Appropriate NMTB Size For New Mill...

I have a Tormach PCNC 1100 in my garage and I use their TTS tool holders. My machine has their air operated power draw bar, and I can change a tool on about 3 seconds. If you only have 3 horsepower, NMTB30 tooling is way overkill, and if you have visions of building a ATC, your NMTB tooling will not work for that.

I considered the NMTB30 optopnal spindle when I bought my machine, but I decided the tool holders were far too expensive for what I wanted to do. I run my machine like a job shop machine, and have absolutely no regrets for my decision.
 
Ray,

you may want to double check to make sure a 40 taper is available as an option. When I was looking for a mill in that size R8 and 30 taper were the very common options but when I asked about 40 taper from multiple vendors it was not an option.

I went with 30 taper based on theoretical better rigidity and the shorter length. However, as everyone has suggested, the availability of inexpensive or used tooling is considerably less than 40 taper.

Just my experience, YMMV,
Arvid
 
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

Hey Ray your head spinnin, auto tool changers ? Power drawbars. Thought I had spinning head problems so I make my own. Nice to do during a
snow storm. Whats a auto tool changer? something from this century i guess. Nerer heard of it back in america (not this one the real one ,the twin
dimentional america)
 
If you get really fancy, believe it or not, a robotic arm grabs the tool on the spindle, a power drawbar mechanism unscrews the drawbar, the robotic arm puts the tool on a rack, it grabs the next desired tool, puts it in the spindle and the drawbar tightens up... The the machine goes and does the next cuts until it needs a new tool.

Don't worry... I'll be changing tools manually for a while to come (I'm still pretty well grounded in the Old America).

Ray


Hey Ray your head spinnin, auto tool changers ? Power drawbars. Thought I had spinning head problems so I make my own. Nice to do during a
snow storm. Whats a auto tool changer? something from this century i guess. Nerer heard of it back in america (not this one the real one ,the twin
dimentional america)
 
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.

[FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]Ray
[/FONT]

[FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]A machinist friend of mine recommends the opposite. his two main points are 30, 40, 50 taper machines all have larger tapered surface and are thus more rigid, he also mentioned that you can usually get less stick-out than you can with R8.[/FONT]
 
I am using the Tormach’s tooling system on my PCNC 1100 as well, and it seems to work well. As far as the higher horsepower on your mill, it depends on how that horsepower is delivered. I notice that the machine comes in a step pulley arrangement and a variable speed arrangement. The 90 RPM speed on the step pulley means it is delivering that 90 RPM at a full 3 hp, which gives quite a lot of torque. The PCNC uses a Variable Frequency Drive, so it has almost no torque at speeds below 200 RPM. If you are opting for the variable speed machine, it depends on whether they use a variable pulley system or a VFD as to whether you have a lot of torque at the low speeds. Low speed and high torque are the combination that makes using the NT tapers with their drive lugs worthwhile on smaller machines. You see it on smaller horizontal mills, as even a relatively small horizontal mill might be swinging a 6" HSS cutter at 50 RPM and full hp. I've used the TTS with up to 3/4" EM in mild steel with no problems. I have to take very light cuts and run at about twice the recommended speed for a 4" HSS slitting saw in steel due to the low power at this speed, so there isn't much strain on the spindle that way. I would determine if the mill you are getting will be the variable speed or not, and if so how that speed is varied. If it uses the VFD for speed control, I think the TTS would do a good job for you. Otherwise, the prior suggestions as to which you can obtain and has the cheapest tooling is valid. If you decide on the TTS system or for anyone using collets, there is a good white paper on the Tormach website on proper preparation of collets for use. I had some problems with tools coming out of collets until I read that and implemented the recommendations. I have no problems with tools slipping now.
 
The full torque at the motors rated speed. For a 1 hp motor at 1750 RPM that would be 3 lb*ft of torque. Horsepower is defined as (torque (in lb*ft) x RPM)/5252. So what they claim is constant torque up to the motor design RPM, then constant Hp above that. What that means is that with a 1750 RPM motor, at 875 RPM you will have half the horsepower. The horsepower increases linearly from 0 RPM up to the design RPM, at which point the VFD limits current to maintain the design Hp of the motor, which reduces torque. So if you are direct driving the spindle (1:1 ratio) then at 200 RPM with a 1750 RPM motor using a VFD you will have about a tenth of a Hp available. Constant torque sounds good in the marketing literature, but what it means is the motor has very little power at low RPM.
 
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