contouring a new blank

Woodhunter said:
You guys are making this way too complicated. It is basic machining 101: Turning between centers, offset tailstock.

Use bell center drills on both ends of the barrel.

Carbide tooling only. You have to grind a special deep chip groove with a thin razor leading edge, it has to be very sharp.

I grind 4 tool bits, this way I can pull one out of the 4 position tool holder and regrind while the lathe is making a cut. You only get one pass out of a tool bit, then regrind. HSS will not do as it will not stand up to a full length cut.

....a exhaust fan on one end of the shop and open the windows on the other end.

Grind the OD as shown below, starting with 80 grit, then 220 and finally with 400. This is not a tapered barrel, but the grinding procedure is the same.
Click to expand...

This method is simple??

As to using HSSCo, I have turned multiple cuts on several barrels with the same sharpening. You use 4 carbide tools??
 
I have one HSS cutter that I ground 20 years ago, I can get a couple of barrels tappered before I sharpen it. The last time I used it I turned down a barrel liner I never had to sharpen it once. It would drive me nuts to sharpen after each cut, I guess thats why I dont use carbide to turn barrels.

Bob
 
I can't amagine why you would have to re-sharpen a carbide tool, that is unless you let the work chatter, which will chip ithe edge.

I take a 1/2 inch shank cemented carbide, (I like 883 for SS), and with my tool grinder, I grind a positive rake chipbreaker in the cutting edge, qbout a 1/8 radius. I then sharpen the back and front to a near zero nose radius. With a soft rock on the tool grinder, I can place a very sharp edge on the tool. It will curl a nice little shaving at about 150 RPM. No coolant, just black sulphurized cutting oil.......jackie
 
Hope I can help a little in regards to tapering a barrel. It's really not a big deal. I start by using a drive plate and a dog between centers. Run my lathe at about 130 rpm's and use a sharp high speed tool (no radius) at about a .007 feed taking .025-.030 on a side. Set my steadyrest about a third of the way up the barrel (tail stock & muzzle end). With a taper attachment you lock up your cross feed and work off your compound. Forgot to mention that you should cut a short parallel spot for your steady rest jaws to ride on while using a rag and your hand wrapped around the barrel to reduce chatter. The chatter factor will be worse with a lighter cut and slower feed. I also sometimes use the rag and hand trick when I am cutting the taper. I will take about 6"-8" at a time completely finishing each section as I go. I then move my steady rest and some times the cutting tool to get the most support for my next 6"or8". I should mention here that when you have finished a pass get your tool out of your work BEFORE you disengage your feed. If you disengage your feed first the tool will want to plunge in resulting in extra lathe file work. I also readjust the tail stock after each pass. When you start your cut engage the feed first an then run your tool in to pick up your last cut. The only measurement of concern is the muzzle diameter. The rest you blend in. If you have a taper attachment the following should help. Take the two diameters where you want the taper to start and to end. Subtract the two and divide the length of the taper into that number. Then multiply times 12. The result will give you taper per foot. Most taper attachments have 1\16" graduations per foot. Sometimes if I think the barrel is getting a little to warm I will take it out of the lathe an run cold water over. This is easy when your working between centers. It usually takes me a couple of hours. When things are going right I can sometimes sneak in a cup of coffee or do some other little thing while keeping a close eye on the lathe. I have never had any stress related problems. One year I had a shilen HV barrel that was mediocre I retapered it to a LV and my daughter shot a .186 100 yd. agg. at Kane with it. Didn't hurt that barrel a bit.
 
In the past I have discussed this with fellows that have recontoured barrels. They told me that the way to avoid heat is to not let the tool stay in one place for very long, to sharpen the tool to a point and use a fast feed, which makes a horrible looking finish, like really ugly shallow threads....but no heat. After you get the contour, with multiple light passes, you can get to the finish that you want with one of those long belt grinders, that don't have the belt backed up with a platen, holding the barrel between centers in one of those barrel spinners that you hand hold. You can control the barrel spin by holding it at an angle to the belt so that it doesn't just spin at belt speed. Slow feed and trying to maintain a pretty cut is counterproductive. It makes too much heat. Most of the fellows that I know have built the grinders and barrel spinners. The spinners use plastic centers, which turn on ball bearings.
 
Forgot to mention that you want your high speed tool to be ground with a positive rake. When I'm finished cutting the taper I use a lathe file an last a belt sander with 220 grit. As was stated above I stay away from the platen so the belt conforms to the barrel. I use an old long bed 9" lathe for my filing and grinding.
 
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