Both internal and external threads. I couldn't find that many references to people doing it this way.
Any reason I can't cut threads with a TCGT insert?
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Yes, way too much nose radius on the insert. A thread cutting tool needs to have a sharp nose. Usually threads are cut slow , shallow, and with a lot of lube, inserts are usually not the right answer for this operation.
A thread cutting HSS toll is one of the simplest tools to make and will make a far better tool for threading than carbide insert tooling. (unless you get a specific "profile" cutting insert)."Those who hammer their guns into plows will plow for those who do not."~ Thomas Jefferson
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Originally posted by beanbagBoth internal and external threads. I couldn't find that many references to people doing it this way.
I think I have even seen a commercially made holder to do this, can't remember where though.
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Glenn, the side clearance is going to be a big factor as well. The cutter will rub in the thread if it's not ground such as to clear it. That's why there's a steep side relief on threading tools. If you started hogging into the holder to create that clearance, you're likely to weaken it's performance on regular stock removal, so it doesn't make much sense to do it.
You can cut threads with a parting tool if you grind the end such as to allow for the clearance and get the 60 degree angle right.
I picked up a whole vardex internal/external carbide insert threading set on fleabay for $100. Two holders and a whole slew of geometries.
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Originally posted by CarldYep, side clearance is an issue. Just buy the right tool holder and the right threading inserts."Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."
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Iv threaded with those cheapo triangle TCCT inserts (or whatever those UBER cheap chinese 'my first insert' kits are) its ok for REALLY course big OD threads (like 1/2" and bigger) if you get the fine nose inserts and have like 7~14 degrees of releif on your inserts.
I also have a weird tool that appears to use a carbide square 'shaft' thats tiped with a carbide shaped threading profile, the tool itself looks much like some of those cutoff blade holders but it holds a square tool insted of a rectanglar tool.
But yes. HSS bits are soo easy to grind, I made one with an angle grinder and diamond coated files to hone it and to manualy grind off the last few degrees to make it a perfict fit to my thread gage.
Idealy you want to try against a real bolt at that point and check/fix the nose radius too (for best bolt strength anyway)Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.
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I Have done it with TPG inserts with no nose radius and that worked . Not sure just what insert you have with out looking it up.Every Mans Work Is A Portrait of Him Self
http://sites.google.com/site/machinistsite/TWO-BUDDIES
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Sorry, I should have provided more info upfront.
I'll be cutting internal and external threads approx 10-12 tpi on something that has a 3.5" diameter. So I think the clearance will be ok using a TCGT insert. The nose radius is 0.008, so that should be sharp enough as well. However, I think as a final pass, I will have to shift the insert over sideways to get the proper depth vs length of crests and troughs.
Also, this insert was designed for aluminum (the material I am working on), so it has a big ol ramp at the cutting edge. However, since the diameter of the piece is large, this shouldn't matter.
This insert cost me $11, whereas otherwise I'd have to get separate internal and external thread cutting inserts at $16 each. Such a cheapskate, I know.
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I'd have to look to verify, but as I recall the laydown style triangular threading inserts don't have a great deal of relief ground on the front edge. They tilt the insert down radially and axially to achieve the relief.
The higher end threading holder insert combinations use replaceable angular seats under the insert to achieve correct front relief. The amount of angle on the seat varies with the pitch and diameter of the thread being cut. Of course, this is the ideal situation, but double the cost, insert plus seat needed. These are usually only found on external holders since there isn't enough room on the tip of smaller internal holders for the seat + insert.
There's also the issue of how close to the bottom of a blind hole you can get using the TPGT style insert. Not a problem for through hole threading though.
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