Mill Boring bar cut a taper... how did this happen?

Tozguy said:
Would you elaborate on this please.
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I had a boring bar in the head already, a fairly small one. I only needed to take a bit of material, so I just used that.

I went back today and used a larger boring bar, and went up/down about 6 times and still got the taper, though only about 5 thou this time.
 
See the pic, originally used the one on the left. Just swapped to the one in the head after I pulled off the wax (made in India btw).
 

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That's progress. As with any boring bar the shortest thickest one is best.
With those brazed carbide ones we need to grind them for best results, sharp and with sufficient relief.
 
How deep a hole were you boring ? Those grinds on the shown bars don't look good in my opinion . Lack of clearance for one . Sounds like you were rubbing the bar shank for that much taper to occur .
 
1" deep it ended up being. Hopefully that is all this is :) I've not really used a boring head but once before, but don't remember having trouble with that one.
 
1" deep in brass ? It should be straight as an arrow . If your bar was flexing or rubbing , you would have heard it when breaking thru the bottom . A rubbing sound vs. a cutting sound .
 
Since we are on this subject! How about some recommendations for 1/2" indexable boring bars? I have a good 2-1/2" Enco head and have been using the brazed bars. I did 5/8" & 3/4" holes in 1018, 1 inch deep. Had about a hair over .002 taper. It was for a slip fit on a vise work stop. The shaft was turned on 1" square 1018 to 3/4" and had a .001 taper over 6". I liked that. The bore was OK but I would like to do better.

I need a small bar to handle around a 3/8" hole and then some different lengths to take over from about a 7/16" hole. Can't afford the expensive ones, so what brands/sets are you guys using? Looking for good quality import tooling that uses a common insert.

Saw this one. https://www.ebay.com/itm/4-Pc-1-2-I...485788?hash=item1ec767c61c:g:uBYAAOSwVqlaNFW4
Then just add a smaller dia one. Ideas? Good? Bad? Recommendations on other sets?
Thanks!! Charles
 
Chewy said:
How about some recommendations for 1/2" indexable boring bars? I need a small bar to handle around a 3/8" hole and then some different lengths to take over from about a 7/16" hole. Can't afford the expensive ones, so what brands/sets are you guys using? Looking for good quality import tooling that uses a common insert.
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I don't think I've ever seen an indexable bar with a 1/2" shank that can go into a 3/8" hole, although it very well may be out there. Even if it were, I would suggest you consider a cobalt HSS set instead. It will be cheaper to buy, last for many years, will cut finer and finish better. LMS sells a set. I own Borite cobalt bars and they are just excellent.
 
You are going to find that inserted carbide used in a boring head has its limitations but I won't go into that here. I own cobalt bars, brazed carbide bars and inserted bars for use in the mill and 99% of the time I use the cobalt bars.
 
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