8 inch "slow speed" (1725RPM) Grinder

[Captain777]

Hi,
I need some advise about a new 8" grinder that I have. I will use this for (mostly) for grinding HHS lathe tools, and of course, for many other miscellaneous jobs.
There are a ton of YouTube videos so I am "fairly ok" about normal grinding wheels, but I have not seen much on the "CBN" wheels. They are expensive so I want to get
some advise on whether they are worth it for sharpening metalworking tools or just use the abrasive wheels that machinist have used for years.
Dan

 

[goldstar31]

In my humble opinion, getting an 8" Double ended grinder will end up with you paying 'a lot' for the wheels. You did mention the possible use of CBN stuff.
If you have been trying to follow my usual drivel, you will find that the maximum diameters in my kit are 6" and if I had drifted off further, I have quite a number of the 4" variety.
All that I can deduce is that you had a 920 and now a South Bend. Nothing much wrong with either lathe but you give no details of what you are going to use a 7' wheel.
So without more details, I for one need more information

 

[Tug40]

I had not heard of CBN grinding wheels before this thread.
Turns out I have one, although a 6” 180 grit pretty worn out one.
It’s off of a 6” Darex drill sharpener at work.
We bought a new wheel for it and we’re scrapping this one, so I took it home, thought I’d use it for something.
I have an 8” double grinder & a 6” double grinder, both 3500 rpm.
I didn't know these wheels could be used free hand, thought they were for fixture/jig applications only.
Seems I learn every day.
Sorry I can not help you, I hope someone else chimes in, as i’m kinda curious now also.
*EDIT* I mistakenly said the 6” Darex wheel i have is a CBN wheel.
It is a 6” 180 diamond

 

[ajoeiam]

Hi,
I need some advise about a new 8" grinder that I have. I will use this for (mostly) for grinding HHS lathe tools, and of course, for many other miscellaneous jobs.
There are a ton of YouTube videos so I am "fairly ok" about normal grinding wheels, but I have not seen much on the "CBN" wheels. They are expensive so I want to get
some advise on whether they are worth it for sharpening metalworking tools or just use the abrasive wheels that machinist have used for years.
Dan

Well - - - you don't NEED a CBN wheel but it does enable you to make tighter corners when you're grinding.
A diamond wheel is even better at that!
The problem with a diamond wheel for grinding cemented carbide tools is that as soon as you're grinding on the substrate - - - - well diamond has an affinity for carbon, AIUI, so as you're grinding that steel you're eating up far too much diamond.
So yes a CBN wheel is useful but at least IMO not totally necessary. (But - - - - if you've got the $$$$ - - - - away you go - - yes?)

HTH

 

[Captain777]

Thanks for the replies.
Dan

 

[Tug40]

I just edited my post #3 and added photo.
My bad.....

 

[Chiptosser]

CBN, is not ment for general grinding. If you are touching-up and drill or and endmill, that's fine. They are not intended for hogging material.
You will have to make a very accurate or true running mount for the Darex wheel to be able to use it.

Load the grinder with a good 60 grit and 36 grit wheels and get or make an adjustible diamond dresser to true the wheels.
Then start practicing grinding tools. Keep a water cup close at hand.

 

[ajoeiam]

CBN, is not ment for general grinding. If you are touching-up and drill or and endmill, that's fine. They are not intended for hogging material.
You will have to make a very accurate or true running mount for the Darex wheel to be able to use it.

Load the grinder with a good 60 grit and 36 grit wheels and get or make an adjustible diamond dresser to true the wheels.
Then start practicing grinding tools. Keep a water cup close at hand.

Addendum to above.
(As explained by an instructor when I was an apprentice) Watch for the heavy tools! (meaning you WILL drop the hot ones! (And they get hot FAST!)

 

[awake]

If you are grinding HSS tooling, aluminum oxide works great IF you have the right softness of wheel. Unfortunately, a lot of grinders come with overly hard grinding wheels, which do not work well at all on tool steels. It is counter-intuitive, but for hard steel you need a softer stone, and vice-versa. You need something in the H range of hardness for HSS tooling.

Note that the speed of the grinding wheel makes a difference in how "hard" the wheel acts. If you spin an H grade grinding wheel significantly slower than its rating, it will seem softer. Note also that as the wheel wears down, the speed at the circumference will reduce, so it will seem to get softer and softer.

 

[Richard Hed]

If you are grinding HSS tooling, aluminum oxide works great IF you have the right softness of wheel. Unfortunately, a lot of grinders come with overly hard grinding wheels, which do not work well at all on tool steels. It is counter-intuitive, but for hard steel you need a softer stone, and vice-versa. You need something in the H range of hardness for HSS tooling.

Note that the speed of the grinding wheel makes a difference in how "hard" the wheel acts. If you spin an H grade grinding wheel significantly slower than its rating, it will seem softer. Note also that as the wheel wears down, the speed at the circumference will reduce, so it will seem to get softer and softer.

I bought a general grinding stone in the Philippines which was very hard and would not grind ANYTHING. Never went back to that store. Thing is, good stones are hard to find in the Phils, however, I eventually found a good one, bought two.

 

[goldstar31]

If you wat to send yourself into realms of ecstasy order a White Aloxite WA wheel in either 80 or 100 grit. Ask for K or LV bond.

 

[awake]

Last time I looked, it was hard to find a 6" stone of the proper grade here in the US as well - the only ones I could find were really expensive. I resolved that by building my own grinder that could take a 7" stone - 7" grinding wheels, made for surface grinders, are widely available, including relatively inexpensive options that still perform quite well. 3/4" thick stones are not common in this size - mostly 1/2" or 1/4" - but the 1/2" stones I get work just fine for all of my tool steel sharpening needs.

I don't have an 8" grinder, so haven't ever looked to see what the availability is in that size ...

 

[goldstar31]

I simplynn settled for the common 6" DE Grinder with a Aloxite wheel at one end and a 160 grit diamond one at the other. The rest of my Pandora's Box
Supplies here in the UK are straightforward, suitable and moderately priced-- and wave the old flag-- UK made!
Frankly, I get pissed off with the moaners here who are afraid that if they open their wallets/pocket books there will be a blinding flash-- never ever to be repeated.

 

[awake]

Goldstar, I hear your point ... but there is another side to the equation. When I started out hobby machining some 20 years ago, money was very, very tight. Choosing to spend more on consumable A meant that I could not purchase consumable B - even if I needed both. To be sure, there are "cheap" options that really are not cheap in the long run ... but there are also expensive options that don't really add any value. Tell me again - why does choosing to look for the best value for the money - not the cheapest, but the best value - constitute "moaning"?

Even now, when I have more disposable income to devote to my hobby, I don't have any desire to throw my money away just so that I can talk about how much I spent. Tell me again - why does that equate to "moaning"?

In the US - where I live, so the UK pricing is unfortunately irrelevant to me - it seems that there is a bit of a racket with regard to 6" grinding wheels. You can buy the awful way-too-hard wheels anywhere, for just a few bucks, but the only place you can get a 6" Alox wheel of the proper grade (the last time I looked, anyway) was through a Lee Valley or other higher-end woodworking store, and by the time shipping was factored in, it would be upwards of $50. Meanwhile, you can buy professional-grade 7" grinding wheels of the proper grade for less than half that price, and discount wheels - that still work very well indeed - for less than 1/5 the price. Tell me again: why does it make sense to pay more than double, or worse yet, five times more, for something that is no better? Oh, right - because that is just moaning.

Okay, I've laid it on rather thick above, and no doubt that reflects the fact that it has been a long and stressful week. But I too get very p---- off when people smugly state that they can find good pricing in their country ... which is 15,000 kilometers from the Philippines, where this particular discussion began. And I get very p---- off when people pat themselves on the back for being willing to spend money, apparently without any concern for the actual value.

And I may be unfairly characterizing you, and if so, I apologize. Did I mention an long and stressful week?

 

[Richard Hed]

I simplynn settled for the common 6" DE Grinder with a Aloxite wheel at one end and a 160 grit diamond one at the other. The rest of my Pandora's Box where I keep my pandemonium has 4" wheels.
Supplies here in the UK are straightforward, suitable and moderately priced-- and wave the old flag-- UK made!
Frankly, I get pissed off with the moaners here who are afraid that if they open their wallets/pocket books there will be a blinding flash-- never ever to be repeated.

My wallet exploded once when I opened it. Blew my face off and I died. Am still ded too. Oh heck, have to have a cig. Don't forget, you claim to be a billionaire while the rest of us peons use pesos--and have very few at that.

 

[goldstar31]

But it must be explained that I am NOT the OP. I know how to build and to use a tool and cutter grinder. I have several and whatever advise that I have gleaned is or WAS passed to the forum.

There is a maxim in England about not looking at a gift horse in the mouth.

 

[Richard Hed]

But it must be explained that I am NOT the OP. I know how to build and to use a tool and cutter grinder. I have several and whatever advise that I have gleaned is or WAS passed to the forum.

There is a maxim in England about not looking at a gift horse in the mouth.

I guess I forgot to tell you, along with my other faults, being ded, being a moaner (as ghosts will be), being a winer (with many flavors from the N.W. of USA and Philippines), not listening to my wife (and particularly not doing what she says) and others, too numerous to enumerate, I also have the fault of looking a gift horse in the mouth, as times have changed when this useful maxim made sense:= If I accepted a horse close to death, and it died soon after I accepted it (well, I could ride around on the ghost part anyway), then I would be responsible for getting rid of the carcass. I could always tell the authorities that I doesn't know where the carcass came from and therefore not responsible, but we all know about that--died on your propeerty, it's your responsiblitly. And Thanx you for your information and thanx you for your wonderful stories. Does you have any more? Ah, I remembers . . . .

 

[petertha]

These might not fit (primarily width dimesnion) & probably on the spendy side relative to most conventional wheel options. But the Tormek system is all about slow rpm grinding, for primarily knife & cutting tool blades. But also other edge tooling like woodworking chisels, gouges & the like (once you've shelled out even more $ on holding accessories).

Anyways, I mention only for you to have a looksee & see if anything resonates with your application. There are a ton of YouTube videos , many sales orientated, but also some that are quite technique/technical & also demonstrate their results on quantifiable measuring deices. PS - I don't own a machine, I'm intrigued but my Lotto tickets haven't intersected Happily-ever-after-mode yet.

https://www.sharpeningsupplies.com/Stones-Wheels-C175.aspx

 

[Chiptosser]

AWAKE
Didn't you have to make 1.25 adapters to use the 7" grinding wheels?

 

[awake]

Yes, of course! A quick and easy job on the lathe. Also the "dished washers" that grip the wheel on either side.

AWAKE
Didn't you have to make 1.25 adapters to use the 7" grinding wheels?