Grinding disc with depressed center?

I bought a 4-1/2" angle grinder from Harbor Freight, I don't have much grinding to do so I just wanted to get a cheap one and use it for this project which requires grinding off a few door hinges that has been set into metal door jambs that extended into the slab. The grinder came with metal disc but I also need to make some cuts in concrete so I went and got a 4-1/2" diamond blade from the big box store only to find that those discs do not fit...apparently the metal grinding disc that came with it has a depressed center so that the locking nut can be secured from the outside. If I put in a flat disc there is not enough room for the lock to catch - well even if there was I am not sure it's a good idea as the lock may break the thin disc.
I have never used this type of grinder before does it mean I need a special depressed center diamond cutting blade or do I need a special fitting to use standard blades?
Thanks,
MC
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Go back to HF, I think I recall seeing cheap diamond blades for that grinder.
--
Roger Shoaf
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On Sun, 23 Mar 2008 23:24:17 -0400, "MiamiCuse"

If you bought it at Harbor Freight (Harbor Fright), I'd toss it in the garbage before it kills you or causes a serious injury. Even if it does work and you are lucky enough not to get hurt, it will burn up after a few hours of use. Harbor Freight only sells one thing.... GARBAGE.
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On Mar 24, 3:42�am, snipped-for-privacy@deleted.com wrote:

ahh HF tools are fine for occasional use, when you dont need it enough to buy a dewalt or other expensive unit
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snipped-for-privacy@deleted.com wrote:

Wrong, and anyone who believes that is missing out on some very good deals. HF certainly does carry some stuff that is indeed garbage, but there are a number of gems in their lineup as well. Having a HF store nearby where you can inspect the items in person is a big help in finding those gems. It's been reported by many knowledgeable folks that the HF orange 4.5" AG lasts many years under frequent use. The blue line has mediocre reviews. As for the disk issues, try reviewing the manual for info and if you can't find good info there try looking at the manuals online for the brand name angle grinders that might have better instructions.
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snipped-for-privacy@deleted.com wrote:

You're letting "perfection" get in the way of "good enough."
I've got a HF catalog in front of me. Pray tell me why one should spend more on the following items:
10pc foam brush kit - $1.99. 6" stainless pocket ruler - $0.99. London police whistle - $1.99. 4-piece funnel set (2,3,4,5") - $0.49.
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I'll tell you why you shouldn't shop at HF...
- 10pc foam brush kit - $1.99.
1 of the 10 brushes I got wasn't centered on the handle. All my paint lines were 1/8" off.
- 6" stainless pocket ruler - $0.99.
I don't have any 6" pockets, so it doesn't fit.
- London police whistle - $1.99.
Only works in London and I have no plans to go there. They don't carry US police whistles.
- 4-piece funnel set (2,3,4,5") - $0.49.
All 4 of the funnels in my kit - every one of them - was upside down. I'd pour stuff in the little hole (missing it for the most part) and then the liquid would come out of the big end and make a big mess. I went to return them, but all of the kits had the same defect.
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"DerbyDad03" : All 4 of the funnels in my kit - every one of them - was upside down. I'd pour stuff in the little hole (missing it for the most part) and then the liquid would come out of the big end and make a big mess. I went to return them, but all of the kits had the same defect.
I used to have the same problem with spoons - I always seemed to get the ones with the convex side up and the soup just rolled right off. What a PITA. Tomes
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LOL good one.
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What happens when you tighten the grinder's shaft nut? Does the diamond wheel still rotate? Try flipping over the nut - does it snug down on the diamond wheel now?
On many grinders, the washer that sits against the gear case has a small raised boss that is designed to keep the grinding wheel properly centred. The nut has a similar raised boss, and it's supposed to face the washer when using thick discs. But with thin disks, the two raised areas contact each other before the disc is clamped. The other side of the nut has a recess in the same area, so flipping over the nut allows it to clamp even very thin discs.
All of this is independent of whether the wheel has a depressed centre or not. The thick wheels intended for grindng on the face of the wheel always seem to have the depressed centre, presumably so you can get the wheel face down almost parallel to the work without striking the nut. But abrasive cutoff wheels, where the edge does the cutting instead of the face, are available with depressed centre or flat. And the edge-cutting diamond wheels always seem to be flat.
    Dave
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On Mon, 24 Mar 2008 19:26:30 +0000 (UTC), snipped-for-privacy@cs.ubc.ca (Dave Martindale) wrote:

Whoa. A grinder is a high speed tool working under a heavy load. Get the part that fits properly and is meant for that application. No bailing wire and duct tape solutions for this kind of tool. It's a gruesome accident waiting to happen.
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snipped-for-privacy@yahoo.com writes:

You don't know what you're talking about. The shaft nuts I'm describing are *designed* to be flipped over for thin grinding discs. The grinder manual tells you to use the nut one way for thick discs, the other way for thin discs. It "fits properly" in both orientations, since it's designed to be used both ways.
The difference is that, when used with thick discs, both the backing washer and the nut have a raised shoulder that projects into the disc center hole, helping keep the disc properly centered on the shaft axis. But with a thin disc, if you use the nut in the same orientation the two raised shoulders touch each other before the disc is clamped, and the disc is free to rotate. So you flip the nut over, and now there's a recess in the nut that matches the shoulder on the backing washer. This allows the nut to clamp any disc no matter how thin, while it is held centered by the shoulder on the backing washer.
For an example that I'm familiar with, look at the Makita 9554 manual at <http://www.makita.com/assets_product/9554NB/owners_manuals/9554NB.pdf . On the right side of page 5, it shows a depressed-center grinding wheel being mounted using the shaft nut with its raised boss facing the wheel. There's a little inset drawing to make sure you see the orientation. Then on page 7, on the lower left, it shows how to mount an abrasive cut-off wheel, and this time the lock nut has the shoulder facing *away* from the disc. (Although the diagrams don't show it, I have a Makita grinder and I can assure you that the nut does have a recess on the face opposite the shoulder).
It sounds like the original poster might have had a grinder with a backing washer and nut of this design, and not known about reversing it when using thin discs. I've seen these double-sided nuts on several makes of grinder, not just Makita.
    Dave
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On Mar 24, 3:26 pm, snipped-for-privacy@cs.ubc.ca (Dave Martindale) wrote:

The item I purchased is:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber1309
* Includes 4-1/2'' x 3/16'' depressed center wheel and 3-position side handle * 120V, 5.5 amps, 10,000 RPM * 8 foot power cord * 5/8''-11 spindle with 7/8'' arbor adapter * 12''L x 2-7/8''W * Double Insulated
So it says "4-1/2'' x 3/16'' depressed center wheel". I will take another look tonight. Basically if I remove the thick depressed blade, there is a "cone shaped" part that goes in, then the diamond blade, then it's almost flushed with the thread rod in the middle so the but has no room to secure itself, I didn't want to force it and not use the tool the way it's intended to.
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says...

I have used the diamond blades on mine just fine, and really like the way they work. I got the 3 pack for less than ten bucks on sale, really hard to beat. Are you saying the diamond blade is just too thin? You can turn the locking nut over, one side has a raised hub and flipping it over allows that hub to grip a blade of zero thickness.
--
Dennis


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On Mon, 24 Mar 2008 16:42:31 -0500, snipped-for-privacy@wowway.com (DT) wrote:

That's cool. I'm getting engaged next month, if she says yes, and I'm going to get her some of these diamond blades. We're both very thrifty and I'm sure she'll understand. Diamonds are forever, regardless of what form they are in.

Maybe the blade is too thick.
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