Barrel Crowning, Threading On A SB 10K ???

[HugoStiglitz]

I've been employed as a Racing Engine Machinist for nearly 20 years and have ALOT of experience operating Automotive Engine rebuilding equipment. Was taught the business originally by Gary Myles of Myles Eng. notoriety for 8 years in Cleve., Oh. Spent the next 12+ yrs with Greg Greulich in Phx., Az. Greg would take on ALOT of ODD jobs requiring turning, milling, grinding, welding or a combo of ALL 4. He never quite knew HOW he would do it though, and would say "here ya' go Joe, figur' it out". As a result, I've always been able to make do with what I have, not what I would want. Recently unemployed after 2 years working for a Vintage Mercedes Benz restorer making ALOT of repro parts, I've inherited the SB 10K (4 1/2 ft bed) I used those 2 years. I'd like to explore using that lathe to crown and thread muzzles for rifle barrels. I KNOW the Heavy 10 (with Spiders) would be better, but I got what I got. Has anyone any ideas for driving the actionless barrel (Face Plate, Dead Center, Dog; 4 jaw Chuck)?? Use a Steady Rest near the muzzle (what type of fingers)?? Would you consider threading with a Threading Die Holder?? I have enough firearms experince to know that Bores and Barrel IDs aren't always concentric and that the crowning and barrel attachments can have Negative affects on accuracy if not done straight and true. Any feedback would be greatly appreciated. Best Regards !! Joe

 

[Gthphtm]

What Dia. barrels are you trying to machine.If I remember that lathe has at least a 1" ID. but I might be wrong.It sounds like it would not be a problem for You to make a spider for the headstock and the rear of the spindle.For the headstock I would make one with recesed set screws,those expesed screws and bolts can cut the S... out of you.

 

[jkl]

Follow Gene Beggs thread on BENCHREST CENTRAL in the gunsmith post. There are some top gunsmiths posting on Gene's thread you may enjoy it. It will be like setting at a round table with people you will never get time to talk to.

Gene beggs on chambering

John

 

[MilGunsmith]

Gene's method is similar to what I use with my South Bend 9A. It works.

 

[MetalMunger]

Gene's method or variations have been used by many with great success.
Below are a couple of links to what appears to be a very rigid shop built steady rest with a built in spider. I have considered building one of these (probably substituting a roller bearing) if my super bull barrel project ever gets off the ground.
From CNC Cookbook: Blog

http://www.cnccookbook.com/img/OthersProjects/FancySteadyRest.jpg

http://www.cnccookbook.com/img/OthersProjects/FancySteadyRest2.jpg

Once you have a rigid setup similar to to the setup shown in in the first link you would indicate your bore axis with a range rod the spider would be used to bring the bore to center. At that point your muzzle crowning/ threading or chambering is straight forward.

 

[HugoStiglitz]

Thanks guys !! THATS sort of what I envisioned. Just wish I still had access to my old employer's mill. Best Regards !! Joe

 

[HugoStiglitz]

Gene's method or variations have been used by many with great success.
Below are a couple of links to what appears to be a very rigid shop built steady rest with a built in spider. I have considered building one of these (probably substituting a roller bearing) if my super bull barrel project ever gets off the ground.
From CNC Cookbook: Blog

http://www.cnccookbook.com/img/OthersProjects/FancySteadyRest.jpg

http://www.cnccookbook.com/img/OthersProjects/FancySteadyRest2.jpg

Once you have a rigid setup similar to to the setup shown in in the first link you would indicate your bore axis with a range rod the spider would be used to bring the bore to center. At that point your muzzle crowning/ threading or chambering is straight forward.

This ball bearing tailstock rig is ingenious. Maybe I'm looking at it wrong, so bear with me. If you were going to make this, HOW would you ensure that the C/L of the bearing was equal to that of the spindle ?? The spider just allows you to get the bore turning on center relative to the bearing, not especially the spindle. Any error would be magnified as the barrel length between centers was increased ?? And what do you think that tool holder on the parts view is for. Thanks !! Joe

 

[MetalMunger]

....If you were going to make this, HOW would you ensure that the C/L of the bearing was equal to that of the spindle ?? ....

hmmm....
Hadn't gotten down to actually planning on how to machine the thingy but a couple of thoughts come to mind the first is mill out the rest without boring, mount the rest on the ways and slide up against a center in the headstock to mark the center, then rough bore the rest on the mill. Fasten the rough bored rest to the carriage in place of the follower rest, fabricate a horizontal boring bar to run between centers on the lathe the cutter on the boring bar would be raised incrementally by shimming to finish.
The second method is asking the OP on the CNCcookbook site how he set it up
I am not sure how true to the C/L the bearing needs to be you are not going to be turning very fast so as long as the bore is true and you aren't vibrating you should be ok, or go the easy route.
http://i20.photobucket.com/albums/b221/bluevtx/SouthBend Lathe CL145D/DSCF5332.jpg
Check the South Bend forum for this thread:
http://www.practicalmachinist.com/v...smithing-spider-heavy-10-a-214492/index2.html
As for the toolholder, not a clue.

 

[HugoStiglitz]

Something in your last post clicked with me, as a result I think I know what that tool holder is now. It appears to be a tool holder mounted on a taper. The taper has a drawbar attached. The radius of the tool in the holder seems set to cut the bearing O.D.. I guess this rig is mounted in the spindle and the block is fed into it using the carriage some how. Does that sound plausible ?? Now to figure how to feed the block properly into the spindle.

 

[lazarus]

To make sure you mark it on center, mount it on the ways next to the chuck, with the tailstock close to the other side. Use a carbide(HSS probably fine) dead center in the tailstock to mark your starting point. Drill, rough bore, remount on ways and check with a collet w/a test bar. Make corrections-if necessary. It'll be as good as your lathe will get it.