Ed has done a VERY good write up on choice of 2X72 grinders. I agree with 99% of what he says, and don't really take issue with the other 1%, especially for a full time knifemaker where time is money. When Ed speaks (writes) I pay attention because I know he's got the experience and knowledge I can always learn from. Ed has always been so good about sharing knowledge with us mere mortals.
Ed's statement about
*** DO NOT TRUST AND INTERNET SEARCH WHEN SEEKING ADVICE ON A GRINDERS!****
can't be emphasized too much.
I think Ed tends to come from a commercial view point where time is money. I tend to come from a hobbyist view where I've got more time than money, and I enjoy making tools and attachments almost as much as using them. The views I offer below are a reflection of my hobbyist viewpoint..... AND my enjoyment of "tinkering"
#1, "IF" a "dabbling" hobbyist is wanting a grinder, then they need a quality grinder. I tend to think the minimum basic grinder is a VFD with direct mounted 3 ph motor with a tracking setup like either the TW-90, Reeder, or KMG-TX grinders. Each of those use a bit different method and each of the 3 methods work good.
I've built 3 (4?) grinders and it's just not that hard to build a really NICE grinder that will run smooth. I tend to think anybody that can make a nice looking knife has the skill to build a nice grinder that will run smooth. BUT - I do have to remember I've been working with tools all my life and it's second nature for me to grab a tool for repair or fabrication. I've also got the shop equip to work with, lathe, milling machine, 4 drill presses ranging from a micro size for drilling with .020" drill bits to a big 2 hp floor mounted drill press. I LOVE tools
Here's a photo of my 2nd grinder running at 4,000 SFPM with a nickel balanced on edge showing how smooth it runs.
#5 - a grinder doesn't have to be heavy like a tank to be smooth (see nickel above). I personally prefer aluminum for grinder builds. I do use steel helicoils for threaded adjusting holes so the aluminum doesn't wear out. If a grinder is going to be bolted down to a bench and never moved, weight doesn't matter. My grinders are moved in and out from time to time and less weight helps in moving.
#6, Ed correct on tool arm size - 1-1/2" for sure. While there are a few grinders that use 1-1/4" tooling arms, if the idea is to purchase commercial equip, by far the industry standard is 1-1/2" size. I like aluminum tool arms, they're not so heavy and are easy to handle. BUT - remember I'm speaking from a hobbyist viewpoint. Ed's equip gets used more in a week than my stuff does in months of use.
#8 - can't agree more, a VFD with 3 ph direct drive motor only for a 2X72 grinder. My first grinder was a 3 step pulley setup and I thought it was just fine. Didn't need anything else (I thought). I finally built a direct drive with VFD and there was no comparison. While the KBAC VFD is for sure the best VFD around, for almost $400 I'll pass and use the $75 NEMA 1 enclosure Chinese VFDs. Again, for a full time maker who MUST have equip working all the time, perhaps the KBAC makes sense. I get around 5 or 6 yrs from each Chinese VFD, and that was before I started putting filters over the cooling air inlets, now I expect they should last longer.
The Chinese VFDs I've used are easy to program, and I really like the LED display that can show the belt SFPM.