Thanks Rich. I saw that one at HF but didn't know about quality. I haven't had time to do any research on this type of machine and I have wondered if the grinding and buffing wheels are interchangeable, given the right opening and spindle. What I mean is if I buy something with two grinding wheels, could I substitute buffing wheels as needed. Or is there an issue with debris, torque etc?

Thanks

Sandra

Well, to answer my own question I guess you can't swap buffers with grinders, I read the online manual for the HF buffer grinder. Oh well.

Thanks again for the info.

Sandra

Sandra,

Well, there are some issues involved with changing wheels on rotating equipment. You generally do not want to change direction of rotation of wheels willy-nilly - doing so increases the risk, (albeit minimally) of spontaneous disintegration of frangible grinding wheels due to centrifugal force. Similarly, buffing wheels develop a "grain" after being run in a given direction for a while and changing that can cause them to go out-of-balance. Out-of-balance wheels are never acceptable as they greatly increase the danger of disintegration and/or tendency to "grab" the workpiece disastrously.

All frangible grinding wheels are required to be marked with their maximum safe running speed. It is folly to exceed that rating. Likewise, different buffing wheel media tolerate different speeds - follow the manufacturer's rating or recommendation.

Decent grinders/buffers are totally-enclosed, fan-cooled (TEFC) motors, so no debris can enter the motor. They should also have shielded bearings. The ones with extended spindles, such as the one I linked to, are generally much handier for buffing. Short arbors don't leave you room to maneuver the workpiece safely, nor do they allow for effective dust collection apparatus around them.

As for substituting a buffing wheel for a grinding wheel, sure you can. Again, heed the speed limits and buy quality buffing wheels. Cheap ones are a nuisance and do a lousy job. Some grinders run too slowly to work well for buffing and vice versa. That said, you can still swap wheels with good success provided that the arbors match your wheel centers or can be safely adapted to do so.

My recommendations might be a bit different than what would be best for your particular situation since it sounds as though you mostly do fairly small jewelry-type work and I mostly do heavy blacksmithing and architectural work. With that caveat, I'd actually recommend that HF one I linked to or their 8" double spindle buffer. I have one of the latter and it works every bit as well as does my fifteen times more expensive Baldor pedestal grinder.

When it comes to grinder and buffer recommendations you'll have to give me pretty specific details of what you want it to do. There's a special tool for every task if look hard enough, and there's also some general-purpose tools that can handle an extraordinarily wide range of tasks.

F'rinstance, I have a shop-made 3HP 2"x72" belt grinder that is one of the handiest tools I have. I use it for grinding, polishing, and even buffing by changing belts and speeds. When it comes to speed for grinding and buffing, what matters is NOT RPM but rather surface feet per minute (SFPM) of travel. Each type and grit of abrasive or polishing compound has a speed at which it works best for any given metal. Thus, a variable speed machine is a distinct advantage though not mandatory. Variable speed adds significantly to the cost of motors and drive systems, so it may not make sense to opt for it until you are sure you can justify the expense. As for amps of current draw, electric motors are generally rated in horsepower. One horsepower is roughly equal to 740 watts of electric power. Using Ohm's Law we can see that at 120 volts that 740 watts would mean a current draw of 6.2 amps, not accounting for losses. Amps times volts equals watts. For rough shaping of gravers, dressing chasing tools and general fine grinding, a 6" grinder of 1/4 to 1/3 HP would be adequate. If you want to shape hammer heads and grind knives and axes than I'd suggest an 8" grinder or a belt grinder of at least one horse power and preferably bigger.

One of the handiest bench grinders you can have in a metalsmithing studio is a 1" x 42" belt sander like this: Belt Sander  Depending on the type and grit of belt you put on it you can use it on wood, plastic, non-ferrous metals or steels.  I have one of these that I've been using for more than thirty years with no problems at all. The belts, even high quality ones, are fairly inexpensive and readily obtained. 

The advantage to the belt grinder is that you can use it with the belt running against a flat platen for facet grinding or run it "slack" (without the platen) for softer contour grinding.  I have one of these and have used it to profile and dress hundreds of chasing tools made form scratch, sharpen tools, even dress cut glass edges.   It is the little brother to the much bigger and more powerful 2x72 belt grinders like the Bader B-3  a 3HP variable-speed metal-eating machine that will set you back a couple of grand.

With a 1x42 belt grinder and an 8" double spindle buffer you would be well positioned to do almost anything you wanted, I think.  So there you have my recommendation.

Rich

Thanks for your recommendations,I can really see the usefullness of an 8" grinder, especially since I want to be able to sharpen my knives, and will have the occassional axe to grind :)

Not too sure if the belt sander is for me, I think I will probably get a small jewelry buffer since I mostly want to be able to touch up stones that might get scuffed while setting and do some buffing of chased pieces. I have two foredoms and a flat lap so I do have those options also.

Thanks again, your knowledge always amazes me!

Sandra

Do *not* sharpen knives on an 8" grinder. At least not with abrasive wheels. You will ruin the temper. It is however safe to *hone* them on a grinder if you use a felt wheel with something like this:

http://www.leevalley.com/en/wood/page.aspx?p=32984&cat=1,43072

Having said that I have not seen many 8" felt wheels.

crquack