Thread: Slow speed grinder vs wet stone grinder for a novice

1. I guess since I am now looking for a machine specifically for sharpening, then I should only consider a slow speed grinder or wet stone sharpener. Is that correct?

For wood turning using HSS chisels a slow speed grinder is not necessary.

Or can I buy any old $100 grinder and stick an Alu Oxide white wheel on it and be happy?

In principle yes.
Well, I would make sure the wheel is sized correctly for the grinder, 6" grinder with 6" wheel, etc
More power is better as you can grind it quicker (also make mistakes quicker too)
Less power takes longer to grind especially if a chisel tip reshaping is needed.

This tends to be a can of worms... but...

With woodturning tools the edge really doesn't stick around for that long. Depending on the piece of timber I'm turning, on a good day I'll be resharpening around every 10-15 minutes. On a bad day, every 30secs or less. No joke.

Consequently I consider both slow wheels and wet wheels a waste of time when turning. They'll get the tool extra sharp, but a few seconds after first contact with the wood they're no sharper than you could expect off a bench-grinder.

I like turning, sharpening is just a chore that needs to be done to get there.

If you have a select few chisels that are reserved solely for finish cuts, then they can merit from the sharper edge gained from a slow/wet grinder. But in general a bench-grinder with a good wheel should suffice. (What type of wheel is another can of worms... but I've been using Al₂O₃'s for a couple of decades now and I feel no urge to change! )

Now... if you also have carving chisels, plane blades, etc. that don't have to stand up to the abuse that turning chisels invariably see, then a slow or wet wheel is definitely of benefit. (Although my bench-grinder w/Al₂O₃ wheel would still be my goto when turning.)

Dave, I have used a normal Alox wheel for grinding of turning tools, prior to going to the Tormek/CBN route.
For a beginner and good jig system is more important than the latest and greatest in grinders.
A wolverine/Oneway etc combined with a 2 hand Aussie made grinder (GMF, A&A etc) and correctly sized and dressed wheels will get you on the road of consistent grinds and that is the key to sharpening, consistency.

The reason I went, eventually, to all CBN, is my Alox wheels required replacing and the CBN's do not need dressing, thus set and forget.

As with Skew, sharpening is a necessary evil and I try to minimise the amount of time doing the function, I much prefer turning.

I'm looking to buy something so that I can sharpen woodturning chisels because I'm told I will need this a lot to be able to do any turning.
I am also told I need to sharpen my new woodturning chisels even before first use. So they are collecting dust with the lathe just now. (and not in a good way).

Aside from that I would also use it to sharpen my ordinary wood chisels, the cheap hand planer blade and also the good kitchen knives. Probably also a few other things around the workshop that don't come to mind just now.

I'm told that a slow speed grinder is necessary because a high speed grinder heats the metal and will degrade the temper of the metal. But then I see that some woodturners use an ordinary (high speed) grinder with Alu Oxide white wheels. So I'm left confused. Are Aluminum Oxide wheels magic? Must be.
but if they are magic then how much better is a slow speed grinder? Confused!

I don't really get the risk of degrading the temper to be honest. My wood turning chisels claim to be HSS. High Speed Steel is tempered at something like 1,200C. So how hot does it need to get to undermine that? Obviously it is not going to turn red hot while I'm holding it to a grinding wheel. (Reckon I'd notice). Although, it's all just black magic to me.

I can see that a strop or hone would be a waste of time if I have to repeat it every 15 mins. So that clears up one aspect.

I can also see that slower is better while I'm learning how to sharpen stuff. In fact that might be a key point in my case.

Dave

The cheapest best set up is a simple 6" high speed grinder with at least one CBN wheel. If one wheel, then get a 180 grit. If more than one, possibly also a 350 grit. I am not sure if 6" CBN wheels are available in Oz, but they are in the USA. Otherwise 8".

Just be sure to match the grinder arbor size with the wheel. There are metric and imperial around.

Regards from Perth

Derek

180# cbn in 150mm diameter from Carroll's Woodcraft Supplies, Geelong Victoria.

Originally Posted by DaveVman

I don't really get the risk of degrading the temper to be honest. My wood turning chisels claim to be HSS. High Speed Steel is tempered at something like 1,200C. So how hot does it need to get to undermine that? Obviously it is not going to turn red hot while I'm holding it to a grinding wheel. (Reckon I'd notice). Although, it's all just black magic to me.

It's actually far less about the temperature than it is about time.

There are dozens of types of HSS.
The most commonly used for turning chisels are M2.
These are tempered between 200 and 600ºC but any form of tempering only changes the initial hardness by <5% which will not affect most woodturning.
More importantly the tempering times are in the region of hours so a few seconds or even minutes even at cherry red will not change the temper.
Annealing (softening) is performed by heating to only 870ºC and then the temperature is reduced at around 20ºC per hour down to ~500ºC ie this takes around 20 hours!

Short of leaving HSS in a hot fire for many hours you won't do much to it's hardness.

Originally Posted by BobL

It's actually far less about the temperature than it is about time.
[...]
Short of leaving HSS in a hot fire for many hours you won't do much to it's hardness.

True.

Where temperature becomes a concern is older Carbon Steel. Whether it be woodturning chisels, firmer (etc) chisels or plane blades, CS is much more temp. sensitive.

If you blue the edge, you've lost the temper and need to grind past to find good steel again. Hopefully without making the same mistake a 2nd or 3rd time!

Fortunately, once you know how it's easy enough to sharpen 'em even on a bench-grinder. Basically lots of quick, light passes, with time to cool down between once they start to warm up.

If you don't know that what you're trying to sharpen is HSS, it's always best to err on the side of caution and treat it as CS.

If you have non-turning non-HSS tools that you also need to sharpen consider a separate sharpening system for them. There are many economical and effective hand sharpening methods for those.

For HSS turning tools a full speed bench grinder with any wheel will do the job [full stop]. Anything beyond that is just nice to have.

I used one like this for many years (note: this one is a secondhand 200mm GMF that is currently up on eBay, so that link will eventually disappear, with a starting price of $49.99 with no bids as yet with 2 days to go).

Next step up from there for me was to make better tool rests and jigs for it. And, it was not until well after that I upgraded to better wheels. By then you will know if turning is something you want to invest more time and money in.

Personally, I don't have enough turning time left in my life to squander it standing around waiting for my turning tools to become sharp on a slow dry grinder....


PS - there is probably more than a few white 200mm Al-Ox wheels sitting on the shelves of forum members that were displaced with CBN wheels, which could come your way for a small consideration, that is if you don't decide yourself to go straight to CBN from the grey SiC/carborundum wheels.

Like most of the above have pointed out a bog standard grinder will do for turning chisels. A white wheel improves things a bit. Early in my venture into turning I got a Sheppach wet grinder and while it gets things nice and sharp and you really can not burn the steel it is a slow process and setting up jigs for each tool becomes an exercise in frustration. Mine mostly sits gathering dust and only comes out if I have to put a new bevel on on a mangled old tool being restored. I pretty soon went back to my cheap grinder with a white wheel. Sharpening has to be done but how much of your time do you want to be at it.
Regards
john

I just popped in to draw a distinction between a slow speed grinder and a wet stone sharpening system such as a Tormek. A wet stone system is good for honing your edge and touching it up, it is too slow for shaping and grinding. A slow speed grinder is just a bench grinder that runs at 1500rpm instead of 3000rpm, and when it comes to a quick sharpen is no slower than a normal speed grinder. You can grind and shape a tool on a slow speed grinder, it might be slightly slower than a high speed grinder of the same power - it’s quite easy to overheat a tool on a slow speed grinder too, and heat is a function of the work being done on the metal.

Slow speed grinders became popular among turners as people started moving to CBN wheels becuase the linear speed of an 8 inch wheel at 3000rpm is on the theoretical high end for a CBN wheel, but I don’t think it’s as much of an issue now that many people have been using that setup for a few years with no problems.



tl;dr A slow speed grinder still works well as a grinder but a Tormek isn’t really suited to grinding.

I agree with all of the above.

Some years ago I bought a lathe which came with an 8 inch slow speed grinder and a white and gray wheel, along with the Wolverine grinding jigs. I put another white wheel on in place of the gray wheel and have a flat tool rest on that side for the skew and scrapers, other side for bowl gouges.

Later I bought a used Tormek 7 with a bunch of jigs, rests, etc. for close to what I paid for the lathe, grinder Wolverine jigs, Oneway chuck, and bench.

The Tormek is wonderful for bench chisels, scissors, knives, etc., puts a razor sharp edge on everything. Same can be achieved with a piece of 400 grit paper on a granite sink cutout, or the lathe bed for about $700 less.

Knowing what I know now, the hot set up would be a generic slow speed grinder with two white Aluminum Oxide wheels and the Tormek bar and bowl gouge jig, and a flat rest for scraper and skew. Later, even much later, replace the Alox with CBN.

I would hone the skew with a piece of 400 grit on the lathe bed to get that razor sharp edge - which will be gone in a minute. Hone the inside of the bowl and spindle gouges with a piece of rolled up 220 - 320 sandpaper for the finish cuts. When hogging out the inside of a bowl a little tearout does not matter, go grinder to bowl.

If the object is to make turnings, there is little time for elaborate sharpening rituals. I walk in shed, turn on grinder 12 inches from the tail end of the lathe, sharpen, turn, sharpen, turn, etc. finish bowl, turn off lathe, turn off grinder, leave shed.

Always a very diverse range of opinions when it comes to sharpening.

Its a matter of horses for courses when it comes to belt vs wheel, Alox vs CBN, 6" vs 8", wet vs dry, fast vs slow grinder options. However the most significant issues to determine what options are best for you is the style of turning you prefer, the timbers you use, how often you turn and is your available time very limited.

Bridge carpenters don't spend a lot of time honing tools and conversely fine carvers don't rely upon an edge straight off an 80 grit wheel on their tools. The same applies to wood turners!

If you intend to turn medium to large bowls and platters from Red Gum or the like, that may have embedded objects that destroy edges, then there is little benefit using a finely honed edge. There is no functional gain and all you do is waste time. However if your preference is for smaller projects, fine spindle turning, finials etc then honing and wet stone systems such as the Tormek are well worth the extra effort, time and expense.

As a novice, beginner, you are testing the waters so an appropriate versatile low cost system is what you are chasing. To that end a generic run of the mill 200mm (8") grinder plus an Alox wheel and a basic jig system is your most economical option until you decide what style of turning is for you. It will handle the hack sharpening of big bowl gouges etc for those bowl & platter blanks that knock an edge off as fast as you touch the blank and it can be used to create a much finer edge more suited to hand honing for spindle gouges and skews.

The big secret for using conventional HS spark grinders to create finer edges - run the grinder up to speed, turn off the power, then sharpen on the run down. Alox wheels are relatively cheap, so a couple can be purchased for way less than one CBN wheel.

$400 will set you up with a new slow speed grinder plus 80 and 120 grit Alox wheels. Its well worth spending the $60 on the EZE-LAP Hone & Stone 3pk (very versatile set) and / or the $150 or so on a EZE-LAP Double Sided Plate Fine/Coarse 600/250g diamond plate IF you do spindle turning and use skews a fair bit.

The next expense and probably the one to guarantee you sharpening success is a jig system - again many choices and as many more opinions on what is "best". Again it comes back to turning preferences & budget. There are many very good systems about. A simple platform and turning tool angle jig will set you back around $70 and will handle skews plus spindle roughing gouges. Around $150 - 200 will set you up with a "complete system" something like the Woodcut True Grind units and will handle most woodturners requirements.

Now if you choose the Tormek T8 ($1250) plus Woodturners Kit ($550) option be prepared to spend upwards of $1800. The Tormek system is very well thought out and does deliver the goods IF you are an AUDI / BMW / Merceedes type turner. Why Tormek do not offer a T8 plus CBN wheel instead of the conventional Supergrind wheel ($389) is beyond me????

This one is not in Brisbane itself, but already has an Alox wheel on it, but it is not clear if its a 150mm or 200mm grinder.

https://www.gumtree.com.au/s-ad/beau...ner/1201767127

Revision: After looking up the Carbatec website, that grinder looks like their 150mm model which is now selling for about the same price, so not such a good deal after all.