Internal Threading With Carbide Index Inserts. Tooling Question.

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Degull

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Hello everyone. I am making a component (basically a nut) out of 17-4 stainless steel rod. I would like to tap a 5/8-11 thread in the center of the rod on the lathe with index tooling. I know that I can thread it manually with a 5/8-11 tap, but I've learned the hard way that tapping 17-4 stainless is not forthe weak. I would like to avoid it and I have a bunch of nuts to make.
I have 11IR and 16IR inserts and the appropriate bars (cheap ebay stuff). 16IR inserts will not fit in the hole and 11IR will not cut a 11 tpi thread. Any thoughts on tooling I should be using for internal thread a of 5/8-11 hole?
 
You might consider this one from Micro 100: https://www.ebay.com/itm/MICRO-100-...082119?hash=item1a333244c7:g:sYYAAOSwF7lZlLdU

0.360" min. ID
0.75" max hole depth
0.75" shank diameter, 2.5" OAL
10-32 tpi

I have a smaller version of this tool. You can sharpen these with a diamond stone and the carbide has minimal flex so it produces very accurate threads. Mine is about 10 years old, has seen a lot of use and it is as sharp as it was when new.

I also have a Circle Machine QCMI 3/8" bar that will cut that thread. Retail for a single threading insert will cost what that Micro 100 bar costs.
 
Those micro 100 look tempting and I might even attempt to grind my own. I was hoping to find a cheap insert solution but I guess insert tooling and cheap do not go together.
 
I've ground a bit or two in my time so I know that grinding an accurate internal threading tool that won't deflect is not that easy. For me, I would buy that Micro 100 tool bit and get it done.
 
I'm kind of surprised that no one has said not to thread with a carbide tool due to the possibility that it will chip, and you won't be able to pick the thread up again. Maybe I'm older than dirt, but that's what I was told way back in Tech school.
 
In today's world of manufacturing, a small thread like this is milled in the part using live tooling on a CNC lathe. As far as I know, and I've dealt with a lot of insert tooling in my time, there is no insert tooling out there that will get into a bore that small to cut a 11-pitch thread. Now, I have some Everede boring bars that the tool bit can be ground to cut that thread easily. I have one ground up to cut a 7/16-10 Acme thread in a brass nut!
 
4gsr said:
In today's world of manufacturing, a small thread like this is milled in the part using live tooling on a CNC lathe. As far as I know, and I've dealt with a lot of insert tooling in my time, there is no insert tooling out there that will get into a bore that small to cut a 11-pitch thread. Now, I have some Everede boring bars that the tool bit can be ground to cut that thread easily. I have one ground up to cut a 7/16-10 Acme thread in a brass nut!
Click to expand...

Send your nuts to Ken!
 
mikey said:
Send your nuts to Ken!
Click to expand...
LOL!!!

The OP mentioned he has lots of these to make. I would suggest getting a couple of Emoge (sp) or one of other high performance taps offered by MSC and along with Ridgid thread cutting oil for stainless steel or my favorite Mobil Mobilmet 766 and power tap the threads in the lathe in the same setup as the hole was made. And I suggest drill and bore to size the hole so you have near perfect alignment for the tap to start into also. Oh, and chamfer the lead in of the hole too.
Here's a few tap brands I found in my MSC flyer that came in the mail recently.
Kennametal "GOtap" Spiral point taps
Accupro Spiral point taps
OSG "HY-PRO" High performance taps
Just to name a few. Price ranges of these taps for 5/8" size about $30 ea., not too bad in my opinion when you need something to get the job done right.
 
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