Thread Milling From Top to Bottom or Bottom to Top?

[imachine909]

When treading mill on a production job that runs for the most part unattended. Do you thread mill top to bottom or bottom to top? I understand you will be cutting conventional vs climb. How do you make sure the hole is ready for the thread mill?

 

[Milland]

For regular threads, I usually do it climb, bottom to top. You do want to ensure there's not a ton of chips in the hole, and that the drill didn't break before the threadmill is called.

Whatever you have for probing should inform you of tool breakage, and for the threadmill entering the hole, if there's a risk just enter slowly so chips can be pushed out or flushed out by coolant.

 

[Hardplates]

Mitsubishi makes a threadmill that runs counterclockwise climb milling from top to bottom with no predrilled hole.

 

[dodgin]

Mitsubishi makes a threadmill that runs counterclockwise climb milling from top to bottom with no predrilled hole.

Epoch-D, I think it's called. Never used it but always looked impressive.

Carmex has an entire line in which the cutting geometry is backwards so you can thread mill top to bottom and climb cut. I've always thought of Carmex as a cheap brand but we use that line quite a bit and they work really well.

 

[CORONA VIRUS]

The whole idea behind bottom to top is that you are not recutting chips.

 

[CarbideBob]

The whole idea behind bottom to top is that you are not recutting chips.

Very confused here.

 

[DavidScott]

Since you are more likely to have chips in the bottom of the hole after cutting the threads than before bottom to top sounds best to me. As for making sure there is a hole first that logic applies to many other tools so a bit redundant.

 

[Hardplates]

The Op's machines have more than enough HP on reserve to recut chips

 

[CORONA VIRUS]

Very confused here.

When you cut from top to bottom chips fall into the hole and get caught in the tool. This make the tool recut chips that have already been cut. It is like digging a hole and throwing the dirt back into the same hole you are digging.

 

[CORONA VIRUS]

Yeah? How does the cutting tool like that? LOL

 

[Hardplates]

Yeah? How does the cutting tool like that? LOL

I never though of that, I guess it could be hard on the tool huh?

 

[CORONA VIRUS]

uhuh. And hard on the surface finish.

 

[imachine909]

I should have stated in the original post my current process. Here it is...

Create hole. This is sometimes done with only a drill and other with drill then end mill. Then run a .0625 diameter plastic rod in a collect holder. This rod has a score so it snaps very easy. We take this to and feed to the bottom but stay up .01 then do the same thing going around the diameter of each hole. After that we run this tool through the laser for breakage detection. Once that gets the green light we thread mill bottom to top.

Does anyone else have a faster method to keep the machine safe?

 

[Hardplates]

uhuh. And hard on the surface finish.

Please tell me more

 

[boosted]

I should have stated in the original post my current process. Here it is...

Create hole. This is sometimes done with only a drill and other with drill then end mill. Then run a .0625 diameter plastic rod in a collect holder. This rod has a score so it snaps very easy. We take this to and feed to the bottom but stay up .01 then do the same thing going around the diameter of each hole. After that we run this tool through the laser for breakage detection. Once that gets the green light we thread mill bottom to top.

Does anyone else have a faster method to keep the machine safe?

Why not just check the drill/endmill on the laser, then go straight to the threadmill? That's how we've always done it. I've never seen a drill leave enough material at the bottom of a hole it's just drilled to make a problem. Even if something crazy happened and it did break on the way down, broken threadmills are a lot easier to dig out than broken taps.

 

[Strostkovy]

Just check the thread mill after the operation? The slim chance of a problem that doesn't leave a broken drill bit but results in a damaged thread mill seems like not a huge deal to just have a reserve thread mill on hand.

 

[CarbideBob]

I do very much like the finish of climb milling.
I do not bore bottom to top on a VMC very often because of mean ole mister gravity making me recut chips.
For sure a small single end carbide threadmill will die fast if it recuts a chip.
I see the climb mill as the advantage and better surface finish if the hole to thread mill diameter has enough room to allow the chips to drop.
Some thread mills have a rake/helix to push the chip one way. They do not like being run the opposite way as the cutting geometry and side relief is wrong.

Good makers will say how the tool is designed to work. Both directions is a compromise and you give up some tool life.
This is a pain in ass so just make uni-directional for the world.

If "threading mill on a production job that runs for the most part unattended." I'd ask for the maker of the cutting tools help.
Bob

 

[gregormarwick]

I do very much like the finish of climb milling.
I do not bore bottom to top on a VMC very often because of mean ole mister gravity making me recut chips.
For sure a small single end carbide threadmill will die fast if it recuts a chip.
I see the climb mill as the advantage and better surface finish if the hole to thread mill diameter has enough room to allow the chips to drop.
Some thread mills have a rake/helix to push the chip one way. They do not like being run the opposite way as the cutting geometry and side relief is wrong.

Good makers will say how the tool is designed to work. Both directions is a compromise and you give up some tool life.
This is a pain in ass so just make uni-directional for the world.

If "threading mill on a production job that runs for the most part unattended." I'd ask for the maker of the cutting tools help.
Bob

As much as it pains me to agree with covidman, every threadmill manufacturer that I have ever paid any attention to recommends to climb out of the hole whenever possible for exactly the reasons he explained. And as Hardplates/Dodgin explained quite a few make left hand cutting threadmills so that the same process can be used to machine left hand internal threads.

Threadmills with axial through coolant help a lot when you have to cut conventionally.

 

[ChipSplitter]

The whole idea behind bottom to top is that you are not recutting chips.

Very confused here.

The Op's machines have more than enough HP on reserve to recut chips

When you cut from top to bottom chips fall into the hole and get caught in the tool. This make the tool recut chips that have already been cut. It is like digging a hole and throwing the dirt back into the same hole you are digging.

I never though of that, I guess it could be hard on the tool huh?

uhuh. And hard on the surface finish.

Please tell me more

Hmmm..........

 

[VTM]

Well, I thought like most here for a long time. But we have this one app where were doing .250 deep #4-40's in 6AL-4V (4) per part. We had been Roll Tapping them and having to manually apply tapping fluid. Was working OK, but kind of a pain. Quantity got bigger and we started looking for a better way. My local guy brings in the Emuge rep so I pick his brain about It. Says thread mill Is the way to go. Mill from top to bottom. They even sent me the code. I had my doubts. Just looking at the tool I was like no way is that going to last long. We're getting over 400 holes with one tool with nothing but flood coolant milling from top to bottom right to the bottom of the hole. I never would have believed that tool would perform that well If I hadn't seen It with my own eyes.