Newbie looking for expert advice on PCNC 770 and RT

[mega128]

Hi everyone,

I have decided to step into the world of Tormach and have some CNC experience with Carbide 3d Nomad 883.
I think it's time to make some chips. I am going for all the bells and whistles. ATC, digital probe, tool setter, 4th axis etc.

My questions is about Rapid turn:

Rapid turn Vs. Vertical milling
Why should I wait for rapid turn (waiting for it as it is out of stock) when one can use vertical milling...?
Is it slow or cumbersome to use vertical milling than rapid turn?
My need is to turn kinda washers but with threads out of cylinder rods that can be 1 inch in diameter or even up to 3-4"
Can rapid turn or main spindle be used with a 3 jaw chuck to hold and turn 3 to 4' cylinder shape stock?

Also, I would need a gang tool holder that will turn and part the components. What is the best advise for turning parts where I don't have to baby machine for each parth if I am turing 10 washers?

Thanks all,
Jay

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[kstrauss]

A few comments that may be useful:
The RapidTurn has a spindle sensor so threading is supported. There is no spindle sensor so no threading if you are vertical turning.

The RapidTurn comes was a 5C mounted 3-jaw chuck and you can also use a 5C pot chuck. The mill spindle is R8. I've never seen an R8 mounted 3-jaw but someone probably makes one.

The RapidTurn uses 5C collets which can pass a 1-inch rod which may reduce waste when making your smaller washers. With vertical turning you will waste an inch or so of each piece of stock since the drawbar prevents passing stock up the mill spindle..

With the horizontal axis of the RapidTurn you may get better chip removal (gravity assist) when parting. With vertical turning you'll probably need an air blast to clear chips.

You didn't mention material but with steel both the RapidTurn and the vertical spindle may have insufficient low speed torque to take a reasonable DoC.

Watch Keen's videos to get some ideas of what is possible with each choice. If washers are your only product the SlantTurn lathe is probably a far better choice.

Just a few quick thoughts. I'm sure that Keen and others will chime in.

[mega128]

Wow, I am already very impressed with the help I am getting here on this forum - Thanks very much Kstrauss, I really appreciate it.
I have space constraints in the basement and can't have separate turning machine. Based on the points you have made RapidTurn sounds like what I need. I will be milling/turning mostly aluminum and brass.
Occasional threading as well.

My next question would be about RapidTurn and 6" Super Spacer Motorized Rotary Table with 4ths axis kit.
I assume 4th axis can't turn and thread (at least not as fast as rapid turn). Correct?

I will be milling some small double sided parts on 4th axis using 2 jaw chuck (aluminum stock 4" plate).
The part will be a around 3 dia circular shape.
Is it possible to mill small parts as above when the plate is not too long, and no tail stock attached?
Would the vibration be too crazy? The tolerance is not critical as long part has descent finish.

Thanks again

[SomeWhatLost]

My next question would be about RapidTurn and 6" Super Spacer Motorized Rotary Table with 4ths axis kit.
I assume 4th axis can't turn and thread (at least not as fast as rapid turn). Correct?

I don't know about the 6" but my 8" 4th does live one complete revolution in like 10 minutes... well, it isn't really that slow, just seems like it, but anyway, it is just way to slow to do any sort of threading with... well, maybe if you had a week or so to wait...
I would imagine the 6" is about the same?

[kstrauss]

I'm not certain that I understand what you're making but I'm guessing it is something like threaded camera lens caps. If that is the case I think that you're not thinking about things the right way. I would mount a 3-jaw chuck directly to the mill table and hold cylindrical stock vertically. Then use normal milling operations to produce the desired diameter and profile, thread mill the threads and part off using a slitting saw.

Which orientation will you have the axis of the 4th axis? If the axis for the 4th axis is vertical then I don't see the point since mill movements without the 4th axis would give the same cuts with better rigidity and less complication. If the axis of the 4th axis is horizontal then the only way to cut threads would seem to be using a V-bit.

I'm having trouble visualizing the last setup that you mention. Tell us more about your parts and we might be able to offer better suggestions.

[IMT]

You might want to look into "The InTurn" 4th axis. It will cost about the same as the rapid turn and super spacer combined but can do turning and indexing.

[kstrauss]

Will it fit on the 770?

[mega128]

The part I am looking at is similar to lens cap as you assumed but for electronics projects enclosures and some other parts. I understand the process kstrauss mentioned using spindle and slitting saw. However, I need to have a machine that is ready for any unforeseen parts too. Therefore I definitely need a turning machine such as RapidTurn, BTW 4th axis i will use horizontally. The idea is to have all three tools (spindle, rapid turn and 4th axis) ready for disposal.

I really like the InTurn idea. Need to do some more research on this.

Thanks

[kstrauss]

You sound about like me; I make mostly prototypes or very short production runs and want to be able to produce whatever is required.
The super spacer seems nice (I have the older 4th axis) but do you realize the weight? With chuck I would have great difficulty lifting it onto the table.
The ATC interferes with the spindle mounted tool holder for the RapidTurn so it has to be removed prior to using the ATC.

[mega128]

The ATC interferes with the spindle mounted tool holder for the RapidTurn so it has to be removed prior to using the ATC.

This was going to be my next question. I am glad you brought it up. That means I can install rapidturn on the right hand side of table, may be?
Then the direction of tool holder (mounted on spindle) will be on the right hand side and I don't need to remove it before using ATC?

I am sorry I am a beginner and thinking loud.

Thanks

[kstrauss]

Sorta. The RapidTurn just mounts with the T-slots so it could go on either side. However, if you mount the RapidTurn on the right the motor may interfere with the front of your enclosure. Plus, I think, the conversational turning wizards (and maybe other stuff) will be confused since directions will be reversed. Also, look at Keen's videos for his enhanced tool holding system. I believe that I also posted some photos of my toolholders.

I've avoided these problems by not purchasing an ATC!

[mega128]

Thanks Kstrauss! I really appreciate it.

Can anyone please tell me the clearance between ATC (medium size cutters held in ATC) and 770 bed?

Thanks again

[IMT]

The super spacer seems nice (I have the older 4th axis) but do you realize the weight? With chuck I would have great difficulty lifting it onto the table.

So don't lift it. I have the 8" super spacer and it is too heavy for me to lift safely. I use a lift cart and raise it up to the same height as the table, put a 3/8" piece of particle board on the table and slide the SS onto the board, then kind of walk it off the board onto the table. No lifting required.

[kstrauss]

I mentioned never having seen a 3-jaw chuck with R8 shank.
See 4''/100mm R8 Precision Lathe Chuck, 3-Jaw Self Centering Scroll, #0225-0237 | eBay for one! I'm certain that there are other sources...

[IMT]

I mentioned never having seen a 3-jaw chuck with R8 shank.
See 4''/100mm R8 Precision Lathe Chuck, 3-Jaw Self Centering Scroll, #0225-0237 | eBay for one! I'm certain that there are other sources...

I have the 4" version that Shars sells. It works OK. The part ends up sticking out of the spindle too far and you can only do really light cuts. On one of the larger parts (4.5" dia) I ended up roughing it by milling and then machining a 3/4" diameter boss, 1/2" long so I can put it directly in the TTS collet when turning (basically recreated the geometry of a TTS holder on the end of the workpiece.) Much more rigid that the R8 chuck.