A grinder with guts!

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awake

A grinder with guts!

Post by awake »

Hmm -- somehow my first attempt to post this didn't work. So I'll try again:

I have finally gotten around to building a grinder to replace the awful, underpowered import bench grinder that I have used for too long. I took advantage of Harold's advice on a few points. :)

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As you can see, this is powered by an old washing machine motor -- 1/2 hp, 1750 rpm. The drive pulley (stock die-cast pulley that I had on hand) is twice the size of the driven pulley (had to make that one!) to get to 3500 rpm. I was concerned about whether it would have enough power -- the answer is yes! yes! yes!

Following Harold's advice, I set the grinder up to take 7" x 1/2" x 1-1/4" wheels. I also made the post such that the grinder is mounted at chest height.

The difference in grinding with this setup versus the old sad wimpy grinder is incredible. Grinding has gone from long and painful to quick and easy and even fun!

Many, many thanks to Harold for the wisdom he has shared!

Andy
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Harold_V
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Post by Harold_V »

Hey, Andy! Well done. Very clever use of wood, too.

I'm pleased to have been a small part of your new grinder. I hope it serves you well. Once you're used to not having a rest, it will be hard to go back to one.

Harold
Lew Hartswick
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Post by Lew Hartswick »

My only comment is with a big smiley:
Are you sure this is a metal working shop? :-)
...lew...
Richard_W
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Post by Richard_W »

Isn't a washing machine motor a 2 speed motor? A slow speed for washing and a high speed for spin cycle.

Richard W.
Peter.
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Post by Peter. »

Looks cool.

Make sure you cover the top of that motor to stop it from filling with grinding dust over time.
Black_Moons
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Location: Canada, Bc

Post by Black_Moons »

Very nice, though im a tiny bit worryed about that top plate of plywood.. I can't really come up with a reason why.. but I guess in 10~20 years that wood might rot or warp or decay.. and any chance of those 2 wheels and there bearing blocks escapeing would be.. very bad. Id probley use a plate of 3/16" steel or something.

Other then that I love it, the little tool box below is great. I love the 'through the table' belt mount. And the cute little box bearing guard to make it look all beefy like a normal grinder. (But still recessed so you can use the inside of your wheels if you need them)

Any plans for tool rests? or just leaveing it open?

Hows the vibration? Iv allways wondered if lighter 7 or 8" grinders can 'work' if you just got good enough wheels for them so they started off balanced. (All stock grinders with stock wheels iv tryed walk across tables to say the least)
[url]www.Cyberlazy.com[/url]
awake

Post by awake »

Thanks to all for the affirming responses!

To respond to some of the questions/comments:

Richard, most of the washing machine motors I have scavenged have indeed been two speed, and I do have one rare three speed motor as well. I don't recall the washer from which I scavenged this one -- it has been many years ago! -- but it must have been a very simple one. It is definitely one speed, and one speed only. :)

Peter, if you notice in the first picture, the motor is indeed covered. When I made all the guards, I also made removable plywood coverings (baffles) for the motor -- leaving it open on the bottom, and with plenty of room for air to circulate. So far it seems to be happy -- not running hot.

Many of you commented on the wood -- I do both wood working and metal working. Sometimes I find that I am so fixed on one material that I overlook how much easier it would be to complete a project in the other material. This was one example -- one reason I had put this off for so long was that cutting the steel plate to make it was going to be rather tedious. (Yes! I need a plasma cutter. Please tell my wife! :) ) When it occurred to me to use wood for some parts of the project, I was thinking it might be more in the way of a prototype ... but now that I see how well it is working, I'm thinking it might stay this way for a long time. :)

Vibration is minimal, once I dressed the wheels. It actually increased after I had unmounted the wheels and remounted the wheels in the process of putting the guards on. The "regular" wheel to the left (which may not stay on very long!) has an oversized central hole. After I fiddled with it, it is back to a relatively balanced condition.

Definitely no tool rests. I haven't used tool rests for years, since the ones on the wimpy import were so cheesy. However, not using tool rests on a sadly underpowered bench grinder mounted on a bench (surprise!) using the wrong kind of dresser was quite a different experience from not using tool rests on this grinder with properly dressed wheels!!

By the way, in case any are still doubting that this is ALSO a metal working shop -- check out the home-made wheel guards. :)

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Andy
Willy B
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Post by Willy B »

Andy, I think the use of plywood for the base is a good example of using a material where extreme strength is not critical and will soak up vibration. As they say across the Pond. "Good show!"

I do have one comment. I have seen several "old timer" belt driven grinders. They all had considerable rotating mass on the driven shaft. If, as you use your new tool, you discover some rather subtle deficiency, consider the effect that 10 pounds of rotating iron might have. Just don't think they put it there because they could.

Bill
SteveM
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Post by SteveM »

Andy,

Nice job on the wheel guards!

What material? Steel or aluminum? Thickness?

Are they welded or soldered?

Steve
websterz

Post by websterz »

Oh great...ANOTHER thing I have to build now. :roll:

Just kidding...that grinder looks great!! I too have a wimpy little import bench grinder and, as luck would have it, a spare 1/2 hp washing machine motor. I see a new project coming in the next couple of weeks!
gmann109
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Nice Work!

Post by gmann109 »

That's a very nice job on your grinder. I prefer home-brewed machines like that. The best part is, if it ever breaks, you'll know how to fix it. LOL


Keep up the good work!
Last edited by gmann109 on Sun Apr 19, 2009 2:16 am, edited 1 time in total.
awake

Post by awake »

SteveM wrote:Andy,

Nice job on the wheel guards!

What material? Steel or aluminum? Thickness?

Are they welded or soldered?

Steve
Steve, the wheel guards are made of 1/8" thick mild steel. The end caps began life as rough squares cut from some sheets that I had on hand -- a relatively easy cut, since the sheets were already a suitable width. I put a couple of sheets together and let the vertical band saw do its thing ... it couldn't quite get all the way through, but I just flipped the sheets over and let it finish it off.

Once I had squares, I marked and punched the middle and scribed in a circle (just to know approximately where it would be); that let me know where to drill some holes to use to screw it to a piece of plywood that I had attached to my faceplate. Once on the face plate, I trepanned out three circles: first the inner circle, 2" diameter, to clear the end of the shaft; then a circle at around 7.375" diameter, but only about .050" deep, and then the final circle to cut the outside. The .050" recess captures the edge of the middle piece.

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For the middle, I happened to have some strips on hand already the right width. I bent these around a wooden form -- just a couple of pieces of plywood screwed together and cut into a circle of slightly smaller diameter. It took a little fine tuning to get it to fit into the recess, but not too bad.

I welded the middle to the inner guard "face"; in one of the pictures above, you can see where I had tacked it on the inside, and that I ground these tacks down. Once it was tacked together, I welded it in four places, each about 1" long, around the outside -- I didn't do a continuous weld, not only because it didn't need it, but much more because a continuous weld would surely have led to major warping. If you back up to my previous post, you can see some of the outside welding in one of the pictures.

Before welding, though, I marked each circle for the screws that hold the outer faceplate to the rest of the assembly -- five evenly spaced holes. I drilled and tapped the inner faceplate for 8-32 (mostly because that's what I had on hand in the right length), and drilled the outer faceplate slightly oversized to make it easier to assemble. Of course, another option would have been to drill clearance holes on both sides, and use a nut with each screw.

Thanks, all -- I appreciate the interest!
Last edited by awake on Sat Apr 18, 2009 10:46 pm, edited 1 time in total.
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