Diamond coated steel disks for grinding from China

[Martin DowingParticipant @martindowing58466]

Ordered few via Banggood. Dirt cheap. Diameter 150 mm.

What are reasonable speeds of rotation for said discs?

I have motor with large pulley, entire setup was assebled in such a way that once discs have arrived, they will be supported by/fitted to side of pulley.

Side supportive surface of the pulley will be made flat and I will ensure, it runs true.

Cooling bath can be provided (wheel would be partially immersed in it).

Decent grinding table will be arranged.

Intention is to have realiable setup for grinding and lapping carbide tools, carbide inserts, also these tipped with CBN, HSS, and odd surface grind job on small items to remove machining marks.

I have *slow* rotating motor (700rpm, 3phase, 1/4Hp), can double the speed or go down to 100-200 rpm with frequency modulator.

Now what do you think about such a slowly rotating setup?

Diamond wheels are known to be used up to 15m/s. This setup will rotate up to 1 m/s.

High speed of metal removal is not my priority here. It is also known that lapping is done at low speed to work well. Cooled wheels are also moving slow on many machines, eg those used for knives sharpening. Fast grinding of steel with diamonds is also problematic because steel dissolves diamond at temperatures involved, hence CBN is often used because diamond doesnt last long enough.

Do I have a chance to achieve expected results with proposed setup, or such a slow grinding machine is just a nonsense?

Martin

[Martin DowingParticipant @martindowing58466]

[Peter KroghParticipant @peterkrogh76576]

I have a 6" diamond disc that rotates at 1725 rpm and another that rotates at 170 rpm. Both speeds work well with lapping/shaping carbides. The 170 rpm unit is the second I built and I can mount, magnetically, discs from 300 mesh to 3000 mesh. All the meshes work well at those speeds.

Higher speeds can be used for much faster material removal but need a liquid "wash" of some sort to clear the swarf.

Pete

[mark smith 20Participant @marksmith20]

Ive used those diamond discs from Hong Kong , they are cheap and very good. I was using them on this contraption i put together to grind mother of pearl. But ive used them dry and wet on lathe bits carbide tips and allsorts of steels . They cut very fast and with light pressure never had the so called problem of steel dissolving the diamonds.

I had a water drip feed fixed to the back of it also put a tap on the bottom of the old aluminium pan. Controlled with a variable speed dc motor.

 

 

 

Edited By mark smith 20 on 02/11/2017 00:47:01

Edited By mark smith 20 on 02/11/2017 00:48:24

[Michael Cox 1Participant @michaelcox1]

I have been using these diamond discs,

https://www.aimtools.co.uk/products/141026-marble-granite-diamond-cutting-disc-115-22-23-20

on a modified bench grinder running at 3000 rpm for some time. They work very well for grinding carbide. I also use the set up to grind HSS, particularly drill bits, see:

http://mikesworkshop.weebly.com/new-uses-for-an-old-grinder.html

The secret of a long disc life is to use only a gentle pressure against the disc when grinding. High pressures can rip the diamond particles from the disc.

Mike

[Martin DowingParticipant @martindowing58466]

Many thanks for your comments.

So it seems that I should get some good use of these discs as well. Once they have arrived setup should be ready.

Martin

[John ReeseParticipant @johnreese12848]

I have several of those discs in various grits. I plan to make an aluminum backing plate then mount it and the disc on a 6" bench grinder. Speed will be about 3600 rpm. Next step will be to make a suitable tool rest.

[Martin DowingParticipant @martindowing58466]

@ John Reese,

Bench grinders like to produce considerable vibration, particularly if on one side stone will be left.

It is good idea to get the same weight on both sides of the spindle. Otherwise everything is fine, as long as wheels are perfectly true etc. If that condition is not met you will face troubles due to precession.

It will result in vibrations and considerable increase of load on bearings.

[John ReeseParticipant @johnreese12848]

Martin,

I am fortunate that my bench grinders vibrate very little. The 6" grinder has a narrow wheel on one side. I use that to thin the webs of twist drills. The other side now has a green wheel for carbide. That is the one I will replace with the diamond disc and backing.

[mark smith 20Participant @marksmith20]

Ive found these discs don`t need to be run all that fast .I doubt if i run them any more than 1000rpm never mind 3600rpm, and they work fine. Running at higher speed will just cause excess heat on the tool.

[John ReeseParticipant @johnreese12848]

Mark, That is true but 3600 rpm is the speed on all my grinders.

[richard 2Participant @richard2]

I bought some from fleabay have mounted them on both ends of grinder that had worn out wheels.

One end has a Pioneer drill grinding jig and the other has a tiliting table for sharpening lathe tools which it does excellently.

richard2

[Pete RimmerParticipant @peterimmer30576]

I have been using these discs on my grinder too but you have to be careful with the 3000rpm not to scorch them and if you have a cheapo 6" grinder you might struggle to get them running true enough not to 'bounce'.

Just recently I've made a slow speed grinder from a comparatively cheap wet stone grinder with adjustable angles for lapping carbide scrapers. This works wonderfully well at 350rpmand the discs should last a very long time. The other difference I have found with the slower speed is that it needs a finer grade disc than the grinder to get a very fine finish.

http://www.practicalmachinist.com/vb/machine-reconditioning-scraping-and-inspection/made-cheap-ass-carbidescraper-sharpener-341604/

If you have a lathe with a faceplate you can stick the disc onto that with some double-sided tape and choose any speed your lathe can run at. The faceplate will provide good solid backing for a good finish.

Edited By Pete Rimmer on 12/11/2017 00:32:31

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