C max chipping

[rayf24]

Hi to all members I have been busy of late and had little time scratching till today.
The question has any one else had problems with C max chipping and tip braking even when cutting a straight line its like the heel is cracking off approximately 0.1 of a mm and in some cases a small piece behind the tip will crack off .
Any ideas whats happening its like floors in the steel when you look close with max magnification.
Thanks in advance.
Ray

 

[tim halloran]

rayf24: Dub the tip of the graver. Hold it at a ninety degree angle to the surface of a ceramic wheel and swipe it lightly across the surface of the wheel. You don't need much pressure , I usually swipe mine about three eights of an inch. Try This and you will cut down on tip breakage.

 

[Choppers_rule]

Is dubbing the tip onto a piece of wood also prevent breaking?

 

[monk]

any grinding scratches left behind can cause problems if far enough up near the tip. a good final polish would reveal such if it's there.

 

[Andrew Biggs]

I've struck this before with all the carbides. It took me a while to get used to them and now I use them a lot, particularly the C-Max carbide gravers.

Dubbing slightly helps for sure. So does altering the face angle to 55 and even 60 degrees depending on the metal being engraved. Also technique comes into it. Carbide is unforgiving and twisting the graver tip in the cut, even slightly will break it every time.

However I also think that on some carbide blanks you get spots that are weak (i have no proof of this)..........When I strike a carbide that keeps breaking for no obvious reasons I grind back a millimetre or so to get over the weak spot and that usually works.

Cheers
Andrew

PS. When you stab the graver into wood it's not dubbing the tip..........you are simply getting rid of any tiny burs on the edges of the graver that can be caused during the sharpening process. Particularly if you are using a coarse grit to sharpen with.

 

[Brian Marshall]

Sticking the tip of a graver into hardwood after sharpening is a leftover from the days when all we had were carbon steel gravers...

The idea was, that if there were any tiny burs left from the sharpening and final polishing - they would break off.

We did not use microscopes then, so I have no solid evidence that it actually works?

It became a habit however, and I have always done it without thinking about it much. I rarely use carbon steel any more, 'ceptin' a few liners and "trick" gravers that cannot be made from HS and exotic alloys. Maybe next time I sharpen one I will look and see if indeed there are any burs, and whether habitually sticking it in the wood actually does something? Other than transfer stresses of the day... to a defenseless chunk of wood...


Brian

 

[rayf24]

Thanks gentlemen I shall give these things ago the more I played I now think it is a brittle spot but will also dub the tip thanks for taking the time to answer I shall let you know what I find .
Ray

 

[James Ashley]

Aside from a weak spot or technique I found if I had even a hint of vibration when cutting tough material this also caused me to break the tips like you describe. I found going back and tightening my setup down and eliminating vibration has been one of the single best things I have done to improve the cutting technique. Just a thought!

 

[quickcut07]

I am no expert on carbide but do cut a lot of stainless and hard steels. I do use carbide quit a bit and as you may or may not know carbide does not like chatter. As a milling tool, lathe bit or drill with a constant speed it will go thru most hard metals. If you chatter the tooling 9 out of 10 times it will chip and need to be sharpened. Now to take this to the world of engraving reduce the intensity of the stoke, increase the face angle, and watch your speed. Tight corners will almost always break the tip. Choose how wish to approach the design, do your straighter cuts and slowly ease into a scroll. Do not try to cut intricate detail quickly slow down. At times I stop and come back into a cut from the other end with a light cut. Then go over it a little heavier a second time. Remember if you break your tip that piece is lodged in your work you will need to get it out before you ram a fresh ground graver back into the same spot. This is not always the case but it does happen. Now what Andrew has stated is very true. If you break the tip you will need to grind back a bit before proceeding, micro fractures at times occur in the tooling and need to be completely removed before proceeding. Personally I have 4-5 carbides sharpened at the same time same shape. If I have problems with one I switch it out, if it breaks then you could have hard spots in the metal. At this point throwing the graver, banging your head against the wall cursing the work piece sometimes helps. All hard metals are an exercise in tool sharpening, go slow and sharpen often. I could add more but this is very lengthy as it is. Good luck. PS. HSS works good on hard metals just take it easy.

Eric

 

[Idaho Flint]

However I also think that on some carbide blanks you get spots that are weak (i have no proof of this)..........When I strike a carbide that keeps breaking for no obvious reasons I grind back a millimetre or so to get over the weak spot and that usually works.

I two have had this happen to me, and believe the same as you do Andrew. There seems to be parts of the graver that are prone to breakage, due to being to weak or to brittle I do not know.

A couple of things that also helped me was to only grind the face down up to 600 grit wheel, and not go all the way to a mirror finish. I do use a lap with diamond dust to create the heal. I also noticed that if I put any pressure on the graver while grinding (to try and speed up the sharpening) that it will leave behind a jagged edge that is more prone to breaking. I found that I need to have a lighter hand on sharpening, especially at the lower grits.

Mike

 

[jerrywh]

I use Cmax a lot. I always grind my face angles at 55 to 60 deg. If I am cutting very hard tough metal I will put a very small flat on the bottom of the heel. I do not dub the tip and honestly have never tried it. The tiny flat on the belly will make mine last about three times longer. Cmax must be polished to the max. I have also found that when coming to the end of a cut I don't try to flip the chip out. I just stop and then shave it off. When you flip it straight up it replicates the same action that you do when chipping flint and it will chip off the tip sometimes.

 

[Dani Girl]

I have found trying to flick the chip will often break a c max. I love them though. I have taken to putting a decent finish on them and a polished heel seems to help a little.

I just found some cheap pipe on ebay i am going to go and cut to different lengths if anyone wants the link for using sharpening templates to change how far the graver sticks out consistently.

 

[Dani Girl]

Does this look like the correct angle for a 60 degree graver.

I haven't tried changing from the factory set angles before.

That's tube 6.43mm long.

 

[Dani Girl]

Like this angle for 60?

 

[Dani Girl]

http://www.ebay.com/itm/16136026975...49&var=460383200045&ssPageName=STRK:MEBIDX:IT

10mm tubes work on Lindsay Template sharpening system.

Equation for working out correct tube length for different angles. Ask me if you want an angle and I'll happily crunch the numbers for you.

 

[James Ashley]

Steve has these lengths published on his website in a sticky thread. biggest problem I found is it also increases the heel angle and may make it uncomfortable to engrave with. It did for me.

 

[Dani Girl]

I wander if it's worse to change the heel angle or to not have ''úniform' parallel point.

 

[Brian Marshall]

You can make your own "templates" for your favorite grinds. I've made a few over the years. I have one around that Benno Heunne made 40 years ago, built with a nothing more than a saw, a file and a drill press. Oh, yeah, and a tap to thread the collet for setscrews...

Use brass cartridge cases (or whatever tubing) for "spacers". Cut 'em to the length that gives you the angle you need/want.

Not rocket science. You can make whatever you'll need with minimal tools and a few math skills - or at least access to someone who has those skills.

Dani has the math skills, and I believe she has or can learn the "physical" part. Easily cut from 3/16" (4 to 5mm) aluminum stock or even steel.


Brian


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[Dani Girl]

I have taken to using a steeper face now while leaving the heels the same as the factory template length. I put the usual tube on to set the length and sharpen face and heels a little, then slip the shorter tube on and give myself a steeper face angle.

I'm happy with how that's working