Most all knife grinders are copies of the basic KMG/Bader style. The differences are in the number of tool/work arm slots, metal thickness, bored vs threaded holes, accesories, etc.
To make something professional grade, the difference is mostly in durability. It is usually heavier built from heavier or higher quality materials. Professional tools are used for many hours a day, not a few days a month. They must be able to run for hours without issues. They need features like fine adjustment, and simple use.
On a grinder build the difference may be only a couple hundred dollars, but the difference in longevity may be many years.
1) Use heavy steel and weld everything that can be welded. The heavier the base plate the better.
2) Wherever possible, use a threaded hole, not a nut and bolt. Use grade 5 or grade 8 bolts.
3) Use good grade wheels and bearings. The money spent here on proper grinder wheels and bearings is money well spent. If skateboard wheels were sufficient, KMG and Bader would use them. The reason they don't is because they aren't sufficient. Same for cheap poly contact wheels. Also, use standard size holes for mounting. If the standard wheel mount shaft is 12-13, use that.
4) Build it for the future. Think about the next things you want to add. If you are planning on going VFD in the future, use a mount for the first motor that will be the same. Put at least two tooling arm slots. Put a mounting post for the VFD and put the ON/OFF switch there now.
5) Features like using an air spring (gas piston) for the idler tension is a really professional upgrade with almost no actual cost difference.
6) Use comfortable star knobs and/or ratchet levers for all adjustment places. These are cheap, and make the build very professional grade.
7) Use sufficient power for your growth. While a 1HP motor will work when you are brand new, 2HP is sometimes barely enough when a pro is hogging steel. If the 2HP is only $50 more, get it now.
8) VFD - using a 3Ph motor and a matching VFD is a good bit of money more, and may need to wait .... but if at all possible, do it in the beginning. The difference in the function and versatility of the grinder will be significant. A professional grinder is VFD in my opinion.
9) Make a half dozen tooling arms in the beginning, and fit them with various platens and wheels as needed. A professional setup will have arms with a flat platen, a large wheel ( 8-10"), a medium wheel 2-4"), and a small wheel fork ( 1/2 - 1"). Things like curved platens and platen chillers can come later, but these four are the work horses of a professional shop.
10) Buying materials that you can get the same thing later on is a good idea. While you may get a good deal on something from the scrap yard, if you can't get more of it later on, it may not be such a good deal.
