[Don Clement]

Another alternative with the Tormach is to thread mill instead of tapping.

[David Bord]

Mike,

You havent done anything wrong! These forums are for asking questions and the vast majorities of guys on the forum are extremely helpful so ask away.

You may want to search as well, I found some decent info on the same subject.

Im in the same place as you regarding a tapping head. I think you can count on Tormach to provide accurate info on what works well on their machine and what would be a good fit for you. That and this response from the forum should get you what you need.

David

[David Bord]

So..... Seems to me all of these would *require* a spindle encoder if running CNC, to be able to set the feedrate with sufficient accuracy, no? If the downfeed is too fast, looks like very had things will happen, no? *Slighty* slow is OK, if not preferred, as long as it's not TOO slow, right?

Regards,
Ray L.

Not as I understand it. They only thing that requires an encoder is rigid tapping.

You should make sure your commanded spindle speed is calibrated though.

David

[SCzEngrgGroup]

Not as I understand it. They only thing that requires an encoder is rigid tapping.

You should make sure your commanded spindle speed is calibrated though.

David

Well, that kinda says the same thing. If the spindle speed is not pretty close to what you command, it won't work right, especially if the spindle speed is faster than commanded. Might work OK if the spindle speed is slower than commanded, as I believe a reversing tapping head will deal with that by just disengaging, or possibly even reversing occasionally. The cheapest/easiest way to achieve accurate spindle speed is to add a spindle sensor, and feed than into Mach3/EMC/whatever.

Regards,
Ray L.

[Don Clement]

Thread milling doesn't require accurate spindle speed.

Don

[SCzEngrgGroup]

Thread milling doesn't require accurate spindle speed.

Don

Yeah, but I don't think you can thread mill small holes - like 6-32, 8-32, etc.
What is the smallest size you can thread mill? And the thread mills themselves are awfully pricey....

Regards,
Ray L.

[Don Clement]

Well, that kinda says the same thing. If the spindle speed is not pretty close to what you command, it won't work right, especially if the spindle speed is faster than commanded.

The lead accuracy on the tap itself determines the lead accuracy of the tapped hole with a tension-compression head or reversing tap head because variations in spindle speed are compensated with the axial play in these type of tapping heads. The tap feeds itself. Rigid tapping without a axial play may require the need for accurate spindle speed but not with a with a tension-compression head or reversing tap head.
BTW It does work right as I have tapped 10s of thousands of holes on my Tormach using a reversing tapping head and even some with a tension-compression head with excellent results.

Don

[Don Clement]

Yeah, but I don't think you can thread mill small holes - like 6-32, 8-32, etc.
What is the smallest size you can thread mill? And the thread mills themselves are awfully pricey....

The OP talked about 1/4-20 size holes that are well within the ability of the Tormach to thread mill. So are 6-32 and 8-32. Thread mills are way less expensive than a reversing head or Tormach tension-compression head set. I'll bet even less expensive than a spindle sensor with software. Certainly less expensive than a servo spindle.

Don

[txcncman]

I have thread milled #4-40 in both stainless and aluminum.

[SCzEngrgGroup]

The lead accuracy on the tap itself determines the lead accuracy of the tapped hole with a tension-compression head or reversing tap head because variations in spindle speed are compensated with the axial play in these type of tapping heads. The tap feeds itself. Rigid tapping without a axial play may require the need for accurate spindle speed but not with a with a tension-compression head or reversing tap head.
BTW It does work right as I have tapped 10s of thousands of holes on my Tormach using a reversing tapping head and even some with a tension-compression head with excellent results.

Don

Don,

Perhaps I'm over-thinking this.... I suppose with tapping, the total distance is typically small-ish (normally an inch or less), so if the tapping head, be it reversing or simply tension/compression, has a reasonable amount of travel (3/4" seems typical, I think), then the downfeed just needs to be within 20-30%, and all will work out.

My machines spindle is bloody slow at stopping and reversing, though that could probably be fixed with a better VFD. So, for now, tension/compression is not practical for me.

Now, thread-milling is interesting, and my machine is quite capable of that, but where are you finding inexpensive thread mills? All the ones I can find are $100 and up for each one! And that's a recurring cost, where the cost of a reversing head is a one-time cost, and after that it's just inexpensive spiral taps.

Regards,
Ray L.

[Scott_M]

I have been using this supplier for over a year now. They make absolutely top notch stuff at a fraction of the cost of anyone else. I even special ordered 4-48 threadmills from them. Really good stuff. I would put their endmills up against OSG and Niagara any day.

Online Carbide

Scott

[txcncman]

Tapmatic tapping heads run $400-$900. That buys about 4-9 thread mills @ $100 each. I think you should be able to get solid carbide single point thread mills a little cheaper than $100 (but not sure and not going to look it up at the moment). If you don't do something stupid and break it, a single point thread mill will last a long, long, long time. Even in stainless. I think I am recalling we would get 500-1000 holes out of one #4-40 thread mill in stainless. In aluminum they last foorrrreeeeverrrr. How much will you spend on taps for the same number of holes? How many scrapped parts with taps broken in them will it cost? In the final analysis, it really probably comes out close to the same cost, for both money and time. It just becomes a matter of preference. Which do you like better?

[SCzEngrgGroup]

I have been using this supplier for over a year now. They make absolutely top notch stuff at a fraction of the cost of anyone else. I even special ordered 4-48 threadmills from them. Really good stuff. I would put their endmills up against OSG and Niagara any day.

Online Carbide

Scott

OK, now we're talkin'! Those are pretty reasonable.

Am I correct in understanding the correct usage is:

1) Plunge into the center of the hole
2) Move out to the side
3) Helical cut upwards one thread
4) Back to center and retract

Regards,
Ray L.

[Don Clement]

Don,

Perhaps I'm over-thinking this.... I suppose with tapping, the total distance is typically small-ish (normally an inch or less), so if the tapping head, be it reversing or simply tension/compression, has a reasonable amount of travel (3/4" seems typical, I think), then the downfeed just needs to be within 20-30%, and all will work out.

My machines spindle is bloody slow at stopping and reversing, though that could probably be fixed with a better VFD.

The travel on a reversing tap head need only be a small amount when used with my Tormach. I use 100% feed no dwell with my Procunier when tapping blind holes with excellent results. BTW I have about $1K invested in the Procunier which includes many Pro-quick quick change tap holders. I bought the Procunier before my Tormach CNC and it can still be used on my manual Rockwell vertical mill.

My three digit Tormach 1100 was slow to start and stop until upgrading with a new VFD with braking resistor. The Tormach VFD upgrade and PDB were well worth the money IMO.

For thread milling I use a TTS adapted Vardex insert TM tool. http://i72.photobucket.com/albums/i1...dification.jpg

http://i72.photobucket.com/albums/i1...cationrear.jpg

Thread Milling M60-0.75mm Thread video by miltons_stuff - Photobucket

http://s72.photobucket.com/albums/i1...t=100_3100.mp4

For me I just put in a new two edged carbide insert so cost is about $30 for two TM cutting edges.

Don

[txcncman]

One thing we did not mention, with a thread mill, you can cut OD threads also. 2 tools in 1. Try to do that with a tap.

[Don Clement]

One thing we did not mention, with a thread mill, you can cut OD threads also. 2 tools in 1. Try to do that with a tap.

BUMP I show videos of both internal and external thread milling on my Tormach. I just change the insert from internal to external.

Don

[SCzEngrgGroup]

That Vardex insert tool is very cool, but I rarely do anything bigger than 3/8", and most is smaller, so I guess I'm stuck with solid cutters. I'll have to get some and give it a try.

Thanks for all the info, guys! I have REALLY hated to have to do all my tapping by hand, and a tapping head won't really help once I get a tool-changer going. I think this should be the solution I've been looking for.

Regards,
Ray L.

[MichaelHenry]

So with my 3 digit Tormach I am only limited by the maximum feed rate for retraction which is 65 IPM.

Don

Have you considered upgrading to the new Series III drives and steppers when the upgrade kit is available? Seems like a good idea for me and you probably use your mill far more than I use mine, so the payoff should be better.

Mike

[dbrija]

Have you considered upgrading to the new Series III drives and steppers when the upgrade kit is available? Seems like a good idea for me and you probably use your mill far more than I use mine, so the payoff should be better.

Mike

I doubt the economics of improved rapids versus the upgrade cost would make sense.

[David Bord]

There are these types of threadmills as well that I believe you can cut different size thread/diam with a single tool.

If this is the case, anyone have any info or good sources for them?

Scott, does online carbide make these?

[ame=http://www.youtube.com/watch?v=pQ83XRgRCyg&feature=related]Thread milling - YouTube[/ame]

Another video that was produced by tormach that gives some great detail using the same type of cutter. He says you can cut different pitch, metric and standard, all with the same thread mill.

[ame="http://www.youtube.com/watch?v=T4ZVoHei1uE&feature=related"]External Thread Milling with a Tormach PCNC 1100 - YouTube[/ame]

David