My belt grinder went through several upgrades to what it is now.   I used skateboard (longboard actually) wheels for the top and bottom of my flat platen and I made a drive wheel from 2x4's and Gorilla Glue on the first iteration. That drive wheel is now used on my DIY power hammer along with the same 1 hp motor originally used on my belt grinder.   It was definitely better than not having a belt grinder, but it didn't take long for me to want more.

 

[George N. M.]

I was recently was looking at getting a 2x72 grinder kit but the deal fell through.  I spoke to my cousin's husband who is an electric motor guy about what size motor I should get and he told me that about 1.5 hp is the largest I could do with 110 v service and 20 amp breakers.  Also he told me that what a VFD contoller does is maintain torque at lower speeds by adjusting the phase to the motor rather than adjusting the voltage.  I do not understand how that works but I will trust what the wizard tells me about his spells.

GNM

[Frosty]

VFD is actually pretty simple in principle. It changes the speed of the motor by limiting cycles in AC current. For example the motor turns 60 rpm on 60 cycle current, the standard in America. polarity (+ in one wire - in the other) alternates from + to - 60 times per second. So our hypothetical motor is spinning at 60rpm, you reduce the cycles to 50 and an AC motor MUST spin to match the cycles so the motor would turn 50 rpm. However the current carries the same voltage and amperage so the wattage remains the same. Wattage = torque. so your motor turns slower but with the same amount of power / torque.

Make sense or did I muddy it up? 

Frosty The Lucky.

[Jason L]

Well, that escalated quickly. I'm afraid most of that knowledge is above my paygrade. I'm actually not sure what sort of motors I have, they have no markings of any kind anymore. They are pretty old. The one I've been using is not very big but it's powerful enough that I don't stall it under normal circumstances, unless the belt slips. I'm not going to make that the permanent motor more than likely, I'm just going to use it to fine tune whatever contraption I end up with and see if I like using it. If everything goes ok, I'll upgrade the motor, and maybe a few other things that I haven't thought about just yet. Right now I'm going for proof of concept. I don't know that the motor doesn't have enough power to run a grinder, I'm just guessing on the power it has by the size of the motor and the fact that the shaft isn't 5/8". For reference, it's about as big around and half as long as the 3 hp motor that Harbor Freight sells. It drags when I first turn it on so I relieve tension until it warms up or spins up to speed or whatever it does. Usually less than ten seconds. Once it's running though, it keeps running. I think it'll do well enough to make sure I've lined everything up properly and got everything where it needs to be. I started working on it a week or so ago and so far all I've had time to do is cut two pieces of square tubing to length and use a couple of small cutoffs to test some measurements for a tracking mechanism. The measurements were good but my drilling was off. The holidays and work are killing my time on this thing but hopefully after next week it will calm down with the Christmas parties and shopping and all that other time eating stuff and I can do something. Out of curiosity, is there a way to ballpark the HP of a blank motor without special testing equipment or a fully functional brain?

[Buzzkill]

I don't know how to DIY test an old motor for hp, but if you had the RPM rating, the voltage, and the amperage draw, I *think* you could calculate it reasonably accurately.

One other thing to keep in mind on the motor:  You really want a Totally Enclosed Fan Cooled (TEFC) motor for this application.  If you use a motor with internal components open to the air, the abrasive and metal dust will most likely ruin your motor in short order.

[Frosty]

An inexpensive multi-meter will have a draw test setting and there are charts for loaded and unloaded draw/HP. The last one I bought had several sets of folding charts with it.

Frosty The Lucky.

[Steve Sells]

No need to calculate, NEC section 430 lists all motors and their voltages, amperage's and Hp ratings, look it up

[Buzzkill]

I'm not sure how that would help, Steve.  He mentioned that the motors he has have no markings of any kind on them any more.  My understanding of electric motors is limited though.  How could that be used to identify the hp of the motor?   What are the pertinent features to look at or measure?   I've got a few old motors myself that I'd like to check out.

[Jason L]

I'm not sure who made these motors but I'm guessing they are some sort of alien technology. They have sat outside in the weather for about 12 years just since I had them because I never thought I would use them. I didn't even know they worked till a couple of years ago. I have no idea where they were before I got them. I was going to throw them away originally because I didn't want them but the guy made me take them with the rest of the stuff. One has a 4 step pulley on it, which I only noticed today, I thought it was three up till now. It runs like a champ though even though it's old and has a nice coating of rust on the housing.  One of the others I did find a plate on. I thought it was blank but upon closer inspection it's just very badly faded. I can't read anything at all on it but I'll post a pic and maybe someone with better eyes can make something out. I've searched the others and can't find any identifying marks of any kind. One is considerably heavier than the others even though it's about the same size. The one I've been using  has a plate covering the wiring and it looks like someone lost the original plate and replaced it with sheet metal. It doesn't look like it came on it anyway. I have three total so I'll try them all and see how they perform. They might not work for a grinder but I'm sure I'll think of a use eventually. 

[Buzzkill]

I think I could make out that it's rated at 115v, Type S, and the manufacturer was Packard Electric Division then I could make out the word "Motors"  and of course Ohio.

Applying a little Google-fu, I came to the conclusion that the motor was made by General Motors in the Packard Electric Division, which is based in Warren, OH.

I can't tell if it's S 7033, S 7035, or S 7036 stamped in at the top.

I did find a 7035 OEM replacement motor on Grainger's site that is 1/2 hp, 1725 RPM, 115v and used in HVAC applications.  I don't know if it's a match or not though.

[Steve Sells]

a photo showing size will help cant tell it its 1/2 HP or 20 HP from that photo  lol

[Jason L]

It's a head scratcher all right. It's ok though. It works but I haven't put a load on that one so I have no idea if it's still factory strong. It has a three step pulley on it though so I might be able to scavenge that off of it, if it'll come off. My biggest concern with the pulleys is that the set screw is stripped or the shaft rusted and swelled to the point that they are effectively fused on. Won't stop me from trying. I've had them so long whatever I paid for the whole lot has long since paid for itself. I can't remember what it was but $20 seems to pop into my head for some reason. It'll be no loss to me if they get destroyed trying to take them off. They came with a setup that has a grinding wheel on one side and a wire wheel on the other with a single pulley so I might use it to power that. It also came it a large cylinder that has a shaft running through it with a drill chuck on one side and a cutoff wheel on the other. I have no idea what to do with that though. The chuck is rusted but still functions and I can't think of a reason to have a stationary cutoff wheel with no guard whatsoever. It seems like a bad idea to use that. Besides that I have no idea how to mount the cylinder to anything.

[Jason L]

I've read a lot about crowned wheels and the consensus seems to be only one wheel needs to be crowned. I read the article on tracking and it seems the drive wheel is the preferred crowned wheel. I've looked at as many places to buy wheels as I can find and it seems the drive wheels and tracking wheels they sell are both crowned. Obviously I can just buy a regular wheel that isn't crowned and attach it to a tracking mechanism, but why do they sell them like that in the first place if it's not ideal? I trust the people here because they take the time to explain the reasoning behind something in a way that makes sense, so I'm going to replace the crowned tracking wheel with a non crowned wheel. Does anyone know why wheel sets come with two crowned wheels when only one is necessary? I feel like it's the classic 10 hot dogs/8 buns scenario.