Boring Bar

[Cross Slide]

(12-22-2019, 10:45 PM)Highpower Wrote:

(12-22-2019, 06:37 PM)Cross Slide Wrote: I have a Piston Type QCTP
I have a set of Accusize Boring Bars that look just like the ones you attached the picture of.
I didn’t try sharpening them. 
How much clearance angle should I be looking for?

Here is a page that shows a couple of different options for holding a boring bar in your QCTP. http://www.micro-machine-shop.com/boring_bars.htm

Toward the bottom of the page they show a set of simple bars that you can make yourself if you want than can be used to hold round or square bits. Grind your own in HSS tools and clamp them into one of the through holes in the bar.

The import brazed carbide boring bars generally have a rounded relief below the carbide and I just grind it away as needed if it is rubbing the bore. They typically have a 0° end angle as well, so I grind about a 5° positive angle on mine to keep it from rubbing on the bottom of a bore.The idea is to have just enough clearance but not too much. The side 'angle' needed will change with the size of the bore.

rleete said: "Decent carbide, but not sharpened worth a fart in a windstorm. My set actually had a round edge on some of them."

I have a couple of sets that came the same way. The cutting edges were indeed rounded and wouldn't even cut Delrin (plastic) they were so bad. It would just rub on the side of the carbine and burnish the material. After putting a good sharp edge on them with the grinder they cut like buttah...

Thanks for the link Willie

I went to my shop today and tried grinding the carbide and adding a relief. 
Cut way better. Not sure if I got the best surface finish possible. But I’m happy with what I got for the first time trying boring bars. 
Trevor