Contact Wheels & Advice Please...

Ok, so I've jumped into it with both feet and have ordered a Polar Bear Forge "Grinder in a Box" today. This looks to be the most solid of the self made 2x72 grinders available.

Basically, I'm going to copy Brad's grinder...except for the color, sorry Brad...but THANK YOU for all of your input & advice.

I wanted to get an idea from you guys who have made some razors and used your grinders to make some suggestions on a couple things:

What two sizes of contact wheels?
I was thinking of a 3 or 4" and a 6 or 8"

Anyone got a spare they aren't using? Please PM me...

Where is the cheapest place to get them?

I'm on a budget and will more than likely "start" without a VFD and just go with a 1800rpm 2hp 220v set-up. Will probably use the guy mentioned on the PBF website for the motor unless someone points me into a better direction. I can/plan add the VFD later once the funds break loose a bit.

ANY experienced advice would be greatly appreciated.

Thanks in advance,
Scott

USA knifemakers Supply has poly tread wheels that are less expensive than the rubber ones. I have an 8 inch, and so far it seems to be fine. An 8 inch wheel will grind a 1/4 hollow. I have no experience with other sizes - I'll let someone with more time in grade comment on them. I do have a 2 inch rubber wheel at the top of my flat platten set up, so I can grind smaller radii when I have my flat platten set up on my KMG. I have a separate 1.5x1.5 bar for my 8 inch wheel.

I would watch Craigslist for a motor. 220v motors come up often, and for very cheap, since they are in lower demand. Check to see if there are any thrift shops dealing with construction items around your area -- I have one nearby that construction companies donate excess materials to when they finish jobs... They've always got electric motors in there for some reason...

I ordered my drive wheel and 8" contact wheel from Sunray.... and my tracking wheel and 4" contact wheel from USA knifemaker supply.. .but to be perfectly honest the wheels from usa knifemaker look absolutely identicle to sunray.. I cant see a difference. My sunrays run true as well...

Plenty of other places to get contact wheels though, shop around prices may have changed since I put my stuff together.. also I am not the best person to answer questions as I have limited experience thus far -- keep that in mind.

As for my paint color.... it was chosen by my son, so, in my eyes, it couldn't be better ;)

USA knifemaker has Sunray make their wheels they offer. Difference is that with USA knifemaker you can order it and it's mostly always in stock.
With Sunray it will take about 3 weeks to get your order and if you have them balance the wheel(s) you will pay nearly as much for the balancing as the contact wheel itself. As to what contact wheels. I would say 4" and 8" strike a good balance in your setup.

Max pretty much covered the wheels. I have three sunray wheels 4,6,8 two of them are great one wobbles a bit.

I know the grinder in a box is set up for a direct motor mount, but you could put a flange mount bearing and rig a pillow block and put a step pulley there and run the grinder with pulleys. ( just thinking out loud)

Charlie

Thanks you guys! One more question on RPM:

Just ordered 8" & 4" contact wheels, tracking wheel, and a few ceramic belts...2-40 grit & 2-80 grit.

What do you think in regards to the rpm using a 1800 rpm vs a 3450 rpm, 2hp, motor and a 4" drive wheel?

I had considered the step-pulley system, but really plan on a vfd. I've seen a few on the bay for a couple hundred and am sure there are other suppliers (something other than Chinese) in that price range.

There are no locations that I am aware of that I can pick up a used motor, so I'll more than likely go with a new one...shoot, the fuel to a place that I could pick up a used motor (Dallas is the closest that I can think of other than Sherman, TX) would make up the difference of a new one (my truck gets about 16 mpg & the bike only gets around 30). Then we have the most cherished thing...time. If I take the wife to either of the places, then we have to hit a steakhouse...so it's definitely cheaper to mail order...

I went to a local used sport and exercise equipment store, and the gave me, free of charge, a treadmill they were throwing in the dumpster. It has a 2 1/2 hp, variable speed, DC motor. I made it work on my KMG grinder. It looks a bit odd, because I had to use the treadmill control panel to get the variable speed, but - free variable speed motor. My step daughter jokingly wants to know which of the programs (climbing hills, running beaches, etc.) I use to grind a razor. Now what can I use the motorized incline jack for------?

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Originally Posted by shooter74743

Thanks you guys! One more question on RPM:

Just ordered 8" & 4" contact wheels, tracking wheel, and a few ceramic belts...2-40 grit & 2-80 grit.

What do you think in regards to the rpm using a 1800 rpm vs a 3450 rpm, 2hp, motor and a 4" drive wheel?

I had considered the step-pulley system, but really plan on a vfd. I've seen a few on the bay for a couple hundred and am sure there are other suppliers (something other than Chinese) in that price range.

There are no locations that I am aware of that I can pick up a used motor, so I'll more than likely go with a new one...shoot, the fuel to a place that I could pick up a used motor (Dallas is the closest that I can think of other than Sherman, TX) would make up the difference of a new one (my truck gets about 16 mpg & the bike only gets around 30). Then we have the most cherished thing...time. If I take the wife to either of the places, then we have to hit a steakhouse...so it's definitely cheaper to mail order...

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1800 or 3450 rpm?

I do not know what rpm motor, it depends on drive wheel and VFD, I tend to grind pre heat treat about 2700 fpm and post heat treat about 400 fpm.

Charlie

Thanks for the reply! I totally forgot the FPM math. I have a feeling that with a 4" drive wheel, the 1800 rpm would be closer...just couldn't post treat grind with it until I got the vfd or did some sort of pillow block system & pulley's. Do you feel that your system is fast enough?

It is fast enough for me. It takes me about 10-15 min to rough grind the blade part on a stock removal blade. I have used a few KMGs and KMG clones and some other home made grinders. I am a grinding oddity I like my little grinders they are what I am used to. I have a little different perspective on grinding than most other people.

Charlie

Oddity or not, your workmanship is out of this world! This is why your opinion is greatly appreciated. I need to look you up sometime...

Update...getting it all together, found a Baldor 2HP 3ph motor for $100 & its brand new. I stopped the train at an electric motor place that I have been wanting to stop at and it was a surplus motor that he had from buying out another shop. I just need a drive wheel, VFD, and some small stuff to have it ready to go...I think.

Do you have 3 phase service in your shop, or do you use a converter? Is the motor single speed or variable? Good find, in any case!

The Variable Frequency Drive will take single phase and convert it as well as slow down the 3450 rpm to wherever I want it...

Cool! I am using a variable speed, DC motor from a thread mill, and it has 10 speeds to choose from - much better that step-pulleys!

well im a bit late to this but
my KMG is
2hp 1750ish 4 inch drive wheel driven withought pullys powereed by a VFD

i have a 10 in ch rubber wheel that was used and a good price a 5 inch sunray form tracy and a 2 inch rubber for the top of my platten setup (thats way more useful then jsut for full hollow grinding )

i have a 3500RPM motor sitting but for me thats way fast so im going to build a new grinder and pully it down and runa truely big wheel

Your setup is a lot like mine. I love the idea of the contact wheel on the platen. I'll be getting one asap.

Phillip

+ to that - I've had a 2inch contact wheel at the top of my flat platten set up for several years - very handy in many applications!

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Originally Posted by skipnord

+ to that - I've had a 2inch contact wheel at the top of my flat platten set up for several years - very handy in many applications!

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Could you show of photo of yours please?

Here is my flat platten set up, with and without a belt.

Attachment 71373Attachment 71374

Here is a photo of my control panel. I would like to find an electric motor expert that could tell me how to replace it with a simple DC motor control - but it is good for laughs!
Attachment 71375

Hey man, it works...so why fix it?

Once I am up and running I will look into a 2" contact wheel for sure! Thanks for sharing...

Just ordered my 7/8" shaft, keyed & set screwed 2"w x 4" diameter contact wheel & a 2" x 2" contact wheel from Sunray (had to order both to meet the minimum order of $100) and my new VFD from Dealers: 2HP 230 Volt -- USE AS A PHASE CONVERTER PLUS GET VARIABLE SPEED, Model JNEV-202-H1, Single Phase Input ONLY, Three Phase Output, variable frequency drive, variable frequency drives, ac drive, vfd, afd, frequency drive, drive, inverter, adjustable sp

Now I just have to wait patiently for the wheel to be made (they say up to two weeks) and everything to come in...then wire it all. Should be making dust within 3-4 weeks...Yippeee!!!!!!!!

Thanks for all your help guys, especially you Brad, I truly appreciate it.

The drama is finailly over and I have to say I would have bought a grinder turnkey if I had known all of the "issues" I would run into. The first motor, the Baldor I bought new, was no good...so the electric motor repair shop says. I get another motor, still nothing. I break down and order a VFD directly from KMG and guess what...works. I've got a little more adjusting/tweaks & I'll be making sparks. Talk about a frustrating journey.

I know, no pics or it didn't happen. Give me a lil bit & I'll have some up...

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Originally Posted by shooter74743

The drama is finailly over and I have to say I would have bought a grinder turnkey if I had known all of the "issues" I would run into.

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Which is why I bought a turnkey grinder. 2011 till now is a long time to be building a grinder. :)

I allowed myself to get discouraged, then distracted. Shows you are the smarter one...

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Originally Posted by shooter74743

I allowed myself to get discouraged, then distracted. Shows you are the smarter one...

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Meh. Wouldn't say I am smarter. But I know myself pretty well, so I knew it would be better to pony up the 1800 euros for a full option grinder with VFD than to try and make one myself. :)

After I got frustrated, my "other" hobby compensated for me and I kept my focus on guns for a while. My goal was quality & not quantity & to get rid of some of the wildcat's I had. Everything, well for the most part, fits into just one safe now! Time to start making dust again...

I've got a few things to customize and finish on the grinder, but it runs true. I still need to make up a flat platen attachment to work on in-between the 3" & 4" wheels & some tool rests. I'm actually worried that it may be a bit slow as the motor is an 1800 motor. May get a larger drive wheel if need be, but it will go nice and slow for that work after HT.

I think the biggest thing when looking at speed is the power you have with the motor the 2hp ballpark is good, and with your 1800 rpm motor- the speed of the motor is irrelevant really as long as your getting the correct sfpm. I run around 1800 for just about everything. I have a 3650 rpm motor and with the step pulleys I get around 1800 sfpm at it's slowest setting and I never move it to go faster. But I would slow it down a bit at times if I could.

So IMO a slower RPM motor is the way to go, it gets you in a workable SFPM range much easier. I think you'll be happy with the speed.

You will see what speed you like best, but if you want higher speed for profiling and rough hollowing than you will have to use a very big drive wheel. Imo a 8" drive wheel is about right, that gives you a top speed of about 3500-4000 sfpm if you don't overclock your motor. That speed is about the most you would need, even for profiling. I wouldn't buy a faster motor for just 1-2000 sfpm more, it isn't really needed.

Here ya go, added the flat platen today. Have yet to start making sparks, but I think I am ready. I'm sure there will be some tweaks here and there, but that goes with everything that is made like this.

Attachment 140283
Attachment 140284

Really makes sense to use your contact wheels in your flat platen setup. Saves the cost of two aluminum wheels and mounting hardware, and no set up time between the three available ways to grind. I still have an AL wheel on the bottom, but have a 2 inch contact wheel on the top. Happy sparks!

I have the GIB too and I really like the 2 tooling arm slots. One thing you could add to your build that may help is a piece of ceramic glass on the surface of the flat platen. It helps keep the flat of your platen from wearing out.
Something like this

To mount it, I welded a very thin piece of mild steel to the bottom of the platen. The glass sits on top of this and is held on by epoxy. If the epoxy ever gives out, the little shelf will hold the glass in place.

If you grind a lot, you will appreciate the wear resistance of the fire glass.

+1 to the above. The glass is cheap, and the wear time is outstanding. Almost half a year of use, and not even a scratch on it, I don't think that thing wears at all :D