Boring Bar

[rleete]

Interesting workaround, Tom. I'll have to try that sometime.

[Highpower]

Good reason not to throw away broken/chipped end mills too. You can grind/modify them for use as single point tools.

[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

[Cross Slide]

(12-23-2019, 09:46 AM)TomG Wrote: If you are boring a 1/2" hole with those boring bars, they are likely rubbing below the cutting edge. Sharpen them up and add a secondary clearance angle so the area under the cutting edge doesn't rub on the bore. For most jobs you would be better off with high speed steel bars instead of carbide. They are easier to sharpen and much more forgiving.

Another option I've used in a pinch is to substitute an end mill as a boring bar. You just have to orient it so a cutting edge is horizontal and on the center of the part.

Tom

Tom
I definitely want to get a boring bar that uses HSS. 
Is there any info on the angles to grind the HSS for a boring bar that you know of?

I would never have thought about using a End Mill. May have to try that in the future!

Trevor

[TomG]

(12-23-2019, 09:50 PM)Cross Slide Wrote:

(12-23-2019, 09:46 AM)TomG Wrote: If you are boring a 1/2" hole with those boring bars, they are likely rubbing below the cutting edge. Sharpen them up and add a secondary clearance angle so the area under the cutting edge doesn't rub on the bore. For most jobs you would be better off with high speed steel bars instead of carbide. They are easier to sharpen and much more forgiving.

Another option I've used in a pinch is to substitute an end mill as a boring bar. You just have to orient it so a cutting edge is horizontal and on the center of the part.

Tom

Tom
I definitely want to get a boring bar that uses HSS. 
Is there any info on the angles to grind the HSS for a boring bar that you know of?

I would never have thought about using a End Mill. May have to try that in the future!

Trevor

The bars I'm referring to are solid HSS. As far as grinding them goes, it's the same theory as used to grind turning tools. You can look on my website (Toms Techniques) in the reference section for that information. Here is a link to a source for those boring bars:

Travers Tool

Tom

[Dr Stan]

This is what I have:


https://www.travers.com/200-series-10176...4-570-383/


EVEREDE Series 200 10 Degree Lead Angle Regrindable Tool Bit Boring Bar Sets

They are pricey, but well worth the money.  I didn't pay full freight as the set I bought was "used" but had never made any chips.  I don't remember what I paid for it, but it was well below list.  Nice thing is they take both HSS and carbide blanks.

[Highpower]

That is a nice looking set Stan. What size/shape blanks can they use?

[Dr Stan]

(12-24-2019, 11:30 AM)Highpower Wrote: That is a nice looking set Stan. What size/shape blanks can they use?

The end view is a triangle and when inserted into the boring bar they are a right side up triangle.  However they do not have a positive stop like a regular insert.  I really like the fact one can get the inserts in HSS or carbide.

[Highpower]

(12-24-2019, 12:20 PM)Dr Stan Wrote:

(12-24-2019, 11:30 AM)Highpower Wrote: That is a nice looking set Stan. What size/shape blanks can they use?

The end view is a triangle and when inserted into the boring bar they are a right side up triangle.  However they do not have a positive stop like a regular insert.  I really like the fact one can get the inserts in HSS or carbide.

OK, thanks. The pictures on their web site don't show a clear image of the business end of the tool, and the bits looked like square stock to me. And they don't have any links to the inserts on the boring bar page either!

I finally found them though. https://www.travers.com/regrindable-bori.../c/297793/

The lack of a positive stop might not be as secure and rigid, but it does give you the benefit of being able to adjust the 'stick out' from the bar when needed. Opposite sides of a coin I suppose.

[EdK]

I had a couple of those Everede boring bars. They went with my lathe and mill. I bought them because I could get the HSS inserts for them. They are nice.

Ed