Which spindle taper - new knee mill purchase?

Hell all,

Getting ready to pull the trigger on a new manual knee mill (9”x49” / 3HP with Newall DRO X, Y, Quill & Knee) and have a few spindle options to choose from below:

R8
#30 NST
#30 NMTB
#30 QC

I would really like to hear which you would choose and any opinions you may have?

Planning to leave specific tools/ offsets setup for the small family of parts I make and have pretty much ruled out the R8 but look forward to all thoughts.

I thank you in advance!

Murf







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I use 30qc with a power drawbar on a etrak and it's great

It would really slow me down to go back to R8 and no power drawbar not to mention no cnc even if only 2 axis

I would never consider a 30 taper because of tool holder costs and availability alone. The R8 standard is world wide common. Before you pull the trigger,do your own tool cost comparison. Keep in mind that power draw bars are available in R8 as well. There are 2 standard threads for R8 draw bars 7/16-20 and M10. The metric thread is very rare, but they are out there. That is no issue though, I simply have two draw bars.

Murf said:

Hell all,

Getting ready to pull the trigger on a new manual knee mill (9”x49” / 3HP with Newall DRO X, Y, Quill & Knee) and have a few spindle options to choose from below:

R8
#30 NST
#30 NMTB
#30 QC

I would really like to hear which you would choose and any opinions you may have?

Planning to leave specific tools/ offsets setup for the small family of parts I make and have pretty much ruled out the R8 but look forward to all thoughts.

I thank you in advance!

Murf







Sent from my iPhone using Tapatalk

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I have 1 r8 and 1 NMTB30 both with power drawbar. NMTB30 is best by far.

Any #30. R8 is handy for small cutters but has limited driving tougue for shell and face mille. The R8 is simply not suited for shell mills, face mills, sweep tools, etc. Personally I'd prefer NMTB because most other versions will fit using the appropiate draw bar.

Naturally I have lots more to say:

A handy tip: the key in the R8 spindle is merely a dog point set screw intended to prevent R8 tool shank rotation as the drawbar is spun to effect tool changes. It has no significant torque capacity and will shear on even modest overloards. A few recent posts have hollered for help because a tool shank or collet was stuck in the spindle. There's a 99.999% chance the tool shank was spun in the spindle shearing the hardened dog point of the indexing set screw. The dog point spun with the tool, gouging up the pilot bore way up inside the spindle, in effect, locking the tool shank to the spindle. The tool in extreme cases can be very difficult to extract.

The #30 mill tapers you listed all have robust key drives. They will not slip in the spinde from torque overload.

BTW, it might be tempting for a noob to use #30 and R8 tooling interchangebly. Don't. The tapers may look the same but they are slightly different. R8 is 16 degrees 51 minutes, #30 is 8 degrees 17 minutes+. A significant difference - about 0.009" in the length of the taper - considering the customary fit tolerance for machine tapers is about 0.0002".

My turret mill has an R8 spindle. I bought it 40 years ago before I was aware of this vulnerability and, yes, the pilot bore is scored up. Since then I've had dozens of encounters with R8 equipped mill owners all with buggered spindles. My prescription is to remove the dog point set screw on reciept of the machine before you ever connect it to power.

I'd avoid the R8 for the reasons above. I only have used 30NMTB, not the other 30's you list, but I'd take it any day over R8.

I have qc30, and nmtb30 works in the spindle with a drawbar. Get a power drawbar too and you can use either or. The toolholder availability isn't that bad but you'll pay a little for them. Should only need to buy them once though. I have had the same experience as the others with the R-8 issues in pretty much every shop I've worked in. Once the drive key breaks and does the damage, most leave it out. Then there's even less drive torque.

mine is a # 30 and i wish it had been a # 40 as tooling is more abundant in # 40
but even with a ton of tooling included in the deal i would not take an R-8 in a new machine.

Yeah my machine was available new with a #40. Wish they'd have gotten that option! Tooling for that is everywhere. I'll still take #30 over R-8 though.

steve-l said:

I would never consider a 30 taper because of tool holder costs and availability alone. The R8 standard is world wide common. Before you pull the trigger,do your own tool cost comparison. Keep in mind that power draw bars are available in R8 as well. There are 2 standard threads for R8 draw bars 7/16-20 and M10. The metric thread is very rare, but they are out there. That is no issue though, I simply have two draw bars.

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You buck the stereotype of a German by prioritizing cost over everything. I certainly understand not wanting some obscure B&S or such but 30 taper is also very common the world over. ebay, shars etc... all have plenty of cheap nmtb 30 sets of endmill holders, face mills, etc... what else do you need?

If I were buying a brand new knee mill, I would certainly look for a 30 or 40 taper of whatever type. R8 is limited and really won't turn larger face mills and such . 30 or 40 should be no problem.

If I were buying a brand new knee mill, I would certainly look for a 30 or 40 taper of whatever type. R8 is limited and really won't turn larger shell or face mills and such as mentioned above. 30 or 40 should be no problem.

Thanks for the thoughts and past experiences fellas!
I spoke with the dealer again this morning and had him confirm with the tech guy at manufacturer that if ordered the #30 quick change spindle option that i would also be able to utilize the #30 NMTB with a drawbar and he said yes.
With that said I will be placing my order for the new machine.
If you all have any questions for me whatsoever, don’t hesitate to ask. Thanks a million for helping me decide!

Murf


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My mill is NMTB 30 taper--I'd certainly take that over the R8. No chance you could get a 40 taper instead?
I really wish that was what my machine was equipped with.

All of the 30 tapers interchange with minor modifications...

Machine Tool Shanks (Tapers)

#30 over R8 for me - every time.

Limy Sami said:

#30 over R8 for me - every time.

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Perhaps my preference of R8 over a 30 taper is misunderstood. Yes, the 30 taper is more stout, but only by a bit. Certainly the difference does not warrant the cost difference of tooling. Both R8 and 30 taper tooling is just fine for light mill work. I don't do heavy mill work on my R8 machine. I have 2 40 taper machines that I can use, but 90% of the mill work I do, I do on my R8 machine. It is simply easier to use.

Pay attention to Forrest about that stupid key, but also keep in mind his machine is 40 years young and still going with, I suspect the original spindle. If owning two mills is an unaffordable luxury, then a 40 taper is of course, a better choice, but not a 30.

steve-l said:

Perhaps my preference of R8 over a 30 taper is misunderstood. Yes, the 30 taper is more stout, but only by a bit. Certainly the difference does not warrant the cost difference of tooling. Both R8 and 30 taper tooling is just fine for light mill work. I don't do heavy mill work on my R8 machine. I have 2 40 taper machines that I can use, but 90% of the mill work I do, I do on my R8 machine. It is simply easier to use.

Pay attention to Forrest about that stupid key, but also keep in mind his machine is 40 years young and still going with, I suspect the original spindle. If owning two mills is an unaffordable luxury, then a 40 taper is of course, a better choice, but not a 30.

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It aint the stout that makes the 30XXX taper preferable. Its the positive keyed spindle nose drive. No up-spindle socket damage possible.

Forrest Addy said:

It aint the stout that makes the 30XXX taper preferable. Its the positive keyed spindle nose drive. No up-spindle socket damage possible.

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plus the #30 has a better direct collet, be it that they are rare and expensive

janvanruth said:

mine is a # 30 and i wish it had been a # 40 as tooling is more abundant in # 40
but even with a ton of tooling included in the deal i would not take an R-8 in a new machine.

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Now yer talkin'. 3 hoss is too much by far for R8 to handle.

30-taper CAN handle it, but 40 is both better-yet, and not terribly larger (50 sure as f**k IS..).

MOST of all? 40-taper (NMTB, CAT, BT, Ericsson...) is way to Hell and gone more common... thus lower cost and in far greater variety of holders and adapters, "QC" tribes included, with the larger market.

40 taper. NT40 can easily be converted to accept CAT40 tooling by changing the drawbar. Mine has the Maxi Torque Rite. Got a new drawbar and cut approx 1” shorter and CAT40 fits great.
What dro package are you going with? I went the newall Dp1200 and also have quip, x,y, knee readout.