Harold and I corresponded via email and both felt the content would have been better posted here so:
----- Original Message -----
From: Marty Escarcega
To: 'Harold and Susan Vordos'
Sent: Sunday, January 28, 2007 4:21 PM
Subject: Grinder & Wheel
Harold, I was very intrigued by your article on building a dedicated grinder for tool bits. I went on a mission, and found a motor on eBay:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0084295596
I would like your opinion on this wheel:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0072550827
Or this one:
http://cgi.ebay.com/Norton-Grinding-Whe ... 0085526196
Or this one:
http://cgi.ebay.com/7-Norton-Surface-Gr ... 0077143892
Harold, if you use a 60 grit on one side what do you have mounted on the other? Diamond? Do you see any benefit to machining an adapter to fit the 4 hole flange of a typical carbide grinder plate wheel?
Thanks Harold, those treatises are very welcomed by all of us!
I checked the motor you bought-----and think you did real good! That's exactly the motor I'd be looking for if I was in the market. I use one that's similar, just a lot older. The bearings in mine are the lowest quality you can get and still have balls----they're a stamped affair that don't run a perfect circle, so that's always been a sore spot with me. It was fine for my father's application, driving some wood working equipment, just not adequate for my application. When I finally finish the house I'll dedicate enough time to it to install a better grade of bearing. That will require re-machining the end bells, but I know a machinist that can handle the job. <g>
I know you will understand adding a switch for reverse, and if you intend to grind diamond, you'll want to replace the original start stop with a double throw so you can use the pump only when you want to. My reverse switch is an addition, and is mounted at the rear of the motor. You can see it clearly in one of the photos I've included. Sorry about the dreadful conditions around the grinder, that's our storage area, and it's a mess. I can use the grinder, but the diamond side is not setup to be used------there's no coolant.
The first wheel, the "I" hardness, would be fine, but it's rather expensive. The 32A abrasive is good enough for the purpose, although the 38A is their most recommended. You may not see a difference in practice, especially if you didn't have one of each to make a comparison. If you're not in a hurry, keep watching ebay. I made some wheel purchases a couple of years back that were exceptional. Could be that won't happen now, I haven't been looking at ebay for a long time. I'll probably get back to it when the shop is running.
The second wheel would work, but it's approaching a wheel that can be too hard. It will grind hotter and slower, but otherwise is fine. The one serious negative is that you often use the corners of the wheel and must dress the balance to restore a sharp corner. Being ¾" wide, there's more wheel to dress, but that's not really a big deal, as you might imagine. A sharp corner can be important such as when you're grinding grooving tools, where you try to keep them as short as possible to keep their strength high. It's nearly impossible to do that with a radius on the wheel.
Don't let the width interfere with buying it if you're interested------it will be useful for finish grinding things like parting tools (assuming you choose to grind your own) or even deep boring bars like I showed with the original post. You can use the width to good advantage if you like your tools ground without multiple faces. I've always taken great pride in my ability to grind them that way. Just make sure that adapter you make will cover a broad range of widths. I screwed up on mine and made it expressly for ½" wheels. I'll probably make a new one that will accommodate wheels from 1/4" through 1"------and include wrench flats this time. It's a mistake to leave them out, which I didn't realize when I made mine those many, many years ago (1967).
I'll have to reserve judgment on the third wheel, although I'd be inclined to steer away from it myself, if for no other reason, it's way too wide for the way I grind tools. A ¾" wheel would be pushing it for me. I'm not familiar with the 48A abrasive----and would be somewhat concerned about the "G" grade (hardness) of the wheel. That may not be an issue with that particular abrasive, judging from what the listing said. Norton has formulated various types of aluminum oxide abrasives for particular functions----the ruby color being one of them. I'm just not experienced with that particular one----it wasn't out there when I was grinding. The amount he's asking for shipping is really a deal killer, but it may end up reasonable if few bid.
In answer to your question on the "other side", yes, I have a diamond wheel mounted. I made an adapter to accommodate a type D resinoid bonded wheel (do NOT buy a metallic bonded wheel). The wheel you're most likely to encounter will be 6" in diameter, 3/4" thick at the face, with either 1/16" or 1/8" depth of diamond, which is also 3/4" broad. The center of the wheel is recessed and mounts via 4 flat head screws. You'll see a good picture at the bottom. You use the side of the wheel, which is actually the grinding face. These wheels are like plate grinding wheels. I prefer a 220 grit wheel, which will move carbide quite rapidly, and leave a very nice surface finish. That's important for good tool performance. I never stone a carbide tool after grinding---it doesn't need it, and anything you do by hand will usually degrade the cutting edge. I use a table for all my carbide grinding. Carbide isn't nearly as forgiving of offhand grinding as HSS. One more thing. You must provide a coolant setup to run a diamond wheel. I made a large stainless pan that houses the table and directs the coolant back to the little sump that hangs beneath the grinder. I don't have any sketches, but you can design something with little effort. The table should be able to tilt through about ten degrees from a right angle down, and shouldn't move towards the wheel as it moves. It's important that you never grind towards the top of the cutting surface, so you must be able to reverse the motor to keep the wheel running down at all times, regardless of which side you choose to use.
The table on mine pivots in the wrong place, so the gap gets larger as I lower my table. It hasn't been a problem, but I'd like it if it didn't do that. I did what I had to do at the time. I was setting up my shop without having much to work with. The tilt part has no calibrations----I trust my eye. You get to know what you need and want. I've never regretted not having a tilt gauge, if that means anything to you.
I'll eventually post a last article with a RH tool, HSS, with a chip breaker. It will likely be short, for once you understand the concept, anything you say beyond that is redundant.