Education on thread milling

[cuttergrinder]

We have some double nuts at work that need threaded. They are basically just 2" thick 4140 that needs two holes threaded 2 1/2" -4 thread. We have done these before on a horizontal boring mill and just power tapped them. The problem is the thread doesn't come out as nice as we would like. I would like to thread mill these with a Mazak vtc16 with a mazatrol m32 control. Is this possible and if it is, what kind of tooling do we need. Sorry for the dumb questions but I have never thread milled or seen it done.

 

[WABOOM]

here's a pic of the threadmilling cycle on a Mazak Multiplex . Using EIA mode. Hope it helps.
Using an Advent 4 fluted threadmill. No chatter.

 

[deadlykitten]

if coding is the problem :
... you need a code to generate a helix
... is like when machining a hole with a smaller endmill, only that there is no full circle at the bottom

can you explain this a bit ? The problem is the thread doesn't come out as nice as we would like

 

[cuttergrinder]

When we tap these threads, it usually tears the first few threads. I can generate the code with bobcad but What I was really wondering is if the mazatrol m32 had a cycle for thread milling. I'm thinking it does not. If I use bobcad, would I mill the thread in just a rough and a finish pass or multiple passes? Also I'm having trouble finding a thread milling cutter that will cut this coarse of a thread. Could the lead of 4 threads be too great to where you cant thread mill it?

 

[WABOOM]

I'm sure there is an inserted thread mill for that pitch thread. Iscar, Seco, Sandvik etc. Write an EIA sub program for your Mazak. You know you can straight line G&M in that machine.

 

[WABOOM]

That sequence I gave you is for a lathe but the Helix values are in it.

 

[WABOOM]

Different pitch but its a great start to help you get where you need to be.

 

[Larry Dickman]

First, what is your quantity? You can use a multiple profile tool which will cut more than one thread per pass. A single profile threadmill will only cut one thread at a time, so it will take longer. However, it's more versatile since you can use it to cut different pitches, inside/outside, left/ right, etc.
Since your doing a double lead thread, you'll need to create the code with a start at 0 deg, and then again at 180 deg. For a 2-1/2" thread in 4140, you'll probably need a couple rough passes.
You also need to decide whether to go with a solid threadmill, or an insert one. Again, depends on your quantities and how much you want to spend.
There are a lot of good threadmills out there, I would start by calling Vardex. They'll set you up, and they will also prograsm it for you.

 

[cpifer3]

If your only doing a couple parts, this can be done with a boring bar and an insert capable of cutting whatever pitch it is you are cutting. In other words, what ever tooling you would use to single point the thread in a lathe, can also be used in the mill to thread mill. Its like having a single tooth ,single profile thread mill, but alot cheaper if you already have it. Now for the down side, this is extremely slowwwwww. With a pitch that coarse probably gone need tw0 or more passes. If your doing more than a couple parts probably gonna to have to get some tooling.

 

[cuttergrinder]

We only have four pieces to thread and each piece has two holes. I probably confused you, its not a double lead, its just sort of like a huge t-nut with two threaded holes.

 

[cuttergrinder]

You know you can straight line G&M in that machine.

What do you mean by straight line g&m codes. I can send a g code program to the machine using the "tape" button but I have to reload the program after I run every part. How can I send a g code program to this machine and get it to store the program?

 

[Dan from Oakland]

The straight line G&M code comment- if your control does not allow helical interpolation, the work around is to have your CAM system generate the toolpath with many short straight line/arc segments. Makes for a long program, but it works. The drawback is the control may stall waiting for code to be transmitted because of the small moves.

 

[WABOOM]

With a disk or network cable. Data I/O

 

[WABOOM]

You can send and receive files like normal.

 

[cuttergrinder]

Ive tried to send a file using the Data I/o with a null modem cable but it always gives me an error. What is the proper way to do it? do you start it at the mill at the laptop. I was trying to send it with bobcad. It works fine using the tape button but you have to resend it for every part.

 

[G00 Proto]

If your only doing a couple parts, this can be done with a boring bar and an insert capable of cutting whatever pitch it is you are cutting. In other words, what ever tooling you would use to single point the thread in a lathe, can also be used in the mill to thread mill. Its like having a single tooth ,single profile thread mill, but alot cheaper if you already have it. Now for the down side, this is extremely slowwwwww. With a pitch that coarse probably gone need tw0 or more passes. If your doing more than a couple parts probably gonna to have to get some tooling.

How in the world do you get the cutter back out of the part? Stop the machine and move the cutter in?

Oh wait, I get it... run it like a threadmill. I though you meant to set the boring head at major diameter and feed in with the spindle speed and Z feed synchronized like a tapping cycle. That would be a neat trick, and could probably be done...

 

[G00 Proto]

Ive tried to send a file using the Data I/o with a null modem cable but it always gives me an error. What is the proper way to do it? do you start it at the mill at the laptop. I was trying to send it with bobcad. It works fine using the tape button but you have to resend it for every part.

You're probably going to need to get this figured out. RS-232 is a pain in the ass, but needed to get code into these older machines.

You will also need a good solid carbide single point thread mill that can accommodate the thread pitch you need. For these low volumes, you will be better off with a single point tool that will have uses for multiple threads. I am completely dependent on 3 or 4 of these tools for the majority of my threads. I would rather thread mill than tap for non-production pieces, because it is safer, makes better threads, and you can get closer to the bottom of the hole. Once you get it figured out, it isn't hard. Bobcad will make you work a bit harder than more advanced cam packages, but it can be done.

 

[cpifer3]

How in the world do you get the cutter back out of the part? Stop the machine and move the cutter in?

Oh wait, I get it... run it like a threadmill. I though you meant to set the boring head at major diameter and feed in with the spindle speed and Z feed synchronized like a tapping cycle. That would be a neat trick, and could probably be done...

Yep, run it just like a thread mill.

 

[Larry Dickman]

Since you're only doing 4 parts, and you already have a tap, I would just cut the minor dia toward the high limit and hand tap them using a spring center. Just get it over with.

 

[moonlight machine]

How is it possible that a Mazak can be such a pita? I thread mill all the time on my Centroid controlled V2xT Bridgeport. Caned cycle, takes about 30 seconds to program, done deal.