Buckshot
07-19-2009, 03:59 AM
.............I had a bit of time available the other day and had had a need which has been irritatingly circling around in my head like a gnat for a couple weeks. My scheutzen rifle in 32-40 is crabby about rim thickness. Of course just dragging the breechblock handle up will handily shave off some offending brass, but I don't think it's supposed to be used like that :-) While I have a ton of other things I want to tinker with, I haven't been able to use the milling machine lately, and I wanted to so this project got the go ahead.
http://www.fototime.com/6A3AEAFCA19293E/standard.jpghttp://www.fototime.com/6960941CF1C4A0A/standard.jpg
I made a rim thickness dealie-bob. I used a piece of .75 x 1.5" 6061 aluminum 3" long. Because it was pretty simple to do, but accuracy would be important it gave me a chance to really do it right. First of all I actually designed it on paper first, which goes against the grain of flying by the seat of the pants. This is my normal routine, and sometimes it even works. The DI is a snug fit as it is but I added a nylon 8-32 sockethead screw as a positive retainer.
http://www.fototime.com/A35A00930CF9145/standard.jpghttp://www.fototime.com/26EB1289D8ED3A5/standard.jpg
First was to mill the ends square to the other sides of the block. Once that was done it was stood on end with 1/2" extending off the edge of the vice, and checked again to be sure it was 90* to the table. I touched off and zeroed the DRO on the side and face of the piece. Then I located the centerline of the case and the hole to hold the DI. The casehead at the rim of my W-W brass is .413", but the hole for the spindle of the DI is .375" so the end sticking up would be the bottom.
Centerdrilled, then step drilled 1/4", 21/64 (.328") then letter U (.368"), then went into backgear and reamed .375". I even remembered this time that going into backgear reverses the spindle rotation! Out of backgear and drilled with a letter Z bit (.413"), then into backgear and reamed .416" as I did need a bit of clearance for the case. Since the center of the block was to be milled out, this depth wasn't critical.
As you can see in the above right photo my neatly drilled and reamed .416" hole became square. I had visualized the slot for the case to slip into as being tapered. Why? Well the case is tapered so it seemed the thing to do. As I removed the aluminum blck and laid it on it's back and was indicateing it flat, I realized that the cartridge case slot didn't HAVE to be tapered to match the case. What reason would the tapered slot serve, and it was just extra work to no good end.
http://www.fototime.com/C871A08F9D79112/standard.jpg
The top arm where the DI went was to be 1/2" thick. I used a 4fl 1/2" rougher. I stuck a slip of .004" thick paper stuck on the end of the block and wound the table up to it until it snatched the paper off, then went in another .0035" to zero. The endmill was 'just' marking the layout blue. Advanced an inch, zeroed the quill touching the top of the block, and dialed it down the full .750" and took a full width cut (slowly!). After that I took .250" cuts, then two .125" cuts to finish the 1.5" length.
To finish up doing the slot for the case I went to a 1/4" 4fl endmill and slotted down the center in 2 passes, then a full depth pass removing .083" on both sides for a total width of .416" which pretty well wiped out my nice reamed .416" hole. I raised the endmill up halfway and took another thousandth off each side (total .418") thinking it would be easier to slide the case in. Probably made no difference at all.
http://www.fototime.com/EF30CB149E81144/standard.jpg
It's easy to insert a case. As in the above photo you tip the case rim in under the spindle head and take your reading. This is the first time I've ever checked rim thickness and it's an eye opener!
This was a fun and simple project that gave me a chance to do a couple things I hadn't done before (besides draw a plan out with coordinates on paper!) and it turned out well. It took a bit longer then I thought it should, but most of that was me double checking myself against the coordinates I'd plotted out. I thought I had a suitable DI tip to use but didn't so I had to make one up, and just used some brass so it wouldn't, er ...............clash with the brass case :-)
...............Buckshot
http://www.fototime.com/6A3AEAFCA19293E/standard.jpghttp://www.fototime.com/6960941CF1C4A0A/standard.jpg
I made a rim thickness dealie-bob. I used a piece of .75 x 1.5" 6061 aluminum 3" long. Because it was pretty simple to do, but accuracy would be important it gave me a chance to really do it right. First of all I actually designed it on paper first, which goes against the grain of flying by the seat of the pants. This is my normal routine, and sometimes it even works. The DI is a snug fit as it is but I added a nylon 8-32 sockethead screw as a positive retainer.
http://www.fototime.com/A35A00930CF9145/standard.jpghttp://www.fototime.com/26EB1289D8ED3A5/standard.jpg
First was to mill the ends square to the other sides of the block. Once that was done it was stood on end with 1/2" extending off the edge of the vice, and checked again to be sure it was 90* to the table. I touched off and zeroed the DRO on the side and face of the piece. Then I located the centerline of the case and the hole to hold the DI. The casehead at the rim of my W-W brass is .413", but the hole for the spindle of the DI is .375" so the end sticking up would be the bottom.
Centerdrilled, then step drilled 1/4", 21/64 (.328") then letter U (.368"), then went into backgear and reamed .375". I even remembered this time that going into backgear reverses the spindle rotation! Out of backgear and drilled with a letter Z bit (.413"), then into backgear and reamed .416" as I did need a bit of clearance for the case. Since the center of the block was to be milled out, this depth wasn't critical.
As you can see in the above right photo my neatly drilled and reamed .416" hole became square. I had visualized the slot for the case to slip into as being tapered. Why? Well the case is tapered so it seemed the thing to do. As I removed the aluminum blck and laid it on it's back and was indicateing it flat, I realized that the cartridge case slot didn't HAVE to be tapered to match the case. What reason would the tapered slot serve, and it was just extra work to no good end.
http://www.fototime.com/C871A08F9D79112/standard.jpg
The top arm where the DI went was to be 1/2" thick. I used a 4fl 1/2" rougher. I stuck a slip of .004" thick paper stuck on the end of the block and wound the table up to it until it snatched the paper off, then went in another .0035" to zero. The endmill was 'just' marking the layout blue. Advanced an inch, zeroed the quill touching the top of the block, and dialed it down the full .750" and took a full width cut (slowly!). After that I took .250" cuts, then two .125" cuts to finish the 1.5" length.
To finish up doing the slot for the case I went to a 1/4" 4fl endmill and slotted down the center in 2 passes, then a full depth pass removing .083" on both sides for a total width of .416" which pretty well wiped out my nice reamed .416" hole. I raised the endmill up halfway and took another thousandth off each side (total .418") thinking it would be easier to slide the case in. Probably made no difference at all.
http://www.fototime.com/EF30CB149E81144/standard.jpg
It's easy to insert a case. As in the above photo you tip the case rim in under the spindle head and take your reading. This is the first time I've ever checked rim thickness and it's an eye opener!
This was a fun and simple project that gave me a chance to do a couple things I hadn't done before (besides draw a plan out with coordinates on paper!) and it turned out well. It took a bit longer then I thought it should, but most of that was me double checking myself against the coordinates I'd plotted out. I thought I had a suitable DI tip to use but didn't so I had to make one up, and just used some brass so it wouldn't, er ...............clash with the brass case :-)
...............Buckshot