[ihavenofish]

.... then the Belleville washers will be more than sufficient of holding your tools in, regardless of what toolholder/spindle you use.

the Belleville washers are exactly sufficient for anything that wont damage the spindle or tool. these aren't designed with random guesswork like some of the stuff on cnczone :P

1870N drawbar pull force (according to the drawing) is 420lbs of downward force before the tool moves out of it's taper. if you are exerting that much force on this machine, you have a lot bigger problems to worry about. 1870N would also pull the HEAD down against the force of your small Z stepper.

to note, in order to exert 1870N downward from just cutting forces, you are talking about a 10-20hp cut at 7000rpm with a 10mm tool.

[handlewanker]

Hi, I quite agree that the Bellville washer system is sufficient to HOLD the tool holder up in the taper once the washers have been compressed enough, seeing as it gets its force from the combined efforts of a series of spring washers etc.......very neat and simple, and I do quite like it.

BUT........ you have to exert a similar but larger increasing force to move the drawbar down a distance of 20mm or so to release the ISO 20 tooling gripper, and the more you move the drawbar down the greater the force required due to the fact that the washers are being compressed and so increasing their force.

Although it is par for the course and standard accepted practice, I find that increasing a force instead of decreasing it to release a load is bad mechanics, even though due to the nature of the Bellville washers, this is what must occur.

On the other side of the coin, the nut and bolt principle purely decreases the holding force when the load needs to be released, and that is my aim in a new approach.

It is after all, without any argument that would hold water, a more desirable way of life.

I'm fully aware of the need to have a certain amount of holding force to make sure the tool taper stays seated in the spindle taper, but I'm not wowed by the Bellville washer method, so another crusade for another holy grail is on the cards........my choice, you can stay with the Bellville washers if that is what pushes all your buttons.

I have to wonder why the guy on the other forum went to the lengths he did for the Novacon just to make something that goes against industry accepted practices........did he also realise something that I have been aware of for a while?

I doubt very much that the tooling will be pulled out of the taper by any cutter forces the SVM-0 will be subjected to, so the need to exert tons of force to hold it in with springs I find is very unneedful.

I expect Thomas Edison came up against the same opposition to the incandescent light bulb from the candle and oil lamp brigade in his day, especially when the usage of DC was being challenged by the AC forum.

BTW, back in the 70's the firm I worked for had a Bridgeport mill and the drawbar pressure was exerted by a knurled knob 60mm diam in place of the hexagon nut that frequently got overtightened by the ignorant users in the factory......the spindle taper was 3 Morse so I will concede that it also had a contributory factor to overtightening.

I don't think I am alone in looking for a better way than the Bellville washer method, so that is the path I am exploring.

You HAVE to constantly keep thinking outside of the box, or you'll just keep on following the herd no matter what.

I don't intend to argue the pros and cons as it's purely something I intend to work on for my own benefit, seeing as so much opposition is expressed for a different approach, and if it comes to naught then the Bellville washer compressed by the cam and lever method with air cylinder can also be used, I just don't like that approach too much.

BTW, I can exert 1 ton (2,000 lbs) of force with a simple rack and pinion mechanism as is used on my arbour press, so who needs compressed air?
Ian.

[handlewanker]

the Belleville washers are exactly sufficient for anything that wont damage the spindle or tool. these aren't designed with random guesswork like some of the stuff on cnczone :P

1870N drawbar pull force (according to the drawing) is 420lbs of downward force before the tool moves out of it's taper. if you are exerting that much force on this machine, you have a lot bigger problems to worry about. 1870N would also pull the HEAD down against the force of your small Z stepper.

to note, in order to exert 1870N downward from just cutting forces, you are talking about a 10-20hp cut at 7000rpm with a 10mm tool.

Hi again, no one has yet devised a method to measure the force needed to retain a non stick taper (ISO 20, 30, 40, 50 etc) in a taper spindle housing, so it is an empirical approach that is applied from experience to prove that enough is only as good as you think it is to stop the tool from coming loose.

You CAN measure the force required to hold the tool in, but you can't measure the force you are applying when you tighten the drawbar, and that is by any method be it nut and screw or springs.....it's pure guesswork for the masses and at best a recommendation as laid down by the spindle tooling manufacturers when they supply the spindle.
Ian.

[ihavenofish]

Hi, I quite agree that the Bellville washer system is sufficient to HOLD the tool holder up in the taper once the washers have been compressed enough, seeing as it gets its force from the combined efforts of a series of spring washers etc.......very neat and simple, and I do quite like it.

BUT........ you have to exert a similar but larger increasing force to move the drawbar down a distance of 20mm or so to release the ISO 20 tooling gripper, and the more you move the drawbar down the greater the force required due to the fact that the washers are being compressed and so increasing their force.

3-5mm is the release throw on ISO20. generally you need twice the force to get to that distance (although every design will be a little different). these are the rules set by the company that has engineered the pull stud and gripper.

Although it is par for the course and standard accepted practice, I find that increasing a force instead of decreasing it to release a load is bad mechanics, even though due to the nature of the Bellville washers, this is what must occur.

why is this bad. there is only one potential drawback here and that is a load on the bearings. this load is within the normal load of the bearings in the spindle and wont cause damage, but if it was a worry, the collar at the top of the spindle can be used as a gripping ledge so that zero force is exerted on the bearings when the drawbar is released. it requires a slightly more complex mounting of the air cylinder so it can float.

On the other side of the coin, the nut and bolt principle purely decreases the holding force when the load needs to be released, and that is my aim in a new approach.

It is after all, without any argument that would hold water, a more desirable way of life.

it is not in any way more desirable. it creates wear on the system, which in turn means continuous compensation, then replacement of parts. the threads on an r8 drawbar do not last very long and are not designed to the kind of constant use a quick change system (or worse ATC) will see. it is a system that is ONLY used when the use is restricted by an existing configuration that cant be changed.

I'm fully aware of the need to have a certain amount of holding force to make sure the tool taper stays seated in the spindle taper, but I'm not wowed by the Bellville washer method, so another crusade for another holy grail is on the cards........my choice, you can stay with the Bellville washers if that is what pushes all your buttons.

I have to wonder why the guy on the other forum went to the lengths he did for the Novacon just to make something that goes against industry accepted practices........did he also realise something that I have been aware of for a while?

no. the reason he is using the method of a threaded drawbar is to keep compatibility with existing R8 tooling, and to create a drop in "no modification" system on an existing machine. since none of these "legacy" issues affect the iso20 setup, you are only creating unnecessary problems for yourself.

I doubt very much that the tooling will be pulled out of the taper by any cutter forces the SVM-0 will be subjected to, so the need to exert tons of force to hold it in with springs I find is very unneedful.

the force needed is dictated by the design, and is set at 1870N. any less or more would possibly damage parts of the spindle. it isn't guesswork here. it is precisely measured (yup, they have tools for that). remember this is NOT R8. the force does not vary based on the size of the collets, it is a constant.

I expect Thomas Edison came up against the same opposition to the incandescent light bulb from the candle and oil lamp brigade in his day, especially when the usage of DC was being challenged by the AC forum.

BTW, back in the 70's the firm I worked for had a Bridgeport mill and the drawbar pressure was exerted by a knurled knob 60mm diam in place of the hexagon nut that frequently got overtightened by the ignorant users in the factory......the spindle taper was 3 Morse so I will concede that it also had a contributory factor to overtightening.

I don't think I am alone in looking for a better way than the Bellville washer method, so that is the path I am exploring.

You HAVE to constantly keep thinking outside of the box, or you'll just keep on following the herd no matter what.

I don't intend to argue the pros and cons as it's purely something I intend to work on for my own benefit, seeing as so much opposition is expressed for a different approach, and if it comes to naught then the Bellville washer compressed by the cam and lever method with air cylinder can also be used, I just don't like that approach too much.

BTW, I can exert 1 ton (2,000 lbs) of force with a simple rack and pinion mechanism as is used on my arbour press, so who needs compressed air?
Ian.

anyhow, do what you like, just don't complain later when you need to buy a new spindle

[ihavenofish]

Hi again, no one has yet devised a method to measure the force needed to retain a non stick taper (ISO 20, 30, 40, 50 etc) in a taper spindle housing, so it is an empirical approach that is applied from experience to prove that enough is only as good as you think it is to stop the tool from coming loose.

You CAN measure the force required to hold the tool in, but you can't measure the force you are applying when you tighten the drawbar, and that is by any method be it nut and screw or springs.....it's pure guesswork for the masses and at best a recommendation as laid down by the spindle tooling manufacturers when they supply the spindle.
Ian.

im confused... .or rather, I thin you are, haha. you can calculate rather easily the linear force needed to hold the tool in the taper under various loads. basic math, and done in computer simulation these days. you can also pair this with FEA data to find out the "safe limit" of the system.

you can also rather easily calculate the exact force being exerted by a threaded drawbar OR Belleville spring stack with simple math.

lastly you can check the precise force being exerted by the system while in use with a specially configured newton scale.



there is absolutely zero guesswork involved in this system.

[louieatienza]

Hi, I quite agree that the Bellville washer system is sufficient to HOLD the tool holder up in the taper once the washers have been compressed enough, seeing as it gets its force from the combined efforts of a series of spring washers etc.......very neat and simple, and I do quite like it.

BUT........ you have to exert a similar but larger increasing force to move the drawbar down a distance of 20mm or so to release the ISO 20 tooling gripper, and the more you move the drawbar down the greater the force required due to the fact that the washers are being compressed and so increasing their force.

Although it is par for the course and standard accepted practice, I find that increasing a force instead of decreasing it to release a load is bad mechanics, even though due to the nature of the Bellville washers, this is what must occur.

On the other side of the coin, the nut and bolt principle purely decreases the holding force when the load needs to be released, and that is my aim in a new approach.

It is after all, without any argument that would hold water, a more desirable way of life.

I'm fully aware of the need to have a certain amount of holding force to make sure the tool taper stays seated in the spindle taper, but I'm not wowed by the Bellville washer method, so another crusade for another holy grail is on the cards........my choice, you can stay with the Bellville washers if that is what pushes all your buttons.

I have to wonder why the guy on the other forum went to the lengths he did for the Novacon just to make something that goes against industry accepted practices........did he also realise something that I have been aware of for a while?

I doubt very much that the tooling will be pulled out of the taper by any cutter forces the SVM-0 will be subjected to, so the need to exert tons of force to hold it in with springs I find is very unneedful.

I expect Thomas Edison came up against the same opposition to the incandescent light bulb from the candle and oil lamp brigade in his day, especially when the usage of DC was being challenged by the AC forum.

BTW, back in the 70's the firm I worked for had a Bridgeport mill and the drawbar pressure was exerted by a knurled knob 60mm diam in place of the hexagon nut that frequently got overtightened by the ignorant users in the factory......the spindle taper was 3 Morse so I will concede that it also had a contributory factor to overtightening.

I don't think I am alone in looking for a better way than the Bellville washer method, so that is the path I am exploring.

You HAVE to constantly keep thinking outside of the box, or you'll just keep on following the herd no matter what.

I don't intend to argue the pros and cons as it's purely something I intend to work on for my own benefit, seeing as so much opposition is expressed for a different approach, and if it comes to naught then the Bellville washer compressed by the cam and lever method with air cylinder can also be used, I just don't like that approach too much.

BTW, I can exert 1 ton (2,000 lbs) of force with a simple rack and pinion mechanism as is used on my arbour press, so who needs compressed air?
Ian.

For Pete's sake, can we have a discussion without invoking Mr. Edison's name, as if somehow you believe you are on par with the man. It was Edison who was the proponent of DC current, and demonized Nicola Tesla's invention of AC because Edson had a huge stake in DC, not because it was better. In the end Tesla prevailed (to the benefit of Westinghouse.) Otherwise the world would be consumed with electrical poles with thousands of wires, and repeater stations every mile.

For the record, I'm not opposed to experimentation and exploration. What I am opposed to are Napoleanic complexes, and the demeaning of standard practice. Po-tay-to, po-tah-to. Can there be a better way? Sure. It doesn't mean that thw way it's done now is somehow magically irrelevant. If you have a better way, prove it, as Edison did. So explore as you wish, just don't put everything down before you (or expect to be elevated above everyone else.) There wouldn't be exploration without the works of the past.

[Skyfire]

Hi Sky, if you can supply that same vice mode typel with 125mm wide jaws that would be fine........a price, a price, my kingdom for a price....LOL.....I don't think Richard 111 was into CNC milling.........but he certainly would have pawned his crown jewels for a horse.

So, if you can source a vice like the pic I posted, let me know how the payment must be made......the shipping cost savings will be a bonus.

I think you have the right design format in the SVM-0, as it can be down to a basic but still very sophisticated economical mill with the ER32 spindle and still allow a later retrofit to go to a more exotic package as the user needs without having to commit surgery to get it to happen......I assume the split head casting will be standard to allow this retrofit to happen.....it's more work initially but being able to change over to a high speed spindle without a huge outlay is a big selling point.

Just as a matter of interest, one of the photos you posted shows the high speed spindle mounted in the head, and the note that the ISO20 spindle will be fitted in a similar manner......does this mean the drive motor for the ISO20 spindle would need a spacer to bring it up to the spindle pulley level?

I'm interested in that aspect as I would like to have the bottom of the ISO20 spindle housing flush with the bottom of the head casting to give maximum clearance to the Z axis travel, and I assume the top stick out of the ISO20 spindle will need the motor to be fitted onto a spacer to achieve this.
Ian.

Hi handle,

I checked the vice price and the 125mm is about $120--frankly it's almost double of the common milling vice as I posted. Of course, no extra shipping cost..lol

If you think it's okey, I can send you a Paypal invoice. For such small parts I can acceptable Paypal payment now.

Yes, I agree all of your points--I'd always try to fit all possible needs that different people want---I think the economic SVM-0 maybe a good start machine to get into CNC field..lol

Yes, the ISO20 spindle will stick out of the head top and the spindle motor will need 2 spacer to adjust the height. I will measure the right dimensions and make the spacers for you.

[Skyfire]

Defeng,

Great pics there! The electronics boxes look great, and I kind of like that color myself. I see you have a few split-head mills there; looks like you and I started a trend...

What's nice with the head clamp design is I could position the spindle as needed depending on the job at hand.

Hi louie,

It makes me some comfortable that you think the color is not too bad... lol

Yes, I found actually more users will like the 80mm spindle system as you want..lol so I began to think to make 80mm as standard for SVM-0- or at least I guess half people will like 80mm high speed spindle or ISO20 spindle.

I tested the head clamp and it's very tight. There is one issue I have to say is that actually 4 bolts at the 4 corners will be better than 6 bolts because the 2 bolts at the middle positions actually not useful..

I just received the small stainless parts that delayed long period.. so the assembling works can go forward now. And I also got the breakout PCB samples and testing now too. Will post them here soon.

[ihavenofish]

If you have a better way, prove it, as Edison did. So explore as you wish, just don't put everything down before you (or expect to be elevated above everyone else.) There wouldn't be exploration without the works of the past.

what Edison did for the light bulb is equivalent to using stainless steel Belleville springs instead of mild steel, since the incandescent bulb was invented some 30 years before he was even born and all he contributed was a small modification of materials - and a lot of marketing.

just saying :P

[ihavenofish]

Hi louie,

It makes me some comfortable that you think the color is not too bad... lol

Yes, I found actually more users will like the 80mm spindle system as you want..lol so I began to think to make 80mm as standard for SVM-0- or at least I guess half people will like 80mm high speed spindle or ISO20 spindle.

I tested the head clamp and it's very tight. There is one issue I have to say is that actually 4 bolts at the 4 corners will be better than 6 bolts because the 2 bolts at the middle positions actually not useful..

I just received the small stainless parts that delayed long period.. so the assembling works can go forward now. And I also got the breakout PCB samples and testing now too. Will post them here soon.

there is also an 80mm iso20 high speed motor spindle up to 42000rpm. expensive, but provides another "drop in" option for the 80mm clamp.

[louieatienza]

what Edison did for the light bulb is equivalent to using stainless steel Belleville springs instead of mild steel, since the incandescent bulb was invented some 30 years before he was even born and all he contributed was a small modification of materials - and a lot of marketing.

just saying :P

Yes well even Edison still used carbon impregnated filament, but under better vacuum. It was really the Hungarian company Tungsram that made what we'd call the modern incandescent bulb, with tungsten filament and argon. It wasn't that long ago (maybe 20-25 years) when GE still had commercials about this. Edison I believe IS credited with the screw-in sleeve which we still use today.

The point is, even Edison DID something, he didn't just write about why something wasn't good enough; and he porduced working prototypes, not typed words...

[louieatienza]

Hi louie,

It makes me some comfortable that you think the color is not too bad... lol

Yes, I found actually more users will like the 80mm spindle system as you want..lol so I began to think to make 80mm as standard for SVM-0- or at least I guess half people will like 80mm high speed spindle or ISO20 spindle.

I tested the head clamp and it's very tight. There is one issue I have to say is that actually 4 bolts at the 4 corners will be better than 6 bolts because the 2 bolts at the middle positions actually not useful..

I just received the small stainless parts that delayed long period.. so the assembling works can go forward now. And I also got the breakout PCB samples and testing now too. Will post them here soon.

Happy New Year Defeng!

Great to hear that you finally got those parts! The machines are looking great so far; the trimmings are the icing on the cake.

I can see the demand for high-speed spindles with the smaller machine, especially with the smaller tooling I plan to use (and I think more than a few would) with such a machine. But it's good to know that another spindle can be bolted on and set up relatively easily for other tasks.

I don't mind the 6 bolts and it does give the head a "stronger" look even though the center bolts may not be necessary.

[ihavenofish]

Yes well even Edison still used carbon impregnated filament, but under better vacuum. It was really the Hungarian company Tungsram that made what we'd call the modern incandescent bulb, with tungsten filament and argon. It wasn't that long ago (maybe 20-25 years) when GE still had commercials about this. Edison I believe IS credited with the screw-in sleeve which we still use today.

The point is, even Edison DID something, he didn't just write about why something wasn't good enough; and he porduced working prototypes, not typed words...

sure. my point was that he didn't throw away 80 years of knowledge, but rather just refined it. handle suggested he'd have had resistance to the idea... but the idea was already well accepted by that point.

handle's idea throws away all the knowledge gained in the last 40+ years and tries to reclaim an idea that has been abandoned on every single industrial level power drawbar.

but that's not really why i'm still poking at him. it's the fact that he seems not to understand how either system works. i'm trying to make him see the expensive mistake he's going to make before he commits.

[handlewanker]

"Hi Sky.......$120 for a 125mm toolmakers vice is absolutely fantastically good value.......please send an invoice for that amount and I'll make a Paypal payment ASAP......the savings in the shipping costs will be enormous.

I would be most appreciative for the spacer offer, it will solve my needs.

BTW, Happy New Year, things are looking great in the SVM-0 build program.
Ian.

[handlewanker]

Hi Louie and Avno, the whole point of the discussion (from my side of the table) is to bounce ideas off anyone who cares to comment in order to see where the smoke ends and the fire begins etc.

The industry has criteria far beyond the needs of the average mill user and the forces encountered by the average small time user not in serious or any production are far less than someone pushing the envelope to the limits etc in order to make a buck.

For the record, I am fully aware of the differences of the R8 system needs and a non stick taper system like the ISO20 and others.......the forces required for the R8 are such that the collet is compressed to hold a cutter in it, whereas the pull pin of the ISO system tool holders has to hold the tooling in the taper against cutter loading etc, but at the end of the day using either a manual screwed drawbar or an air operated one, the holding force is still a factor to hold the tapered tool shank in or compress a collet.

I don't think at any one time a manual worker tightening a drawbar with a spanner on a nut for an R8 tool holder was able to ascertain the exact amount of force he was applying to hold the cutter in the collet.....it is a guestimated tightening force that the operator "thinks" is sufficient to hold the cutter in the collet, IE it's better to have more force than less when you work with R8.

Coming to a non stick taper like the ISO 20 etc, and you are using a different approach.......the manual mill operator is still applying a spanner to tighten a nut to pull up a drawbar to hold the taper tool in the spindle, but with less force as it's locating and holding as opposed to a requirement that needs to compress a collet to grip the tool shank against cutter forces.

I'm not deterred or swayed by criticism, and even if metal has not been cut to "experiment" with a hypothesis it does not mean the thought that provides the method cannot be pursued.

I was not aware that Ray (watsisname) of Novacon fame had designed and actually made a similar drawbar pull system to the one I amused you with, but it goes to show you when the ideas are flowing the plethora of them gives you a field to explore as you see it, and it is great news to know that what I am thinking of has actually been done, and therefore my point of view has been vindicated by the principal having been made.

The principal, as I understand it from the hurried perusal of the entire thread to get an idea of the workings of Ray's design, uses EXACTLY the same method to tighten a draw bar as I proposed without using Bellville washers, and is becoming if not already commercially available.

But Of course according to those in the know this is going against the stream and ignoring 40 years of Bellville washer appied force for drawbars.

Did I hear cries of "woe to those that step outside the box", for the path to being different is strewn with broken cutters and tool holders smashed beyond repair?

I will agree that the Bellville washer method is compact, but also agree that it is not exactly easy to compress the stack without becoming hot under the collar.

BTW, the force compressing the washer stack will ALWAYS be applied to the inner race and hence to the balls and also the outer race of the bearings when the washers are further compressed by an outside force to release the tooling.....it cannot be otherwise, but as the bearings can cope with this static force that is gradual and not impactive, no harm is done.

The method I proposed ALSO uses a rotative method to tighten/untighten a nut type of device on a drawbar, but not on the actual threads of the drawbar itself.

As I have not shown even a sketch of the design I proposed, I have to wonder if anyone can be aware of how it will work and be so intuitive to criticise it at so great a length.

BTW, a fellow in Holland proposed a different method that uses a drill type driver to tighten/untighten a nut on a drawbar, using the existing nut and manual drawbar mechanism, ( video on UTUBE) and as it's possibly prone to crossthreading the screw threads, that method WOULD and DID invoke a lot of criticism.....mine is fundamentally completely different.
Ian.

[Dylwad]

Ray did the power draw bar for R8 collets and tts, since Tormachs Belleville setup for their PDB has been known to have some issues if you don't maintain the system.

I'll bet if he did a PDB for iso20 it would be Belleville and pneumatic, for simplicity, since the force needed to retain the tool holder is lower than with an R8 + tts adapter + tool sticking out, on a machine that's more rigid and more powerful than the Tormach ~ which is what tts was designed for.

Most Belleville and pneumatic PDB setups don't put any sort of load on the spindle bearings.

If there was a better mouse trap, you wouldn't see Belleville washers on big money industrial machines.

[ihavenofish]

BTW, a fellow in Holland proposed a different method that uses a drill type driver to tighten/untighten a nut on a drawbar, using the existing nut and manual drawbar mechanism, ( video on UTUBE) and as it's possibly prone to crossthreading the screw threads, that method WOULD and DID invoke a lot of criticism.....mine is fundamentally completely different.
Ian.

you do realise there is NO existing nut or manual drawbar mechanism right? this spindle is design and equipped with a precisely engineered Belleville spring system. it HAS the setup already. there is NOTHING that needs to be added, changed, or adjusted. I get the feeling you think this is a half complete setup that needs a drawbar mechanism and you want to devise one. it doesn't need one. its already there.

the only thing you need is a mechanism to push on the drawbar, which is super cheap and easy with a small air cylinder. a single stage 3" bore cylinder at 90psi will work and cost under $150 with a pushbutton solenoid. just mill some aluminium stand offs to hold it above the head and voila, finished.

BTW, the force compressing the washer stack will ALWAYS be applied to the inner race and hence to the balls and also the outer race of the bearings when the washers are further compressed by an outside force to release the tooling.....it cannot be otherwise, but as the bearings can cope with this static force that is gradual and not impactive, no harm is done.

this is wrong. or you wrote it wrong. in operation, the drawbar and springs exert no force on anything but each other. there is no connection to the bearings. i'm not sure what you are thinking here. when you force the drawbar down, you do exert a force on the bearings, but it is well within the load ratings. you CAN eliminate this force altogether as I mentioned before with a floating air cylinder.

remember that on this spindle (which is equipped with internal Belleville springs a drawbar and gripper) you have no way of locking the drawbar so it cant spin. you have no way of locking the spindle itself so it cant spin. you'd need a 80-100mm tall steel spacer to replace the springs - preferably balanced.

so the modifications you want to make may be both unnecessary and impossible.

[wizard]

…

If there was a better mouse trap, you wouldn't see Belleville washers on big money industrial machines.

In a nut shell this sums it up!

Not that I think we should stop looking for a better mouse trap. But you need a really compelling idea to make a discussion worthwhile.

[louieatienza]

Hi Louie and Avno, the whole point of the discussion (from my side of the table) is to bounce ideas off anyone who cares to comment in order to see where the smoke ends and the fire begins etc.

No one's stopping you from doing what you want, so when you get your spindle, you can mod it to your heart's content!

[handlewanker]

Hi, so true.....just been browsing on UTUBE and noted the various methods for PDB's etc.....the screw type is quite common, so is the air cylinder in various forms, but the difference is, the air cylinders are compressing the Bellville washers whereas the screw type aren't.

The simplest PDB I saw was with an impact wrench that got pulled down to engage a socket with the drawbar nut and so is fail safe in that you have to actuate it to make it work and when not actuated is out of the way....that is simple, so there are many ways that you can do it.

I see one that is just a cam operated lever arm that just bears down on the top of the drawbar.....it still has Bellville washers for the retention method, so that is not what I had in mind.

All a draw bar has to do is pull up with enough force and maintain it to make the taper shank of the tool fit tightly in the spindle taper and keep it there.......it's that simple, anything can do it, even a bunch of spring washers stacked one on top of the other, which is what I dislike for a system..........my preference.

How I go about designing the method is purely based on current users' experience, seeing as the method I proposed has ALREADY BEEN DONE, which means I am not reinventing the wheel, just modifying the inner workings to my satisfaction.

You don't actually need Bellville washers to provide the holding force, even though it's a simple method and used in industry.....I just don't like applying brute force to overcome the force.....there must be a better way etc.

Supposing I removed the Bellville washers and replaced them with a nut/screw system........would that be heretical thinking....the end of the World?

I don't think so, seeing as how that is how non stick ISO tapers on manual mills have been held in since the beginning of the Industrial Revolution, or at least on most of the vertical mills I have worked on.

The Bellville washer method is a quick fix solution to drawbar activation without having to apply a spanner to a nut by hand.

Having a nut on the drawbar end means the nut can be powered to raise or lower the drawbar as required with the required torque to apply the holding force, and it makes no difference if the other end of the drawbar has a screw thread to lock into the tool shank end or a retainer method to lock onto a pull pin, the force is still a force.

The movement to release the tool from the retainer, by all accounts, is only 3 to 5mm, so that is no big deal to achieve......how it is achieved is another question which is of no real concern to those that are Bellville washer advocates, but one that I am working on now.

Sometimes the idea you are working on turns out to be either too complicated or too costly compared to the same as has already been tried, even though at first glance the problem is a simple one......that is what I will have to find out.
Ian.