CARBIDE INSERTS AND TOOLS

[jwoitasek]

Back again guy's.

Does any one resharpen or recycle those expensive DAMN inserts for mill's and lathes?
Also
Can you resharpen the cemented type tool bits.
Yes I am aware of the carbide grinding wheels but what grit to use?
My surface does not appear like the factory surface. I believe I have 50 and 100 grit wheels.
Can you reshape the tool bit?
How does one go about reshaping the steel underneath the carbide?
Can you use the carbide grinding wheel to do both the cemented carbide and the steel below it?
What grit?
Thanks again.
JRW

[spaceace]

no one i know sarpens carbide inserts, and for good reason, any change in original geometry has detrimental affect on tool life,
and cutting action usually. why spend hours sharpining tools that aint gonna cut.
cemented carbides can be resharpened, using 100 grit to rough and say 300 grit to finish, BEWARE! the steel tool shank will remove the diamond from your wheel, so relieve the shank first, a bench grinder has been used for that.

[Thrud]

Do not use Diamond on steel!

SiC wheels can be used to sharpen the brazed carbide, but as previously noted insure the supporting steel underneath is ground away with a different wheel first. Carbide can be honed by hand with a 600 grit diamond file for a first rate edge. Leave the top flat side alone - only grind the sides of the brazed carbide.

[Paul Gauthier]

The company I work for sends out all our used ceramic inserts to be reshaped into smaller inserts, price is about $6.00 less Per insert than buying new inserts. As we use 95% ceramic inserts vs. carbide it saves a big chunk o money. The same thing can be done with carbide but the savings isn't as great.
Cemented carbide tools can be shaped by grinding into any shape you need, as Thrud said stay off the top. I use two shapes most often, one 60* for threading and one 45* for general turning and facing.

------------------
Paul G.

[John Stevenson]

Well I'm a bad boy because I do sharpen carbide inserts, probably makes me cheap as well but I have to get a living out of this.
What makes me even badder is I grind the tops as well.
I have a small homemade grinder made from a small 3 phase 1/4 Hp motor the size of a big coffee mug. This carries two wheels, one each end. One is a 3" tapered cup wheel and the other is a 4" alloy wheell with 1/8" of diamond on the side and the 1/2" wide front face. I made the wheel blank and had it coated, cost about 25 UKP to be done, [ $38? }
The reason I do this is because I do a lot of work on laser cut blanks and this eats tools until you are under the cut surface.
Using a reground tip lets me get under the cut easily and rip the material off. If I need to get a good finish, hold a size etc I can switch tools for one with a decent tip.
The job I'm running at the moment are some large disks 12 " dia 1/2" thick with a 4" hole in the middle. The outer and inner diameters need a 1/4" chamfer on them. These are just end plates that are welded into rollers but there are 100's of them, nothing special and not close tolerance work. I have two tool holders machined up to hold the 60 degree tips at the right angle. I mount both tools together and just plunge in along the bed, doing both chamfers at the same time.
Because of the hard laser cut edge the tip always breaks down at the same point.
Using reground tips I can do this job with no tip costs.

I would not think of doing this on a cnc machine where you need to keep the tool offsets but on a manual machine there is no problem. Lets face it when brazed tips first came out you used to regrind those, we still regrind brazed boring bars. Just because the tip is loose what's changed?
I sometimes get the lad to mill some pockets on 1/2" HT bar, braze some old turning tips on them and grind some boring bars up.
We had to that's how we learnt. We have to get away from this everything comes out a catalogue.

Big Bad John

[Peter S]

Can't say I've bothered to resharpen carbide tips for general turning, but have made up various spade drills approx. 25-30mm for drilling hardened steel. Made up steel shank and easy-flowed on two triangular turning inserts, and touched them up on the green wheel. Not nice, but make the required hole. Carbide still seemed to work OK despite this treatment.

[docsteve66]

Me too! John. Hows about tellingus more about the ins and out of getting diamonds on a wheel. I never heard of that one.
Steve

[John Stevenson]

Steve,
To get diamonds onto a blank alloy wheel is called cheque book engineering
No seriously I came across this company at a show and they will make any size and type of wheel you need.
http://www.eternaltools.com/

I just made the blank to suit the motor and got them to coat it. The last one I had, a commercial wheel costing a lot of money lasted about 5 or 6 years. For a home shop guy these would last a lifetime. I must say that this one from Eternal looks to be holding up far better than the last wheel.
I find I don't use the cup wheel on the other end so I'm ging to get them to do me another wheel identical but with CBN for HSS tools. They will be at the Midlands Model Engineering exibition in October so I'll get them to bring me one over.

John S.

[tonydacrow]

There is actually a way to put diamonds on a wheel at home. Lapidaries do this all the time.

Start with a metal wheel. (Lapidaries use copper but steel will also work.) To "charge" the rim, sprinkle the diamond dust on a harder substrate (hardened steel, agate, granite, etc). “Roll†the wheel with some force on the diamond dust. The crystals will imbed into the metal.

This type of charge will last quite a while. To lengthen the time the charge will last, simply electroplate the wheel (nickel is best, but copper or other metals will work as well). Diamonds (carbon) conduct electricity very well and will plate evenly. Try it. It actually works and saves a lot of money!

[Thrud]

Tony

That is true, but resin bond and brazed grit is impossible with common home equipment. The brazed grit last far longer than electroplating and using an aluminum oxide dressing stick opens them up so they cut like you would not believe! CBN is also impossible at home.

John

Thank you for the link! I need some weird stuff and now I know where to get it! I use lots of Diamond - files, wheels, paste, loose crystals. I even relapped a set of gage blocks that had seen better years - used a Webber Carbide Gage block as the master lap with 100,000 mesh Diamond and grease. They now wring as good as my ceramic blocks (my sunday best, as it were) and as I use them in the shop for the rough stuff - any dimensional change is minor. Using my certified blocks and and electronic gage I have compared them and they are only a few millonths smaller but they work better than the new steel ones so I am pleased with the result.

I do regrind old flat inserts, but not the chip breaker style. I still have a hundred pounds of the flat ones and KNUX inserts used in copy lathes of yore. I grind them for specials. I also never throw out the chip breakers - the Scotsman in me says to horde them to make brazed tools. (just more junk around)