1725 RPM vs 3450 RPM grinders

Re: 1725 RPM vs 3450 RPM grinders

Ace Foster in Ben Lomond 95005

>Many of us, including yr. obdt. svt., have had an easier time avoiding burning our tools while sharpening after switching to the slow speed grinder. Forrest Addy, whose opinions on things mechanical are usually well informed, says it's not the speed that matters. You might be able to find his post in the archives; it was some months ago, I think. If I remember correctly, he said it's the stone that matters. The gray ones are harder and less friable and therefore more prone to burning, while the white pink and blue compositions we're seeing more of these days are less apt to burn.

Hope I haven't misquoted him.

Ace

Re: 1725 RPM vs 3450 RPM grinders

Carole in VA

>When I got my Wolverine, I got the Woodcraft slowspeed grinder because (1) the base on my existing 6" grinder wouldn't allow the use of the Wolverine (2) I could afford it and (3) in addition to sharpening turning tools made of HSS, I needed a grinder for plane irons, chisels, etc. and I was tired of burning them on my little 6" highspeed grinder. The slowspeed grinder works great for all my sharpening needs. It came with an 80 grit white and 120 grit white. I use the 80 for shaping and the 120 for quick sharpenings while turning. Best $74 I ever spent. BUT...as I am sure you have noticed, the Wolverine manual says to use a highspeed grinder. The 6" is now dedicated to buffing wheels.

Re: 1725 RPM vs 3450 RPM grinders

Arch

>As with turning tools and techniques, sharpening tools and techniques vary widely and they all work for the person who has learned to use them. The majority use grinders and find that slow speed and friable stones aren't as important as when tools were mostly high carbon steel and Wolverines were wild animals and/or went to Michigan.'G'

The advent of high speed (and beyond!) steels and the general recognition that shaping and sharpening aren't the same has made it easier for turning tools (not necessarily their owners) to hold their temper. Aluminum oxide stones with a variety of grits, slow speed grinders, and tame Wolverines are arguable, but IMO it's more important to use a gentle touch on a well dressed and balanced stone, whether it's pink, blue, white or gray and revolving at 1725 or 3450 or any rpm in between.

Re: 1725 RPM vs 3450 RPM grinders

Bill Sands in WV

>Carole, J.R. Beall, in his Woodcraft video ( http://www.woodcraft.com/videos.aspx?videoid=23 ) recommends that his buffing system be used on a slow speed motor also. Maybe you can mount a 10" combination blade on your 3450 grinder and use it for freehand sawing. You should check with your doctor first, though.

Bill

Re: 1725 RPM vs 3450 RPM grinders

John Lucas

>Carol

You can't hurt HSS by overheating it on the grinder and according to all I've read 3450 and an 8" wheel is the optimum speed for grinding HSS. Not so for Carbon steel tools.

I have played a lot with both speeds because the grinder I've used for 20 years is 3450. My new one has both speeds. I prefer the slower speed. The slower speed cuts slower so I feel I have more control. The slower spinning wheels aren't as intimidating and I'm sure are safer if one should explode.

Freshly cleaned stones, true running, friable wheels and a light touch are what give you sharp edges and long lasting tools. The white wheels have grit that breaks off so fresh sharp grit is exposed. This is called friability or something like that. This make them cut faster and cooler.

A stone that doesn't run true and vibrates will still cut it's just much harder to control and get a really clean cut.

Pink and blue wheels are also good wheels for lathe tools but I've never owned one so I can't tell you the difference.

Re: 1725 RPM vs 3450 RPM grinders

tdaniel

>Carol, the faster the wheel turns, the more important it becomes that the wheel is balanced. I prefer the 1800 rpm grinder for my lathe tools. I also think it is worthwhile to get a grinder that has machined plates that hold the wheel rather than the thin, stamped steel ones that are used on most of the cheaper grinders. The One-way balancing kit contains a set of plates that will hold the wheels 90 degrees to the shaft and eliminate wobble. Having the wheels run true is the most important issue. Rumor is that Delta is discontinuing their slow speed grinders and going with the variable speed grinder. I hope they do not do this but knowing past moves by B&D I think this is likely. The 1800 rpm Delta is the most grinder for the buck you can get. Baldor is better but twice the price. Woodcraft is half the price of the Delta but it is hit and miss with the plates (some are ok, some are not). Buy a good one and it will be the last one you ever have to buy.

TD

Re: 1725 RPM vs 3450 RPM grinders

Carole in VA

>Bill, I don't use the HS grinder for a Beall system ...mostly just for polishing and cleaning up metal and stuff. I use buffs mounted on my lathe for wood. The ER here doesn't seem to need anymore patients so I think I'll pass on the saw idea! ;)

Re: 1725 RPM vs 3450 RPM grinders

Lyn J. Mangiameli

>As usual, Terry offers excellent device on dry grinders. A few observations, I was going to discuss elsewhere, but they fit well here.

I have three dry grinders. Two large 1800 RPM 8 inch, 100 pound Deltas that are the same Terry uses. I also have a cheap 3450, 6 inch, light weight Delta. One of the big Deltas is used with the stock machined cast iron flange collars that Terry is so fond of. The other of the Deltas has been fitted with Oneway Balancers (which means I can't use the stock cast iron flange collars), as is the little Delta. All are mounted to large thick MDF bases. Want to guess which has the least vibration?

Well, it is the Delta running with the machined cast iron collars. It is not because the wheels on it are better balanced, because I have had the balancers on both sets of wheels and I know my presently balancer-less wheels are not perfectly balanced.

This is not to knock the Oneway balancer, it is an extremely effective solution for some (probably most) grinders and wheels. They simply transform my small, fast, cheap grinder into something that for the first time is decent for sharpening. Rather, I think my sample of grinders suggest that balancing is just one component of a system that includes precise and stable flange support, grinder speed, wheel size, grinder bearings, shaft rigidity, wheel balance and truing, and grinder weight. The massive, slow speed Delta with its excellent flange collars simply is not as vulnerable to variations in the other factors.

A bit tangential to this discussion, but I toss it in here to validate Terry's comments.

Sounds a lot like...

Bill Howatt

>what it takes to be a good grinder is the same as what it takes to be a good lathe!

Bill