# Bench grinders



## HLW (Nov 19, 2008)

Is there any advantage of an 8" bench grinder vs. a 6'' grinder when sharpening turning tools? I have been using a 6" grinder with a Wolverine jig for some time but have thought of buying an 8" since they are on sale at Woodcraft.:blink:


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## NCPaladin (Aug 7, 2010)

JMHO but the current 8” has the advantage of being slow speed and having 1” wheels rather than ¾”. That said, I have been using the 6” for many years and I don’t think going to 8” will make you a better turner. The 8” will last long because you have more to grind off but they are more expensive also. If I were buying new I would go with the 8” but I would not spend the money just to change. 
People say you get less heat buildup with the slower speed and I am sure you do, but only if you sharpen badly to start with.
Maybe turners who have used both for several years can give you a better comparison and bring up other points.


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## HLW (Nov 19, 2008)

Well I was thinking along the same lines too and will probably save the money. Believe me I wasn't looking for it to make be a better turner. There is no hope there.:laughing:


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## Ray Cover (Mar 19, 2010)

What are the speed on the two. The 8' May be slower but that does not necessarily mean that your surface is passing your tool any slower.

Here is what I mean.
6" wheel x 3.14 = 18.84" circumferance
8" wheel x 3.14 = 25.12" circumferance.

So for each revolution of you grinder the 6" wheel is running 18.84" of grinding surface past the tool the 8" wheel is running 25.12" of grinding surface past the tool. 

so to gain any advantage as far as heat build up the 8" wheel would have to run less than 74% slower than the 6" wheel. 

Ray


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## wildwood (Jan 25, 2011)

Bought a 6” bench grinder after messing with belt sander on homemade stand many years ago. When old grinder quits will buy an 8” x 1” grinder with ¾ hp motor. Only other requirement have is buy locally. 

Woodcraft grinder would only cost $107 shipped to my house. Nearest store 3 hour drive one way. Great deal if works not so good if have to ship back for exchange or money back.


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## jlord (Feb 1, 2010)

The radius is bigger with an 8" wheel which would grind a different hollow grind on the tool.


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## firehawkmph (Apr 26, 2008)

Ray Cover said:


> What are the speed on the two.
> Ray


1725 vs. 3450

Mike Hawkins


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## Ray Cover (Mar 19, 2010)

The 6" at 3450 is pushing 5,416 FPM
The 8" at 1725 is pushing 3,611 FPM

So at those speed differences there would be a definite difference in how much cooler the 8" would run.

Ray


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## HLW (Nov 19, 2008)

I would have to add that the grade of stone(course vs fine) used would also be a factor in the heat issue, not just rpm's.
When you're talking about speeds of a 6"[email protected](5,416 FPM)or an 8"[email protected](3,611 FPM) I wouldn't think those would be a constant because that would depend on the hp of the grinder.Thanks again for the replies.


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## wildwood (Jan 25, 2011)

1725 & 3450 RPM grinders will both blue your tools if not watching what you are doing while sharpening. You should not blue your tools when trying to sharpen turning tools no matter what kind of steel made from. 

That 1725 or 3450 RPMS no load speeds generated by electric motors that are not continuous duty, efficiency fades during operation. Once my grinder is up to speed cannot tell when it fades even while sharpening. Even if let grinder run after changing wheels no clue about that fading business!

Calling a 1725 RPM grinder slow speed with less heat build-up more marketing hype than fact. People still manage to blue their tools, and put groove in grinding wheel! Dirty grinding wheels will heat up those tools too! 

I can walk away from sharpening my tools on my 3450 RPM grinder and touch the ends without burning my fingers. Yes, end of tool is warm to touch! Just touching up an edge all it takes. Whether have a 1725 or 3450 RPM grinder that should be your goal! Just keep wheels clean too!

If really, want a slow speed bench grinder less than 1,000 RPMS break out your wallet cause cost big bucks or make your own.


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## Ray Cover (Mar 19, 2010)

All is true... but it is easier to avoid heat up the slower your grinder surface is moving.

I have one of the slow grinders from Grizzly that runs in a water trough that I have been sharpening Rachel's on. Its been a while back but I think I only paid about a $125 for it. It takes awhile but it does a decent job and never gets warm.

I have also used my belt grinder when I was in a hurry and didn't have time to wait on the slow wheel and it works too. 

I have to agree with you, if you watch what your doing and are careful you can get the job done with just about anything that will abrade the metal from a bench stone to a high speed wheel. 

Ray


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## wildwood (Jan 25, 2011)

When started turning majority of folks used bench grinders to sharpen their tools, many people used various belt sanders, and very rich had Tormek wet grinder and jigs. Commercial or homemade sharpening jig for both grinders and belt sanders.

Not much has changed except variable speed bench grinders, couple less expensive wet grinders, and sharpening systems like Worksharp on market today. Still discussing whether to buy 1725 RPM and 3450 RPM bench grinders. What size is better 6” or 8” bench grinder. Topic of bench grinder size and speed will never end. Just buy whatever feels right for you.


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