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8" 1HP 1725 Grinders?

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I'm using the Rikon 1HP and like it a lot. I heard a week or so ago that Woodwerks over in Columbus, OH has a few of the discontinued Steel City grinders available that are very well reviewed.
 

Bill Boehme

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I have an old Delta 23-275 grinder that was discontinued probably about ten years ago. It is ¾ HP and more than enough power. I would say that any grinder that puts out an honest ¾ HP is more than enough power for the heaviest of steel CBN wheels. Some other members in my club have the same model grinder with CBN wheels and they work just fine. Another member had a different brand ¾ HP grinder (don't recall the name) with CBN wheels and it worked just fine as well. Even a real ½ HP grinder should be just fine ... just a bit slower starting up, but once up to speed sharpening or grinding turning tools, even heavy grinding take very little power. Even if you put some muscle into it the way that Doug Thompson does you're not putting much load on the grinder.

Start-up is the only real heavy load because the initial current surge is equal to the LRC (locked rotor current, i.e., the current when the rotor isn't turning). The LRC can be as great as six times the FLC (full load current). As soon as the rotor begins to turn, the current drops rapidly and at about 75% of full speed centrifugal switch opens the start winding and the motor acceleration decreases as current drops from FLC to no-load current which is typically about 25% of FLC. A motor with no external load will usually reach 75% of operating speed in less than a half second. Steel CBN wheels have a high moment of inertia, but according to Leeson data, things should be fine as long as the motor accelerates to 75% speed within 3 seconds. If the acceleration time before the start winding disconnects is much longer than that it could lead to accelerated demise of the start capacitor. I don't know if any of the half horse grinders are taking much longer than three seconds to come up to speed, but if so and if you are making frequent trips to the grinder to touch up the edge on a tool, consider just letting the grinder run during those periods.

I would recommend buying a decent grinder. I think that ¾ HP grinder motors are sufficient and based on anecdotal information some of the ½ HP grinders are also OK. I would steer clear of the cheap ones because they may not be real half horse motors. Look at the nameplate current and compare it to same size motors in the Grainger catalog as a sanity check. If no current is mentioned then scratch it off your list.

The FLC of a ¾ HP motor will be in the neighborhood of 8 to 10 Amps.
 
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That's interesting info, Bill. My older 1/2 HP Steel City grinder takes at least 3 seconds with the heavier D-Way wheels. My main grinder is a 1 HP Rikon, under a year old, and it hits full speed with the D-Way wheels quickly.

For the money, it seems like the Rikon is pretty good value. The LED light is a complete joke. I keep meaning to remove it completely.
 

john lucas

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Bill I have an older off brand 8" slow speed grinder and with one CBN wheel and one White wheel takes about maybe 4 or 5 seconds to get to full speed. I would say it hits close to 75% speed in 3 seconds or so. Anyway I've been using it that way for close to 3 years now with not problems. My next CBN if I get one will be aluminum so shouldn't change things much.
 
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Wow Bill, thats a lot of info, thanks. The crazy thing is that I have a Dayton 1.5 HP variable speed and it takes a long time to come up to speed. Maybe that's because I always start it on "Low", but I doubt it. I can't check until I'm back in a few days.

Does anybody else have a big Dayton grinder?
 
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Tom,

Just FYI. I did a couple short videos awhile back when I did an upgrade to my grinder and CBN wheels. You can see the difference in start-up speeds of a 1HP Rikon and I think the Delta was a 1/2HP (maybe 3/4hp). Start up speed was not "my" biggest reason for changing. I never liked the fact that the shaft length of these (and other mfg.'s) regular grinders was too short to accommodate the newer CBN wheel hubs. Plus the arbor shaft shoulder that the wheel sits against is much more substantial on these newer version 1HP machines.

http://vid191.photobucket.com/albums/z132/davedelo/Grinders/Rikon Grinder_zpsvdfs0ezh.mp4

http://vid191.photobucket.com/albums/z132/davedelo/videos/Delta Grinder CBN_zpsl8gtzlql.mp4
 
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Thanks Dave. I was just wondering if my 1.5hp Dayton has a problem, because it sounds just like that Delta in your video and takes about the same amount of time to get up to speed. Once up to speed, she's fine. It is big and has plenty of shaft length for mounting the wheels.
 

Bill Boehme

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The Delta grinder uses a different type of motor most likely what is known as pole switching or pole changing type motors. Basically, the speed can be varied between the 4-pole speed and the 2-pole speed. In actuality the speed range is a bit smaller than that. From what I found it appears to be 2000 RPM minimum to 3400 RPM maximum. There are all sorts of variations and Delta has no technical information available about their particular speed control scheme. I presume that the motor is either a PSC (permanent split capacitor) or shaded pole. If it has a run capacitor then it would be a PSC type. This type of motor has very low starting torque, but once it is up to speed it will have full torque.Since PSC motors use run capacitors, the long start up time is not an issue to capacitor longevity. The actual horsepower would be a bit less than a half horse, probably between 0.4 and 0.5 HP. Delta doesn't advertise the specs on the motor in the owners manual, but the current and speed range can be found by searching the web. I don't see any reason for the variable speed range since the minimum speed is slightly faster than the generally preferred speed for use with CBN wheels.

Although the Rikon is advertised to be 1 HP, there is some creative physics going on in their marketing department. Based on real world motor performance, I would say that the actual power is a bit less than 3/4 HP. However, if the grinder delivers the desired results, the numbers are only of secondary importance. From the video it is clear that the grinder is more than adequate to accelerate the CBN wheels up to running speed and that is all that matters.
 
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I can't believe the $$$$ increase of grinders in the last 5 to 8 years, especially with the no inflation figures that the fed has been claiming under Yellan.
 

Bill Boehme

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I can't believe the $$$$ increase of grinders in the last 5 to 8 years, especially with the no inflation figures that the fed has been claiming under Yellan.

The price of nearly everything made of iron, steel, brass,copper, aluminum and probably most other metals has gone through the roof. The cost of the low end grinders haven't changed nearly as much as the high end industrial grinders.
 
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The materials iron, copper crashed with crude oil , should have deflation, have not seen any price roll back.
 
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I can't believe the $$$$ increase of grinders in the last 5 to 8 years, especially with the no inflation figures that the fed has been claiming under Yellan.

As I was taught in school, there are three kinds of statistics:
- lies
- damn lies and
- statistics

You are right, the CPI values are not accurate.

The problem with CPI, is that since the Reagan administration, the CPI has been methodically misrepresented. How? http://schiffgold.com/key-gold-news/the-lie-of-the-cpi-real-inflation-is-everywhere/

Why?
Because many of the government benefits are indexed to the level of inflation.
Artificially loweri inflation and the government reduces its costs by many billions annually and even more long term.

The other consequence is, as you say, the older ones are most heavily built. The expectation was that machines should last a long time, not be disposable. Machines tended to be built more locally, so shipping was not as much of an issue.

I have a 1960's 1 HP grinder, that weighs close to 250 lbs.
12" wheels come up to speed in seconds, but take 3 mins to coast to a stop. No vibration, awesome to use.
5018104_orig.jpg

Cost me a whopping $50

So....buy old.
:)
 
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The price of nearly everything made of iron, steel, brass,copper, aluminum and probably most other metals has gone through the roof. The cost of the low end grinders haven't changed nearly as much as the high end industrial grinders.

Interestingly, raw material prices are down quite a bit from their highs.
I've heard of supposed dumping of raw materials in Asia, but dont know if thats true.
Shipping prices are definitely down, since the oil price collapsed.

upload_2017-1-16_8-0-39.png
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upload_2017-1-16_7-59-13.png
 

john lucas

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Costs of the cheap grinders haven't gone up too much. I bought my slow speed grinder from Woodcraft tor $99 about 12 years ago or more. Now they cost $139. That's not too bad when you look at the price of almost everything else.
 

hockenbery

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Inflation and CPI - cost of living are two different values.

Cost of living is a what it costs to live - this includes things like food, shelter, healthcare and tranportation. When things like housing and gasoline get lower in cost the CPI went negative a few
Years back.
Inflation is the change in the value of currency itself. Today often measured by the value of money in the global market.
 
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I'm in agreement with Olaf here "buy old". By old, I mean quality and not everything old is automatically quality.

You look at a 1hp grinder that sells for $139 at Woodcraft. Then go to the Grainger industrial supply online site. You can't even buy a plain 1hp motor for that money, not figuring in the extras of the grinder with its double shafts, wheel guards, tool rests, wheels, switch and power cord.

I'm a tool freak and like to work with quality tools. My 30+ year 1/2hp old Craftsman grinder is my lowest quality among 3 bench grinders. It has never failed me, does its job as well as it did when I bought it for 10 bucks used 30 years ago. The Craftsman has coarse and fine wheels for general grinding and deburring steel. There's just something about the Craftsman grinder that sets the "tone" for the day when a project requires its use. The tinny, almost rattling sound when you turn it on is aggravating. Quality-wise the Craftsman would probably be a cut above the popular Rikon's (switch, light, bearings, tool rests, etc).

My favorite of my grinders is a WWII era Stanley 8" 1800 rpm of unknown hp. The Stanley is Navy surplus DC motor with a $2 full wave bridge rectifier from Radio Shack to run on 115V AC. It must weigh at least 100 pounds, solid cast iron, and runs so smooth it's hard to tell when its running, just a pleasure to use.

With all the emphasis on getting the best lathes, turning tools , chucks and all else needed it's interesting that a Rikon grinder would be considered satisfactory. Yes, I do know what a high quality grinder costs these days.
 
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odie

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I believe my Delta 8" grinder is the same one Bill Boehme has. I believe it was around $200 a dozen, or so years ago. It's much more heavy duty than what you can get for the same price now. Not sure the HP rating on it, but starts up pretty quick.....only a few seconds to come up to speed.

After having this one, I don't think I could be happy with anything less than what it is.......

ko

Shop April 2016 (3).JPG
 
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Hmm, maybe it was another forum, thought I posted here. I have 2 Baldor grinders, and the newer 1 hp Rikon. They both get the heavy CBN wheels up to speed in the same amount of time. With the Rikon, first thing I did was take the rubber feet off because I wanted it bolted firmly to some plywood for travel purposes. I had to grind 1/8 inch off of one foot to get it to sit flat on the plywood. I took the lamp off because it wasn't bright enough, and didn't reach far enough to be of any use. With the wheel guards, on the left side I had to grind off a tiny bit of the crimped over flange so my robo rest would slide up to where I needed it. On the right side, I was half an inch away, so had to ream out the bolt holes and rotate the guard about 3/8 inch down so I could slide my robo rest up to where I needed it. It has a whirring sound that I don't care for while I can barely hear the Baldor grinders. I had to raise the Wolverine platform up on about 5/8 inches of plywood to get it to proper height. For the money, it is a good deal.

My old blue no name grinder from Woodcraft served admirably. Funny thing to me is that it had same HP rating as the Baldor, but higher wattage. It would get the wheels up to speed much more slowly, but wouldn't take much pressure without slowing down. It did find a good home though.

robo hippy
 
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Funny thing to me is that it had same HP rating as the Baldor, but higher wattage. It would get the wheels up to speed much more slowly, but wouldn't take much pressure without slowing down. It did find a good home though.

Well, not so funny (humor or oddity) really. Just goes to illustrate the fact that you can’t go by HP ratings on any electrical motor any more; comparing amp ratings at the same voltage are much better indicators of available power.
 
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I have an 8 inch Baldor. Found it used. It is steady and quiet. As stated earlier in this thread, a 5/8 inch lift is required in order for this grinder to allow the one way system to fit beneath the guard.
 
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