I just had to share this with folks who'd understand
Sorry, I couldn't take any photos as I didn't have my camera with me...
A few years ago I posted a thread about enlarging a hole in hitch spade. Turns out these damn things are made out of some forged steel that is all but impossible to machine through conventional methods.
I've machined material like titanium and 316 SS with much, much better success than this stuff. It goes from "cutting" to "harder than the hobs of hell" in a blink of an eye.
I did it in a Smithy 3-in-1 machine and it was a royal PITA. My machine didn't have the horespower to do it and the spindle definitely didn't have the rigidity to handle it even if it did have the power. I had to run it slower than the carbide wanted and it still rattled around and stalled the machine. I had to stop and sharpen the carbide after one pass. All in all, it took me the better part of 6 hours to go from 2" to 2.25"
Well yesterday I had another one of these hitches to do. This time I had the advantage of a 16" Pacemaker, a 1.5" Kennametal boring bar with CNMG Ti coated carbide inserts and a 12" 4 jaw chuck with T-slots.
So I got the spade in the chuck using three jaws and all four t-slots plus some double sided tape and some spacers. It was a little nerve wracking setup, but I got it dialed in to within 0.04", which is pretty good for a tractor hitch that was all beat up. The holes are cast/forged to nominal accuracy and tend to "waller" out over time anyway.
I tried it first as a fairly low speed and a 1.75" boring bar with Rex 95. It cut, but it didn't want to. I had to sharpen the bit after every pass and it was still leaving grooves in the work corresponding to the hard and soft sections.
I decided it was time to ramp up the speed and check out the carbide. Long story short, it worked beautifully. I ran at 385 rpm and .0156 ipr (IIRC) and the chips popped off in a spray of bronze colored chips. Miracle of miracles, the Ti coated carbide insert held up wonderfully. The coating wasn't even worn away when I was finished.
By the time I was done, I went from about 1.9 inches out to 2.2 inches and then cut a 12* taper on either end that enlarged the opening to 2.5" at the top and bottom of the hitch spade. All without any chatter and leaving a smooth surface.
The really amazing thing to me was how accurate it was. I was taking .015" and .025" DOC and the bore measured damn near exactly what the dial said it should be (+/- 0.001 - every time I measured it my jaw dropped. I kept expecting it to change from boring bar flex or accumulated error in the screw or something!) I've never had that happen in any other lathe (even on external turning jobs) saving the 10EE I used over the summer. Even the degrees on the compound worked out properly. I think my 3-in-1 has rolled acme threaded rod so it accumulates error very quickly. Also, the degree markings are really close together and don't seem to be suepr accurate.
All in all, I was sure glad to have this machine!
Sorry, I couldn't take any photos as I didn't have my camera with me...
A few years ago I posted a thread about enlarging a hole in hitch spade. Turns out these damn things are made out of some forged steel that is all but impossible to machine through conventional methods.
I've machined material like titanium and 316 SS with much, much better success than this stuff. It goes from "cutting" to "harder than the hobs of hell" in a blink of an eye.
I did it in a Smithy 3-in-1 machine and it was a royal PITA. My machine didn't have the horespower to do it and the spindle definitely didn't have the rigidity to handle it even if it did have the power. I had to run it slower than the carbide wanted and it still rattled around and stalled the machine. I had to stop and sharpen the carbide after one pass. All in all, it took me the better part of 6 hours to go from 2" to 2.25"
Well yesterday I had another one of these hitches to do. This time I had the advantage of a 16" Pacemaker, a 1.5" Kennametal boring bar with CNMG Ti coated carbide inserts and a 12" 4 jaw chuck with T-slots.
So I got the spade in the chuck using three jaws and all four t-slots plus some double sided tape and some spacers. It was a little nerve wracking setup, but I got it dialed in to within 0.04", which is pretty good for a tractor hitch that was all beat up. The holes are cast/forged to nominal accuracy and tend to "waller" out over time anyway.
I tried it first as a fairly low speed and a 1.75" boring bar with Rex 95. It cut, but it didn't want to. I had to sharpen the bit after every pass and it was still leaving grooves in the work corresponding to the hard and soft sections.
I decided it was time to ramp up the speed and check out the carbide. Long story short, it worked beautifully. I ran at 385 rpm and .0156 ipr (IIRC) and the chips popped off in a spray of bronze colored chips. Miracle of miracles, the Ti coated carbide insert held up wonderfully. The coating wasn't even worn away when I was finished.
By the time I was done, I went from about 1.9 inches out to 2.2 inches and then cut a 12* taper on either end that enlarged the opening to 2.5" at the top and bottom of the hitch spade. All without any chatter and leaving a smooth surface.
The really amazing thing to me was how accurate it was. I was taking .015" and .025" DOC and the bore measured damn near exactly what the dial said it should be (+/- 0.001 - every time I measured it my jaw dropped. I kept expecting it to change from boring bar flex or accumulated error in the screw or something!) I've never had that happen in any other lathe (even on external turning jobs) saving the 10EE I used over the summer. Even the degrees on the compound worked out properly. I think my 3-in-1 has rolled acme threaded rod so it accumulates error very quickly. Also, the degree markings are really close together and don't seem to be suepr accurate.
All in all, I was sure glad to have this machine!
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