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randyc
12-07-2010, 11:11 PM
(I evaluated an imported 6-jaw chuck recently. I wasn't happy with the product, it didn't suit my purposes so I returned it to the distributor. But the Chinese are capable of making high quality metalworking equipment, as we know. I'd like to share the following experience as an example of this point. I'll post the other - less favorable - review at another time.)

After being disappointed by a recent experience, I selected a different distributor this time. I've dealt with the distributor before and would characterize them as follows: the products are fairly typical with a slight advantage in cost, depending on what you are buying. They have a good return policy (that's the common characteristic of these importers, right ? They HAVE to have a good return policy or we'd never buy anything from them, LOL, since the return rate is high).

This is the workholding device that I required for various needs, in the form of a packaged set:

http://i97.photobucket.com/albums/l219/randy9944/P1010925.jpg

The set consists of a NMBT-40 (similar to CAT-40) collet chuck, locking nut and spanner wrench plus a set of ER40 collets from 1/8 inch to 1 inch diameter in 1/16 inch increments. I received the shipment a couple of nights ago and finally got around to removing the individual parts from their sealed-in-oil plastic baggies. The Chinese manufacturers have improved greatly over the past two decades in their manner of packaging and preservation, especially for small parts. (Machinery is a slightly different proposition, the use of a gummy protective coating, applied liberally to near-inaccessible areas is a source of frustration when trying to clean and lubricate a new machine.)

These parts cleaned up nicely in a plastic bucket of mineral spirits with a soft cloth, and they look great ! Except for the spanner wrench, the external surface of the locking nut and the large driving ring on the NMBT-40 chuck every surface is ground (all of these parts appear to be forgings, black-oxide coated, by the way). The fifteen collets are likewise ground on all surfaces except for the rear and the thin slots on each collet that allow the devices to collapse over a wide range. The number of slots varies, depending on collet size, from sixteen down to twelve on the very smallest collets for obvious reasons.

It is because of the many slots (and the fact that the collets are slotted from both the face and the rear) that these devices have come to be greatly appreciated for their precision, gripping power and the ability to accommodate a wider range of diameters than any other collet device except for the steel-blade-in-rubber-bushing types like those found in tapping heads. Here is a close-up photo showing front and rear of typical collets:

http://i97.photobucket.com/albums/l219/randy9944/P1010926.jpg

Most popular workholding collets (e.g. 5C and R8) have three, sometimes four slots and the useful range is the nominal diameter minus perhaps .001 or .002. The reason is simple: larger workpieces "spring" the collet tapers outward and they no longer fit the spindle taper properly. Smaller workpieces achieve only line contact along the center of each individual "finger" of the collet rather than the desired area contact. The accuracy is slightly degraded by this condition but more importantly, the gripping power is reduced substantially and there is risk of permanent damage to the collet if the drawbar is torqued excessively to provide more grip.

After looking around for a while, I formed the impression that ER collets seem to be more widely used when spindle horsepower is greater than around 2 HP. The various "ER" series of collets with their many more "fingers" to hold the workpiece, maintain a tighter grip over a wider range of workpiece diameter. Frankly, I'm no expert regarding these collets but I have read that they are capable of accommodating a diametral variation of 1/16 inch (imperial sets), which suggests that 1/16 increments should be able to grip any diameter between the minimum and maximum collet diameters, provided that the workpiece isn't tapered. Here is an intentionally exaggerated sketch of the two types of collet construction:

http://i97.photobucket.com/albums/l219/randy9944/collets.jpg

The diameter of the workpiece and the diameters of the collet "fingers" are identical in both sketches. Notice how much greater the gripping area of the second collet has become by doubling the number of slots and narrowing the fingers. And because the individual fingers are more flexible, they can accommodate greater deflection and therefore greater variation in workpiece diameters. (The actual ER-40 collets have even more slots thus greater flexibility and gripping power.)

After cleaning and wiping down the set, I installed the NMBT 40 chuck in my horizontal milling machine, snugged the drawbar and arbitrarily selected a 3/8 collet for my first "qualification" measurement. Placing a four-inch length of ground 3/8 drill rod in the collet, I tightened the locking nut and measured the minimum/maximum runout. I wasn't at all pleased to see runout of .0030 inches when the booklet that came with the set stated that the factory specification is 0.0008 inches. I tried a 1/2 inch collet and saw similar results. My initial thoughts were, "Here we go again !"

I removed the NMBT-40 chuck and cleaned the tapers of the spindle and chuck again, then I measured the spindle runout of the machine itself (although I knew it was true). No problem, hardly a flicker on the DTI (I was using a .0005 dial test indicator for these measurements since one was already parked on the mill table in a magnetic holder. (I'm usually reluctant to install the 0.0001 indicator, both from laziness and because I use it only when I must, due to the limited range of .005 travel.)

randyc
12-07-2010, 11:11 PM
Repeating the runout measurements, I obtained substantially the same numbers so I got out the camera and started documenting the runout numbers, reluctantly conceding that this set had to be returned. After taking several photos, on a whim I removed the CAT-40 chuck and rotated it in the spindle 180 degrees.

BINGO ! The following are the minimum/maximum runout measurements (0.0005 inch graduations):

http://i97.photobucket.com/albums/l219/randy9944/P1010922.jpg

Maximum runout measurement (0.0005 inch graduations):

http://i97.photobucket.com/albums/l219/randy9944/P1010924.jpg

I was pleased with the 0.0006 inch runout, measured 1.6 inches away from the collet face, which corresponded nicely with the factory specification of 0.0008 at the same distance. Now I don't know if the collet chuck actually has to be oriented in this exact manner to obtain these results or if I simply dislodged a particle of dust when I turned the chuck around, LOL. Doesn't make a bit of difference to me if it has to be mounted a certain way, I have no objection to doing that. After all, that is routine practice to obtain best performance from a 3-jaw chuck in a lathe. What could be simpler than punching a couple of marks on spindle and on chuck ?

So, that's it - after checking a couple of different collet diameters, I pronounce this experience completely satisfactory. I don't know if I got a particularly good set for my $175 or if the distributor received a particularly good lot - but I am sufficiently happy with the tooling that I promptly ordered both morse taper and R8 collet chucks from the same vendor (to accomodate the set of collets). This will allow the same set of collets to be used in other machinery.

http://i97.photobucket.com/albums/l219/randy9944/P1010954.jpg

The two tools on the left are new ones. The small Morse Taper/ER-40 fits the vertical head for my horizontal mill and the other is R8/ER-40 in the event I may want to use the ER collets in the other vertical mill. A further use for this versatile holding system follows from the fact that the Morse Taper in the horizontal mill vertical head is the same as the one in my lathe tailstock. The ER-40 collets in the lathe tailstock are handy for counterboring (with end mills) as well as holding drills, some reamers (if floating reamer isn't required), broaches and other tailstock tooling. (An additional benefit is the ability to hold tooling that is too large to fit in a 1/2 or 5/8 drill chuck.) Here's a photo of a one inch ball end mill with 3/4 inch shank held in the tailstock for making a finishing pass on a ball-socket joint:

http://i97.photobucket.com/albums/l219/randy9944/P1010955.jpg

randyc
12-07-2010, 11:12 PM
One reason for tooling the horizontal mill with ER-40 collets was the high cost and limited availability of suitable arbors. For best utilization of the machine, the one-size-fits-all arbor may not work well and probably explains why so many used arbors are bent (from using arbors that are too long for heavy work). Some of the tooling that came with my mill included a shell mill arbor and two full-length arbors (7/8 and one inch diameters).

Here's a photo of the shell mill with carbide inserts making a finishing cut on some HRS without coolant. The electronic flash did a good job of "freezing" spindle rotation:

http://i97.photobucket.com/albums/l219/randy9944/P1010956.jpg

This photo shows the full-length arbor with slitting saws and various spacers installed:

http://i97.photobucket.com/albums/l219/randy9944/P1010898.jpg

I wanted the ability to install intermediate length arbors so that the end support could be "choked-up" on any cutter (or combination of cutters) for maximum rigidity. That led me to consider simple ways of making arbors of any particular length and diameter.

Here's a sketch of a "typical" stub arbor. Although spindle interfaces are standard, the end configuration isn't. The end needs to be threaded for a retaining nut, turned to suit a bronze end-support bearing, center-drilled for a hardened end-support center, combinations of several options and so forth. Unless you're lucky, any arbor - used or new - is going to require some modification.

http://i97.photobucket.com/albums/l219/randy9944/arbors.jpg

The lower part in the sketch depicts a fairly simple arbor that can be made to any arbitrary length that suits a particular set of cutters. The material can be ground drill rod (or a semi-hard alloy of reasonable cost), I think three feet of ground one inch drill rod from Enco costs about $25.

But the ER-40 system has a lot more going for it than this single reason; that's why I decided to go ahead and buy collet chucks for several other machines. I hope that my experience with this system might be helpful to others who are considering it.

Cheers,
Randy C

Bguns
12-08-2010, 12:40 AM
I have run ER's TG100, R8, B&S, Rubberflex, and MT collets, and they all work to some extent. I prefer TG for tough work.

Using a collet to drive a 3 inch or larger keyed cutter on an arbor, is a poor choice.

The cutter will at some least wanted time, get hung/overloaded/clogged.

The arbor will then spin in your ER WUNDER collet, taking the collets precision with it. While spinning the feed is still moving, bending arbor or taking off more teeth/breaking cutter. Also possibly bending collet out of shape...

Collets are one form of toolholding, not the ONLY form.

A under $50, NMTB 40 1in or 3/4in endmill holder, would allow you to also use a flat (weldon style) on your arbor stub. And 1 in end mills, boring head shanks, etc. The end mill holder will also give you a lot more vise clearance without the clunky collet nut in the way.

The amount of runout on a typical milling machine saw cutter mounted on an typical arbor is a bit amazing..

randyc
12-08-2010, 01:15 AM
I have run ER's TG100, R8, B&S, Rubberflex, and MT collets, and they all work to some extent. I prefer TG for tough work.

Using a collet to drive a 3 inch or larger cutter on an arbor, is a poor choice.

The cutter will at some least wanted time, get hung/overloaded/clogged.

The arbor will then spin in your ER WUNDER collet, taking the collets precision with it. While spinning the feed is still moving, bending arbor or taking off more teeth/breaking cutter. Also possibly bending collet out of shape...

Collets are one form of toolholding, not the ONLY form.

A NMTB 40 1 or 3/4in endmill holder, would allow you to also use a flat (weldon style) on your arbor stub. And 1 in end mills, boring head shanks, etc.

The amount of runout on a typical milling machine saw cutter mounted on an typical arbor is a bit amazing..

Thank you for your comments, Bgun.

I don't recall suggesting that collets were the ONLY form of toolholding. I do have some NMBT-40 tooling and I'd love to have a full set of NMBT-40 stub arbors, shell mill holders, end mill holders, and so on. That's NOT going to happen - I don't support a family with this machine.

The machine (and the workholders) are not required for heavy work since I am a home shop machinist, as the forum title suggests. This post (and ALL of my posts) was intended for those who share my interests and do not own multi-horsepower machinery OR the budget for an extensive tooling inventory. I don't doubt that, for your needs, ER-40 may be a "poor choice" but CAT-40/ER-40 collet tooling systems seem to be very common in 2 - 3 horsepower production machinery - just a personal observation.

The tooling that you recommend is exactly what I didn't want - that was the point of the last couple of paragraphs of my post. Collet-held tooling is easy to make and completely adequate for my needs and probably for those of us for whom this is a "hobby". Industrial tooling is expensive and I do not have the option of deducting it from my self-employment tax.

Cheers,
Randy C

brian Rupnow
12-08-2010, 11:04 AM
I have an honest question, and I'm not being facetious here. Why do people use collets? Is it because of increased accuracy i.e. runout over that of a 3 or 4 jaw chuck?

photomankc
12-08-2010, 11:43 AM
I have an honest question, and I'm not being facetious here. Why do people use collets? Is it because of increased accuracy i.e. runout over that of a 3 or 4 jaw chuck?

In a lathe as I understand it... yes. You can easily beat a 3 jaw for runout and it's a lot faster than dialing in a 4 jaw. On the mill, since I have a by 1/16's set of ER25's I can hold most any drill bit in the collet and get much better runout than in the drill chuck.

If I start planning to chew out significant amounts per pass I generally go back to end mill holders or normal R8 collets.

Toolguy
12-08-2010, 01:31 PM
Also, on the lathe, with a lever collet closer and collet stop if needed, you can change parts with the lathe running. On a production run this saves a huge amount of time and effort over stopping the lathe, twirling the chuck key 2 times and restarting for each part. I use the lever collet closer a lot of times anyway just for the convenience factor. It is THE easy way to open and close a collet. For production on the mill I use a lever indexing head or an air powered collet closer. This is for 5C collets. I have a full set in 1/ 64 increments plus numerous specials. I also made a 5C to R8 adapter that comes in handy on occasion.

PixMan
12-08-2010, 01:44 PM
Personally, I'd always prefer using the lever-closed 5C collet setup on dad's lathe for fractional inch size parts or raw stock 1" and under. I use the 3 jaw for most other things because it's a 10" Pratt Burnerd Super Precision and runout is less than .001" everywhere. Failing those two options, we've got a 12" 4-jaw Pratt Burnerd chuck that's been mounted only once or twice so far. That's only because the other two options work as well as they do.

I have used ER collets in the smaller sizes (ER16, ER11, & ER8) for years. I think they're best used for toolholding rather than workholding, but whatever works best for you is the right choice.

Duckmang
12-08-2010, 02:34 PM
I recently bought a very similar set of collets with an MT3 arbor. They were cheap and I initially had real difficulty getting them to hold anything worth a damn. Figured I got my money's worth until I realized that the clamping nut had it's taper ground off center. After chucking it into the lathe and cutting a new taper on center they work like a charm. Now I find them near indispensable for many tasks.

djc
12-08-2010, 04:03 PM
...The lower part in the sketch depicts a fairly simple arbor that can be made to any arbitrary length that suits a particular set of cutters.

One possible pitfall with this is that it has no shoulder against which to tighten the cutters and relies on the ER nut to provide both this resistance and a true-running surface to keep the cutters true. Also tends to pull the arbor out of the collet as you tighten the cutter-retaining nut and as it self-tightens during use. Also, also means you have to run the spindle in the direction such that the ER nut is not loosened by the cutting forces (a lot of arbors have LH threads).

Easily solved with an integral shoulder on the arbor.

KEJR
12-08-2010, 07:47 PM
I response to Brian Rupnow, I like collets because they are easier to work with (5C collets), don't leave that many marks on the parts, and they are safer. You can hold your file or tool right up near the collet without nearly as much fear as when using a chuck.

As I have stated here before, I got sucked into the ER collet scheme for holding parts in a lathe and I think it is a sham if you want to hold short parts. You can make discs to put int he back of the collet to support it, but if I have to go through all that I might as well have used a chuck! Basically on a large collet like a ER40 you have to have maybe 3/8" to 1/2" into the collet to engage enough into the taper to lock down. On large parts or bar stock going through your spindle its not so much a problem though. On a 5C collet you don't have this problem at all.

KEJR

dalee100
12-09-2010, 12:49 AM
Thank you for your comments, Bgun.

I don't recall suggesting that collets were the ONLY form of toolholding. I do have some NMBT-40 tooling and I'd love to have a full set of NMBT-40 stub arbors, shell mill holders, end mill holders, and so on. That's NOT going to happen - I don't support a family with this machine.

The machine (and the workholders) are not required for heavy work since I am a home shop machinist, as the forum title suggests. This post (and ALL of my posts) was intended for those who share my interests and do not own multi-horsepower machinery OR the budget for an extensive tooling inventory. I don't doubt that, for your needs, ER-40 may be a "poor choice" but CAT-40/ER-40 collet tooling systems seem to be very common in 2 - 3 horsepower production machinery - just a personal observation.

The tooling that you recommend is exactly what I didn't want - that was the point of the last couple of paragraphs of my post. Collet-held tooling is easy to make and completely adequate for my needs and probably for those of us for whom this is a "hobby". Industrial tooling is expensive and I do not have the option of deducting it from my self-employment tax.

Cheers,
Randy C

Hi,

I think you missed his point. You don't need a full set of NMBT40 holders. Just one. Get either a 3/4" or 1" end mill holder. the set screw that holds the Weldon flat secure will provide better grip than an ER collet. Particularly on large cutters. Then you just need matching straight shank arbours with a flat for your face mills and boring heads or what ever other tooling you want to use. You can use the straight shanks you already have, just mill or grind a flat into them. Nor will it hurt their continued use in your ER collets either. Or make some new arbours yourself.

And as Bguns also suggested, those Weldon style end mill holders are often a lot more convenient to use in a horizontal mill. They reach over the solid vice jaw easier than a holder with a big nut on it.

I understand about the money part. But that one NMTB40 holder would have cost you less than half of that ER collet set and holder.

dalee

randyc
12-09-2010, 01:00 AM
One possible pitfall with this is that it has no shoulder against which to tighten the cutters and relies on the ER nut to provide both this resistance and a true-running surface to keep the cutters true. Also tends to pull the arbor out of the collet as you tighten the cutter-retaining nut and as it self-tightens during use. Also, also means you have to run the spindle in the direction such that the ER nut is not loosened by the cutting forces (a lot of arbors have LH threads).

Easily solved with an integral shoulder on the arbor.

First - the post evaluated the ER-40 system, rather than the afterthought of being able to quickly and inexpensively make an arbor for a special purpose.

However, since the arbor is now part of the topic, the sketch depicts a shoulder on the arbor that prevents the arbor from being forced into the collet (should the arbor not be bottomed against the drawbar). Spacers are always installed between the collet face (or any other toolholder) before a cutter is installed - otherwise the table can't be cranked close enough to the column for effective work. The spacer provides the shoulder function that prevents movement of the cutter.

I'm not getting the "pull the arbor out of the collet" thing. The ER-40 system offers a major improvement over other systems: dual tapers, front and rear. But perhaps that's not what you refer to - insofar as any other mechanism that would produce that effect, maybe I didn't emphasize adequately the point about being able to support the arbor by "choking up" ?

That was the entire idea of making short arbors. The overarm not only supports the free end of the arbor but also applies adequate axial pressure to prevent movement of the cutters (note the thrust washer in the sketch). Perhaps all horizontal milling machines don't include the features of my small machine.

I also don't get the "loosening" of the ER nut during operation - the only effect that could do so is the inertia of the nut - IF the spindle was reversed at some very high speed which is definitely not within the capability of any machinery that I own, LOL. (Check out the recommended tightening torque for ER-40 systems, as a matter of interest.)

Thanks for your comments.
Randy C

randyc
12-09-2010, 01:13 AM
Hi,

I think you missed his point. You don't need a full set of NMBT40 holders. Just one. Get either a 3/4" or 1" end mill holder. the set screw that holds the Weldon flat secure will provide better grip than an ER collet. Particularly on large cutters. Then you just need matching straight shank arbours with a flat for your face mills and boring heads or what ever other tooling you want to use. You can use the straight shanks you already have, just mill or grind a flat into them. Nor will it hurt their continued use in your ER collets either. Or make some new arbours yourself.

And as Bguns also suggested, those Weldon style end mill holders are often a lot more convenient to use in a horizontal mill. They reach over the solid vice jaw easier than a holder with a big nut on it.

I understand about the money part. But that one NMTB40 holder would have cost you less than half of that ER collet set and holder.

dalee

Thanks, for explaining and that is a good point. NMBT-40 end mill holders are great toolholders and it would be fairly simple to make 3/4 or 1 inch toolholders to fit a single holder ... but the ER-40 set works on THREE different machines, provides good performance and is very cost-effective.

The system covers 90% of the range that I normally require with LOTS of holding power. I can grip any particular piece of scrap (or the two or three diameters of OH drill rod that I keep around) used to make a temporary boring bar, reamer, angle cutter or whatever ... don't have to turn something to a specific diameter to accomodate the single NMBT-40 end mill holder that I own.

Cheers,
Randy C

edited to add: regarding Bguns comment, that little milling vise isn't a normal feature on the horizontal - there are a pair of substantial moveable jaws normally mounted on the table that don't have the drawback of the small vise (regarding the overhang).

dp
12-09-2010, 03:09 AM
I'm enjoying your posts. Your writing style is unrushed clarity and purposeful. Your posts are to this forum what TubalCain's videos are to YouTube. Interesting and well written.

Bguns
12-09-2010, 05:40 AM
Back again.

Any nose clamped collet adds significant overhang on spindle. Adding flexible joints to system, does not make it better... Run an arbor off of that and you have lost 2 inches of Y travel.

Young's Modulus has not changed. Steel bends.

Clearance is THE major issue with any job.. Enough is good.. Not enough and it is not going to happen.

Gee I guess a home machine has more Y axis travel than a production machine, and can afford to waste the travel................

I work on guns.. not exactly production. That is a 40 taper mill and has the power to slip any sub 2 in collet with a 3 inch or larger cutter in a second.

I could go to R8/ER and fit it to 4 of my machines, but R8 sucks as a collet (and even as a regular tool holder). A NMTB taper requires far less cranking, to make a tool change for example.

ER on my lathe.. NOT, (I have 5C) My lever 5C collet works just a bit faster than an ER nose nut..

Having an only collet system will be a headache if you have a DRO, tool offsets change in a collet... Sure you can work around by setting tooling off of work or vise, but why not just punch in tool #4 ????

My writing is not clear and concise enough, profusely illustrated with pictures on how WUNDERBAR the short grip length ER system is..........

SORRY. for my poor writing and larger 50 taper machine...

Been there done that.

How a simple 15 dollar used 40 taper end mill holder, is not good enough to drive a simple arbor is beyond me.. While retaining maximum clearance and minimum investment.

Spend money and dissagree if you must...

How many pages of this thread, are going to consist of duplicate quotes of a
simple previously written paragraph????

I think I can remember what I read in the last 15 minutes................

Toolguy
12-09-2010, 11:22 AM
randyc - Thanks for taking the time to show your different uses of the ER collets. I have a lot of solid Weldon holders with setscrew(s) and the ER holders and collets like you do. Each kind of holder has it's place. Each kind is better at something than the other. The important thing about this thread to me is showing others some options that they may not otherwise have known or thought about. The more choices one has for tool and workholding, the easier it is to get the job done.;)

2ManyHobbies
12-09-2010, 12:01 PM
Bguns, you are coming at this from a different angle than the OP. ER series collets are a good compromise on cost, function, and performance. They can hold work or tools (within limits) depending on your setup and machines and they can be shared among different machines for the low cost of a collet arbor for each system.

Sure I'd love to have an MT3 endmill holder for every size I need followed by a every MT3 collet with a 5C setup as well, but then I'd be washed for more money than I put in my lowly little 3-in-1 to start with. If at some point my income is more shop based than anything else, then it makes logical sense to have all of my tooling with the same offset (of course that means new machines and 3x more floorspace), retain some clearance, and save me some cranking on tool changes. Until then I'm in the same boat as randyc. It makes sense to spend 85% less on tooling that will work 90% of the time and handle the one-off needs as I get to them.

lazlo
12-09-2010, 12:08 PM
Wow, I've been using an (ETM) ER-40 collet chuck all these years, and never realized how special it was! :D

http://i164.photobucket.com/albums/u15/rtgeorge_album/Servo%20Plate/ServoPlate015.jpg

As I've mentioned in my posts before, the ER collet chucks, especially a big one like and ER-40, does substantially increase the stickout/spindle flex. And it takes a hell of a lot of torque to crank the nut down (140 ft/lbs for ER-40). But it definitely has it's place -- it's really nice if you're going back and forth between a bunch of different tools, including drills.

Like others have said, I prefer 5C's for stock holding, since it's a through-hole design, and will clamp extremely short pieces.

randyc
12-09-2010, 01:12 PM
Back again.

Any nose clamped collet adds significant overhang on spindle. Adding flexible joints to system, does not make it better... Run an arbor off of that and you have lost 2 inches of Y travel.

Young's Modulus has not changed. Steel bends.

Clearance is THE major issue with any job.. Enough is good.. Not enough and it is not going to happen.

Gee I guess a home machine has more Y axis travel than a production machine, and can afford to waste the travel................

I work on guns.. not exactly production. That is a 40 taper mill and has the power to slip any sub 2 in collet with a 3 inch or larger cutter in a second.

I could go to R8/ER and fit it to 4 of my machines, but R8 sucks as a collet (and even as a regular tool holder). A NMTB taper requires far less cranking, to make a tool change for example.

ER on my lathe.. NOT, (I have 5C) My lever 5C collet works just a bit faster than an ER nose nut..

Having an only collet system will be a headache if you have a DRO, tool offsets change in a collet... Sure you can work around by setting tooling off of work or vise, but why not just punch in tool #4 ????

My writing is not clear and concise enough, profusely illustrated with pictures on how WUNDERBAR the short grip length ER system is..........

SORRY. for my poor writing and larger 50 taper machine...

Been there done that.

How a simple 15 dollar used 40 taper end mill holder, is not good enough to drive a simple arbor is beyond me.. While retaining maximum clearance and minimum investment.

Spend money and dissagree if you must...

How many pages of this thread, are going to consist of duplicate quotes of a
simple previously written paragraph????

I think I can remember what I read in the last 15 minutes................

Clearly you are not in the same situation as I am. As you say, duplicate quotes shouldn't be required and I don't care to contribute further to what seems to be shaping up as an argument rather than what it should be: an exchange of ideas, suggestions and opinions.

You have no idea what machinery I own and to what use I put it. Nor do I have the least idea of what you are required to produce with your machinery. You're happy with your methods and tools, I am very content with mine and I'm NOT critical about how you do what you do -

Cheers,
Randy C

djc
12-09-2010, 03:51 PM
First - the post evaluated the ER-40 system, rather than the afterthought of being able to quickly and inexpensively make an arbor for a special purpose.

Your idea of an arbor has much merit, and my comments were intended to help you refine the design of it rather than as criticism.


...Spacers are always installed between the collet face... The spacer provides the shoulder function that prevents movement of the cutter.

With respect, unless they are prevented from moving axially on the arbor, they don't. Think what happens when you fill the arbor with spacers and a cutter and then tighten the arbor nut: one end of the assembly will press against the ER nut and the other end against the arbor nut. As the arbor nut is tightened, the force will try to pull the arbor out of the collet (the arbor is in tension and the spacer assembly is in compression).


...The overarm not only supports the free end of the arbor but also applies adequate axial pressure to prevent movement of the cutters (note the thrust washer in the sketch). Perhaps all horizontal milling machines don't include the features of my small machine.

This is a very unusual arrangement and means the arbor is over-constrained (have a look at ball screw support strategies). One end of the arbor is restrained axially in the spindle taper; the other end would normally be free to move axially (if for no other reason to accommodate expansion due to heat). The overarm support bearing conventionally provides radial support only.


I also don't get the "loosening" of the ER nut during operation

With hindsight, perhaps I should have said that my comments on the above relate only to UNkeyed arbors/spacers/cutters.

Imagine looking head on at a horizontal milling machine, with the spindle rotating clockwise. Hence the pointy bit of the teeth on the cutter face to the left at the bottom (and you would feed the table from left to right if conventional milling). As the teeth bite into the stock, the cutter will try to rotate anti-clockwise on the arbor and will transfer this force to anything it is touching (spacers, arbor nut, ER nut). Hence if either of the nuts have right hand threads, this force will try to undo them. As long as the cutter is keyed to the arbor, it is a non-problem, but with slitting saws especially, I always run with no key as then they rotate rather than shatter if they dig in.

randyc
12-09-2010, 05:37 PM
Let me discuss the following in generalities, nothing directed at any specific person, just random thoughts as they occur to me, OK ?

I'm unfailingly surprised at the amount of advice one can receive without asking for it, LOL. There seems to be a universal presumption that the OP has put absolutely no thought into his topic. Because I didn't take the time to completely discuss my reasons for choosing a particular configuration or methodology - or even a particular tool - that is not a basis for concluding that reasons don't exist.

This type of discussion seems to follow a common direction, depending upon the forum where the post originates - it's very interesting to consider. There are three types of metalworking forums where I have participated - although this applies to ANY forum having a common interest, doesn't have to be metalworking.

The first includes a membership that largely consists of those who earn their living with their machinery - an example of that group would be "Practical Machinist". (I am a long-time member of that particular forum and fit nicely into the definition of "those who earn their living with their machinery" up until a couple of years ago.) Discussions in that group can be lively but rarely do I infer a lack of professional respect between the members.

At the other extreme are the forums that are oriented toward those who are just beginning to learn about metalworking. Many of the people are so young that industrial arts classes never existed throughout their educational experience. The level of dialog among this type of group is rather elementary but the level of courtesy is very high. For the most part, the individual members don't know enough to question a design, a procedure, the choice of a certain tool. Not to mention the fact that most are too timid to voice a strong opinion because of peer pressure. Heaven forbid that one could be "wrong" and thus bring down the dreaded "piling on" effect, LOL.

And then there are forums like this one with a wide variety of members but mostly experienced ones. Having been absent from this forum for several years and recently rejoining it, I can note a difference in the "culture". In the past the average member tended to be an experienced amateur with extensive interests in other areas that are supported by the ability to make parts to implement designs or ideas for projects that do not necessarily include metalworking.

However it seems to me now that a larger part of the membership consists of those who might fit the loose definition mentioned above regarding the "PM" membership. These are folks who largely earn their living by metalworking and their interests are focused perhaps on the most efficient manner of removing maximum material in minimal time. It's healthy, I believe, to have a mixture of members that include those who practice the trade daily because we can learn from proven industrial methods and tooling.

The disadvantage, depending on the tolerance of the members and of the administration, is that it is very easy to stifle individual contributions. This particular post is a reasonable example, the purpose of which was to point out the utility of an inexpensive workholding system to others who may be interested in one that can be used on several machines. (The post quickly degenerated into why I couldn't/shouldn't do something a specific way, rather than staying on topic.)

As I've seen on so many forums (music, woodworking, engineering, bicycling, photography) there tends to be a hard-to-resist temptation to skim a post, rather than reading it. The impulse may be unintentional but the frequent result is that a member notes a nit-pickable technique, tool or suggestion and jumps on it - ignoring anything else in the post that COULD be useful. The reasons for this range from a genuine desire to be helpful down to a desire to demonstrate personal aptitude, experience, intelligence and so forth.

And that may also lead to the dreaded "pile-on".

The message when this practice becomes common is very clear: if one wants to avoid controversy and discourteous responses then DON'T POST ANYTHING. Because once the negatives start raining down, the entire point is lost and anyone who MAY have been interested originally goes elsewhere to read something more constructive.

I've observed MANY times that a post brings on a negative response that is clearly incorrect - and that MANY members KNOW is wrong. But they do not speak up, why rock the boat ? That's an individual decision, of course, but that attitude tends to spread and soon a forum sort of takes on an environment that tolerates discourteous behavior. (It's just an observation, I'm not trying to make a speech, LOL, nor am I suggesting that it has happened here !)

A few years ago, I did a survey on "Practical Machinist" about this sort of thing and asked members for their opinion on how an internet conversation should be conducted. A number of very constructive comments were made - maybe one or two of you participated:

http://www.practicalmachinist.com/vb/general/ot-questions-answers-part-2-a-191053/

It is interesting to note, from those who responded to the second summary, that confusion, misunderstanding and even confrontation may be here to stay - it seems to be accepted as part of the internet "experience. I don't buy into that, there are any number of forums where courtesy is the rule - even without heavy-handed "moderation".

Many people post here daily without controversy. And that probably has a lot to do with folks getting to know one another: who can offer practical suggestions and advice and who cannot. In other words, there may be an unconscious decision taking place when reading as to whether or not the OP has paid his dues. After guys have become acquainted (even if it's an internet acquaintance), it's natural not to attack or question another with common interests. Pecking order and the like ...

I've recently been considering another item of interest. I get the impression that some people don't like the way that I write, as odd as that seems. I was described by a long-time member once as being "snobbish" - that little problem was a typical misunderstanding and was easily straightened out to our satisfaction. I can't really do much about how I write because I also TALK like this, LOL. I hope that I'm wrong about this, I really do, because I'd not like to have to write like a high-school dropout in order to be taken seriously.

At any rate, if I choose to explain my thinking or debate, point-by-point, areas of disagreement, I'm regarded as either being "defensive" or "making excuses". Believe me, I've tried this and it does NOT work. So I'm going to decline to answer those detailed questions and thoughts provided in the last response. And that naturally brings up a third alternative: if I decline to answer then I must be copping out (= not having confidence in my opinions).

Readers will have to form their own conclusions about what I write and whether or not it has validity in a Home Machinist Forum. I can say that I've enjoyed a long and successful career, including owning and operating two businesses (the last one formed the basis for acquiring almost all of my metalworking machinery). I would still be operating that business, despite being past retirement age, were it not for medical problems.

I think that one should make the assumption that - unless a person is asking an obvious question - he has considered the reasons for posting the topic. That is NOT to say that he has considered ALL of them and that there aren't ALWAYS better ways of doing things. But it is pretty arrogant to assume that he hasn't considered how best to do something with the resources on hand and his particular skill-set.

Sorry for not being able to satisfy everyone but just satisfying myself is sometimes impossible ... so if I get THAT far along the road I figure I'm doing OK. When I was young I thought that I was right about 90% of the time - as my wife frequently reminds me, my actual batting average probably hovered around .500 !

Cheers,
Randy C