Thread: Slow Speed bench grinder with CBN wheels

Originally Posted by derekcohen

A few comments ...

For example, the old Stanley blades really did not need grinding, unless it was to remove a chip. You could simply "grind" a primary bevel on a stone. Now the modern, thick blades are made out of harder and more abrasive-resistant steel, and trying this with one is a fool's game.

Learned this the hard way. It's possible to do it by hand, but it takes a long time, and it's not very... good. I'm never quite satisfied with the result, but I also don't want to invest more time to fix it, so I carry on with a less than ideal edge.

Patience is the key for everything. My preference is half-speed, as there is more leeway/safety in less speed. You can indeed use a high speed grinder. Just do so more carefully.

I'd read a previous comment from you similar to this, which led me toward half speed in the first place. However, I know you have the older Carbatec/Axminster grinder that seems to be a different beast the one currently being offered. Others seem happy enough, although noted that both owners in this thread didn't rate the integrated tool rest as being up to the job.

I'm also thinking about other future uses for the tool, like buffing, wire wheel, or perhaps the multitool attachment at some point. For all of those reasons, I think the full speed Linishall grinder with cast alloy tool rest is going to win out. I expect the integrated tool rest wont be amazing, but probably good enough grind chisels and plane irons no problem. If it's up to the job, it eliminates a workshop project (to setup a custom tool rest), and that's great because I can only manage a couple hours a week in the workshop at the moment!

My opinion don't buy the Linishall, not what they used to be, if you want to "Buy once" purchase the Multitool.

I don’t actually want/need the multi tool attachment at present.
seems as though Multitool only sell their own motor as a kit?

there’s the Abbott and Ashby option, but it doesn’t appear to be as well built as the linishall. Particularly regarding the tool test.

Originally Posted by Chief Tiff

Unless you’re going to be using Tormek jigs the BMG-100 is a very expensive tool rest that really doesn’t offer any advantage over more basic aftermarket models.

I have the Tormek jig with a CBN wheel and it excels in setting up the blade square very quickly if the blade or chisel has parallel sides. I put the blade in the jig and push it against the side of the wheel which is square to the cutting face and tighten the clamping screws that hold the blade. No mucking around with squares and it always results in a perfectly square grind.

Originally Posted by Chris Parks

I have the Tormek jig with a CBN wheel and it excels in setting up the blade square very quickly if the blade or chisel has parallel sides. I put the blade in the jig and push it against the side of the wheel which is square to the cutting face and tighten the clamping screws that hold the blade. No mucking around with squares and it always results in a perfectly square grind.

I take it you’re using the SE-77 square edge jig that comes with a Tormek wetstone grinder? That’s another $150 on top of the $180 price tag of the BGM-100 mount; effectively the same price as the grinder it’s getting mounted to. Plus you really need the WM-200 angle setting jig at another $50. That is reason I made the comment about Tormek jigs; if you have them then the BGM can be worth it but as a standalone system $380 is a lot of coin to spend on a tool rest. The basic SVD-110 tool rest is $75; so that, the angle setter and the BGM come to $305 but for $230 you can get the Veritas tool rest with both the skew and straight edge jigs/attachments.

Don’t get me wrong; I have the BGM for my slow speed grinder but that is because I also have a Tormek T8 plus several jigs.

And thanks for the tip on setting blades square using the side of the wheel; that’s a good one!

I would like to add one thing. I went spare trying to grind square. I had been so fussy mounting the BGM and getting everything square.

What was letting me down I realised was... minute flex on the shaft. It is much less closer to the machine but noticeable when you're trying to get it perfect.

It's very good kit but certainly not a "cheat mode" and requires some nouse.

Originally Posted by BobL

That's an equivalent surface speed to an 8" wheel doing 864 RPM. I wouldn't exactly call that slow. I call 100 rpm slow.

I deleted my response. THought I was getting off track for what the OP was looking for...

But to answer your point. I forgot to say there's a 4" pulley on the grinder shaft and a tiny one on the motor. It needed that to keep the motor rpms up as much as possible... At 12 htz the rpms are roughly 100

Originally Posted by Chief Tiff

I take it you’re using the SE-77 square edge jig that comes with a Tormek wetstone grinder? That’s another $150 on top of the $180 price tag of the BGM-100 mount; effectively the same price as the grinder it’s getting mounted to. Plus you really need the WM-200 angle setting jig at another $50. That is reason I made the comment about Tormek jigs; if you have them then the BGM can be worth it but as a standalone system $380 is a lot of coin to spend on a tool rest. The basic SVD-110 tool rest is $75; so that, the angle setter and the BGM come to $305 but for $230 you can get the Veritas tool rest with both the skew and straight edge jigs/attachments.

Don’t get me wrong; I have the BGM for my slow speed grinder but that is because I also have a Tormek T8 plus several jigs.

And thanks for the tip on setting blades square using the side of the wheel; that’s a good one!

I certainly did not pay those priced and wouldn't buy them for that. I bought the Tormek jog and angle gauge when it first came out and from memory the whole lot was about $150 but don't quote me on that. It would not be rocket science to make one, this one was made by somone who no longer posts here.
IMG_1998.jpg

I’m in the process of buying a slow speed grinder and a CBN wheel from Carbatec. Any one have experience with the Carbatec CBN wheel.

Just been reading all these posts and wondering if I can ask a question based on a similar topic. I currently have a Record 250mm Wet Stone Sharpening System. I have just purchased several Tormek jigs and am also wanting to get a CBN Grinding Wheel. I see that the Record Grinder has noted “Max 500 rpm”. Can anyone tell me is it possible to fit a 250 mm CBN sharpening stone to my Record Grinder. If so, what grit might you suggest from what is on the market, and can you use it as a dry stone wheel, or do I get a wet stone wheel. Any ideas would be most welcome, thank you.

The Carbatec CBN wheels are 25.4mm wide.

I went with Vicmarc as it's 40mm wide.

I use a very simple home-made tool rest on my Axeminster slow-speed grinder - just a piece of 16mm SS bar (salvaged from tossed-out lab gear) that extends across the grinder & can be adjusted fore & aft to take care of stone wear. I use various simple clamps on the blades, this one is for cambered blades:
curved edges r.jpg

A square clamp for straight blades or a skew - makes it very easy to keep both sides of a skew even!
Straight blades r.jpg

The 16mm bar is just sufficiently rigid for the job, especially if you use a light touch (as you should).

As you can see, when the pics were taken, I was using a white ('alox') wheel which is a cooler-grinding wheel (grit-size for grit size) than a grey vitreous wheel. I switched to a (Vicmarc) CBN wheel ~5 yrs ago on that side - very happy with it.

As pointed out, you can still cook blades with a CBN if you are heavy-handed. The main reasons for over-heating with older style wheels were allowing them to become glazed & clogged (the very soft white wheels won't glaze so readily but they do clog); & being too heavy-handed. Apart from impatience, the temptation to press too hard is often due to using too fine a wheel. A 60 or 80 grit wheel is preferable if you have a lot of metal to remove - I keep a 60 grit grey wheel on the other side for 'rough' or heavy grinding (mower & chipper blades for e.g.), which is always cleaned before use with a "star" wheel (cheap gadgets that are extremely effective), & regular cleaning every few minutes if it's a long session.

I am very happy with my CBN wheel, it is definitely a step up on the alox wheel for cool grinding, and the flat side is a very useful feature. I used to (guiltily) use the side of my grey wheels, which is a risky thing to do according to safety manuals (though my fitter uncle did it all the time), but now I can use the flat (which remains flat to boot!) guilt-free.

There is one other factor that hasn't been discussed so far - grit size. It's a common tendency amongst amateurs to go for finer grit wheels because they leave a 'better' surface. However, they do so at the cost of slower (& hotter) grinding. It is often better to use a very coarse grit when there is any significant amount of metal to remove, it's not only faster, but can also be cooler. In fact, the surface off my 60 grit wheel is surprisingly good and the scratches are easily removed on my medium diamond stone. Unless you are a turner, I'd get a coarser CBN wheel than 180 - which is good if you want to take HSS tools directly from grinder to wood, but for general grinding I think you may find a coarser grit both quicker & safer....

Cheers,

An update.

I looked at 2nd hand GMFs (thanks for the tip @China), but I don't want another project on my hands.
I don't like the vibe of the Linishall, and there's a few reports of quality issues they've changed manufacturing in recent years.
So I'm gonna get the Abbott and Ashby 8" Industrial for a few extra bucks.

I think an external tool rest will be necessary. Anybody using the Woodcut Trugrind? Looks like the wolverine system (but that's not easy to buy here), and should suit my needs.
Tormek looks good, but I don't think it makes sense, since I don't have any of their other gear whatsoever. Becomes too expensive.

Originally Posted by IanW

There is one other factor that hasn't been discussed so far - grit size. It's a common tendency amongst amateurs to go for finer grit wheels because they leave a 'better' surface. However, they do so at the cost of slower (& hotter) grinding. It is often better to use a very coarse grit when there is any significant amount of metal to remove, it's not only faster, but can also be cooler. In fact, the surface off my 60 grit wheel is surprisingly good and the scratches are easily removed on my medium diamond stone. Unless you are a turner, I'd get a coarser CBN wheel than 180 - which is good if you want to take HSS tools directly from grinder to wood, but for general grinding I think you may find a coarser grit both quicker & safer....

Cheers,

Sounds like good advice Ian, I think I'll heed that. I really don't about fine finish, and I absolutely will be grinding a secondary bevel, probably on a 1000 diamond plate, before polishing on ceramic stones.

I'm still completely stuck on what jig to get though!
Trugrind, wolverine, and vicmarc systems are all really geared up for turners.
The veritas grinder tool rest looks okay, and I like the sliding mechanism, but it would need to be modified to fit a 40mm wide CBN wheel.
Tormek bar is very expensive for what it is, as discussed earlier.
I don't want to make one (another project).

The Vicmarc V00438 has got my attention. The grinding rest has the slidey slot with the triangle gauge. I'd probably only use 90 degrees and 23 degrees, but I like that it's repeatable and holds the tool steady for side to side grinding for wide plane irons.

I do know this system is aimed at turners though. So I'm not certain it will suit basic chisel and plane iron sharpening.
Can someone who knows more set me straight?!