Milling radius in scope rail blank

Hey guys, I'm just getting into some hobby machining. I've got a little Sieg X3 mill. I got an EGW scope rail blank that I want to mill the bottom of to fit an action that I have.The diameter of the action is 1.457". My milling machine head doesn't tilt. I was wondering if it would be OK to mount the rail vertically and using a boring bar set at the right radius to mill the bottom of this scope rail blank?

Buy a set of XXX high weaver rings and I believe its a #63 weaver base. Clamp the rings on the base without the ring tops. Clamp the 63B in your mill vice and mill off one side of the ring tops. Loosen the vise and turn the base and rings around in the vice and mill the other side the same. This will center the stub you create on your rings side to side in your mill vice. Then you can put the base into your inventory and sell it to some fool with a marlin 336. To mill short bases set it up as to photo. To mill long bases invert your vise on an angle plate on the mill table and use both rings to hold the base to be modified. Find center and the radius you want to cut, set up your boring head and have at it. If you can justify it go out and buy a heavy metal anti vibration boring bar. I have one which I think I got from Kennemetal. I believe its 9/16ths x 8 inch. It does a wonderful job with no chatter and you can use it in the lathe or mill to true action cylinders if you like to true them up. Some guys make special fly cutters to do this as well and they work fine. You can make a fancy jig to hold the base and I have done that in other shops but the weaver rings work equally well especially if your on a budget. Plus if you do a lot of bases at once the weaver rings are more handy to work with. I can modify a couple dozen of the #55 or #45 weaver base for the stripper clip hump in a half hour or less from start to finish.

TO ADD: I also set the rings upright in the mill vise and run ball mills down the base as well. It does work but the finish is not as nice. High speed and LOTS of kerosene helps with aluminum and ball nose mills but I prefer to set em up vertical. I color the bottom of the base with a Bavarian Bluing Stick (black magic marker). When doing short bases I will usually set the base vertically as I would with the boring head and use end mills if it is a known common radius like 1 inch, 1 1/4, 1 3/8, 1 1/2 ETC. It saves time monkeying around with a boring head. For long bases you can cheat some times and do half at a time with the end mills. Just flip the base over.

Hey man, thanks for the info. I would love to see some pics if you are able to find some!

rcampbell said:

Hey man, thanks for the info. I would love to see some pics if you are able to find some!

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Bar on the left has the M700 Rem radius. Held by a 7/8" endmill holder in the vertical mill. Used both for milling scope bases and the end of pillars that contact the receiver bottom. You guys do mill a radius in the M700 pillars, right? If not, guess you have a "tippy" receiver".

Bar on the right has the radius for the M70 Win rear bridge, I use it for milling receiver ghost ring sights. Held by a 1" endmill holder in the vertical mill.

Set the downfeed to the finest position.

Short and stiff!

SilveradoHauler said:

Bar on the left has the M700 Rem radius. Held by a 7/8" endmill holder in the vertical mill. Used both for milling scope bases and the end of pillars that contact the receiver bottom. You guys do mill a radius in the M700 pillars, right? If not, guess you have a "tippy" receiver".

Bar on the right has the radius for the M70 Win rear bridge, I use it for milling receiver ghost ring sights. Held by a 1" endmill holder in the vertical mill.

Set the downfeed to the finest position.

Short and stiff!

View attachment 43000

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Cool, did you make those tools yourself are are you able to buy them somewhere? What type of end mill holder? I have R8 collets to hold my end mills, would those work as well?

I hear there are lots of ways to skin a cat. Here is another. Use a smaller ball nose to generate a large arc. This is not my idea but I have used it several times. My first exposure on this method was in Home Shop Machinist. I bought Guy Lautards's book and use it as a basis, but always seem to improvise. I think I attached the book cover and the chart I used to mill the 1 piece base I put on my Dad's 1917 Enfield. The chart shows the depth in Z and the corresponding adjustment in Y(with a 5/8 ball nose mill). After making all the cuts in Y positive make all the same cuts on the other side with negative Y values. I blued and scraped both ends that contacted the reciever, but another way would be to make a mandrel the diameter of the bar less the thickness of wet or dry paper and do a little polishing to take out the slight grooves this process leaves. For short 2 piece bases, I like Speer chucker's fixture.