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How to grind lathe bits on HF carbide tool grinder?

I'll admit it right off the bat - I'm not the sharpest tool in the shed ;). I especially have trouble thinking in 3 dimensions. I'm the type that has to turn the picture of the tool bit the same way as the one I'm holding in order to get the angle right...

Anyway, I got one of the HF carbide tool grinders today (nice sale: $129.95). I thought that the tilting tables and miter gage would make it so simple that even I could do it. BZZZTT - Wrong!

Getting the end cutting edge and the end relief angle is pretty easy. I tilt the table down at the angle I want the end relief angle to be and set the miter gage to the desired end cutting edge angle and push the front of the tool into the side of the wheel.

I can't figure out anything after that! It seems that I need to have a slot for the miter gage that is perpendicular to the side of the wheel (actually four of them). The only way I could figure to do the side cutting edge angle was to use the miter gage and do it on the outer edge of the wheel. Problem is, I'm hitting the wheel below the center line and my side relief angle is wrong.

Hope I explained this in a way that is understandable. If anyone can give me some pointers (pics would be great!), I would appreciate it.

Thanks, Wallace

Reply to
Wally Blackburn
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I kinda hoped a better wordsmith than myself would answer you.

This is something easy to show and hard to explain. First I'd suggest you buy a good textbook for machining that has a chapter on bit sharpening. The text I used twenty years ago is the same as my son used two years ago; "Machine Tool Practices", multiple authors, has a GREAT section with lots of pics on this.

If you have a clone of the baldor carbide grinder (my understanding here), you can make a workable tool bit by grinding three planes with two of them the same. All work is done on the side of the wheel on these grinders if you want correct angles.

Plane 1: side relief, tilt table down by relief angle, say 7 degrees. Hold bit in the same line as the side of the grinder wheel and grind the last 1/2 inch until you're just up to the top edge of the tool bit.

Plane 2: Other side relief, same as 1 but on adjacent side. You'll have to use the other wheel or the other side of the same wheel and reverse rotation of the grinder.

You should now have a bit with two sides ground so they meet at the edge of the toolbit for the last 1/2 inch. Hope this is as clear as mud

Plane 3: This plane is on the end of the tool bit and is a compound angle. It needs to fall away from the cutting point going either way from the cutting point. Hold the bit on the right side of the grinder table with the cutting side facing up and back toward you. You're grinding the end of the bit here, with the bit almost perpendicular to the grinding face. Now, slide the outside edge of the bit forward by say 7 degrees and grind this face.

You should end up with a bit that has three planes meeting in a sharp point on the front top corner of the tool bit. The beauty of this system is this bit can be either a left or right hand cutter just by the way you place it in the tool holder. (After you get used to this, you will find that making a slight radius on the cutting edge improves performance a lot)

Hope this is some help.

-- An apple a day keeps the doctor away. Two apples a day gets the doctor's OK. Five apples a day makes you a fruit grower, like me.

Karl Townsend in beautiful Dassel,MN

Reply to
Karl Townsend

I have read many pages on tool grinding. None was as short and as easy to understand as the one here by Karl.

Regards,

David Heidary

Reply to
David Heidary

How about a rerun on it...?

Thanx,

Paul

Paul in AJ AZ

Reply to
Pep674

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