Thread: Baldor Bench Grinder

What size are your CBN wheels?

Originally Posted by BobL

What size are your CBN wheels?

To some extent it depends what there is waving about your shop but I my case its crowded and there are pieces of metal being moved over it. This is one reason for keeping a sort of a guard over a CBN wheel. If a piece of steel falls onto the CBN it can knock a divot out and this may lead to more CBN being lost from the wheel.

Originally Posted by Luke Maddux

It is my understanding that Baldor is the gold standard, and should be the last grinder anyone needs to buy.

My understanding is the same Luke, but you know how it goes - ANYTHING can happen to a good brand name these days, either through an accountant purchasing the company and trashing it, or the current owners dropping their standards in the case of severe price competition. Best to do some research on the current models (such as making sure they are still USA made - even that may not necessarily guarantee they are still good).

A USA forum may be the best bet for the question.

My grinder wheels are 6" diameter. One is an inch wide and the other is an inch and a half. Both are 1/2" arbor.

I've confirmed that Baldor are made in the USA. That was one of the first things I looked up.

I've found a review/comparison of the model I plan to get if I move forward with the purchase.

The Best Bench Grinders Are Put to the Test

I'm also considering the Dewalt and the Jet, but they rave about the Baldor, and also comment that it's more compact, and I like both of those things.

One thing that I don't understand is this... The Jet has a half hp and the Dewalt has a whopping 5/8. But yet the Baldor outperformed both. How is one company able to get more power out of a 1/3hp motor than another company is able to out of a 5/8hp motor? This is something I've never understood, so maybe someone can clarify?

Right now, all signs point to Baldor, but I could be swayed. The Dewalt is a third of the price, but I don't want to make the same mistake twice.

Cheers,
Luke

Generally, with a reasonable quality grinder experiencing runout, it is caused by the wheels, and in turn causes vibration. The first step I would be taking would be to remove the original supplied wheels and test the unit for runout with bare shafts, then power up to test for vibration. All wheels for grinders are moulded and have a degree of runout and also imbalance built into them by the moulding process and need to be dressed to minimise runout or imbalance. Another issue is the bushes supplied with the wheels and used to locate the wheel on the spindle are extruded (plastic) or wound (cardboard tube) and are never perfect in themselves, particularly if more than one is needed in a wheel bore.

1/2in shafting seems to be fairly standard for 6in grinders, and is potentially to light to control bad wheels, given that the wheels are mounted at the ends of the spindle, and are generally substantially heavier than the armature in the middle of the spindle, sort of a tail wagging the dog situation. Another issue can be mounting method for the grinder and the weight and rigidity of the surface that it is mounted to. The heavier and more rigid the host surface, the better it is at absorbing vibration and keeping the grinder controlled.

With regard to power ratings and performance tests, some people spec motor power as what the motor can safely develop (i.e. deliver to the wheels) while others might spec them as the power that the motor can safely draw from the supply continuously, and others might spec them as the peak or surge power that they can draw for a short time. Motors generally have significant losses due to friction and electrical and magnetic losses, and the smaller the motor is, the more inefficient it is. By their nature, grinder motors tend to be sealed and do not have forced air cooling internally or externally, so heat build up becomes an issue. A motor specced for mechanical output power will always have more grunt than a motor specced at the same power for input power, whether continuous or peak. Also by using different winding and starting arrangements and the amount of magnetic material in the armature core, manufacturers can control the drop off in wheel speed as the motor is loaded. Combining all of these factors, it is conceivable that a motor can perform better under test than another that has higher power specs but lower quality design and manufacture.

There are many reason why the power ratings may be different.

Workshop machinery manufacturers usually specify motor power as "output power" whereas power tool manufacturers usually specify input power.
Input power is always more than output - it looks like more and that's why it's often quoted.
On a small motor that in-efficiency difference may be as much as 30-40% - on larger motors e.g. 5HP plus the difference is much less.
Grinders seem to be a cross over market in terms of quoted power. Cheaper grinders are usually rated by input power and only the better quality grinders quote their output power.

There's no such thing as a definitive output power for a motor.
When you turn on a grinder - just idling it's using maybe 1/4 of its rated power.
The power the grinder eventually develops varies with the load - putting more load onto a motor means it will develop more power up until the motor stalls.
BUT
Running the motor constantly at the point just before it stalls will always overheat the motor so quoted max power specs for motors are around 2/3rd to 3/4 of stall power. A cheaply made motor with poor cooling and cheap bearings may draw a lot of power with much of that wasted as heat so it won't even be able to run constantly at it's (over rated) rated power for too long. OTOH Some (few) companies that make a more efficient/cooler motor may quote much more conservative powers.

All in all, motor power specs (especially for grinders) are somewhat kind of arbitrary.

I have tested the real output power of a bunch of grinders and while they all could develop their rated power , just how long some could keep it up for is another question.

One especially smooth efficient grinder used mainly by metal workers (made in AUS) are the Brobo-waldown grinders.
They used to make some smaller tool and cutter grinders , but from the looks of it the smallest bench grinder they currently make is 200 mm and uses a 1.4HP motor.
BENCH / BUFF GRINDERS – Brobo
Make sure you are sitting down if you look up prices.
They also make a serious 350 mm /3HP pedestal grinder with variable speed.

One of the best thing about my 3phase grinders is that they are variable speed and I don't know why more grinders are not available with this feature.

I have a 7" Baldor and can't fault it. I'd suggest going with the 17XX RPM models.

Luke, forget the Baldor you need one of these, I also need one.

Tradesman DC Variable Speed Reversing Bench Grinder

Originally Posted by Chris Parks

Luke, forget the Baldor you need one of these, I also need one.

Tradesman DC Variable Speed Reversing Bench Grinder

Interesting to see they come with Variable speed, guards and reverse.
I'd be interested to know what they use reverse for.

Because my 3P grinders are fitted with a VDF reverse is available but I have locked this out because the wheels tend to come loose. However if there was a good reason for it I would make some locking collars that would hold the wheels on in reverse.

Simply because it is a DC motor I suspect.

Which way are knives best ground? Towards or away from the edge?

Originally Posted by BobL

I'd be interested to know what they use reverse for.

If you want to use a honing wheel with a tool sharpening jig.

Originally Posted by Bohdan

If you want to use a honing wheel with a tool sharpening jig.

Ah ha. What about without a jig - just hold it the other way?

Yes