PDA

View Full Version : Carbide Tip Sharpening



Auskart
5th September 2012, 07:55 AM
What is the best way to sharpen Carbide tips ?

pipeclay
5th September 2012, 08:06 AM
On a grinder with the correct wheel.

Chief Tiff
5th September 2012, 08:12 AM
Are you talking about replaceable tipped tools or brazed on tips?

Generally you need a "green" or diamond wheel to grind anything this hard. However, if your referring to replaceable tips....why would you try to sharpen them?

Auskart
5th September 2012, 08:25 AM
Thanks Chief, they are the Brazed type.

eskimo
5th September 2012, 09:01 AM
However, if your referring to replaceable tips....why would you try to sharpen them?

after you brazed them to a bit of steel for new turning tools:2tsup:...or so ive been told:rolleyes:

Chief Tiff
5th September 2012, 09:14 AM
No worries. You need a silicon carbide grinding wheel (a "green" wheel) in a bench grinder, take gentle cuts with no lubricant or quenching. You can also hone the tips with fine diamond files between sharpenings.

Chief Tiff
5th September 2012, 09:24 AM
after you brazed them to a bit of steel for new turning tools:2tsup:...or so ive been told:rolleyes:


Hmmm.... never actually thought of doing that! Then again, I absolutely hate having to grind tools and have always tried to use a TCT every time.

I've turned chipped tips into negative rake tools for roughing out harder materials but generally I just chuck 'em away once they're unserviceable.

Graziano
5th September 2012, 09:33 AM
A diamond wheel with the diamond particles embedded in phenolic resin cuts fast and is pretty cheap these days from the Internet. The only thing you have to watch out for is avoiding contact with the steel base of the tool and the diamond, as the steel will ruin the diamond, something to do with the carbon content of the steel and the carbon of the diamond crystal. It will need some form of lubrication too like water or kero or wd spray.

If you undercut the steel below the carbide piece with a conventional grinder wheel you can then grind the carbide on the diamond wheel without damaging it. I tend to go with 100 grit 100mm dia cup wheels as I picked up a few for $15, on the 'net. Plated diamond wheels are also cheap and worth considering too. I have 250mm silicon carbide wheel but I've yet to get it running on a spindle so i can't comment on it, i have heard it's a lot slower than diamond though and the wheel does wear quickly as it's designed to do.

franco
5th September 2012, 12:25 PM
Does anyone know whether using a CBN wheel to touch up brazed carbide tooling would harm the wheel? I only have 4 brazed carbide tools (from a face mill which originally came with a mill drill) so have never bothered to get a green wheel, and the tool hasn't been used for years. The CBN is so easy and quick making and sharpening HSS tools that I would hate to damage it by grinding brazed tungsen if it is not suitable for this purpose. I have not been able to find any references on the internet which give this information.

Frank.

jack620
5th September 2012, 04:53 PM
Frank,
what shape & grit of CBN wheel do you use for your HSS tools?
Chris

franco
6th September 2012, 01:01 AM
Frank,
what shape & grit of CBN wheel do you use for your HSS tools?
Chris

Hi Chris,

I have the 150 x 20 wheel described here:

http://cws.au.com/shop/category/optigrind-cbn-grinding-wheels

Sorry, I can't remember the grit, and it does not seem to appear in the wheel description in the seller's literature. It is very fast cutting though, but leaves a much nicer finish than the old grey wheels.

Frank.

Chief Tiff
6th September 2012, 09:28 AM
I had a look at the Norton Abrasives website; in their toolroom selection they list diamond and CBN wheels. They state that CBN is second only to diamond in hardness and under the descriptions of each type they list typical uses. They recommend diamond for off-hand grinding of brazed carbides and CBN for HSS and alloy steels.

Maybe try to sharpen one of your cutters on an unused part of the CBN wheel and see how it affects the wheel, but if CBN is really that hard I can't see any potential issues.


(note: It's great to be able to offer advice knowing full well it's not my gear being experimented on :D:D:D)

jack620
6th September 2012, 11:56 AM
Thanks Frank. Pity their thinnest wheel is 20mm. My little grinder only takes 13mm wheels.

I've been considering something like this:

eBay Australia: Buy new & used fashion, electronics & home d (http://www.ebay.com.au/itm/390440433917?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_2573wt_1167)

Your wheel appears to be CBN bonded to steel. The one I linked is diamond embedded in resin. I've also seen CBN in resin. It's bewildering the variety of wheel shapes, abrasives (alox, diamond, CBN), bonds (metal, resin), grits, abrasive concentrations, etc. Makes it hard to choose the right wheel. And then I wonder about the quality of a $30 wheel.

Chris

franco
6th September 2012, 03:19 PM
Chief Tiff,

Thanks for checkiing on the Norton site for the information on using CBN on brazed tungsten. I have not yet found an authoritative source which specifically recommends CBN wheels for the purpose.

In view of that, and your vote of confidence in the information, (which mirrors my own misgivings!)
It's great to be able to offer advice knowing full well it's not my gear being experimented on :D:D:D and the cost of a replacement wheel, I think it would be more sensible to get a couple of sticks of 3/8" square HSS and make a new set of cutters from this if I need to use the tool in future.

Regards,

Frank.

nearnexus
6th September 2012, 07:17 PM
This is basically all you need. Not expensive.

6" SILICON CARBIDE GRINDING WHEEL / HSS GRINDING WHEEL | eBay (http://www.ebay.com.au/itm/6-SILICON-CARBIDE-GRINDING-WHEEL-HSS-GRINDING-WHEEL-/370159967436?pt=UK_Home_Garden_PowerTools_SM&hash=item562f40dccc)

I've been regrinding carbide cutters for use with this type of wheel for years.

It's easy to bronze braze carbide onto DIY boring bars and the like, and grind the cutting facets freehand.

Save yourself a fortune. You lose the indexing function, but so what?

If done correctly you can achieve a razor sharp edge on carbide.

I'm currently using a Norton grey diamond wheel (nearly worn out) that was rescued from a valve facing unit.

HSS is OK for easy machining jobs, but try it on high carbon metal/weld and see how it (doesn't) perform :)

Rob

Graziano
6th September 2012, 07:46 PM
Anyone used Norton/St Gobain SG seeded Gel wheels at all?. I just found out about them today, according to a grinding textbook I read today, they last up to 10 times longer than aluminium oxide and have faster grinding rates. Apparently they grow the particles chemically then fire them in a furnace to obtain grit that has no crushing defects and much sharper particles.

Norton SG (http://www.nortonindustrial.com/ToolroomWheels-NortonSG.aspx)

eskimo
7th September 2012, 08:52 AM
Anyone used Norton/St Gobain SG seeded Gel wheels at all?. I just found out about them today, according to a grinding textbook I read today, they last up to 10 times longer than aluminium oxide and have faster grinding rates. Apparently they grow the particles chemically then fire them in a furnace to obtain grit that has no crushing defects and much sharper particles.

Norton SG (http://www.nortonindustrial.com/ToolroomWheels-NortonSG.aspx)

not me ...but i am going to try them out...if they're not too rich

morrisman
7th September 2012, 04:49 PM
I see that RDG has these green SC wheels in cup form as well , they maybe more suitable for a T&C grinder than the flat wheel would be ? Mike



This is basically all you need. Not expensive.

6" SILICON CARBIDE GRINDING WHEEL / HSS GRINDING WHEEL | eBay (http://www.ebay.com.au/itm/6-SILICON-CARBIDE-GRINDING-WHEEL-HSS-GRINDING-WHEEL-/370159967436?pt=UK_Home_Garden_PowerTools_SM&hash=item562f40dccc)

I've been regrinding carbide cutters for use with this type of wheel for years.

It's easy to bronze braze carbide onto DIY boring bars and the like, and grind the cutting facets freehand.

Save yourself a fortune. You lose the indexing function, but so what?

If done correctly you can achieve a razor sharp edge on carbide.

I'm currently using a Norton grey diamond wheel (nearly worn out) that was rescued from a valve facing unit.

HSS is OK for easy machining jobs, but try it on high carbon metal/weld and see how it (doesn't) perform :)

Rob

RayG
7th September 2012, 09:49 PM
Anyone used Norton/St Gobain SG seeded Gel wheels at all?. I just found out about them today, according to a grinding textbook I read today, they last up to 10 times longer than aluminium oxide and have faster grinding rates. Apparently they grow the particles chemically then fire them in a furnace to obtain grit that has no crushing defects and much sharper particles.

Norton SG (http://www.nortonindustrial.com/ToolroomWheels-NortonSG.aspx)

Hi Graziano,

I've been using the SG wheels on the surface grinder for grinding the forum M2 chisels and plane blades, still not sure I like them. They seem to be harder to keep dressed, but that could just be I'm not really all that experienced in using them...

I was seriously thinking of going back to Alox...

Regards
Ray

PS Still Jet lagged.... :)

Graziano
7th September 2012, 09:56 PM
Hi Graziano,

I've been using the SG wheels on the surface grinder for grinding the forum M2 chisels and plane blades, still not sure I like them. They seem to be harder to keep dressed, but that could just be I'm not really all that experienced in using them...

I was seriously thinking of going back to Alox...

Regards
Ray

PS Still Jet lagged.... :)

Hi Ray, glad to hear you're back again after that month long wild party :rolleyes:. Are your wheels the lower content 3SG or the higher seeded gel content 5SG type?, I hear the 5SG last longer but may be harder to use as a result. SG type is supposed to be self sharpening which I take to mean the grit breaks off the wheel face. I'll be getting one soon as well as the usual white AlOx to try out, the abrasives salesman was claiming to my friend that a lot of his clients have switched to seeded gel in preference to white aluminium oxide....might just have a pallet load to shift though, which has happened before.

RayG
8th September 2012, 12:27 AM
Hi Ray, glad to hear you're back again after that month long wild party :rolleyes:. Are your wheels the lower content 3SG or the higher seeded gel content 5SG type?, I hear the 5SG last longer but may be harder to use as a result. SG type is supposed to be self sharpening which I take to mean the grit breaks off the wheel face. I'll be getting one soon as well as the usual white AlOx to try out, the abrasives salesman was claiming to my friend that a lot of his clients have switched to seeded gel in preference to white aluminium oxide....might just have a pallet load to shift though, which has happened before.

Hi Graziano,

The 3SG60 is the one I've been using, recommended for grinding RC62 M2....

Don't let me discourage you from giving them a try, the results we were getting were pretty good, just seemed to require a bit more care with dressing, and me not being used to a softer wheel is probably all that amounts to.

Regards
Ray

franco
1st February 2013, 06:14 PM
For the record: earlier in this thread I queried whether a CBN grinding wheel could be used for sharpening carbide tooling, having been unable to find any recommendations on the internet. It seems this is not a good idea. The following advice was quoted from the Georgia Grinding Wheel Company on PM recently:

"Diamond wheel on steels and CBN on carbides?

We get asked quite frequently if a diamond wheel can be used on steels and CBN on carbides. We do not recommend this as the wheel life will be greatly reduced and in some cases, the wheels may not even cut at all. A diamond wheel is specifically used for carbides, plastics and other synthetic materials. It will not grind steel well at all. CBN wheels should only be used on steels. There is a hybrid grit available that will grind both; However, it is a compromise in wheel life and grind-ability. But in cases where you must grind both materials at the same time, it can be a real time saver."

It appeared in this thread:

First attempt at grinding a cutter. - Page 2 (http://www.practicalmachinist.com/vb/general/first-attempt-grinding-cutter-259588/index2.html)

I do like my CBN wheel for sharpening HSS!

Frank.