Bench Grinder vs Si Carbide Tool Grinder
quesne
| Posted in Power Tools and Machinery on
My 6″ Craftsman grinder burned out it’s capacitor, and I am in the market for a new grinder.
I have been considering one of Grizzly’s or HF’s Heavy Duty Tool Grinders (links are below). I’ve seen both, and they look like they were produced in the same factory. I like the pivoting and locking tables and the wide wheel faces.
Aside from these two features, I am wondering what the advantage of these grinders is over your average 6″ or 8″ grinder? Also, I am surprised by the lack of eye protection on them. Is this a problem, or is there a good reason for it?
Can anyone suggest why I might consider spending the extra $ for one of these machines?
Thanks!
http://www.grizzly.com/products/h7762
http://www.harborfreight.com/cpi/cta…emnumber=46727
Replies
If you've been happy with the machine and all you need is a new capacitor, why replace it?
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It would indeed be a tragedy if the history of the human race proved to be nothing more than the story of an ape playing with a box of matches on a petrol dump. ~David Ormsby Gore
You might consider spending some extra if those wheels are good quality-the machine is only as good as the wheels. You may find that you have to buy one Aluminium oxide white cup wheel- or two the supplied wheels are inferior.
But they appear to be a definite improvement on the usual diy bench grinder complete with flimsy tool rests and hard wheels for grinding slag. I would want to run one and see how the tables adjust etc.
The price does not seem much at all for what they appear to be.
That coolant thing can't be a lot of use- to be effective it is volume of coolant that counts-no provision for volume there, not to mention the splashing....But one could attach a cool mister there no problem which works by combining air and coolant to make up for a lack of volume.
How much "extra" is one of those compared to the usual diypos bench grinder?
I've ordered the capacitor from Sears Parts ($10 delivered), but one of the service guys told me that there is probably an issue with the motor if the capacitor melted down. He says the new capacitor will likely burn up during the first 20 minutes of use. It's worth a try to fix it but I do not hold out much hope.I went up to a friend's shop yesterday. He bought the HF Tool Grinder last week (prompted by the 15% coupon), and was telling me he liked it. I tried it out and it seems to run pretty smoothly. I can't compare it directly to the Griz, but I thought it was smooth, steady and decently made. Is it worth the $140 it would cost me? Who knows.The wheels are green, and the manual says they are an 80 grit Silicon Carbide, Type 50. It cut a nice edge on the lawnmower blade I brought with me to test it out with. I looked around a bit and apparently you can buy Aluminum Oxide or even diamond wheels for it (I think the Griz uses the same wheels). Based on my limited use, the arbor and wheels seemed true, and the edge was flat.I'm still a little troubled by the lack of eye protection. Is there a reason for this on a "metal-working" tool grinder? I must admit I am pretty surprised.
One shouldn't grind steel with SC wheels. SC wheels work okay on carbide, though. I don't know of Aluminum oxide wheels available for those grinders. Yes, I've looked. If you want to grind steel with that type of grinder you'll need to invest in diamond wheels. Diamond wheels don't last as long with steel as when grinding carbide. The swarf from grinding steel is string-like and quickly wears away the mounting matrix in diamond wheels. Avoid working unhardened or mild steel on anything diamond, you'll shorten the abrasive's life considerably.I would like to find a source for Aluminum oxide wheels that fit one of these machines, it would solve some production problems we face. I've searched and they don't seem to be available.On edit:I did just find some aluminum oxide wheels in the new MSC catalog. They run about $90 each.
Edited 5/7/2007 8:19 pm by lwilliams
Thanks very much for that information.I was not aware that SC grinding wheels are not appropriate for grinding steel. Please advise me further on this. Is it dangerous to us SC on steel? Or is it just inefficient? Assuming it is safe to do, will I find myself dressing the wheels more often than necessary?I had not really considered investing a great deal into diamond wheels (I tend to use diamond cutters for ceramic work only), but I assumed I would get Aluminum Oxide in 80 and perhaps 200 grit.One of the things I like about these grinders is the surface options you have and the size of the tables for support. Another question I was curious about: what is the best tool for dressing these wheels?
The matrix silicon carbide is set in is softer and melts at a lower temperature. You should have noticed a burning smell when using your friend's grinder. I used to grind tool bits with mounted carbide tips using silicon carbide wheels. Doing this, you need to grind the steel backing away before grinding the carbide. If I got careless and ground into the steel, the wheel would start to balk and burn. The first thing I would notice is the burning smell. I never pushed it to see how catastrophic the results might be if I went too far.
Thanks very much to everyone for the information provided in this thread. The advice has been great. A quick update based on my own research:I got the capacitor for the Craftsman grinder yesterday, and I patched it up. I ran it for about 15 minutes under no-load with (almost) no smoke, but with an awful smell of burned plastic blowing out of the motor housing. I stopped it every 3 minutes or so to check for excessive heat, but the motor and capacitor stayed cool. I ran it again for 15 minutes straight with the same results. Time will tell how long it will last!In the mean time, I really needed a grinder, so I decided to give the HF a try. The only real advantage I saw over the Griz is the shipping cost. Grizzly would have been $272 plus tax (this includes $73 shipping), whereas HF was $140 plus tax. As a rule, I don't buy power tools from HF as I've been disappointed in the past. They are very good about taking things back, though, and it's only a 25 minute drive from me. BTW - Grizzly gives you a 1 year warranty, but with HF you have 90 days and must pay $20 extra for the 1 year replacement agreement.In general, it seems to be a solid machine. It spins smooth, the tables are solid and the wheels are true. The tables and trunions are quite clearly less than A-quality machining with tool markings visible in many areas, but they are heavy, flat, tilt easily and they appear to do the job.As for using Si Carbide on tool steel, I spoke to several people before deciding to give it a try. I spoke with 2 folks in tech support at Grizzly, 2 at McMaster Carr and 3 more at J&L. I also called a couple of local industrial machine shops in the Philly area and just asked if they had an opinion one way or the other. Indeed, as others have already noted, Si Carbide is not considered ideal for grinding steel. The reason given to me by several people (and totally consitent with Larry's post :-) is that, if you grind too aggresively, the binding matrix is soft and it "fills up" quickly with steel particles.However, quite a few people did tell me that this is the type of grinder they use with good results on tool steel, even with Si C wheels. The trick, I was told, is to make light passes and keep the steel cool. I did sharpen several of my lathe chisels on it, and I must admit that, using this technique, I got a near mirror-like finish with minor effort. I must say, also, that having a rock-solid table to lean right next to the wheel made a big difference.One of the apparent advantages of these grinders, is that they typically have a reverse switch. This allows you to hold the tool either up or down, yet always be grinding toward the edge. Another advantage is that you can safely grind along the outer edge of the wheel, giving you a non-hollowing cutting surface.I will continue to use the unit as much as I can, but I may well take it back if it does not suit my purposes.One last note: I confirmed that AL Oxide wheels can be had for these grinders. They are available (in lots of 5 on special order, item #38A80-HVBE) from Norton through J&L Industrial for $70 each. I don't need 5 of them, but if anyone wants to share the lot, I'm certainly interested.Larry, you spoke of the AL Oxide wheels being available through MSC for $90 apiece. I could not confirm this in the MSC on-line catalog, but please post the details if you have the chance.An interesting side-note: J&L offers a Chinese/Taiwanese version of this style grinder (ISG-12000J) for $335 and it comes delivered with 2 AL Ox wheels! The only disadvantage I see in their particular unit is that it does not have a reverse switch.
I didn't know the HF version had a reverse switch. I thought I'd have to buy a Baldor for that and didn't want to spend that much. I am curious about the run-out on your grinder. Do you, by chance, have a dial indicator to check?The Norton AO grinding wheels for this have these MSC part numbers:94035755 - 46 grit K hardness. My catalog shows these at 89.04 each but the web site shows them at 91.7199607152 - 60 grit J hardness. These are 89.04 in the catalog and 91.71 on the web site.They also show an 80 grit and I'll get that number if you want. I don't think I'd use 80 for grinding woodworking tools, though.
Yes, it has a reversing switch, as does the Grizzly.I am also VERY curious about the run-out, and I will get a dial gauge asap to test it.Thanks for posting the MSC information. I looked at the quote I got from J&L for 5 wheels at $69.95 each, and it is for the 80 grit Norton (MSC#88791025). I am writing back to J&L to see if the 46 and 60 grit wheels are also available at a discount.
Larry, as a matter of interest,is there a particular reason why you are concerned about run-out? I am thinking that any run out other than the ridiculous is sorted out when the wheel is dressed-even new wheels need dressing in place and the position marked, if to be taken off for substitution with other grits for example.Philip Marcou
Philip,These grinders are designed to grind on the side of the wheel. I need to do that somewhat accurately. Run-out will be side to side slop in a grinder and that makes it difficult to control, you can't dress it out when it's always moving back and forth. Baldor's more expensive model, which is designed for diamond wheels, has double bearings (one thrust) on each side to control this run-out. I don't know how much I'd be dealing with, I could handle a couple thousandths of back and forth motion but not much more. I do have a metal shop and could fabricate a spring type washer to deal with some run-out, I would like to know how much work I'm in for before I invest the money. Given the possible labor involved, it might be smarter to buy the better Baldor and put the diamond wheels on the shelf. We have an oscillating diamond grinder that's better than the Baldor for grinding carbide tooling. Wheels for these grinders aren't interchangable. I'm using the oscillating grinder for the operation I want the carbide type side grinder for now. The problem with that is that diamond also works best on very hard material. I'm now grinding hardened and untempered O-1 for this to try to extend the life of the diamond wheels. Diamond, like Silicon Carbide isn't all that good for grinding steels. Steels and soft metals tend to produce a stringy swarf or tiny chips when grinding, kind of like very fine steel wool. This wears away the matrix the diamond is mounted in. The harder the material the more granular the swarf and this is what Silicon Carbide and diamond wheels are designed for.If I can grind with aluminum oxide wheels I can aggressively grind the unhardened tools I make in this operation. This would probably cut my grinding time by about 75% and save a lot of money by eliminating the quickly wearing diamond wheels I'm using now.
Well I got my Grizzly dial indicator in today (G9849). This is the first time I've ever used one, so I may need a little help. Also, I want to make sure I get meaningful results, so please chime in with advice! Just for starters, I set the tip of the indicator on the edge of the plate that the grinding wheel bolts to (i.e. measuring radial variation at the farthest point from the arbor axis). I realize that this measure could be suspect for a few reasons: 1) the plate may not be perfectly round, 2) the plate edge may not be perfect or 3) the plate mount on the arbor may be imperfect. I was just anxious to get warmed up a little bit, and I didn't want to pull the wheel off just yet!In fact, I can already see that the edge has some minor blemishes that the dial is actually reading. Nonetheless, here are the readings: the spread on the right side was a total of 0.008" (eight thousandths) and on the left side was 0.004" (four thousandths).Now, from what I understand you to be saying, Larry, you really want to know how much the front of the face-plate ocsillates forward and backwards as I look at the grinder from the side rather than the front. Is that right? Would it be best to pull the wheel first, or should I dress the wheel flat and then measure right on the wheel?P.S. I also picked up a 3/4 carat diamond dresser (H5892) which I plan to use to get the edge of the wheel as smooth as the face. Is there anything I should know or has anyone out there got a good technique for doing that?
What do you mean when you say "even new wheels need dressing in place and the position marked"? Thx
I mean that they may not be perfectly round. They may also vary slightly in thickness. The arbour may be slightly out of true and the bushing may not be a close fit-those plastic ones often are a sloppy fit. Ditto for the flanges. So if you dress, in effect shape the wheel, in place then always put it back in that position to have it run true, or at least decrease the amount of dressing needed to make it run true.
For more sophisticated machines such as surface grinders the wheels can also be balanced via the flanges which have a mechanism to enable this.Philip Marcou
OK, thanks Philip. So you mark the orientation of the wheel and line it up at the same point on the arbor? That is really interesting. Is there a good on-line resource that you know of on the basic how-to's for setting up a grinder?
After dressing the wheel with the diamond dresser (using the miter gauge as a guide), it is pretty much as flat as the face. I tested the run-out right at the face of the wheel. I used a piece of vellum to protect the measurement tip from the abrasive.Turning the wheel all the way around, there is less than .002" (two thousandths) of run-out. I also pushed on the wheel at a point opposite from the measurment tip to see if the arbor would move on the bearings. The measurement tip stayed steady and did not move. Is this test adequate to evaluate the arbor run-out?
Hi quesne,
That would be your total run-out, including the wheel. Arbor run-out would be a measurement taken directly on the arbor shaft.
Paul
Keep us posted with the capacitor issue- the service guy may be spinning a story.If the motor is not about to cook why not renew the capacitor-cheap investigation by substitution.
Green wheels are for carbide and do not work properly on steels, as Larry has said. A pair of good quality white wheels from Norton or CUSA cost some money, and diamond wheels are most expensive- unless there is an alternative there.
I don't think the perceived lack of eye guards is a problem-you are supposed to wear the protection. I think a lot of these things are too heavily guarded, making it difficult to see nicely. I think it is more important that the wheels are strongly shielded, in case of a wheel burst.Philip Marcou
Someone, I forget who; maybe Garrett Wade, offers a really slow speed grinder, like 1100 rpms. If I was buying new I'd look at one of those because they cut down somewhat on the heat issues when grinding knives and blades.
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