[rlockwood]

Ray,

Not to imply it will necessarily give you issues, but given that a higher helix endmill should both provide increased material removal rate and present a higher pull out force, i'd suggest repeating the video once you have one available.. just in the spirit of truly demonstrating "any load a 2-3 HP machine can muster."

[SCzEngrgGroup]

Ray,

Not to imply it will necessarily give you issues, but given that a higher helix endmill should both provide increased material removal rate and present a higher pull out force, i'd suggest repeating the video once you have one available.. just in the spirit of truly demonstrating "any load a 2-3 HP machine can muster."

Rob,

Since I'm already power-limited, can a high-helix endmill really make a difference in MRR? My understanding is the high-helix helps in chip removal, which allows the feed to be increased, power-permitting, but I'm not aware it has any advantage in terms of specific power. Based on that, I don't believe I can increase MRR any further, without getting a more powerful spindle motor. I do have a couple of Gorilla mills, which are high-helix, and I'll happily demonstrate the same cut with that. I'm also tempted to try something else - dipping the tool shank in coolant, and installing it wet. I believe that will also work just fine, though I wouldn't make a habit of it.

Regards,
Ray L.

[rlockwood]

Here's an output from HSMAdvisor of two identical operations, except where the helix angle was changed from 30* to 45*..

30* HELIX ANGLE

Material: 7075-T6 Aluminum 150 HB
Tool: 0.500in 2FL Carbide  Solid End Mill
Speed: 1200.0 SFM/ 9172.0 RPM
Feed: 0.0035 ipt/ 0.0069 ipr/ 63.40 ipm
Chip Thickness: 0.0031 in
Reference Chipload: 0.0035 in
Engagement:  DOC=0.875 in   WOC=0.137 in
Effective Dia: 0.500 in
Cross Section: 0.4780 x Dia.
Power: 3.8HP
MRR: 7.58 in^3
Torque: 2.17 ft-lb
Max Torque: 7.90 ft-lb
Cutting Force: 104.1 lb
Deflection: 0.0002 in
Max Deflection: 0.0012 in


45* HELIX ANGLE

Material: 7075-T6 Aluminum 150 HB
Tool: 0.500in 2FL Carbide  Solid End Mill
Speed: 1200.0 SFM/ 9172.0 RPM
Feed: 0.0038 ipt/ 0.0076 ipr/ 69.96 ipm
Chip Thickness: 0.0034 in
Reference Chipload: 0.0038 in
Engagement:  DOC=0.875 in   WOC=0.137 in
Effective Dia: 0.500 in
Cross Section: 0.4780 x Dia.
Power: 3.8HP
MRR: 8.36 in^3
Torque: 2.17 ft-lb
Max Torque: 7.90 ft-lb
Cutting Force: 104.1 lb
Deflection: 0.0002 in
Max Deflection: 0.0012 in

Of course it makes a difference, why else are guillotines angled?

Now, its not the biggest difference in the world.. but as it directly relates to pull out force I think its directly relevant.

[hoss2006]

I don't want to contribute too much to the pissing contest that is probably brewing, but I would like to say that I'm pretty sure tension is tension. If your power draw bar, which I think looks very good, can provide 3500+ pounds of tension that is fantastic. That 3500# is superior to the 2500# that the Tormach setup provides. That being said: a belleville setup that provides, say, 4000 pounds of tension would be even better - and entirely possible. If someone wanted to they could make a belleville stack that would rip the draw bar in half. Getting it compressed in the first place, particularly while sitting on to of a mill, would be something else entirely.

I guess I think your power draw bar design has real advantages without continuing bellevilles vs. torque debate.

I wonder if any of the Tormach guys have thought of trying a higher psi compressor.
If the air cylinders are rated high enough, be sure to check first, a 200 psi compressor isn't very expensive to perhaps double the pull capability with an upgrade to the bellevilles of course.
No need for a big one, I just got a little 200 psi pancake type that will be just for my drawbar.
I'd suggest checking with Tormach first about safety considerations.
Hoss

[SCzEngrgGroup]

I wonder if any of the Tormach guys have thought of trying a higher psi compressor.
If the air cylinders are rated high enough, be sure to check first, a 200 psi compressor isn't very expensive to perhaps double the pull capability with an upgrade to the bellevilles of course.
No need for a big one, I just got a little 200 psi pancake type that will be just for my drawbar.
I'd suggest checking with Tormach first about safety considerations.
Hoss

Higher pressure is one way to increase capacity, but the problem is the vast majority of consumer-level compressors on the market, and virtually all of the small ones (under 5HP or so), are limited to no more than 100-125 PSI (often limited by the rating on their pressure tanks). Larger compressors often provide higher pressure, but many customers would be justifiably upset if they bought an air-powered product, then found out they had to buy an expensive new compress just to make it work. It's not like an air tool like a sander that you can get by with less pressure if you just work slower. A pneumatic PDB either works or it doesn't - not enough pressure, and it don't work at all. Higher pressure air cylinders are also more expensive - most commodity ones are only rated for 125PSI.

Regards,
Ray L.

[hoss2006]

Higher pressure is one way to increase capacity, but the problem is the vast majority of consumer-level compressors on the market, and virtually all of the small ones (under 5HP or so), are limited to no more than 100-125 PSI (often limited by the rating on their pressure tanks). Larger compressors often provide higher pressure, but many customers would be justifiably upset if they bought an air-powered product, then found out they had to buy an expensive new compress just to make it work. It's not like an air tool like a sander that you can get by with less pressure if you just work slower. A pneumatic PDB either works or it doesn't - not enough pressure, and it don't work at all. Higher pressure air cylinders are also more expensive - most commodity ones are only rated for 125PSI.

Regards,
Ray L.

I said I just got one with 200 psi, only $140 on ebay.
Dewalt make several to 200 psi in a range of tank sizes.
They are out there all over just have to look for them.
I suggested they check with Tormach first but air cyclinders of the type used on theirs are common to 200 psi.
If their air cylinders are capable they don't have to buy new ones, I didn't suggest buying new ones.
I don't own a Tormach just the tooling or I would explore this myself.
Just offering a suggestion if any of the Tormach guys want to look into it.
Hoss

[SCzEngrgGroup]

Here's an output from HSMAdvisor of two identical operations, except where the helix angle was changed from 30* to 45*..

30* HELIX ANGLE

Material: 7075-T6 Aluminum 150 HB
Tool: 0.500in 2FL Carbide  Solid End Mill
Speed: 1200.0 SFM/ 9172.0 RPM
Feed: 0.0035 ipt/ 0.0069 ipr/ 63.40 ipm
Chip Thickness: 0.0031 in
Reference Chipload: 0.0035 in
Engagement:  DOC=0.875 in   WOC=0.137 in
Effective Dia: 0.500 in
Cross Section: 0.4780 x Dia.
Power: 3.8HP
MRR: 7.58 in^3
Torque: 2.17 ft-lb
Max Torque: 7.90 ft-lb
Cutting Force: 104.1 lb
Deflection: 0.0002 in
Max Deflection: 0.0012 in


45* HELIX ANGLE

Material: 7075-T6 Aluminum 150 HB
Tool: 0.500in 2FL Carbide  Solid End Mill
Speed: 1200.0 SFM/ 9172.0 RPM
Feed: 0.0038 ipt/ 0.0076 ipr/ 69.96 ipm
Chip Thickness: 0.0034 in
Reference Chipload: 0.0038 in
Engagement:  DOC=0.875 in   WOC=0.137 in
Effective Dia: 0.500 in
Cross Section: 0.4780 x Dia.
Power: 3.8HP
MRR: 8.36 in^3
Torque: 2.17 ft-lb
Max Torque: 7.90 ft-lb
Cutting Force: 104.1 lb
Deflection: 0.0002 in
Max Deflection: 0.0012 in

Of course it makes a difference, why else are guillotines angled?

Now, its not the biggest difference in the world.. but as it directly relates to pull out force I think its directly relevant.

Rob,

That is indeed interesting! The ones I have are, I believe these: CGS FEROCIOUS 2000 SERIES which have a 55 degree helix. If HSMAdvisor is right (and it usually is!), I should be able to increase feed from 110IPM to 125IPM with the same power. I'll give it a try when I have time.

Regards,
Ray L.

[LSM]

1 to 3 hp is a light duty mill.
That said tts is every bit as good as an r8 collet, if you do things right lube where is should be and not where it shouldn't be.
Tormach covers that in one of the white papers or such,

[rlockwood]

1 to 3 hp is a light duty mill.
That said tts is every bit as good as an r8 collet, if you do things right lube where is should be and not where it shouldn't be.
Tormach covers that in one of the white papers or such,

But with adequate tension its probably not an issue..

[vertcnc]

If you get a 4" x 4 stages good for almost 4800 # at 100 psi. They are a little pricey at about $350. But they sure are nice. I have a connection for pneumatic components so does hurt as bad.

[tbaker2500]

Ray, thank you for your info. It is always good to see how useful TTS can be.

I do slightly question your going off on questioning the methodology of measure the tension:

If you'd actually read my response, you'd see I DID answer your question - I did not measure the "pull strength" because I simply don't care what it actually is. All my testing and design was based on measuring and controlling torque, not tension, since that is the controlling variable in my design, and it is much easier to measure accurately.

Because you originally claimed a tension:

Again, the "secret" is simply providing adequate drawbar tension. My power drawbars actually torque the drawbar to 30 ft-lbs, providing a drawbar tension in excess of 3500# - more than can be reasonably achieved using Belleville springs - which is enough to keep the TTS holder in-place under any load a 2-3 HP machine can muster. Many/most TTS users who have experienced pull-out seem to have power drawbars that provide no more than 2000-2500 pounds drawbar tension (many have much less), which is simply not enough to properly retain the toolholder with much more than a 1/4" tool.

While you do, in passing, state torque, the majority of your claims are about tension. So it is slightly disingenuous to go off on somebody for asking your methodology for your originally tension claims, and then claiming that tension doesn't matter.

So what I now understand you to say, is you do not actually know what tension your drawbar is providing, you do know the torque. That is fine, but it makes it harder to compare to Belleville stacks. You can show practical experience, which is great!

All the best,
Tom

[SCzEngrgGroup]

Ray, thank you for your info. It is always good to see how useful TTS can be.

I do slightly question your going off on questioning the methodology of measure the tension:



Because you originally claimed a tension:



While you do, in passing, state torque, the majority of your claims are about tension. So it is slightly disingenuous to go off on somebody for asking your methodology for your originally tension claims, and then claiming that tension doesn't matter.

So what I now understand you to say, is you do not actually know what tension your drawbar is providing, you do know the torque. That is fine, but it makes it harder to compare to Belleville stacks. You can show practical experience, which is great!

All the best,
Tom

Tom,

Thanks. I guess I just have more confidence in the calculations than some people. Despite what some here seem to believe, not everything needs to be directly measured to have a high degree of confidence in the value. Properly used, engineering relationships can be just as good, especially when they're as basic as this one. I can tell you I've never had such things questioned when discussing these things with experienced engineers. They trust the numbers, as I do.

Regards,
Ray L.

[rlockwood]

Tension can be reasonably estimated based on the torque applied to the threads.. There are obviously a lot of factors at work, but having read Ray's previous comments on how he established his estimate, he's being pretty conservative in the first place; IIRC 3500lbs was a near worst-case scenario.

It probably wouldn't be justified, but it wouldn't be particularly difficult to build a load cell to measure the actual draw bar tension..

[SCzEngrgGroup]

I think the pertinent question is: Would knowing the precise drawbar tension make any functional difference whatsoever, or change the opinion of a single person here? I think the answer is pretty clear....

Regards,
Ray L.

[Hirudin]

It would change my opinion.

[SCzEngrgGroup]

It would change my opinion.

Why? What difference does it make?

Regards,
Ray L.

[nitewatchman]

I can tell you I've never had such things questioned when discussing these things with experienced engineers.

I would also like to know what the actual tension in the drawbar is. Not to fuel the argument but to determine what is comparable in other drawbar designs.

I am an experienced engineer and I will question some of your assumptions. My group routinely works with torque verses tension relationships and it is far from an exact science and the results can vary widely with friction and thread form. We use hollow body load cells to verify tension verses torque in bolts by received lots, most frequently 1-3/8" - 6 UN. Target tensile loads (clamp-up loads) are 80kips at 2300lb-ft.

The very interesting thing that you learn is that the relationship between torque and tension is far from linear. As torque is increased for a given bolt and nut set, the tension increase resulting from the torque increase falls rapidly until there is no appreciable increase in tension for a given increase in torque. If this is studied closely you will find that as the tension increases the elongation of the bolt increases with strain but the pitch diameter does not change. This has the effect of increasing the lead or pitch angle of the thread. As the nut is tightened the wedging effect of the 60deg thread angle tends to "barrel" the nut increasing its diameter. The length of the nut does not change. This tends to decrease the lead or pitch angle of the thread.

These changes in lead quickly tend to bind the nut to the bolt, fast lead bolt/slow lead nut, and the majority of the torque applied to fastener simply increases the torsional stress in the bolt. This is why you will rarely see a bolt that has failed in tension with the resulting "necking" during tightening. They are always "twisted off" or present a torsional failure. In comparing torque to tension in a lot of fasteners the data scatter can be greater than 50%. For this reason in any tension sensitive or Friction Critical Joint we prefer Huck Bolts or Tensile Pin Fasteners since they do not rely on torque at all but tensile stress and elongation in the fastener. If the application forces the use of conventional bolts we will use tension indicating or "squirter" washers.

While this is an extreme example for our case, it demonstrates that a simple torque verses tension calculations assuming a constant "k" value are notoriously inaccurate and in our industry considered naïve.

In think that the original theory posed by Ray before emotions became involved is correct. If the tension in the drawbar is increased at some point the TTS Tool can not be dislodged with any amount of force and would failed in tension either in the tool shank or drawbar before slipping. An example of this can be seen in Ringfeder Keyless Couplings. The shaft will twist in two before a properly applied coupling will fail.

If the drawbar utilized works as stated, I would like to know what the drawbar tension is. The torque is a poor indicator of how much force is actually being applied as tension in the bar.


To address some other points:

The Tormach Cylinder, piping, valves, pressure sensing switch, etc. are rated for 120+/- PSIG. 200PSI is likely stretching the limits even if the cylinder is changed. We would have to address the entire system.

Our large mills carry CAT60 tapers with Belville Spring Drawbars. The drawbars utilize 12 pairs of springs. These are large gantries by Ingersoll and Henri' Line' (30 to 75 feet of X Travel).


nitewatchman

[handlewanker]

Hi, I have worked with R8 and the conclusion I draw is that if you want to retain tools with an R8 collet you don't want to do it with springs.

I had a Bridgeport previously and the drawbar applied the pull to the collet with a threaded end directly in the collet......this gives it a direct inflexible force, the tension or foot pounds applied is irrelevant.......you can't pull a tool out of an R8 collet if the draw bar is applying direct and inflexible pressure......something like being pushed against a solid brick wall by a bulldozer.

It's time to design a power draw bar that does not rely on springs and forget about the Bellville washer process.

Bellville washers lose force when they are applying the load, and need more force to release the tool, whereas if you compare it to a simple nut and thread system that increases the force while it is being applied, then this is where the design should go.

BTW, I'm not advocating having a simple nut add bolt system as in manual mills etc to apply the force, just making a comparison for the purpose of a required design principle.

I fail to see the advantage of a huge stack of Bellville washers being compressed with more force to a humungeous loading force just to release the tool when in actuality it is the opposite way around, and then requiring a massive pneumatic cylinder assembly in compound arrangement to apply the releasing load is simply ridiculous.

The answer I have been fed is that this is how it's done in industry, so it must be good......bosh.

Increasing the Bellville washer stack until the tool stays put is not the answer.
Ian.

[vertcnc]

handlewanker,
Isn't this what Ray has done, created a drawbar system using simple nut and bolt, with a gear drive torque wrench. Great system. The only reason you see a lot of Belleville washer use on these small machines here is because of the majority are DIY basement engineers, that can be accomplished with a few off the shelf components.

[philbur]

Hi Ian, the grip of the R8 collet on the tool shank is directly related to the tension in the drawbar and the tension in the drawbar doesn't know if it comes from a stack of springs or from the tightening of a thread. Inflexible force has no engineering meaning, the drawbar stretch is directly proportional to the applied tension, regardless of the source of that tension.

Phil

I had a Bridgeport previously and the drawbar applied the pull to the collet with a threaded end directly in the collet......this gives it a direct inflexible force, the tension or foot pounds applied is irrelevant.......you can't pull a tool out of an R8 collet if the draw bar is applying direct and inflexible pressure......something like being pushed against a solid brick wall by a bulldozer.
Ian.