[Don Clement]

So if you haven't spent a bunch on the TTS, what do you really need?

BW

But I don't want to use R8 toolholders. I switched to TTS toolholders and don't ever use the R8 toolholders I have at all any more. R8 toolholders don't have the height accuracy or repeatability of the double contact TTS holders. Also with R8 one has to completely unscrew the drawbar and deal with all the inches of length to remove them. TTS are inexpensive and work extremely well for me. Measure all my tools using the Tormach measurement fixture and use my #1 TDI height tool and I am set to go. I have even modified ¾” diameter tools such as the Vardex thread milling tool to TTS system. Nope, I won’t ever go back to R8. YMMV Thank you Tormach (Greg Jackson) for such a great affordable product as your TTS.

[BobWarfield]

R8 toolholders don't have the height accuracy or repeatability of the double contact TTS holders.

Don, the repeatability I measured for all my holders is well within the Tormach spec.

If you like the TTS's better, by all means use them. But let's be accurate about what the R8's are capable of and what, if any, advantages TTS may offer.

So far I see advantage TTS for less Z height required and less turns of the wrench to change tools. For me they're both irrelevant as I have tons of Z on my IH and I use a powered drawbar to change tools.

OTOH, I see a cost advantage for my R8's because I can use off-the-shelf tooling available from a wide variety of sources and not just 1 (or I don't have to make my own holders if you prefer making TTS-style). I'll take that trade!

To each his own. Many are extremely happy with TTS. Many are also extremely happy with R8.

Cheers,

BW

[Don Clement]

Bob,

If you are so happy with your IH then by all means post on the IH forum.

[Don Clement]

It's trivial to create a tool like the plunger indicator you show.

That is the idea. I do believe in parsimony. A standard AGD dial indicator as the Starrett No. 25-511 as shown http://i72.photobucket.com/albums/i1...ettToolNo1.jpg has a 4-48 threaded spindle so the foot can be easily replaced. I use an elephant foot for contacting the top of a gage ball, roll pin, or any flat surface. Also a dial indicator tool #1 has 0.150" of overtravel built-in and unlike using an endmill or some other hardened tool will not mar surfaces or chip or damage the hardened tool. http://www.cnczone.com/forums/showthread.php?t=75705

[zephyr9900]

If you like the TTS's better, by all means use them. But let's be accurate about what the R8's are capable of and what, if any, advantages TTS may offer.

Given that this thread is a discussion about a TTS-specific auto drawbar (please note the title), you may be better off moving that discussion elesewhere more appropriate. Thank you.

Randy

[philbur]

What can possibly be wrong with discussing alternatives within a given thread. It's differing opinions that advance your knowledge.

Phil

[Freddy Bastard]

I agree but we should not put the TTS system in question here. TTS is a very accurate and cheap tooling system. I don't know others system where you can do your own holder and get very good accuracy. I do a lot of my TTS holder myself. If I want a custom xtra long reach heat shrink TTS holder I can do it. We should discuss the drawdar here, because no one want to change all their TTS holders for another system.

Question to Poppabear: Now that Tormach is on the way to get a good drawbar, how much do you think a DIY ATC system like yours would cost? If you sell the plan like you said in a previous thread and give a good extimate on the cost of hardware I think you're on something.

[zephyr9900]

What can possibly be wrong with discussing alternatives within a given thread.

1. It dilutes the content of this drawbar-specific discussion by introducing side discussions.
2. It buries the "alternative to TTS" information inside a non-related discussion where it is not obvious to find.

It's differing opinions that advance your knowledge.

No quibble, Phil. But there is a convenient and easily-accessible "New Thread" button at the top of the Tormach forum page that will let Bob or you start a prominently-displayed "TTS vs. other toolholders" discussion where everyone will see it and participate in a focused discussion on that topic.

Randy

[philbur]

The TTS is an integral part of the drawbar design so I think that discussing the pros and cons of the TTS in the same thread is directly relevant. If you buy into the drawbar you also have to buy into the TTS, or a home made equivalent.

The best way to bring a thread back to the original topic is to continue discussing the original topic, so go for it.

Phil

1. It dilutes the content of this drawbar-specific discussion by introducing side discussions.
2. It buries the "alternative to TTS" information inside a non-related discussion where it is not obvious to find.


No quibble, Phil. But there is a convenient and easily-accessible "New Thread" button at the top of the Tormach forum page that will let Bob or you start a prominently-displayed "TTS vs. other toolholders" discussion where everyone will see it and participate in a focused discussion on that topic.

Randy

[zephyr9900]

The best way to bring a thread back to the original topic is to continue discussing the original topic, so go for it.

The best way to have a focussed discussion is to not diverge from the original topic in the first place.

Phil, I agree that it is relevant to discuss the capabilities and limitations of the TTS system itself as used with the new drawbar in this thread. But where I disagree is widening the discussion to compare and contrast other toolholding systems. That is a discussion big enough for its own thread.

In the video, Tormach's senior design engineer Matt states a drawbar tension of 2500 lbs, and that is enough to retain the TTS endmill holder for a 1/2" roughing endmill cut through 1" aluminum in a single pass.

The stack of Belleville springs (and its disengagement stroke) is pretty short relative to other spring drawbars I've seen, so to develop that 2500 lbs of tension there is a pretty high spring rate. That means that setting the drawbar tension will be an important step in the assembly process. It also means that there is not a lot of tolerance in the assembly stackup to maintain that tension. The stroke to disengage cannot be more than .15", if the drawbar in the video has the standard 13mm across flats. The stack looks like a 2-2-2-2-2-2 so each spring would be operating .15"/6=.025" from flat to develop its force, which would be 1250 lbs according to my wild guesses about the configuration.

One prototype is nice, but how will the assembly hold up after disassembly and reassembly? How repeatable is the performance with another set of the disk springs from the same or different manufacturing batches? How will differing instances of user lubrication of the spring stack affect the performance? How repeatable will 10 separate assemblies perform? With the coarse thread (20tpi) of the drawbar in the collet, what will ensure the drawbar stays threaded in without creeping? It will not take a lot of backing out of the drawbar under the cyclic loading-unloading to reduce the drawbar tension significantly.

I hope that Tormach does a good due diligence on the design to ensure it is robust. On the macro scale it is very well designed and implemented and I think it's great. It will be the seemingly little details that make or break the design's success.

Randy

[Art Pentz]

Hi all,

Based on what I learned developing my air over hydraulic design, Tormach has done a great job of engineering on their auto drawbar.

Most auto drawbar designs need a tall stack (HAAS = 125 or more) of bellevilles due to the need for enough excursion to work w/ 30/40/50 taper holders and their pull studs.

The TTS system elegantly eliminates this requirement - I found that less than .020" of drawbar movement was all that was required to get reliable release of my drawbar using the standard Tormach R-8 collet and TTS holders.

A quick note on setting the drawbar tension:

With the caliper type drawbar, the threaded portion is held tightly - more or less "locked" from rotation when the drawbar is activated to release the collet.

This allows you to spin the spindle/pulley by hand and tighten the R-8 collet on the TTS holder until the resistance is optimal for your operation.

Too loose and the TTS holder will fall out, too tight and you will have to use some force to remove the TTS holder from the R-8 collet.

You should not have to use a wrench to set the spring pressure for opimum holding.

It should be noted that this feature facilitates the exchange of R-8 collets as well - engage the drawbar, spin the spindle/pulley until the R-8 collet is out, replace w/ new R-8 collet (engaging the key slot), spin it on until it grips the shank of your tooling, disengage the drawbar and mill...

The regulated air pressure will supply a known force against the bellevilles - by hand tightening the R-8 collet on the TTS holder or tool you are assured that the full spring force is being applied to the TTS holder.

Based on Tormach's "balanced design" philosophy, the holding power being supplied w/ the 2500 pound belleville stack should work fine.

My drawbar is designed for a similar amount of force (around 3000 pounds) and has had no difficulty w/ holding power.

Has anyone heard about price/availability?

Best regards;

Art Pentz

[zephyr9900]

...by hand tightening the R-8 collet on the TTS holder or tool you are assured that the full spring force is being applied to the TTS holder.

Ahh, good point, Art. Engage the cylinder and screw in the collet just hand-tight with a holder in place. That would be an easy thing to do at will as PM.

My drawbar is designed for a similar amount of force (around 3000 pounds) and has had no difficulty w/ holding power.

I have no doubt that the Tormach drawbar will be more than adequate for realistic day-to-day machining. 1/2" cut through 1" aluminum is, in my opinion, overly gonzo (even if it's Mic6) but it's a good "party piece".

Has anyone heard about price/availability?

I get the feeling that the Tormach video is more of a "hey, here's what we're working on now" than a product announcement, since it is titled "Tormach Engineering Sneak Peek".

Randy

[pete from TN]

Would love to see some pics of your power drawbar setup and any specifics of what you used. I am gonna be building something similar sooner rather than later so it would be much appreciated...peace


I never thought about the idea of being able to just kinda screw the drawbar into the collet or toolholder, so I suppose since the drawbar is clinched by the power unit it is lifted off the spindle bore at the top so you can actually spin the spindle using the pulley and hold a toolholder or collet in the taper and go until it is nearly tight. Then release the power drawbar and you are nice and tight huh... VERY COOL> so much for the idea of not being able to use the R-8 tooling too... This is such a cool design..peace......

[Art Pentz]

Hi Pete,

The ability to hand tighten the collet is a function of my caliper design. The Tormach unit may not work this way if they have the caliper act on the top of the spindle.

I initially thought that I would have to index the caliper on a flange attached to the top of the spindle to get reliable release - happily that was not necessary - so my caliper design does not lock the spindle rotation.

I can't tell you how nice it is to have an automatic drawbar!

Check out my posts on the Yahoo Tormach group:

4097

4104

And photos:

http://groups.yahoo.com/group/tormac...unt=20&dir=asc

Best regards;

Art Pentz

[PoppaBear10]

I do look forward to the video of the non-roughing, high helix 1/2" endmill cutting through that 1" bar with the new draw bar.

ATC: I will still sell you the ATC carousal kit, it would be easy to integrate into thier Draw bar activatiion switch.

scott

[zephyr9900]

I can't tell you how nice it is to have an automatic drawbar!

With my full enclosure, I currently need to raise the head to within 1/2" of the home position in order to open the door to change tools. Both the door latch and drawbar top are long reaches that just an automatic drawbar would alleviate (and I could set M6 height a fair bit lower too!)

I do look forward to the video of the non-roughing, high helix 1/2" endmill cutting through that 1" bar with the new draw bar.

Scott, in the video Matt states that it is a roughing endmill doing the cut.

Randy

[PoppaBear10]

in the video I was asked to match it was a Non-roughing....... and that is where the stongest pull out is......

scott

[andypugh]

I was and still would be interested in using hydraulic force rather than air pressure, but that is just a matter of personal preference. I didn't understand pancake cylinders until now, so I may change my ways soon. Those are pretty cool. You will see in the post that I changed my idea from the drawing to something else that is more compact (even more than Tormach's) but a single OEM part in my design cost over $250.00

Late to the thread, but have you looked at brake calipers? The single-piston floating ones are almost ideal for the "pinch" action being discussed.

Plus, they are dirt cheap.