- Joined
- Nov 26, 2018
- Messages
- 291
Hello all. Thought I would share a work project I had this past week. Not home shop, but an interesting work flow and workholding operation that can be observed none the less.
I was tasked with making a nose cone for a solid fuel rocket out of 304 stainless steel. About a foot long and little under 3inch Dia. The shank side is a parallel shaft with a tapped hole to hold to the rocket body. The cone shape is a proprietary profile, A collection of radius to approximate the ideal curve function that will minimize the air resistance when going supersonic.
What might be of most interest here and of most realivance is the work holding and use of a sacrificial backing ring.
This part may be deceptively simple. One may well make the shank first, then simply clamp it in the chuck jaws with a space away from the chuck jaws where the shank to cone transition. However jaw slippage and reference dimensions need to be accounted for. The roughing passes put enough axial pressure that the shank could well retreat inwards in the jaws.
Hence the usage of the sacrificial ring. Made of low carbon steel, it functions as support away from the chuck jaws and a reference tool.
The shank is inserted with the sacrificial ring, concentricity is checked of the 6 jaw, and the primary tool is Zeroed to the ring in Z axis. The shaft is then inserted fully to the ring having a suitable Zero line established one inch away from the chuck jaws. You may notice the tack weld on the ring, that functions as a key or dog leg on the piece to prevent free spinning of it when the lathe tool cuts into the ring, as it rests against one of the chuck jaws.
Once clamped, rough turning can commence, and a single fishing pass with a new insert. The profile is no where a parallel diameter, except for on the sacrificial ring where the curve transitions to a parallel segment. A place where a micrometer can be placed to take measure of the diameter for the profile. The aforementioned finish pass was purposefully. 025" Dia over sized. Where now the delta from programed to actual can be measured and compensated for on the final pass. The final pass is made with a .5 thou competition. Then the lathe process is completed. Another benefit of the ring is that there is now burr on the piece, leaving a purpose full sharp edge. The burr is instead pushed into the mild steel ring close to the chuck jaws. After removal it can then be buffed to a higher shine.
I hope this little glimpse into my work was of interest.
I was tasked with making a nose cone for a solid fuel rocket out of 304 stainless steel. About a foot long and little under 3inch Dia. The shank side is a parallel shaft with a tapped hole to hold to the rocket body. The cone shape is a proprietary profile, A collection of radius to approximate the ideal curve function that will minimize the air resistance when going supersonic.
What might be of most interest here and of most realivance is the work holding and use of a sacrificial backing ring.
This part may be deceptively simple. One may well make the shank first, then simply clamp it in the chuck jaws with a space away from the chuck jaws where the shank to cone transition. However jaw slippage and reference dimensions need to be accounted for. The roughing passes put enough axial pressure that the shank could well retreat inwards in the jaws.
Hence the usage of the sacrificial ring. Made of low carbon steel, it functions as support away from the chuck jaws and a reference tool.
The shank is inserted with the sacrificial ring, concentricity is checked of the 6 jaw, and the primary tool is Zeroed to the ring in Z axis. The shaft is then inserted fully to the ring having a suitable Zero line established one inch away from the chuck jaws. You may notice the tack weld on the ring, that functions as a key or dog leg on the piece to prevent free spinning of it when the lathe tool cuts into the ring, as it rests against one of the chuck jaws.
Once clamped, rough turning can commence, and a single fishing pass with a new insert. The profile is no where a parallel diameter, except for on the sacrificial ring where the curve transitions to a parallel segment. A place where a micrometer can be placed to take measure of the diameter for the profile. The aforementioned finish pass was purposefully. 025" Dia over sized. Where now the delta from programed to actual can be measured and compensated for on the final pass. The final pass is made with a .5 thou competition. Then the lathe process is completed. Another benefit of the ring is that there is now burr on the piece, leaving a purpose full sharp edge. The burr is instead pushed into the mild steel ring close to the chuck jaws. After removal it can then be buffed to a higher shine.
I hope this little glimpse into my work was of interest.
Made thousands and thousands of different rounds up to 120mm for the Howitzers . The larger windscreens were pretty easy on the cncs . The little 20mm tungsten split grenades for the OICW weapon were a ****** ****** but still fun .
