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View Full Version : Slow vs fast Spark grinders



Big Shed
14th Jul 2010, 11:28 AM
I have a very good quality 8" spark grinder with a bluemax and a white Alox wheel. I use this quite successfully for most sharpening tasks, especially my HSS tool bits for the metal lathe.

Not so good with freehand grinding my woodturning gouges and chisels, as some who attended Sunday's do at 's would agree:D.

One of the things I learned there by first hand experience is the value of jigs for this task, thanks to Ken:2tsup:

To this end I will be adding 2 BGM100 bars to my grinder to hold the jigs, then use my Triton Wet Grinder for final honing.

Before I do this I would like to know whether there is any advantage in getting a slow (1400RPM) spark grinder rather than the fast (2800RPM) spark grinder I am using now?

Is there a real difference in results between the 2?

Ed Reiss
14th Jul 2010, 12:00 PM
Before I do this I would like to know whether there is any advantage in getting a slow (1400RPM) spark grinder rather than the fast (2800RPM) spark grinder I am using now?



yep...the slower ones are easier to catch:roll::D

Big Shed
14th Jul 2010, 01:10 PM
yep...the slower ones are easier to catch:roll::D

You must be confused with girls Ed:?:doh:

Sturdee
14th Jul 2010, 05:07 PM
Before I do this I would like to know whether there is any advantage in getting a slow (1400RPM) spark grinder rather than the fast (2800RPM) spark grinder I am using now?

Is there a real difference in results between the 2?

I think that the only difference is that the slower speed will cause less heat being generated, hence you can grind longer if needed. Not really necessary if only touching up your tools.

BTW, thinking of getting the jigs as well for use with my Seppach.


Peter.

Ed Reiss
15th Jul 2010, 12:05 PM
You must be confused with girls Ed:?:doh:
Ha...at my age the slower the better!!:D

cornucopia
15th Jul 2010, 04:40 PM
I dont belive there is any diffrence in the edge quality- but i find that its much easier to blue the edge on a 2800 grinder than it is on a 1400. I know that it doesnt matter if the edge blues just as long as i dont quench it. i also find that that the 2800 is so fast that controling the shape of the bevel etc is difficult- especially when using jigs.

hughie
15th Jul 2010, 05:33 PM
The high speed grinders are very good for rapid removal and I dont really favour them. Mine is 1440 and its plenty fast enough and I use 120 grit
At 2800 on a coarse wheel [ say 80grit ], control is an issue especially if your not used to handling a grinder. If I had to use a 2800 then I would back off on my grit size, at the end of the day we are sharpening, not forming and so I dont see the need for losing tool steel on the grinder.

Heres a bit of info on grinding wheels etc
Google (http://www.google.com.au/#hl=en&source=hp&q=grinding+wheel+grit+size&aq=0&aqi=g1&aql=&oq=grinding+wheel+grit&gs_rfai=&fp=90b329054c573dfd)

Manuka Jock
15th Jul 2010, 05:33 PM
Ha...at my age the slower the better!!:D
Fast horses and slow women eh Ed :U

rsser
15th Jul 2010, 05:38 PM
The Blue Max wheel runs a bit cooler than others cos of the honeycomb structure; with a bit of care you shouldn't be doing any bluing with HSS tools with a fast grinder, even with white or pink alox wheels.

Your best guarantee of avoiding it in any case is to dress the wheel often; when it clogs the crystals at the surface don't break down and you get friction and heat without much metal removal.

AFAIC the best combo is a cheap chinese platform on one side and BGM on the other. For scrapers etc if you only have BGMs you are prob looking at buying a platform to mount on the bar anyway.

orificiam
15th Jul 2010, 11:28 PM
I Fred I read Somewhere don't remember where with fast grinders, if it's for just a touch up =just bring the grinder to full speed and switch off.bring the tool and sharpen as it slows down= No blueing the tool.
Cheers Tony.:)

Ed Reiss
16th Jul 2010, 12:06 AM
AFAIC the best combo is a cheap chinese platform on one side and BGM on the other.

Blue Grass Music :?:D