Rebarreling and Home-Shop Machining

A note on the photos

I have added a few photos of my heavy duty lathe bench to the topic Finished Fifth Column, Heavy Duty Lathe Bench

I have also recently added captions to all the photos in this Journal. I hope this makes it more pleasant to scan through the photos. You are welcome to download the photos. The journal is set up to allow this. The photos are larger sharper and more clear when you download them and display them full screen. Better than the larger view that is available from the journal. Double clicking on your downloaded file will automatically call up the window picture viewer on newer Windows software. Old topics now have links in the right column to make it easier to scan for a topic you are interested in. The best view of the Journal is full screen. Click on the box in the upper right hand corner next to the x to make the journal full screen. Additional topics are available on the CD that comes with “Precision Rebarreling.

Test (new)

I made a fixture to hold the electric screwdriver and keep it on to turn the barrel on the supports which are shown in photo 4 and 5 and to keep both hands free. I bandfiled the barrel with an 80 grit used sanding belt to semi polish it. It was very bright at this point. I bead blasted it with the sand blaster described below. I got a nice satin grey finish shown in photo 1. The marks in the barrel were apparently stenciled into the barrel during a repair at one time. The screw in the funny location is on the right side of the barrel and is not a rear iron sight mount screw.

The best setting for my 5 HP compressor was with the sand control valve at the bottom of the tank at about 40 to 45 degrees open. This setting provided a continuous stream of sand out of the tip. If you open the sand control valve further you get pulses of sand and an uneven finish. Open the sand valve first to 40 degrees, then turn on the throttling valve then the gun valve. Always turn off the air at the inlet valve, cutoff the sand control valve and bleed the tank through the tip before you open the tank. This will keep sand out of your airlines or filters. I also got better results by throttling the hand control valve at the tip part way off. It may be better to do this with the throttling valve that is just under the air gauge to reduce wear on the tip’s valve which carries a sand and air mix. I’ll do some more testing. The finish looked the best hitting the barrel at a 90 degree angle. I used a slow feed while the barrel was spinning and the tip about 1-1.5 inches away. I made a second pass with the tip 2 inches away which smoothed it out for a more continuous looking finish. I was happy with the results. I would probably buy 50 lbs of beads (same price at a different source), then you don’t have to be so careful about collecting all the beads. I plan to strain the used beads (flour sifter maybe) before I finish a good barrel. The beads managed to pick up some dirt from the area that I carefully blew off and scrubbed with soap and water before the job. I did this in an old laboratory fume hood which I had at the house. A large carboard box with a sheet steel bottom would probably work as well. Make it long enough so the sand tends to collect in the ends away from your blast area. The steel bottom will prevent you from picking up shredded cardboard in the beads. My fume hood is about 4 feet long andworked well. I made a 6 inch board dam for the front. The bead blast lathe described below worked great.

Air Supply Required (new)

I did some more tinkering with the sandblaster. It comes with 4 spare ceramic nozzles. I hooked the sandblaster up to a 5 horse power 220 volt air compressor. With the small hole tip, I could maintain 85 psi at the sanblaster inlet with the compressor running and a regulator set at 100 psi. This might come up a bit when I add the glass beads. With the large hole tip, the air runs at 50 psi after the pressure stabilizes. This is probably too low to beadblast, although the air blast feels stronger to my finger than when using the small tip. This is from the higher volume of air. Thes larger tip also causes a large pressure drop during the first part of the job which will affect the uniformity of the finish. You might need more compressor or one of the big vertical tanks to run the large tip at higher pressure.

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Bead Blaster, Satin Finish on Stainless Steel

Photo 2 and 3 show a 40 pound capacity Pressurized Bead Blaster/Sand Blaster that has been available lately at Harbor Freight tools for $80. I have finished assembling the unit and am satisfied with its quality and construction so far. I have 25 lbs of 80 grit glass beads that I plan to use to finish a stainless steel barrel. I am making a jig to support the barrel while I rotate it with an electric screwdriver or by hand (more on this jig to come).

The large cap at the top of the tank is sealed with a huge O-ring. This cap is used to pour the beads in with a funnel. The valve at the top ofthe tank, just below the air gauge, is called a throttling valve and controls how much air is fed through the sand mixing manifold below the tank. A second valve on the inlet controls the input air (on or off). The gun at the end of the hose has a steel valve that will probably get the most wear of all the valves. The tip of the gun is ceramic and is available separately. The second photo shows the sand control valve at the bottom of the tank attached to the mixing manifold. The air and sand mix in this thick walled manifold. The rubber hose is made of thick walled rubber. This side view also shows the air water separator. I plan to use an additional air water separator upstream for the humid conditions here in Houston. The tank can hold 40 lbs of beads, but is recommended to be only 3/4 full in humid conditions. Beads run about $1 a pound for 25 pounds shipped or you can get 50 pounds at some suppliers on the Web for $25 plus shipping. The beads are reusable if you collect them in a clean area, so you may not need 50 lbs. The blaster uses about 30 lbs of media in a half hour with a .1 inch diameter nozzle and 6 cubic feet per minute air supply at 125 pounds per square inch. Finishing one barrel will probably take less than 10 minutes. The unit shipping weight is 57 lbs.

Bead Blast Finish on a Stainless Steel Barrel

A bead blast finish (photo 1) tends to give a bright stainless barrel a much subdued satin grey finish. The round glass beads do not remove any significant amount of stock but simply rearanges the surface into a nice satin finish. Aluminum Oxide or sharp grains will remove material and is not desirable. This satin grey finish is suitable for hunting. You can see a picture of one of my rifles with this finish below in the Caldwell shooting rest topic. A grey barrel looks very nice on a black action and stock. This satin grey finish is a $75 option at some rebarreling shops, so finishing one barrel, if successful, will pay for the blaster. I was also unable to get this finish applied to a barrel blank from Hart. I plan to practice a couple of different methods on an old .270 steel barrel and will report my results here. I chose a pressure blaster rather than a cheaper more compact siphon blaster because they are advertized to work better.

Bead Blaster Lathe

            There are a couple of ways that I could bead blast a barrel. One is long passes along the length of the barrel with a small rotation after each pass. You could do this hand held by inserting some dowels in each end, one to support the muzzle end, and the other to rotate the barrel by hand. Another way is to rotate the barrel at constant speed and feed the bead blast nozzle slowly along the length of the barrel. My goal would be to have a very uniform finish around the circumference to minimize the tendency of the barrel to warp a few ten thousandths from a nonuniform finish, so I am going to try to bead blast with rotation.

            I made a couple of rugged and heavy angle plates from scrap 3/4 inch steel plate. Photo 4 and 5. I cutthe plates with a band saw and made one cut with a sawzall with a metal cutting blade. The band saw cut was much straighter. I secured the vertical plate to the horizontal plates with 5/16 x 1 inch course thread socket head capscrews. I counterbored the hole, in the vertical plate, by first drilling with a ½ inch pilot point drill bit to a depth of .325 inch with the large diameter. Then I finished the hole with a 5/16 inch drill bit. This worked great without changing the setup for each hole. Counterbores are also available from Campbell Tools to cut this hole for a recessed capscrew. I then clamped the angle plate together and used a 5/16 inch transfer punch to mark the holes in the side of the horizontal plates. I drilled and tapped these.

            I used 2.5 inch model aircraft wheels and axles to support the barrel. The axles are mounted in 5/16 fine thread holes which I drilled 5/8 inch deep and then tapped. The axles neck down to 5/32 inch to fit the wheels which are secured with a locking collar. The rubber and thick steel angle plates should tolerate the sandblaster for quite a few jobs. I plan to add a small notch on the muzzle end stand to add more clearance between the muzzle and the angle plate. (A solid rubber tire would be better for bandfiling, but these hollow tires worked great for beadblasting.)

            I used these stands and an electric screwdriver to bandfile the barrel surface. Photo 4 and 5. This worked the best with a slow feed of the bandfile. (I prefer to do the bandfiling on the lathe with a setup that is on the CD that comes with Precision Rebarreling.) Next I will test this shiny steel finish with the bead blaster.

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