[JTJT]

If you're going to take my pictures and drawings, it would be nice if you could get the information correct. This would be better posted in the existing thread.

Not sure what is incorrect about the post, and there is no other thread specifically about power drawbars for the Mill Turn. BTW- all those pictures and hundreds of others are on Google images- as I said, there are as many different designs out there as there are machinists.

[instructor37]

There was some discussion on another thread about adapting a power drawbar to the Mill Turn, and people often ask us if we offer that as an option. We actually built an air butterfly PDB many years ago on our Bridgemill model and it worked great. However back then, there was not as much CNC work as there is now, so we have sort of revived the idea and our factory is working on some ideas for the future. There are as many designs out there as there are machinists, but not too many off the shelf units available. They come in 2 basic types-
1. Air cylinder which compresses a drawbar with a stack of belleville washers to release tension on the collet.
2. The air "butterfly" wrench which loosens and tightens the drawbar threads.
Each has its own advantages and disadvantages.

The compressing air cylinder design is more complex because it has to have a floating design to compress the belleville washers while not putting pressure on the spindle bearings. The air cylinders, valve and air fittings are available, but it takes some engineering calculations to get the proper cylinder etc. And the parts will be more expensive than the butterfly type. However, once engineered it will be a faster and lower maintenance setup. You can buy an off the shelf unit like a Tormach and adapt it to the Mill Turn, but you are looking at 1200.00, which is pretty pricey, considering you could source the parts and make all the components yourself for a few hundred dollars. Here is a simple drawing of how the Tormach unit might look on the Mill Turn.
Attachment 333720 simple idea to attach the Tormach unit

Attachment 333726 Tormach style with belleville washers

Attachment 333728 The Tormach full kit

The butterfly air wrench design is very inexpensive- there are some units on E-bay for 130.00, and one can be built for around 50.00 in parts. The concept is simple, in that the air wrench tightens and loosens the drawbar and with some calculations, it will force the collet down as the drawbar moves up and bottoms out in the socket. Some designs have a lever that you can use to pop the collet loose. However, you will need a better quality drawbar,as the threads are being loosened and tightened a lot. Eventually, the thread on the drawbar and the collet will begin to wear and need replacing. Here are some pictures of variuos styles and a link to a how to build thread.
Attachment 333722 E-Bay unit for 130.00

Attachment 333724 DIY design for 50.00

Here's the link for DIY units
CNC Cookbook: Powered Drawbar for IH Mill

One thing you forgot about the butterfly style design is that the socket on the butterfly is usually in constant contact with the drawbar, meaning that when the spindle is turning, the butterfly wrench spindle is also turning, and that fairly loose connection between the socket and the drawbar will be pretty loud at higher rpm's.

[instructor37]

You can see my spindle is really noisy and runs much hotter then it should.

Not sure how we ended up over here, but I think I can see where your spindle problem is. From the image, all your heat is generating from the lower bearing. it could be something as simple as a seal that was damaged at installation or even dented while installing a tool. The seals run on the inner race, and if they get bumped, it is a very close distance to the cage that retains the balls. If the seal is hitting the cage, it will generate a lot of heat and also be noisy. I would inspect that bottom seal very closely. As an upgrade, I would go with a pair of single seal bearings, with the unsealed sides on the inside of the cartridge like the Skyfire where there is no chance of contamination. This would reduce the seal friction and heat by 50%. Happily, the single sealed bearings in the same quality are less expensive than the double seals- around 35-40.00 each. You could easily end up with a 7K capable spindle for 70-80.00 and an hour or two of labor.
Attachment 333742

[n1tr0]

Not sure what is incorrect about the post, and there is no other thread specifically about power drawbars for the Mill Turn. BTW- all those pictures and hundreds of others are on Google images- as I said, there are as many different designs out there as there are machinists.

The first picture you used is of the CAD model I designed and posted in this thread for retrofitting a SkyFireCNC QTC/Power-Draw-Bar onto a Mill-Turn, not a Tormach unit. The files required for others to make the adapter are published and licenced on Thingiverse under the Creative Commons, Non-Commercial, Share-alike licence, which means anyone can use/modify the design assuming they also share their derivative design and it is not resold for commercial purposes. Anyone needing the design files in a specific format can contact me PM.
Also The SkyFireCNC QTC system is already engineered with all the correct forces and they quoted me ~$300, not $1200. The nice thing with their stuff is that it really is TTS compatible unlike the "TTS-style holders" that shipped with my Mill-Yurn. A collet holder in a collet holder isn't what makes the TTS tool holders work, it's the pre-loaded shoulder contact with the face of the spindle which makes the tool holders more rigid and the height repeatable.

The second picture is not a Tormach-like kit, it's a photo I took of an actual Tormach PDB on a PCNC 1100 minutes after BigBlock asked about it.

Pretending like you just stumbled across my images on Google is a little insulting and quite unprofessional.

[n1tr0]

Not sure how we ended up over here, but I think I can see where your spindle problem is. From the image, all your heat is generating from the lower bearing...

You might be reading too much into the one image. The upper 2/3'rds of the spindle is hidden inside the beam and behind the sheet-metal shroud. The seals look fine from the outside, I have more pictures of those. This has been a problem since I got the VFD working. There is a good chance it may have been assembled/pressed together incorrectly 'tho, there were other problems with it. The dowel pin for the collet was set too deep when I got it, the hole for adjusting that pin was undersized, and instead of shimming the spindle, they appear to have used an angle-grinder on it's mounting face...

I'll definitely take it apart and see what can be done once I have a replacement from Skyfire. I'd like to keep the machine as functional as possible while I sort out all the other problems, like replacing the controller, the motors, getting the belts & pulleys sorted, etc. Now that we have a Tormach at my workplace, I can start fixing some of these parts. It's really hard to fix your mill at home without a working mill...

[JTJT]

[QUOTEPretending like you just stumbled across my images on Google is a little insulting and quite unprofessional.[/QUOTE]

Here's the link- scroll on down and you will find all the pictures and many more
https://www.google.com/search?safe=a...k1.T9V2WwbsUqY

[instructor37]

[QUOTE

I'll definitely take it apart and see what can be done once I have a replacement from Skyfire. I'd like to keep the machine as functional as possible .[/QUOTE]

Yeah, I think I would look into it before dropping 500.00 on a new spindle- might be able to upgrade it for the cost of a couple bearings and still get your 7K rpm to boot.

[n1tr0]

Here's the link- scroll on down and you will find all the pictures and many more

(flame2)
That's a thumbnail that points back to this thread. You're not fooling anyone but yourself. If you want me to post more pictures, just ask.

Attachment 333746
The motor in this picture looks a bit close to the PDB mount, but that represents it's closest position which would be center distance ~162.5mm with a 111 tooth belt. A 116 tooth belt would put it at 175 mm center distance and just past the mid-point motor slots on my machine. If anyone's talking to Skyfire and needs to figure out belt sizing for their machine, I'd recommend the SDP-SI calculator.