Rebarreling and Home-Shop Machining

Tuesday, August 2, 2005

The photos in this topic are part of a 64 photo sequence that can be found on the CD that comes with my book Precision Rebarreling.  I will start a new topic on the inletting  that will generate e-mail alerts if you are signed up for them after a week or two.

Edited on August 31 2005 new Photos 1,2, 3, 4

Notes on Milling the Channel and Stock Size

            The flycutter holder (boring tool) that I made to cut my channel worked OK. If you have a longer lathe you can make a tool supported between centers and increase the rigidity of the tool. Surprisingly, I got my best chips while reversing the bit out of the work at 7 inch per minute at 550 RPM. I got some full circumference chips about 3/16 inch wide. The cutter was acting more like a blade at this setting in reverse. I tried cuts with the cutter extended the full 12 inches and also 8.5 inches which is about the length of the receiver. I got chatter at these two lengths at various points in the cut. A high feed speed of 3 - 4 inch per minute tended to reduce the chatter. Reversing at 3 inch per minute gave an excellent finish. I decided that it was best to cut the piece with 6.5 inches of cutter extension and do a cut from both sides. I got a good finish this way. It helps to stone the bit before each finish cut. Sharpen the tip on the bench grinder in middle of the job on each end. Check the radius with your radius gage. Measure the distance from the bit to the flycutters outer circumference with your dial caliper depth feature to make small adjustments to the cutter radius.

            If my material was aluminum, I would want a little more depth of material behind the recoil lug. Use a 1.5 inch x 1.5 inch block to start with. My stainless block will probably do fine at 1 by 1.5 inch. When I finished cleaning up the sides it measured 1.450 inch in width. This will be a nice fit in the stock and leave enough wood on both sides. I plan to use some stainless steel pillars to the two action screws. You never know if things are going to work out until you finish. The clearance required for the bolt will reduce the amount of bedding block possible in this area. I have gone from 5 lbs to 1.4 lbs already just milling the channel. Narrowing the front and milling out the middle for the mag will reduce this considerably more.

Milling the fore end extension

            I decided to narrow the fore end extension to 3/4 inch and start the curve .2 inch plus .020 for clearance in front of the recoil lug. This will save weight and allow some flex so the forend will not bend the bedding block.I made the setup low so it would clear the bottom of the spindle flange. I added a couple of stops to keep the milling cutter from moving the work. I had room for one clamp in the middle which I moved depending on which way the cutter would tend to move the work.

            On the far side I plunged the cutter on the right side of the cut .2 inch deep and .1 inch wide until I had made a passes the full depth. I raised the cutter above the work to return. Plunging thecutter avoids dragging it back along the work. If the cutter is runningit may make a huge cut at the beginning by trying to “climb mill”. Keeping the cutter running saves wear and tear on the motor capacitors. Once I had achieved the full 1 inch depth, I started tomill inward the full depth of the steel whichwas reduced in height byeach pass. I kepth making bigger cuts. I started at .015 inchand finished with .050 inch wide cuts the full depth. I always plunged to my 1 inch depth before each cut.

            On the near side things were easier because I could see the work. I used the same procedure except that when I started moving inward it helped to make a plunging cut at the far right before each pass, retract the cutter then move to start a new pass. This prevented a light cut turning into a heavy cut at the end of a pass as the material increased in height toward the right at the end of the cut. The plunging cut will prevent the cutter from grabbing a large hunk of steel at the end and moving the workpiece in its clamps.

Milling the Recoil Lug Slot

            I had planned to do a small amount of filing to square the corners of the recoil lug slot after I milled it out. This would preserve thickness on the sides of the bedding block. I put 1/8 inch holes with a cobalt bit at the corners of my recoil lug slot putting the edges of the hole at the proper clearance. I chose a .030 clearance in the front and .010 on each side of the recoil lug. I found the punch marks with the wiggler and then moved the workpiece using indicators to the required drill point. Note that the workpiece is setup on a set of different height shims to cut the slot at the proper angle relative to the receiver. 

            I had some trouble setting up for this cut. My 3/8 shaft 3/16 inch 2 flute cutter would not go to the bottom of the cut with this setup. Should have used 1 inch blocks to raisework. Instead I used a 3/8 shaft 1/4 inch four flute mill thathada long shaft. I drilled a 1/4 inch hole in the center front where I started each cut. I plunged the cutter here. A 0.025 inch depth of cut was about right. I setup four indicators to monitor the movement of the table and carriage and set them to read either 0 or .500 at the edge of the cut. A good set of four stops would have worked as well (I have not made any stops). I then made the cut clockwise plunging only at the center front. I numbered my indicators so that I would remember which one to look at next. I made the feed by hand trying to turn smoothly at about 1-2 inch per minute.

Installing Action Screw Pillars

            I made a few light passes on the back side of the recoil lug recess to smooth this critical surface. I indicated this surface using a 1/4 inch ball on the wiggler then moved back .125 to accurately locate this surface. All further cuts will be made from this reference or a correction applied using this reference for the rear most holes. I moved back to the front action screw and used a fat center drill in the precision chuck to locate the pillar hole. I then drilled with a 1/4 cobalt bit. These cobalt drills drill effortlessly in stainless. I then opened up the hole to 27/64 with a Titanium Nitride Coated drill which worked OK with a pilot hole in this annealed stainless block. Both of my holes were a little off with this procedure. I decided to bore the final hole to .675 with a boring head. This would more accurately place the holes in the bedding block. I decided to make a threaded insert for the front and back that would be silver soldered in place. I have my choice of a 9,000 psi silver solder with about 2 percent silver or some 30,000 psi solder (silver braze) with about 58 percent silver and the rest tin. The braze requires a 1,200 degree temperature to be achieved with a torch. The higher strength is probably not needed for this application, but the appearance willbe excellent,or I may just use a press fitwith Red Loctite to avoid annealing the insert or warping the bedding block.

            I cut a front Stainless Steel pillar from a hard stainless steel bolt. The final install will be with Red Loctite (it can still be removed or adjusted with a little heat applied). For the purpose of making the pillars hollow, I center drilled and then drilled with a cobalt 1/4 inch bit. I tried opening up the hole with a Titanium Nitride coated high speed steel bit (Chinese) and it chattered and then dissolved it seems. I bought a small set of Rigid brand Cobalt bits that had become available only in the last week at Home Depot. They have flats on the shaft and are quite straight. Worked great on the hard stainless bolt. My Center drills which are high speed steel, but from DoAll also worked well on this hardened steel. I drilled the pillars only 1 inch deep with the cobalt bit. Twist drills tend to wander a bit, so I turned the pillars over and drilled from the other side to finish the holes. The threads from an all thread pillar will help hold the pillars in the epoxy in the stock and increase the surface area for the Loctite and allow adjustment of the pillar length. I drilled the front ½ x 13 thread per inch pillar with a 5/16 cobalt bit. Things will be a bit thin in the rear due to the stock and receiver configuration. I tried a 5/8 x 18 pillar in the back but I had insufficient metal to allow for the threads. I solved the problem by installing a threaded insert that will take a ½ x 13 thread per inch pillar and have clearance on the rear trigger and action screw boss on the receiver. I made these inserts from a stainless steel nut.

            I bored the pillars out on the lathe, the front to .345. This improved the appearance by perfectly centering the holes and also lightened the parts.

Pillars and Inserts came in about 1 ounce.  They will need shortening.

Stock Winchester Coyote Bedding

            See photo 5. The rifle is not pillar bedded. It is partially skim bedded with epoxy. Pillar bedding it should be a great improvement if you want to tinker with it just a little. I will be pillar bedding my rifle in addition to adding a bedding block later on. There is release agent on the forward part of the receiver. It might help matters to remove this release agent. The front action screw torque as I found the rifle was in the range of 35 inch pounds. The rear screw was less, but had locking compound on the threads. There is a little plastic spacer push fit into the front action screw hole to space the action away from the stock to provide a reasonably thick layer of epoxy around the recoil lug. Don’t know the recommended action screw torques yet as Winchester says not to disassemble the rifle. Oh well.

            There is a small amount of epoxy touching the barrel so the barrel is not fully free floated. This can be easily removed with a Dremel.

            The Receiver is 8.75 inches long from the rear of the tang to the front of the Recoil lug. The front of the action is pretty square on the bottom. I may be able to reach the curved section of the receiver on the sides of the action in front or maybe not. I will need a curved channel in the back to support the tang area. I’ll take some measurements to see.

Bedding Block

            My 12 x 1 x 1.5 stainless steel block arrived in about a week.  There will be enough material to put a short extension into the fore end.

A Few Dimensions

            Receiver dimension are approximately 1.335 inch in diameter near the recoil lug. I will be able to use about 1.356 inch of bedding block width in the area just aft of the recoil lug. This will give me walls of about .095 inch in the stainless tapering to .010 inch. The stainless should be stiff enough to be solid with this width. The width of the material is limited by the need to clear the flat bottom of the receiver which is 1.165 inch wide. There is no real need for contact with this flat area of the receiver. I may reduce the width of the block aft of the front receiver ring (make it wasp waisted) for appearance sake, to show no stainless or I may show a 1/16 inch satin finish reveal of stainless all around.

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