A grinder for HSS toolbits

This is where bits of wisdom will be stored, a frequently asked question section with answers.

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SteveM
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Post by SteveM » Mon Jan 29, 2007 12:25 pm

Harold_V wrote:I pencil sketched cross sections of the pieces a couple weeks ago for our very own SteveM, so I've copied the sketches, below. They're poorly done, chopped out in haste, buy convey the message.
And thanks very much.

Some of the best "poorly done, chopped out in haste" I've seen.

Just picked up a foot of 3" CRS at the local steel distributor (they have a pile of srcaps in the corner you can pick through - cost me $20). ucked out and they had a peice 12" long (I could have bought less, but it would have cost MORE with the cutting charge). I'll be starting on this project after the backplate for the dedicated soft jaw chuck.

Can you give us novices an idea of the steps to machine this? I can see that you want the bore for the motor shaft and the OD for the grinding wheel to be dead nuts concentric, but between boring it on one side and threading it on the other, I'm not sure what the sequence would be.

Steve

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Marty_Escarcega
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Post by Marty_Escarcega » Tue Jan 30, 2007 8:32 pm

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!
Marty

HAROLD REPLIES:

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.


Harold
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Another Pic of Harold's Grinder
Grinder1.jpg
Picture of Harold's Grinder
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Marty_Escarcega
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Post by Marty_Escarcega » Tue Jan 30, 2007 8:35 pm

Marty writes:
>What model wheel do you use then? I used to have Norton's Grinding >book but I think its still packed away with some of my books >yet.....another project, a bookshelf!

Harold follows up:
I use a ½" wide wheel, which allows for grinding (relatively) short boring tools. As the wheel gets wider, it forces you to grind a wider and wider relief area behind the cutting edge, or, said another way, the shortest tool you'll be able to grind will be a function of the wheel width. It's nice to be able to grind them short, especially if you use small tools, say 3/8" or less. That keeps the tool rigid and chatter at a minimum. You can get around that problem by using the corner of the wheel to grind the relief, but that leaves a tool that looks like it's been chewed out by a gopher. I don't like my tools to look like that. Sort of detracts from the level of accomplishment I've achieved in my trade. If I was to suggest a "perfect" wheel, it would be almost identical to the one on ebay: 7" x½" x1¼" 38A60H8VBE, Substituting an I for the H would be very acceptable. Fact is, until I mounted the H I'm running now, I'd always used an I. Found I liked the H a little better, although it's quick to break down. Keeps the wheel cutting really fast, though, so roughing a tool goes very well.

As far as specifications go, the first wheel was pretty good, although dropping to an H wouldn't hurt. Certainly not necessary. There's nothing wrong with the 32A abrasive, so aside from the price they were asking, it wasn't a bad deal.
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Post by Flybynight » Wed Jan 31, 2007 10:33 am

Sad to say that might not be a bad price.
I had to buy a cup wheel last fall for a piece of equipment.
Paid about $20 3 years ago.
Was list this year for $65.
Found another one for $45 llisted, when I ordered the price was $52.
Check around before dismissing that one.
Jim

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Harold's adapter/flange - steel or aluminum?

Post by rohamm » Sat Jul 28, 2007 8:12 pm

I've got some 1hp 3ph motors and some VFDs sitting around. I'm thinking, instead of buying an 8" grinder so I can use the 7" surface grinder wheels that offer all the good choices, maybe I should set up several of these motors as suggested by Harold_V.

I've checked out ebay and the online metal suppliers, and 2 3/4" rounds are out there pretty reasonable in 6061 aluminum as well as a36, 1018, 1045 and 12l14 steel. Which to choose?

Another option may be grey iron - not ductile - from the local foundry.

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Re: Harold's adapter/flange - steel or aluminum?

Post by Harold_V » Sat Jul 28, 2007 11:51 pm

rohamm wrote:I've got some 1hp 3ph motors and some VFDs sitting around. I'm thinking, instead of buying an 8" grinder so I can use the 7" surface grinder wheels that offer all the good choices, maybe I should set up several of these motors as suggested by Harold_V.
That's an excellent idea, assuming you insure that the wheel can't be run beyond acceptable limits. If you can't do that, it might lead to your early demise. Fact is, as the wheel wears down, having the ability to increase the speed to keep it running near optimum speed is very desirable

If the settings can be referenced, it would be a good idea to have wheel sizes noted so you can dial the correct speed for the wheel at hand (usually by diameter).
I've checked out ebay and the online metal suppliers, and 2 3/4" rounds are out there pretty reasonable in 6061 aluminum as well as a36, 1018, 1045 and 12l14 steel. Which to choose?
Given a choice, there's nothing wrong with using 12L14 for the adapters. It's nice to machine and should minimize the chance of the nut galling. I would avoid aluminum. There's too much at stake.

Best choice, if you discount the ease of machining, would be the 1045. 1018 isn't fun to machine, although it's perfectly fine for the application.
Another option may be grey iron - not ductile - from the local foundry.
You may have that confused. I wouldn't trust gray iron, but ductile, if you were assured that's what you got, might not be a bad choice. It has the potential to rival steel in tensile. No way in hell would I trust cast iron because of the risk of breaking at the motor shaft. Talk about things getting ugly! :lol:

Harold

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Post by rohamm » Sun Jul 29, 2007 8:29 pm

I wouldn't trust gray iron
I figured. Just thought it would be mighty satisfying to shop at the local foundry instead of ebay. They need the business a whole lot more, as you can likely imagine.

The specialty metals outfit a couple towns away likely has 12l14 bar in 2 3/4", maybe even in the off-cut bin, but is it really necessary to turn that much steel into chips? Could I get away with starting out with a smaller shaft and using two washers?

Also, my motors are single ended. They're from large - I mean *really* large - computer disk drives, so I expect they're pretty high quality, and I've got quite a lot of bearings and aluminum plate kicking around.

Should I think about making a double-ended arbor setup driven by v-belt? Making several of these would allow mounting a larger variety of wheels, like dish wheels.

And I promise to use most of them without rests!

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Post by Harold_V » Mon Jul 30, 2007 12:04 am

rohamm wrote:
I wouldn't trust gray iron
I figured. Just thought it would be mighty satisfying to shop at the local foundry instead of ebay. They need the business a whole lot more, as you can likely imagine.
That's mighty noble of you! :wink:

If they're involved in casting iron, and are not using a cupola, I can't imagine they aren't involved in ductile, which is slowly capturing the lion's share of iron work as it's qualities are better understood, with the cost reasonable. Check with them----you might be pleasantly surprised. If you don't know, crankshafts in GM engines are made of ductile iron. It's damned good material when properly formulated and cast.
is it really necessary to turn that much steel into chips? Could I get away with starting out with a smaller shaft and using two washers?
Sure----that would work. I just like the idea of having a fixed flange, insuring that the wheel always runs in a proper attitude.

Regards turning all the material to chips-----I don't give that a thought. It just goes with the territory, and isn't a big deal if you have a reasonably sized machine. I could rough that part in something like three minutes, using negative rake carbide insert tooling. Requires a decent machine and a knowledge of moving stock. It's likely a daunting task for a guy with a small machine.

I assume you're tossing the word "washer" around loosely.

How you mount a wheel should not be taken lightly, not when you spool it up to recommended speeds, and put it to serious work as you stand in line with it. The "washer" (flange) is all important in assuring that the wheel has pressure applied at the proper place, and is evenly distributed such that the wheel is well supported without the risk of cracking. Don't make the mistake of using flimsy washer for this purpose. If they are too thin, you risk splitting the wheel by applying pressure from the inside (a real problem for ham handed people that don't have a clue about what tight means).
Also, my motors are single ended. They're from large - I mean *really* large - computer disk drives, so I expect they're pretty high quality, and I've got quite a lot of bearings and aluminum plate kicking around.

Should I think about making a double-ended arbor setup driven by v-belt? Making several of these would allow mounting a larger variety of wheels, like dish wheels.
Considering you have a generouls supply of motors, I see nothing wrong with using them individually, assuming space is not a problem. All depends on your objective, really. One advantage to a belt driven system is that you can build it such that you can change speeds if necessary. That calls for good sense, so you don't over speed large wheels, but it makes a wheel enjoy a much longer useful life if you can speed it up a little as it wears down.
And I promise to use most of them without rests!
At least the one(s) used for grinding HSS toolbits. To be fair, there are times when I need a rest on my grinder. Not having one has insured that I keep my skills up to speed. You'd be amazed at the degree of precision you can accomplish by using the running wheel as your guide.

Luck with the grinder(s). Keep us posted on your progress.

Harold

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Progress? What's that?

Post by rohamm » Mon Jul 30, 2007 9:40 pm

Keep us posted on your progress.


More questions than progress.

Big one is how to make the surfaces of the flanges parallel.

If one flange was machined as part of the adapter, I'd only have to worry about the flatness of the loose one. That would be problem enough, but I'm doubling it by having two loose flanges.

How do you hold the darned things to machine both sides? Do I need a mandrel?

I realize this is real basic machining, but that's why I come here.

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Post by Harold_V » Mon Jul 30, 2007 9:47 pm

Soft jaws. I can't emphasize that enough. Soft jaws solve almost all holding problems when operating a lathe. They can be effective even with irregular shaped parts, depending on how much trouble you're willing to go through to create the proper holding cavity. Simple round bores are a snap, and insure that your part (flange) is concentric and parallel when finished.

Pay attention to sizes, insuring that the flange grips on the outer portion of the face, only, and is well relieved otherwise. Each side should be machined completely (after roughing) without removing it from the chuck. The exception would be if you're using soft jaws, at which time you can take parts out at will and not have problems with concentricity and perpendicularity.

Are you familiar with soft jaws?

Harold

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Post by BadDog » Mon Jul 30, 2007 9:47 pm

Several possibilities come to mind.

1) Standard chuck. If there is a feature (like a hub), hold the OD and turn one side plus the hub. Flip and hold hub while you turn the other side.

2) If no feature and too thin. Use bored/faced pocket in soft jaws of chuck or e-collet. E-Collet (pot chuck, etc.) probably best for production. Face/turn one side and part off. Flip and set in pocket (jaws/chuck/etc.) to face/turn second side.

3) Least desirable (I think), use a mandrel. But that generally means very light cuts and may flex/move if not careful. A step mandrel with clamp/nut might help eliminate that, but probably requires 2 ops.
Russ
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Post by BadDog » Mon Jul 30, 2007 9:48 pm

Harold beat me by a few seconds. :D
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