[thump]

hello all. i'm wondering a couple of things regarding tormach spindles, and haven't found much info at all in my googlings and other sundry interwebbings...

1.) anybody have experiences with the bt30 spindles? are there accuracy/repeatability benefits to using them? i realize that for a smaller machine the increased rigidity can be as much of a liability as an asset, but that's not what i'm talking about. besides, hopefully feeds and speeds are being set conservatively and by the book so as to avoid running the thing so hard that it's forced to buck and strain in the first place. if not, you kinda chose your own adventure.

2.) anyone know why they selected bt30 instead of cat30 or iso30 or nt30? of all the 30-taper options out there, bt30 is the one i see and hear referenced least frequently (although i'm not working in industry, and realize that this undoubtedly skews my perceptions somewhat).

thanks!

[BlueFin]

From Wikipedia:

There is some degree of standardization of the tooling used with CNC Milling Machines and to a much lesser degree with manual milling machines.

CNC Milling machines will nearly always use SK (or ISO), CAT, BT or HSK tooling. SK tooling is the most common in Europe, while CAT tooling, sometimes called V-Flange Tooling, is the oldest variation and is probably still the most common in the USA. CAT tooling was invented by Caterpillar Inc. of Peoria, Illinois in order to standardize the tooling used on their machinery. CAT tooling comes in a range of sizes designated as CAT-30, CAT-40, CAT-50, etc. The number refers to the Association for Manufacturing Technology (formerly the National Machine Tool Builders Association (NMTB)) Taper size of the tool.

An improvement on CAT Tooling is BT Tooling, which looks very similar and can easily be confused with CAT tooling. Like CAT Tooling, BT Tooling comes in a range of sizes and uses the same NMTB body taper. However, BT tooling is symmetrical about the spindle axis, which CAT tooling is not. This gives BT tooling greater stability and balance at high speeds. One other subtle difference between these two toolholders is the thread used to hold the pull stud. CAT Tooling is all Imperial thread and BT Tooling is all Metric thread. Note that this affects the pull stud only, it does not affect the tool that they can hold, both types of tooling are sold to accept both Imperial and metric sized tools.

SK and HSK tooling, sometimes called "Hollow Shank Tooling", is much more common in Europe where it was invented than it is in the United States. It is claimed that HSK tooling is even better than BT Tooling at high speeds. The holding mechanism for HSK tooling is placed within the (hollow) body of the tool and, as spindle speed increases, it expands, gripping the tool more tightly with increasing spindle speed. There is no pull stud with this type of tooling.

The situation is quite different for manual milling machines — there is little standardization. Newer and larger manual machines usually use NMTB tooling. This tooling is somewhat similar to CAT tooling but requires a drawbar within the milling machine. Furthermore, there are a number of variations with NMTB tooling that make interchangeability troublesome.

Two other tool holding systems for manual machines are worthy of note: They are the R8 collet and the Morse Taper #2 collet. Bridgeport Machines of Bridgeport, Connecticut so dominated the milling machine market for such a long time that their machine "The Bridgeport" is virtually synonymous with "Manual milling machine." The bulk of the machines that Bridgeport made from about 1965 onward used an R8 collet system. Prior to that, the bulk of the machines used a Morse Taper #2 collet system.

[Don Clement]

The much more affordable TTS system (BTW not mentioned in Wiki) works great for me on my Tormach. In addition Tormach’s power draw bar for TTS is almost as good as having an ATC.

Don Clement
Running Springs, California

[zephyr9900]

Yes, I'd think that the only reason to use the BT30 spindle would be if you already had other machines using BT30 and wanted to share tooling. The TTS tooling also requires much less Z clearance than BT30 or solid R8 holders.

The tooling choice is part of Tormach's balanced design approach. If you haven't already, thump, read the design analysis white paper. I probably had parts of it memorized by the time I bought my machine.

Randy

[scudzuki]

Users have reported TTS holders backing out of the spindle under heavy cuts.

TTS is going to be less expensive and will require less work to change tools.

For lighter applications it may be adequate but if you start pushing it, it can't compare to a 30 taper system.

Joe

[Don Clement]

Users have reported TTS holders backing out of the spindle under heavy cuts.

TTS is going to be less expensive and will require less work to change tools.

For lighter applications it may be adequate but if you start pushing it, it can't compare to a 30 taper system.

Joe

Yeah I heard that also. Never had a TTS tool back out on me in three years of usage though. Must be that I know the limits of the TTS system and don't push overly heavy cuts. TTS has worked extemely well for me. YMMV.

[philbur]

It's highly debatable how much more useful a 30 taper on a 1.5 hp machine rather than R8 . If you have R8 then you can use solid holders when you need the beef and TTS when you need the speed. You can't do that with a 30 taper. There are only two good reasons to have a 30 taper on the Tormach.

1) You already have a stack of 30 tooling.
2) You intend to build your own ATC and auto drawbar (for beefy aplications).

Phil

PS: Beefy cuts vs lighter cuts mainly depends on how much of a hurry you are in. If you are in a real big hurry you probably shouldn't have bought the Tormach in the first place.

For lighter applications it may be adequate but if you start pushing it, it can't compare to a 30 taper system.

Joe

[BlueFin]

You can program to help with the backing out issues, your heavy cutting will most likely be a 1/2" end mill to start and then as you get to the detail machining it will either be a light cut with possibly the same end mill or switch to smaller ones, which can't be pushed hard enough to back out. Have tool #1 and tool #2 entered as the same exact size, #1 will rough and #2 will finish. When the machine asks for a tool change you would re-seat the tool holder and go. Just keep your Z on the roughing pass up above where you think it would creep out to on it's own.

[zephyr9900]

With the Tormach's balanced design, no one part is enough stiffer or stronger than the rest that swapping it out would make a significant difference to the performance. A CNC machine can take repeated accurate cuts without tiring or losing concentration. Why compromise that accuracy by taking hogging cuts and pushing the machine past its envelope as opposed to taking reasonable cuts in the first place?

Randy

[Don Clement]

With the Tormach's balanced design, no one part is enough stiffer or stronger than the rest that swapping it out would make a significant difference to the performance. A CNC machine can take repeated accurate cuts without tiring or losing concentration. Why compromise that accuracy by taking hogging cuts and pushing the machine past its envelope as opposed to taking reasonable cuts in the first place?

Randy

Exactly! Why use the same techniques as on a manual mill when you have a CNC mill that can be programmed to automatically take repeated smaller cuts within the power envelope of TTS tool holders. TTS tool holders are inexpensive, accurate, use very little headroom when removing and installing, have height repeatability, and work especially well with Tormach’s power draw bar.

Don

[zephyr9900]

With the Tormach's balanced design, no one part is enough stiffer or stronger than the rest that swapping it out would make a significant difference to the performance.

Obviously I meant more flexible or weaker instead of stiffer or stronger but thank you for reading past that, Don. The point we both get is, use CNC intelligently rather than duplicating the "push it for expediency" that I, for one, used to employ on a manual Bridgeport... CNC never reads the DRO's wrong or makes one too many cranks on the knee (not that I ever did that personally!)...And yes, the power drawbar is high on my priority list when I'm once again gainfully employed and can afford such refinements...

Randy

[justgary]

Folks -

All of this discussion lately about TTS holding power has convinced me to post this little TTS tip that I figured out a few months ago. But first, some background:

Those of you with a router will recall your frustration with the bits pulling out of the collet soon after you feed a little too fast into the wood. The solution, of course, is to never let the bit bottom out as you tighten the collet. Once you learn to keep the bit from bottoming when you install it, you quit having pullout issues.

The same thing happens with TTS.

If you leave a small gap (roughly 0.015" or so) when you place the TTS holder in the collet, it will pull in as you tighten the drawbar. If you get it just right, the TTS holder will just touch the spindle nose as you finish tightening the drawbar. If you get it wrong, it will either (1) touch before the collet is tight, which reduces your holding force a little bit, or it will (2) leave a gap between the spindle and the holder, leaving you with a Z height error.

The error first is much better than the second, since the pullout force is much higher than the normal way you insert a toolholder anyway. With a little practice you will quickly learn how much gap to leave to have the gap just disappear as you finish tightening the drawbar.

Note that this is exactly what the little foam ring from Tormach does, but without the associated (but very small) Z error. Allowing the collet to draw the toolholder in as it closes simply allows it to work properly. Also note that I only use this method when using relatively large mills that I expect to see a heavy load, and I do it only as a precaution. Usually that's when I didn't want to take the time to program something simple like a facing cut and just enter the movement by hand on the MDI line.

Don and Randy have it right, you don't need to load your mill hard to get it to work faster. But just in case, you will get all of the holding power you can stand by letting the collet pull the toolholder in as it tightens.

Regards,

- Just Gary

[Don Clement]

Gary,

I don't agree. In my experience with three years of using TTS tooling it is most likely that people that have had TTS holders loosen don't have the spindle square or are pushing the TTS power envelope too much. If the spindle face isn't square within a "tenth" or so then full contact isn't possible and yeah there could be some loosening under load. Never had a TTS held tool loosen so I don't know where that rumor got started. I don't take any particular precautions such as leaving a small gap, just push the TTS holder up snug and release the button on the power draw bar. BTW the cheap Harbor Fright $20 regulator/filter/lubricator unit won’t let me apply more than 115psi so the drawbar isn’t even up to max force and still never had a tool pull out.

Don

[ihavenofish]

Gary,

I don't agree. In my experience with three years of using TTS tooling it is most likely that people that have had TTS holders loosen don't have the spindle square or are pushing the TTS power envelope too much. If the spindle face isn't square within a "tenth" or so then full contact isn't possible and yeah there could be some loosening under load. Never had a TTS held tool loosen so I don't know where that rumor got started.

its not a rumour, its in the tormach technical documents.
people seem to be generally confused WHY it pulls out. its NOT like a router bit pulling out of a collet, or anything else. its not LOOSENING or losing grip.

the reason it pulls out is that in a heavy side load, the tool holder flexes in the collet - as any tool would. when it flexes, the collar on the holder acts as a lever against the spindle nose multiplying the side force and pulls the holder out a small amount. once the load lets up, its done moving, and its perftcly stable again and wont creep out any furthur under the same load. the only issue is the tool is now a few thou lower than you expect, which can ruin critical work.

basically the levering force on the tool is exceeding the clamping force in the collet. this is why it happens on LONG tools. longer tool equals a longer lever arm.

its probably not hard to calculate what amount of side force is the "limit" for any given length of tool, and then find the coresponding tangential force of a cut with said tool. youd need to know the minimum pull out force of the collet for this.

as for bt30. the only reason id use em is because they are cheap and easy to find a variety of different tools that just arent there in tts.

in a manual situation though with only 2hp or so, its probably not worlds better than R8, which is also cheap and plentiful.

[flick]

collar on the holder acts as a lever against the spindle nose

This is correct. An analogy that has been made in the past is that of a pulling out a nail with a claw hammer:

3/4" shank = nail
collar = claw
endmill = handle

One method of improving the "staying power" of the TTS system would be to increase the diameter of the collar, reducing the mechanical advantage applied by the endmill.

You can't make the collar too much bigger before you run out of spindle face, but I seem to remember that a nearly 30% increase would be possible...

[Don Clement]

its not a rumour, its in the tormach technical documents.
people seem to be generally confused WHY it pulls out. its NOT like a router bit pulling out of a collet, or anything else. its not LOOSENING or losing grip.

the reason it pulls out is that in a heavy side load, the tool holder flexes in the collet - as any tool would. when it flexes, the collar on the holder acts as a lever against the spindle nose multiplying the side force and pulls the holder out a small amount. once the load lets up, its done moving, and its perftcly stable again and wont creep out any furthur under the same load. the only issue is the tool is now a few thou lower than you expect, which can ruin critical work.

basically the levering force on the tool is exceeding the clamping force in the collet. this is why it happens on LONG tools. longer tool equals a longer lever arm.

its probably not hard to calculate what amount of side force is the "limit" for any given length of tool, and then find the coresponding tangential force of a cut with said tool. youd need to know the minimum pull out force of the collet for this.

as for bt30. the only reason id use em is because they are cheap and easy to find a variety of different tools that just arent there in tts.

in a manual situation though with only 2hp or so, its probably not worlds better than R8, which is also cheap and plentiful.

Agreed that some have had TTS pull out under heavy loads. Hasn’t happened to me. But as the Tormach documentation says don’t expect to use heavy cuts with TTS tooling. And with the CNC mill programming a series of lighter cuts eliminates the need to use heavy cuts in the first place. Why does one need to push the TTS tool to the absolute limit anyhow? To me that’s what CNC is all about, getting the repetitive task done by the CNC robot and not having to take the largest heaviest cuts possible because of using a manual machine. Heavy cuts seem to me to be a manual machining mentality. CNC allows different paradigm than manual machining and it is best to take advantage of TTS tooling such as height repeatability using tool tables. TTS is inexpensive with many advantages over R8 tooling, just heavy cuts is not one of them. With CNC it is easy to work around that particular con of the TTS holder. The whole idea of Tormach is cost. If I had the big bucks in the first place I would have bought a VMC with CAT40 tooling or similar and this wouldn't be an issue.

Don

King Arthur: How does it... um... how does it work?
Sir Lancelot: I know not, my liege.
King Arthur: Consult the Book of Armaments.
Brother Maynard: Armaments, chapter two, verses nine through twenty-one.
Cleric: [reading] And Saint Attila raised the hand grenade up on high, saying, "O Lord, bless this thy hand grenade, that with it thou mayst blow thine enemies to tiny bits, in thy mercy." And the Lord did grin. And the people did feast upon the lambs and sloths, and carp and anchovies, and orangutans and breakfast cereals, and fruit-bats and large chu...
Brother Maynard: Skip a bit, Brother...
Cleric: And the Lord spake, saying, "First shalt thou take out the Holy Pin. Then shalt thou count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out. Once the number three, being the third number, be reached, then lobbest thou thy Holy Hand Grenade of Antioch towards thy foe, who, being naughty in my sight, shall snuff it.
Brother Maynard: Amen.

[ihavenofish]

Agreed that some have had TTS pull out under heavy loads. Hasn’t happened to me. But as the Tormach documentation says don’t expect to use heavy cuts with TTS tooling. And with the CNC mill programming a series of lighter cuts eliminates the need to use heavy cuts in the first place. Why does one need to push the TTS tool to the absolute limit anyhow? To me that’s what CNC is all about, getting the repetitive task done by the CNC robot and not having to take the largest heaviest cuts possible because of using a manual machine. Heavy cuts seem to me to be a manual machining mentality. CNC allows different paradigm than manual machining and it is best to take advantage of TTS tooling such as height repeatability using tool tables. TTS is inexpensive with many advantages over R8 tooling, just heavy cuts is not one of them. With CNC it is easy to work around that particular con of the TTS holder. The whole idea of Tormach is cost. If I had the big bucks in the first place I would have bought a VMC with CAT40 tooling or similar and this wouldn't be an issue.

Don

well, the problem isnt deliberately pushing the limits of a small machine, but that the limit changes with any given tool and cut, and you could unexpectedly get a z error on things like deep pocketing on moulds etc. knowing where the limit is on a tool will help you stay well below it and ensure you dont have a really really bad day when it comes time to measure your 24 hour long job.

[Don Clement]

well, the problem isnt deliberately pushing the limits of a small machine, but that the limit changes with any given tool and cut, and you could unexpectedly get a z error on things like deep pocketing on moulds etc. knowing where the limit is on a tool will help you stay well below it and ensure you dont have a really really bad day when it comes time to measure your 24 hour long job.

"Then shalt thou count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out. Once the number three, being the third number, be reached,"

[flick]

Um, I think I see what you're saying Don, but if we can get out of Monty Python land for a moment...

There's nothing wrong with trying to wring a little more performance out of the machine, and ihavenofish is right, that one could fall afoul of the limits of TTS holding power under certain circumstances requiring a long tool stickout using machining parameters that had worked just fine with a short tool stickout.

[Freddy Bastard]

One thing that is really bad for a TTS holder is tool vibrations. All the TTS pullout I got occured when I took a too big cut combined with vibrations. I always try to avoid cutting vibrations (chatters), but when I hear the tool who howls in the shop, I run to the machine to check if the tool pulled out.