04-19-2015, 04:28 PM
Altered the long steel shank of a Walter Screw-Fit adapted B3230.T18.20-26.Z1 precision boring head. The boring head screws onto the tapered, hardened steel shank. The OD of the boring head is 19mm (3/4"), and it's made to bore from 20mm (0.787") up to 26mm (1.0236") using a CCGT050204 (CCGT1.81.51) insert.
The "business end" of the steel shank where the boring head mounts comes down to a little below that 19mm, but I stopped at just a hair over 19mm when I turned it. It was really HARD steel! I think over 55Rc (560HBn) and may have actually been up to perhaps 62Rc. Fortunately I have some Valenite grade 9605 TiAlN coated inserts capable of turning hard steels, no problem. Normally that might be in the range where you go to CBN inserts which I also have, but I prefer using carbide inserts with chip control.
The customer of mine (yeah, a pay job for a change) said the shank cost him "only" $144, so if I screwed it up it wouldn't be a big deal. He needed to reach into a hole by about 3" (76mm), but at an extreme angle so he needed 5-1/2" clear. From there out to about where the original taper started it figured out to be about a 14.2º angle so I used the compound slide at that angle to make the new cone shape. Glad it came out good with no mishaps, because although the steel shank is relatively cheap, that boring head lists for $1,174.00. Ouch. I gotta tell you though, if you ever come across a deal on one those B3230 boring heads are the cat's meow. So smooth!
![[Image: IMG_4022-r_zps4qbr9vl9.jpg]](http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_4022-r_zps4qbr9vl9.jpg)
![[Image: IMG_4025-r_zps2lacef2u.jpg]](http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_4025-r_zps2lacef2u.jpg)
The "business end" of the steel shank where the boring head mounts comes down to a little below that 19mm, but I stopped at just a hair over 19mm when I turned it. It was really HARD steel! I think over 55Rc (560HBn) and may have actually been up to perhaps 62Rc. Fortunately I have some Valenite grade 9605 TiAlN coated inserts capable of turning hard steels, no problem. Normally that might be in the range where you go to CBN inserts which I also have, but I prefer using carbide inserts with chip control.
The customer of mine (yeah, a pay job for a change) said the shank cost him "only" $144, so if I screwed it up it wouldn't be a big deal. He needed to reach into a hole by about 3" (76mm), but at an extreme angle so he needed 5-1/2" clear. From there out to about where the original taper started it figured out to be about a 14.2º angle so I used the compound slide at that angle to make the new cone shape. Glad it came out good with no mishaps, because although the steel shank is relatively cheap, that boring head lists for $1,174.00. Ouch. I gotta tell you though, if you ever come across a deal on one those B3230 boring heads are the cat's meow. So smooth!