[krymis]

this message is pretty much directed towards bob, but also anyone wha can help. I wanted to know if anyone has removed the pin inside the r8 spindle. From the conversation on the iso30 spindle it seems that the pin can be removed without any ill effects. Is this true? I have the same power drawbar from joe that bob has, and put the extra clips and springs on it like bob's. I would like to know as this would expidite my prototype attempt at an atc.

[BobWarfield]

Aaron has said somewhere you can pull the pin. That's good enough for me.

Apparently it is accessible if you extend the quill fully through a slot. That makes it easy to test. Pull the pin, insert your biggest nastiest cutter, set the deepest depth of cut you commonly would use, and see how it works before/after pin. Let us know.

Best,

BW

[philbur]

Whether the tool will slip in the taper is primarily a function of how hard you pull on the draw bar versus how much torque you wish to transmit. The answer is almost for sure calculateable, at least to put you in the ball park, add 50% safety margin and you would be home and dry. Its looks like a relatively straight forward coefficient of friction calc.

Regards
Phil

this message is pretty much directed towards bob, but also anyone wha can help. I wanted to know if anyone has removed the pin inside the r8 spindle. From the conversation on the iso30 spindle it seems that the pin can be removed without any ill effects. Is this true? I have the same power drawbar from joe that bob has, and put the extra clips and springs on it like bob's. I would like to know as this would expidite my prototype attempt at an atc.

[krymis]

this is exactly what i needed to hear. now i just need to set everthing up to get this done. At the moment i have my mill torn apart back to bare bones trying to tidy my conversion back up.

[krymis]

bob,

what size support rods did you use for your PDR? I used .500 for mine and my springs were not as big or long as the ones you used. Do you think this will last? I am kinda concerned about that part....Where did you get your springs too?

[philbur]

Here is a typical calculation. What is intersting is that if you half the speed but still want to transmit full HP then the draw bar tension needs to double. So overall it looks OK for 2 hp as long as you have a draw bar tension of around 1000 lbs and don't go below 200 rpm.

Cone Clutch Calculation for a R8 Taper from (Machinerys Handbook)

large radius of R8 taper r1 1.25 inches
small radius of R8 taper r2 1 inches
half R8 taper included angle a 8.425 degrees
coefficient of friction f 0.7
horse power H.P. 2 hp
spindle speed N 200 rpm
safety factor S 1.5


mean R8 taper radius r 1.125 inches
min. draw bar force Ps 1007.2 lbs

Regards
Phil

this is exactly what i needed to hear. now i just need to set everthing up to get this done. At the moment i have my mill torn apart back to bare bones trying to tidy my conversion back up.

[BobWarfield]

bob,

what size support rods did you use for your PDR? I used .500 for mine and my springs were not as big or long as the ones you used. Do you think this will last? I am kinda concerned about that part....Where did you get your springs too?

Yeah, they are about 1/2". BTW, Vince on these boards (N4NV or some such name) has a Bridgeport he converted and he just built the same drawbar. Looks like he got his to work without return springs, so he musta had a stronger cylinder spring. He's got a post over on the Bridgeport section with a nice movie. Like me, he couldn't resist cycling a tool in and out when he first got the thing working. I was using mine this weekend and it was heaven. Anyone reading this needs to get a set of plans if you don't already have this gadget!

I bought my springs at Ace Hardware. Just grabbed the first thing that looked close. You have to adjust the tension by moving the collars up or down so the is enough force, but not so much the cylinder has trouble engaging smoothly. Frankly, I would have been happier to get mine to go without the springs. I keep pondering a mod to have those rods slide in some UHMW plastic bushings for better performance, but haven't done anything on it.

Krymis, I don't know why yours wouldn't last pretty well. These are not actually high duty devices. Even if you go CNC an ATC, I can't imagine you'd wear it out that fast. Might consider an inline oiler for your impact wrench if you plan to work it hard, though.

FWIW, I have a 3" diameter 7-insert Lovejoy facemill (expensive, but I got a great FleaBay deal and love the cutter) that is my heaviest cutter. Incidentally, it cuts well on the IH mill and leaves as nice a finish as my flycutter did but with much less noise and much faster. I suspect I can do even better if I get some coolant and really dial in optimal feeds and speeds. Anyway, it is good to know the mill is rigid enough to run this cutter on steel, but if I decide to pull my pin, I think this would make a good test.

Philbur, good calculation. We'll want to consider whether there might be a little oil that affects the Cf. I know my stuff has a little Break-Free on it to fight rust--live near the ocean. Certainly explains why the retention knob world uses such a big stack of Belleville washers to hold onto their toolholders. FWIW, there is a company making an R8 change system that claims 600lbs of springing is sufficient on R8. That's close enough to you number of 1000 to make sense. They just thread retention knobs into R8 collets and mill holders. Interesting approach. Don't know that I would prefer it over the power threaded drawbar though. Their system sure is expensive.

Best,

BW

[pstockley]

From my experience, drilling (especially large diameter drills) will be the real test.

[krymis]

thanks guys good to know where everything stands.
anymore info on this subject would be great.

[philbur]

I think this is an interesting point.

Providing you are driving the drill into the work-piece the resistance to slipping in the spindle taper is self-compensating due to the increased force pushing the tapers together. However if you slack off for even a fraction of a second (as in pecking, or just to allow the chips to clear for example) then the tendency will be for the partially formed chip to pull the drill out of the spindle. This will have a tendency to relieve the force holding the tapers together and possibly allow the tool-holder to rotate in the spindle. A clear example of this is the problem with large tapered shank drills in the tail-stock of a lathe.

If you use spring washers with an air actuator and stud arrangement for tool release then your retaining force is limited to the spring washer force which is constrained by your desire not to damage you spindle bearings during activation (unless you are very clever with the design). If you use an air wrench solution then the draw bar tension is only limited by the strength of the draw-bar and the power of the wrench.

So if you really want to make a R8 ATC (a dubious proposition at best) without a drive key then the air wrench solution would appear to be the better solution. If you just want quick-change capability then leaving the drive key in place would probalby be a safer option, either with the spring washer or the air wrench arrangement. Personally I don't think that lining up the keyway is that bigger deal for a manual quick-change solution. Alternatively a damaged spindle taper could reduce you to tears, and I hate to see a grown man cry.

Regards
Phil

From my experience, drilling (especially large diameter drills) will be the real test.

[philbur]

Another interesting modification to the air wrench design might be to include a thrust ball bearing between the underside of the drawbar nut and the top of the spindle. A 51101 looks suitable - 15mm ID and 28 mm OD - max static load 3000 lbs. This would ensure that more of the applied torgue finds its way down to the tool holder.

Regards
Phil

I think this is an interesting point.

Providing you are driving the drill into the work-piece the resistance to slipping in the spindle taper is self-compensating due to the increased force pushing the tapers together. However if you slack off for even a fraction of a second (as in pecking, or just to allow the chips to clear for example) then the tendency will be for the partially formed chip to pull the drill out of the spindle. This will have a tendency to relieve the force holding the tapers together and possibly allow the tool-holder to rotate in the spindle. A clear example of this is the problem with large tapered shank drills in the tail-stock of a lathe.

If you use spring washers with an air actuator and stud arrangement for tool release then your retaining force is limited to the spring washer force which is constrained by your desire not to damage you spindle bearings during activation (unless you are very clever with the design). If you use an air wrench solution then the draw bar tension is only limited by the strength of the draw-bar and the power of the wrench.

So if you really want to make a R8 ATC (a dubious proposition at best) without a drive key then the air wrench solution would appear to be the better solution. If you just want quick-change capability then leaving the drive key in place would probalby be a safer option, either with the spring washer or the air wrench arrangement. Personally I don't think that lining up the keyway is that bigger deal for a manual quick-change solution. Alternatively a damaged spindle taper could reduce you to tears, and I hate to see a grown man cry.

Regards
Phil

[BobWarfield]

Interesting thing about drills if they are the worst case:

There's no drive pin in the Taper to Chuck interface. Sure looks like similar or less surface area too.

In the end, it is easy to just try it out on the IH rather than spend hours wondering.

Best,

BW

[philbur]

But possibly much more expensive if the alternative is that you destroy the spindle taper due to an inappropriate design. Experimental engineering without realistic expectations can be a very expensive hobby, especially with a reworked spindle with high quality bearings. A little bit of theoretical engineering can save you many $$$$$.

A phrase that once again comes to mind is:

An engineer is somebody that can do for a penny what any fool can do for a pound.

It seems we have a fundamental difference in our approach to engineering. However it is clear to me that that my approach is right and therefore yours must be wrong.:boxing:

Best Regards
Phil

In the end, it is easy to just try it out on the IH rather than spend hours wondering.

Best,

BW

[1990notch]

krymis,

My pin apparently baccked out on it's own to the point where it didn't engage the collet at all. I decided to remove it totally so it couldn't cause a problem. I didn't realize how easy it was until I did it though.

Here's how I did it: Lower the quill most of the way. Then looking through the slot in the quill, rotate the spindle by hand until the "pin" (it's just a set screw) lines up with the slot. Then using a small precision screwdriver, turn the screw inwards until it drops through the spindle where the collet's go. Took me 45 seconds to do it.

I haven't had any problems with it out yet. I'll post if/when I do.

[BobWarfield]

It seems we have a fundamental difference in our approach to engineering. However it is clear to me that that my approach is right and therefore yours must be wrong.:boxing:

Best Regards
Phil

Philbur, I never doubted that would be your position and I thank you for your thoughtful lecture.

There are also those engineers who over engineer and over analyze. I run large engineering organizations for a living, and have to do so efficiently. I have some phrases of my own that I pass along to those who tend to over analyze when a simple experiment would do: Why reinvent the wheel? Or, to be more on point, why re-engineer or re-analyze that wheel? I have another engineer friend who is fond of pointing out when things are being over analyzed and a simple experiment would deliver the answer that the answer was "tragically knowable."

There are people such as 1990notch whose pins have fallen out who have run with them without ill effect that have posted on these and other boards. We have the example I presented of drill tapers, which use no such pins. There is Aaron telling us to go ahead, who has more experience than anyone with IH mills.

Let us know how your continued analysis comes out. Try to remember, models without supporting empirical data are often unproductive. Or, perhaps the example of chicken little is another illustrative case to consider.

Best,

BW

[philbur]

Ooops:

http://www.galileo.org/schools/stand...ges/index.html

Regards
Phil

QUOTE=BobWarfield;238564]
There are also those engineers who over engineer and over analyze. I run large engineering organizations for a living, and have to do so efficiently. I have some phrases of my own that I pass along to those who tend to over analyze when a simple experiment would do: Why reinvent the wheel? Or, to be more on point, why re-engineer or re-analyze that wheel? I have another engineer friend who is fond of pointing out when things are being over analyzed and a simple experiment would deliver the answer that the answer was "tragically knowable."

BW[/QUOTE]

[BobWarfield]

Thank you for bringing up the Tacoma Narrows Bridge, Phil, as it is an excellent illustration of what I'm trying to convey about the importance of real empirical data and not just mathematics in engineering.

The original Tacoma Narrows design was reviewed and revised by the same man who designed the Golden Gate bridge, Leon Moisseiff. He designed or collaborated on many other designs at the time, and was considered the leading suspension bridge designer of his day. All of these bridges were designed using the same math that had always worked before.

Unfortunately, in the Tacoma Narrows case, they discovered a new phenomenon that had not been seen before and was not covered in their textbook mathematics of the time. There was no error in Moisheff's calculations, the mathematical models of the day just didn't account for the full physics of what happened because they weren't known. Moisheff had been designing bridges for 20 years at this point.

It is interesting to note that the disasterous oscillations resulting in the bridge's demise were easily detected even during construction of the bridge:

http://www.nwrain.com/~newtsuit/reco...narrows/gg.htm

The bridge was in fact nicknamed "Galloping Gertie" because of these oscillations long before it collapsed. The bridge was in use for four months with oscillations so bad that people of the day made a sport of watching cars appear and disappear as the bridge rocked up and down. As the article notes, several means of strengthening the bridge against these oscillations were tried to no avail.

This was not a case of "under engineering" or going off half cocked, it was a case that the engineering science of the day didn't understand or account for the phenomenon at all. As your link concludes, Phil:

"this bridge disaster still has people talking, well arguing really, as physicists and mathematicians argue about the true reason that the bridge collapsed."

A little more ability to gather and act on experimental data and a little less over confidence in the mathematical models and reputations of the engineers involved safe and sound in their offices might have prevented the disaster.

Pull the pin, watch what happens, if your bridge starts to oscillate, put it back. Phil, you leave your pin in. You've got more engineering calculations to do before you're ready to pull it.

Sincerely,

BW

[Cruiser]

I think the true question regarding the r-8 stop pin is going to be an in use question, There is an "IF" involved, as in our shop with numerous bridgport mills, they occasionally get damaged and sheared off ! If it gets sheared off from a torque application then you can end up with a problem, So, If you remove the pin and have a similar problem, what will be the result ? A spun r-8 holder or collet will cause a lot of friction and pressure that can create for you a general use beater spindle, we have two machines in this catagory now and spindle replacement is not being concidered. It is a fact that with the air drive on the draw bar that the pin will at times be in the way, and that for general light use it is not needed, but it is there for the ocasional high torque needed for some slight reassurance, but without garantee, that your holder won't spin anyway ! Or will it ? A gauled taper, or bell'd out taper will not have the same hold as a good taper and then the sloap gets steaper and the snowball goes faster. So, I conclude my two cents worth with " IF you get away with it" ...........

[philbur]

An interesting point of view and a nice try, but it dances around the basic issue, which of course is the failure to take into account all of the forces involved. Everything else is merely about apportioning the blame. Was the design over or under analysed?

The Challenger space shuttle disaster is an interesting example of managements desire for efficiency (maintaining schedule) that appears to have over-ruled the engineering analysis, with disastrous consequences.

The seven P's comes to mind: Proper Prior Planning Prevents Piss Poor Performance.

Regards
Phil

Thank you for bringing up the Tacoma Narrows Bridge, Phil, as it is an excellent illustration of what I'm trying to convey about the importance of real empirical data and not just mathematics in engineering.

The original Tacoma Narrows design was reviewed and revised by the same man who designed the Golden Gate bridge, Leon Moisseiff. He designed or collaborated on many other designs at the time, and was considered the leading suspension bridge designer of his day. All of these bridges were designed using the same math that had always worked before.

Unfortunately, in the Tacoma Narrows case, they discovered a new phenomenon that had not been seen before and was not covered in their textbook mathematics of the time. There was no error in Moisheff's calculations, the mathematical models of the day just didn't account for the full physics of what happened because they weren't known. Moisheff had been designing bridges for 20 years at this point.

It is interesting to note that the disasterous oscillations resulting in the bridge's demise were easily detected even during construction of the bridge:

http://www.nwrain.com/~newtsuit/reco...narrows/gg.htm

The bridge was in fact nicknamed "Galloping Gertie" because of these oscillations long before it collapsed. The bridge was in use for four months with oscillations so bad that people of the day made a sport of watching cars appear and disappear as the bridge rocked up and down. As the article notes, several means of strengthening the bridge against these oscillations were tried to no avail.

This was not a case of "under engineering" or going off half cocked, it was a case that the engineering science of the day didn't understand or account for the phenomenon at all. As your link concludes, Phil:

"this bridge disaster still has people talking, well arguing really, as physicists and mathematicians argue about the true reason that the bridge collapsed."

A little more ability to gather and act on experimental data and a little less over confidence in the mathematical models and reputations of the engineers involved safe and sound in their offices might have prevented the disaster.

Pull the pin, watch what happens, if your bridge starts to oscillate, put it back. Phil, you leave your pin in. You've got more engineering calculations to do before you're ready to pull it.

Sincerely,

BW

[krymis]

guys please stand down and lets talk and act. I removed the pin from my seig mill and now i need to know what test to do to see if it will work. the seig mill is a good starting point as the spindle can be replaced for a few dollars. This will give us a good starting point and then we can move on the ih mills. also i would lean towards removing the pin if arron has metioned removing it. If he has mentioned it then he 99% surely has done it. if it was good for him then it may be good for us. Tell me what test to run with what cutters and i will do them and post back. I feel the atc in r8 form can be accomplished but there has to be a reason why noone has done it. We need to ask gene if he did in fact get the design drawings and such from arron for his atc. For those of you who did not know arron has been working on one.