about to buy 7x lathe, help me pick out some tooling

[draculia]

i was going to wait for homier to get more lathes in, but i'm just going to order from cummins instead. as you may or may not know, the cummins lathe comes with a bunch of basic tools, steady and follower rests, drill chuck, basic 5 piece cutters, etc. i have absolutely no tooling for machine work, so

this is the basic list of items i'll be ordering:
0-6" calipers
0-1" dial indicator with mag base
center drills
4 jaw 3" chuck, some of the stuff i want to do right away is square
60 deg center gage
cutoff tool holder and blades
1/2" boring bar holder
1/2" boring bar set

now some of the things i want to do right away are making internally threaded weld on bungs. these will be 304 ss and mild steel, 1" in diameter that will come with .188 walls. they will be approx 1/2" thick, and intenally threaded m18x1.5.

my question is what would be good for the internal threads. i don't want to make my own tools right now, though i will in the future. msc has some nice solid carbide threaders with a 1/2" shank that could possibly be used in the boring bar holder? a bit pricey at 50-60 each though. i wouldn't mind spending 100 or so on an indexible one, but all the indexible threaders i find seem to be made for external threads or really big internal threads. i need something that can fit in a .650" bore. any ideas?

[ViperTX]

If you don't have a internal shoulder that is problamatic....then I would opt for a Tap, if you can tap all the way through or if it's a bottoming type of tap and you don't mind having the last or bottom 2 threads as only partial threads.....

[WhiteTiger]

I advise against small carbide tooling until you get real familiar with your machine. I know my carbide learning curve got pretty expensive right at first... things that would just be an "oops" with tool steel turn out to be "buy another" with carbide.

I know you said you didn't want to be making tools right now, but the price of one carbide threading tool will buy you a middlin decent bench grinder, a mapp gas torch and a couple feet of A1 1/2" tool steel to make "learning on" threading tools. There's also the fact that if you grind and harden your own, you can make them your own idea of "just right" for whatever thread pitch you are doing.


Tiger

[RotarySMP]

Get the four inch four jaw. The spindle hole is 3/4" (20mm) but the 3" three jaw chuck only has about a 17mm hole. You need the larger spindle hole to use longer 3/4 inch bars.

You need both HSS and Carbide tooling on the mini-lathe. I find if I want to reduce the diameter of larger steel stock, HSS's limitations on surface speed drives a very slow spindle speed where the PWM motor controller has little torque, so you need very light cuts. With carbide (I use TCMT's with small nose radius off Ebay) you can crank up a higher speed where the motor controller is delivering much more power.

A 1.5mm pitch thread into Stainless is going to be a bear! You will not be able to single point that in one pass on this machine. I have mine converted to CNC, and this would take more like t10-15 passes (in mild steel, I haven't tried it in stainless). My guess is that the flexiblity of the boring bar holding the threading bit would mean you can't single point this thread in one pass on any machine?

[draculia]

yeah, i figure that pitch will be no fun. luckily i only need a few of them.

what i ended up ordering, whether it will be suitable or not, is a 3/8" round boring bar the has a square hole at either end for 1/8" tool bits. i also ordered a few other bits that might do the job. if non are suitable its not like they'll go to waste.

everything was ordered last night, so it looks like i'll be playing in a week or so.

[RotarySMP]

I use one of those boring bars all for about half of my boring, and it carries my internal threading bit.

I have my doubts whether a tap made from hardened drill rod will be up to the task of such a bit thread in Stainless, but that would be the logical way to go. M18x1.5mm is a standard metric fine thread, so I would not expect a quality tap to be that expensive.

[draculia]

woohoo, finished my first two projects on the lathe. i had about 15 jic adapters where the 37 degree taper was machined poorly, so i remachined the taper on them. at about $12 each, this saved me a decent amount of money over rebuying them. i also had to recess a lip on some mild steel bungs.

i also have a bunch of 12l14 hex bar coming in to play with. i can't wait till i actually know what the hell i'm doing with this thing