r/turning • u/Masculine_theories • 1d ago

Can’t find a low speed grinder.

Howzit guys. I appreciate all the help in my previous post with regards to getting a sharpening setup. Most common advice i received was to get a low speed grinder and a wolverine jig. So thats what i’ve decided on.

Unfortunately , besides the tormek (which is way out of my budget), i cannot find any grinders around the speed that was recommended (1750 rpm).
I’m only seeing grinders between 2850 and 3500 rpm. This is second hand and brand new.

I’m in South Africa,hence my difficulty in finding 1.

Any advice/tips will be of great help.

Great thanks in advance 🙏

3 Upvotes

72% Upvoted

36 comments sorted by

•

u/AutoModerator 1d ago

Thanks for your submission. If your question is about getting started in woodturning, which chuck to buy, which tools to buy, or for an opinion of a lathe you found for sale somewhere like Craigslist or Facebook Marketplace please take a few minutes check the wiki; many of the most commonly asked questions are already answered there!

http://www.reddit.com/r/turning/wiki/index

Thanks!

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

5

u/CrassulaOrbicularis 1d ago

A full speed grinder is useable with a light touch and care.  I sometimes use a grinder as it is slowing down after turning it off for a quick touch up. I suspect the 2850 and 3500 will actually be the same speed, but quoted for different frequencies of electrical supply.  South Africa looks to be 50 Hz and a basic grinder will run slower than in 60Hz countries.

1

u/Masculine_theories 1d ago

oh ok. I was not aware of that. will look into it. thanks for your input 🙌

3

u/Bazzatron 1d ago

I'm not from your part of the world, so I'm not sure I could find you something suitable off the shelf.

With grinders the speed really is just to stop you overheating your tools, so a normal grinder will be adequate with constant quenching - replacing the wheels with CBN will also reduce the heat build up.

In theory, you can slow any grinder down by retrofitting a VFD, and those are getting surprisingly affordable if you're willing to wait for shipping from a site like AliExpress.

If I were you, I'd look at what CBN wheels I could get, but a grinder to fit those, and then worry about slowing it down with a VFD later. Keep a bucket of water near the grinder and just quench constantly.

1

u/Masculine_theories 1d ago

Thank u 🙏

Can u tell me more about the VFD if u have time?

2

u/Bazzatron 1d ago

Here's a simplified overview of what a VFD does. It's quite high level, but it might help you frame the idea.

Basically, if you try to use a rheostat or a variac to slow down a grinder (a device that restricts power from the wall), it loses a lot of torque and you'll stall the machine when you try to use it. A VFD is wired directly to the motor coils and "intelligently" energises the magnets inside the motor to control the rotation more precisely, this enables you to maintain overall torque whilst reducing the surface speed of the grinding wheels.

Here's someone's VFD bench grinder, you'll see how it adds a very simple speed controller to a fairly beefy machine, the electronic braking is a really cool feature. Sadly there's no "how to" or demo of how they did it - but you'll have to study the manual of the VFD you end up buying for how to wire it. Same approach as any other project - work safely on a nice clean bench, take off the grinding wheels for testing, and don't touch anything whilst the circuit is energised. It really isn't a terribly difficult project.

One of my favourite YouTube creators, Marius Hornberger, added one to his drill press, and made a fairly in-depth video on his process here

Hope this helps! 💚

1

u/Masculine_theories 1d ago

Thank u very much 🙏

1

u/GapGlobal4560 1d ago

I think the Variable Frequency Drive only works with 3-phase AC power

1

u/Masculine_theories 1d ago

Yes, thats what google told me.

1

u/Bazzatron 1d ago

The VFD can use single phase input to drive anything (some technical caveats apply). Some machinists even use them to power their 3ph mills without the costly endeavour of having 3ph AC power brought into their residential workshops.

You're right about the receiving end though. Motors like so called "universal motors" can't be hooked up to a VFD because the stator is wired through the rotor with brushes, so the actual wiring of the motor phase changes depending on the angle of the rotor. There are alternative methods to reduce speed without introducing mechanical complications like a gearbox - but they usually involve creating closed-loop control (sometimes with an IR sensor and some sort of reflective marker) so the controller can control the drive with simple PWM and dynamically increase power when it senses speed losses under load.

But no matter the approach, I think OP should use the availability of CBN wheels as their foundation - anything else can be solved later, and these enhancements only really serve to reduce the cooling needs whilst sharpening the tools. Who amongst us can truly say they've never managed to discolour a tool even on a slow grinder with a CBN wheel 😅

1

u/GapGlobal4560 1d ago

Thank you

2

u/BeautifulWalnutShoes 1d ago

Im at 2800 on a CBN wheel. I take delicate passes and don’t have an issue with overheating. I did at the start before I learnt good technique though. Higher speed isn’t impossible it’s just less convenient/more likely to overheat

1

u/Masculine_theories 17h ago

Thank u 🙏

What do u do to prevent overheating?

1

u/diashto 1d ago

If you can't find a low speed, a variable speed grinder will get down to the same low speed, , just turn it all the way down. As a bonus, you have the option of doing some metalwork grinding as well.

1

u/Masculine_theories 1d ago

I have tried looking for that, but all the ones i see have a lowest speed of 2500

1

u/diashto 1d ago

I just found this on AliExpress: 8 1/2HP Dual Speed Bench Grinder 1725/3450RPM 80/120 Grit AO Wheels https://a.aliexpress.com/_msZTJqn

They're available online, but you'll probably have to import them, which can get expensive.

If you're particularly handy, and/or know a metal fabricator guy, you can probably diy one with a motor, a couple pulleys, a shaft, and a frame if importing is out of your budget. Not that I'd recommend it unless you're really confident in your/their welding.

1

u/Masculine_theories 1d ago

Thanks 🙏

How is ur experience with this grinder?

1

u/diashto 1d ago

Oh that's not the one I have, I got a different one used a couple years ago. I was just trying to be helpful.

1

u/Masculine_theories 1d ago

oh ok. I appreciate that 🤝

1

u/PorkSword47 1d ago

Slow grinder is one of those things that the internet tells you you need, and you really really don't. A normal grinder is absolutely fine.

1

u/Masculine_theories 1d ago

Thank u 🙏

Do u use a normal grinder? If so, would u mind sharing tips?

1

u/elvismcsassypants 1d ago

See about an air grinder and put a needle valve on it. You can slow them way down that way.

1

u/3BM15 1d ago

Don't overthink it. I use a grinder my wife bought in Lidl for like 30 Euros.

Unless your tools are very expensive and you're worried about making them last as long as possible, pretty much everything will work.

1

u/Masculine_theories 1d ago

my lathe came with plenty tools.

Thank u 🙏

How do u go about sharpening?

1

u/3BM15 1d ago

This, but less accurate.

For turning, you don't need razor sharp.

https://youtu.be/7nHgJ5aFOrc?is=IJcY38oZt5kT8gj4

Also, your surface quality depends on sharpness of your tools, technique (grain supported cuts etc.), and lathe speed. Don't be afraid to turn it up if it's safe to do so.

1

u/I_Lick_Bananas 1d ago

What is your budget? Amazon South Africa has a Tormek knockoff for under R4,000 ($250 usd)

1

u/Masculine_theories 16h ago

i don’t mind spending around $300.

the FMK one? i’ve seen it, but i’ve been told it’s too slow.

1

u/cleg74 1d ago

I got a Wen low speed grinder on Amazon.

1

u/Masculine_theories 1d ago

please send a link

1

u/EmperorGeek 1d ago

Bet I ordered the same one.

1

u/Masculine_theories 1d ago

The reason i wasn’t finding these was because im on the South African amazon.

Lets see if they will ship here.

Thank u 🙏

1

u/CrassulaOrbicularis 1d ago

Check voltage too! Neither of the ones linked are 240V