Lathe boring sizing dies

[Trailblazer]

I want to lathe bore some case sizing dies and need a suitable boring bar. I haven't been able to find anything in the catalogs I have so it looks like I might have to make a suitable boring bar. Does anybody have suggestions about how to make or buy one?

I think my best idea so far is to get one of the small carbide boring bars and braze it to an extension to make it long enough. I have never brazed carbide so any suggestions on how to do that would be helpful.

[Jon K]

Trailblazer,

What is the configration of the carbide bar? Round/Square shank?

Bore a hole, or mill slot in your ext bar to hold the carbide, Silver Solder the carbide to the ext bar. Do Not Make the bar any longer than needed, keep it as rigid as possible.

Jon

[Trailblazer]

Round shank. I am not sure I have any silver solder. Maybe, maybe not! I have plenty of brass rod. Any reason not to use that? Is the temp to high?

[Jon K]

Brass will be too soft. Harder will work better. Use some 4140, if you have it, or any good quality steel.

You can bore the hole in the ext and lock the carbide in with set screws, but make sure the bored hole is a snug fit.
The more rigid, the better......Flex = chatter & sloppy work.

Jon

[smokemjoe]

Use a good grade of steel for the die, so you can heat treat it, If you dont, no matter how high of polish you get in it, it will scatch your brass.

[Morgan Astorbilt]

A long shank 2 flute end mill can be used as a boring bar. Just line up the cutting lip to be slightly above center, and the tool off a few deg.'s from parallel. It just can't cut to a RH shoulder.
Morgan

[JIMinPHX]

If you’re going to be doing this a lot, then a small indexible carbide insert bar from someone like Circle, Valinite, Iscar, or Kenemetal is the way to go. If you are only going to be doing a few of them, then a one piece solid carbide bar is the best thing to have. It’s almost hard to find one of them that isn’t good quality. The solids actually work best, they just don’t give you the ability to easily improve your cutting tip once you chip or dull it. The second choice for small quantities would be the braze on bar. They are also the least expensive option. I’ve also used Morgan’s trick successfully. Any way that you slice it, expect to do some polishing after you cut the bore. Unless you’re reeeealy good, that bore will have some small tool marks in it. I usually allow .0002” for polishing clean up when I want a mirror finish.

[Trailblazer]

Jon, I meant brass brazing material. I would use cold rolled for the extension.

Joe , I hadn't thought of that yet. My idea was to use 12L14. That can be case hardened so maybe I need to order some Kasenite.

Morgan, I will look through my cutter collection. I don't remember any long shank milling cutters but I do have some long reamers. Maybe one of those will work?

Jim, how will the indexable insert bars work to cut the neck portion of the die? I am planning on making a 30 caliber with a 2" case length first so I will have to cut a .340" neck a little over 2" deep. What size boring bar would work?

[JIMinPHX]

Indexible bars (& most others) come with a Min Bore specification. Get a bar with a Min Bore rating that is just under the smallest diameter that you need to generate. You should be able to find a 1/4" bar with a small enough Min Bore rating. I think that the little Circle brand bar that I just used to cut a 32-20 die for a friend of mine had a 1/4" shank. It was something that I got on a sales circular deal from MSC. I think that it was like $100 for the bar with 10 inserts.

Do your bulk roughing with a drill bit first, then have at it with the bar. Be gentle with little bars. Don’t get too horney with the depth of cut or the feed rate.

Bars with carbide shanks have better rigidity & are usually rated for 10 diameters of stick out. Steel shank bars are usually rated for about half of that, although I’ve gone deeper with them by making a lot of gentle spring passes. Steel bars have a tendency to bend when you push them too hard. Carbide shank bars have a tendency to snap off when pushed too hard. Carbide shanks usually cost a lot more than steel shanks.

If you are working in a hard or tough material, then the depth ratings for boring bars are greatly reduced. 12L14 with a case is probably a very good choice of materials for this project.

If you're going to make our own braze on bar, then you want to make the shank out of something a little meaner than cold roll 1018.

Reamers do not double as boring bars the way that end mills sometimes can. Reamers cut good holes to the one size that they are ground to & that's it.

[Trailblazer]

Thanks Jim, I will look at the tool catalogs again.

[Morgan Astorbilt]

Check out the MSC catalog. If you don't have the Big Book, you can use their on-line catalog. If you like you can let me know what the minimum hole dia. is, you're going to bore, and I can look one up for you, in my catalog, this might be easier.
Morgan

[leftiye]

Expected someone to suggest just boring the hole undersized with a drill, and then reaming to just under desired diameter. Then heat treat and polish or hone out to desired diameter.

[Buckshot]

http://www.fototime.com/76745E9F64C31AA/standard.jpg

..............These are solid carbide boring bars that take indexable carbide inserts. They're made by Circle C and MSC will put them on sale a couple times a year. Normally they're well over $200 each, but on sale they were like $107 each or somesuch. The 4 sizes are 3/16x4", 1/4x4", 3/8x6" and 1/2x8".

The minimum bore for the 3/16" bar is 0.200". Using their suggested DOC's and feeds you can go up to a 10 times stickout. They're sure enough nice tools. All but the 1/2" bar come with 10 inserts. It comes with 5.

.................Buckshot

[Trailblazer]

I have a friendly machine shop up the street with the MSC catalog. I just get frustrated trying to find anything in their online catalog. The insert bars are probably the way to go.

[BudRow]

Just a suggestion but if you could find a exsisting die that closely approximates what you are trying to form, then anneal it and go from there. Depending on how much stock you have to remove and it's location, maybe a toolpost grinder with a long quill might suit your needs. Good Luck, Bud

[EDG]

The end mill suggestion idea above will work for such a simple job.
Just drill out the hole about .015 undersize and use an end mill to bore it.
If you can find a carbide end mill that is even better.
For such a short hole you can even grind a piece of Rex 95 to use as a boring bar.

[deltaenterprizes]

Masonary drill bits can be ground to make small carbide tipped boring bars and are cheap and readily available!

[leftiye]

Masonary drill bits can be ground to make small carbide tipped boring bars and are cheap and readily available!

Now that's thimkin'. Takes Kidneys! Might not be as rigid as the solid carbide ones, but could come in handy.