Appropriate NMTB Size For New Mill...

[Ray C]

All,

I'm wondering what is an appropriate NMTB spindle size for the new mill I ordered (http://www.machinetoolonline.com/PM-45M-CNC.html) which has a 3HP motor. By default, it comes with an R8 spindle but, is easily changed to an NMTB type. I don't do heavy hogging operations on the mill and R8 has always been good enough but, it's fun to dream about an automatic tool changer were NMTB is more appropriate. So, given the size/power of the machine, what would be most appropriate, a #30 or 40 size spindle? These seem to be the more common sizes...

I was able to find this information (but not much else). This fellow's idea of a medium machine is 20-50 horsepower... http://www.tyler.net/drspiff/machining/collets/tapers.htm

Ray

PS: I posted a similar question on a CNC-related web site and haven't gotten any replies... Seems like a pretty basic question.

 

[sdconcepts]

nmtb 30 is more than large enough. I a little more rigid than r8. nmtb40 is overkill unless you have 15 hp.

 

[ssaxer1]

I have a 5HP CNC bed mill and it came stock with a NMTB 40 spindle. There many different brands of tool holders available from $ - $$$. I do not have a tool changer (would be cool) but I do have about 30 holders. I keep some permanently filled and loaded into my control ( I number them by 16th (ie a #4 is a 1/4 inch regular end mill.) For cases where I use a long aon a regular basis I number it with a 20 (24 is a 1/4 long). Makes it easy to remember when I am programming.

 

[110octane]

My 1944 Nichols "Hand Miller" came from the factory with what came to pass as a NMTB #40 spindle taper. Nichols originally used the predecessor of the #40 but the drawbar threads were smaller than 5/8 - 11 tpi with something like a 1/2" diameter drawbar. The overall taper and other details were worked out by the National Machine Tool Builder's Association in 1939 (this date may be incorrect, memory bad). The #40 taper is very congruent with this smaller mill.

I truly like the NMTB #40. A huge number of holders, arbors, collets, etc. are readily available for it and the overall picture of cost is reasonable. It is a robust, solidly driven design. My Nichols presently as a 2HP motor. Think about obtaining Brown & Sharpe and other less ubiquitous tooling. When CNC overwhelmed the manufacturing scene, tooling producers dumped tons of NMTB stuff. I haven't looked much at the CAT 40 but I imagine that it would not require much modification to use it in an older "manual" machine. The groove is incorporated for robotic tool changing and the drive tabs may be somewhat different (too lazy to research this). The cost goes up, too, especially with the trough spindle coolant feature. The "pull knob" on the rear of the CAT most always has 5/8 - 11 threads securing it to the drawbar hole in the holder, etc.

If there is room in the spindle, I would recommend the No. 40 NMTB features.
Geoff

 

[Ray C]

Ok, so here's where my learning curve begins... Thanks for all the replies. It's truly appreciated.

Subsequent to posting my question, I've learned there is "BT" tooling which is similar but not compatible (due to the drawbar mechanism) to NMTB. So, if you guys don't mind, I'll re-phrase the question...

For this machine, what spindle type (which might include BT or others) is best for this machine given it's size/horsepower taking into consideration the primary intention would be to support an automatic tool changer? Also, what is the appropriate size? (i.e. 30, 40)...

Sorry for not thinking this through the first time around but, there's a learning curve for me now...
As far as size, I don't necessarily prescribe to "bigger is better" and I think #30 is fine for a machine like this but, economics will be considered if it turns-out that #40 is a bunch cheaper and more available...


Ray

 

[110octane]

Ok, so here's where my learning curve begins... Thanks for all the replies. It's truly appreciated.

Subsequent to posting my question, I've learned there is "BT" tooling which is similar but not compatible (due to the drawbar mechanism) to NMTB. So, if you guys don't mind, I'll re-phrase the question...

For this machine, what spindle type (which might include BT or others) is best for this machine given it's size/horsepower taking into consideration the primary intention would be to support an automatic tool changer? Also, what is the appropriate size? (i.e. 30, 40)...

Sorry for not thinking this through the first time around but, there's a learning curve for me now...
As far as size, I don't necessarily prescribe to "bigger is better" and I think #30 is fine for a machine like this but, economics will be considered if it turns-out that #40 is a bunch cheaper and more available...


Ray

Overall BT tooling is metric and CAT tooling inch. The shoulder at the rear of the holder is of a different diameter and the drawbar setup slightly different. There is a lengthy discussion about the dimensional differences and operational interface on another forum. I am bound by agreement not to mention the post, but google will lead you to it. Suffice to say that it looks as if the systems may be modified to interchange (at least from CAT to BT) but with some difficulty.

As a basic answer to your question, since you are in the US (?), I think that you should dismiss the BT tooling and stick with the CAT system. As I understand it, the BT tooling is generally more expensive than CAT even if you are next door to the plant.
Geoff

- - - Updated - - -

Opps! Forgot to say use size No. 40. Best available and most economical.
Geoff

 

[Dan_S]

For this machine, what spindle type (which might include BT or others) is best for this machine given it's size/horsepower taking into consideration the primary intention would be to support an automatic tool changer? Also, what is the appropriate size? (i.e. 30, 40)...

Sorry for not thinking this through the first time around but, there's a learning curve for me now...
As far as size, I don't necessarily prescribe to "bigger is better" and I think #30 is fine for a machine like this but, economics will be considered if it turns-out that #40 is a bunch cheaper and more available...

I'M just a home shop guy, but everything I have read says that for a given taper all the different holder types are interchangeable if you are willing to make custom draw bars. I'm also considering going with a non R8 set up, and it looks like 40 taper is easier to find than 30, but either is more than enough than for a home shop machine. If you look at Hass for example they don't switch up to 50 taper, until the spindles get into the 30+ hp range.

 

[benmychree]

For a 3 hp mill, 40 taper would be overkill; I have a Fray vertical mill that came with 30 taper, and it would be entirely adequate, and personally I like it lots better than R8. I have found no difficulty finding adaptors for it on E Bay. I have a Brown & Sharpe #2 universal horizontal mill also with 40 taper on the horiz. spindle and 30 camlock on the universal (all angle) head, which I retrofitted to take 30 drawbar adaptors as well as the camlock holders, which ARE not so easy to find. With this modification, I can use the drawbar adaptors on both mills. I find that the camlock holders are not easier or faster to change than the drawbar type.

 

[Ray C]

LOL... Head is spinning and I know for sure, I'm sticking to my plan -which was: Order it with the R8 (because I have about $1500 in R8 tooling) then, upgrade it to something else when I get fancy enough for an auto tool changer.

Keep the replies coming and don't be shy to toss in other info as I'm on the steep side of the learning curve.

Ray

 

[DMS]

The Tormach tool changer runs with the TTS toolholders on a machine with an R8 spindle. It's doable. Not going to be as robust as an 30 or 40 taper, but I don't know if you will be able to push it hard enough to matter. Course the Tormach only has a 1.5hp motor, if you are pushing 3hp, the TTS stuff may get away from you.

Personally, I would love to have a 30 or 40 taper spindle. If I could get one for my machine, I would base it on the price of tooling, and I think that would lean towards some flavor of 40 taper.