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  1. #1
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    Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    You can see more thermal pictures in the general Mill-Turn thread, but my spindle is really noisy and runs much hotter then it should. I've also got some build quality concerns because the mounting face of it was messed up by the factory in order to 'tram' the spindle and the access hole for the pin is too small to actually do any adjustments.


    I reached out to the guys who did the "how to build a CNC from scratch" thread, SkyFireCNC about getting a little higher quality spindle made. Their R8-80 spindle was almost the same size as the unit in the Mill-Turn and it comes standard setup for 6k rpm with optional 10k rpm bearings/balancing. It uses double angular contact bearings top and bottom instead of the single bearings in my Mill-Yurn. They also use an HTD style timing belt on their spindles, so I've requested a matching pulley for the stock motor with a 2:1 ratio. Right now my machine struggles/surges to reach the advertised 5k rpm (at the spindle) which is right at the ~120Hz/3600rpm upper limit @ the motor. The new 2:1 ratio should move the max rpm up to ~7k rpm without much of a drop in low-speed torque and with the timing belt, tensioning shouldn't be as finicky. I think it should fit between a 114-116 tooth 25mm wide HTD(5mm) belt.

    I've also designed up a simple mounting system for SkyFIre's power-drawbar (QTC system) which I believe is compatible with the real Tormach (TTS) system. I'll be releasing my adapter design files on Thingiverse. It's already been published and licensed under the Creative-Commons-Non-Commercial-Share-alike terms.

    Let me know if you're interested in participating in a group buy, there's already at least a couple others.

  2. #2
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Your spindle should have double angular contact bearings on top and bottom. My machine reaches about max temperature within a few minutes of running, then pretty much stays at that temperature for as long as it goes. I don't have a gauge, but I can hold my hand on it no problem. If yours is noisy and getting hot like your picture, then my guess is you have a bad bearing. Shopmaster has a 3 year warranty on parts, so I think all the units out there should still be covered. Another fellow posted about upgrading from grease filled to oil filled bearings for high rpm work. They are pretty pricey at near 300.00 each, but may be worthwhile in the long term. Grinding on the cartridge is not the proper way to tram- using shims is fast and easy, and JT has a nice file on how to do it. A note of caution on the tooth belt drives- I converted one of my earlier machines to tooth belts and it was easy to do, but they are very sensitive to alignment. A V belt can take misalignment and work fine, but a tooth belt just a bit off will want to walk off the pulley and wear the belt, plus it will make an ear-splitting whining noise at high rpm, a sound that will drive anyone nuts. I am really interested in that PDB unit as well, so PM me with the price and some specs. Your drawing doesn't show the detail, but to work properly, it cannot simply put downward pressure on the drawbar, it must support the drawbar upwards at the same time, or the pressure will destroy the top bearing in no time. The overall concept looks like an easy fit on the machine with only a little sheet metal cutout necessary to clear.

  3. #3
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    I'm aware my spindle is defective and improperly trammed by the factory, but the last time I sent something to Shopmaster for repair, it was some broken wires in the DRO and it took a full month for me to get it back, I think the lead time for a new spindle is only a bit longer and the current spindle should hopefully last that long.. I haven't taken my spindle apart, but the Norton_BMW guy did and his weren't double angular contact bearings and the part numbers he sent me match what I can read on mine.

    You bring up a good point 'tho, there seems to be plenty of deviations batch-to-batch with the Mill-Turns, so I'll post all my drawings so people can confirm whether this will fit their machines. This is not something I have any financial interest in, so I don't want anyone trying to hold me accountable if this doesn't work for them. That being said, if anyone needs the adapter mounts machined, I can probably make extras on our Tormach.

    We've got a Tormach PCNC 1100 with the power-drawbar at work now with the TTS system and it's just a ram pushing down on the bolt when actuated the same as SkyFire uses on their own machines. There might be a better method, but this seems to be working for a lot of people.

  4. #4
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Hmm- very strange, the numbers he quoted in his post are classed as Double row angular contact bearings, and the picture certainly looks a lot thicker than a single row bearing. Maybe you need to open your spindle up to be sure. I would like to see a picture of your Tormach PDB, because there has been a lot of discussion on their forum from guys designing their own, and it's universally agreed that direct downward pressure on the drawbar is a death knell for the top bearings.

    Here is a link to a guy who documented the construction of a PDB for a Tormach.
    Experience with the Tormach Milling Machine and Power Draw Bar

  5. #5
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Quote Originally Posted by BIGBLOCK1965 View Post
    I would like to see a picture of your Tormach PDB,
    Attachment 333562
    Let me know if you want any specific shots of it. It sure beats wrenching to change the bits constantly.. With the Mill-Turn it always seems like the sheet metal is in the way when it's time to change bits and it's so slow moving up and down, but I'm working on that problem as well.

  6. #6
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Quote Originally Posted by n1tr0 View Post
    Attachment 333562
    Let me know if you want any specific shots of it. It sure beats wrenching to change the bits constantly..
    Well it sure is putting pressure right on the end of the drawbar and the top bearing. Building one like that would be a snap, as those other styles require a lot more moving parts and extra machining. If it has been working fine for your Tormach, then maybe those other guys are just doing some of that engineering hand-wringing. So what you will be building is a mounting adapter for the Mill Turn, and then we would just buy the Tormach PDB- correct?

  7. #7
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Quote Originally Posted by BIGBLOCK1965 View Post
    So what you will be building is a mounting adapter for the Mill Turn, and then we would just buy the Tormach PDB- correct?
    I've designed up an adjustable mounting system for the SkyFIre QTC system which is very similar to the Tormach unit, but it's about $300 instead of $1200... I'll be posting the design for public/non-commercial use for anyone who would like to copy it for their Mill-Turn. If anyone can't machine it themselves, they're welcome to contact me via PM and we can work something out.
    The 10k spindle was also very well priced as was the custom/matching motor pulley. I'd contact Skyfire directly and talk to Defeng as the pricing on the custom parts was even better than their published prices.
    It'll probably be fairly late tonight before I can post up drawings and such.

  8. #8
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    [QUOTE=n1tr0;1938028] I sent in the DRO and it took a month for me to get it back,

    Sorry, I missed this bit on last response. I had an intermittent problem on my DRO as well, it would work fine, then sometimes one axis would blink off. After trying a lot of tests, we could not figure it out so JT asked me to send it back so his CNC guy could check it out. It arrived at his shop just as the CNC guy went on vacation, and he said he tried it on his machine and it was working fine. Just to save time, he sent me the unit off his machine. I had it back in a few days and put it on, all was fine and then BINGO, same problem. Finally I monkeyed around with the cable from the reader and found one of the pins was slightly bent. I straightened it out and since then it has been fine. But I found a nice surprise, the new display is the upgraded version with the Lathe-Mill display swap. As I'm sure you know, the axes designations are different on lathe and mill, which is not a big problem for manual work, but with CNC, it is confusing. On the mill X axis is longitudinal and is Z in lathe, while the Y mill axis cross slide becomes X in lathe and the Z in mill becomes Y in lathe. Trying to keep all this straight while reading the display and setting zero can be really confusing. The new displays are redesigned so that all you do is push a button and the readings from the scales will go to the proper axis in either lathe or mill mode.

  9. #9
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Here's the pdf/drawing of the spindle I have on order from Skyfire. I've requested a 30 tooth pulley instead of the 36 tho so I can pair it with a 60 tooth motor pulley for my ideal rpm range. The motor pulley will have flanges to keep the belt from walking and I plan to sandwich a thin optical encoder disk between the spindle pulley and the locknut.
    Attachment 333640

  10. #10
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Quote Originally Posted by n1tr0 View Post
    Here's the pdf/drawing of the spindle I have on order from Skyfire. I've requested a 30 tooth pulley instead of the 36 tho so I can pair it with a 60 tooth motor pulley for my ideal rpm range. The motor pulley will have flanges to keep the belt from walking and I plan to sandwich a thin optical encoder disk between the spindle pulley and the locknut.
    Attachment 333640
    Interesting, it looks like an identical cartridge to the Shopmaster, right down to the mounting holes- it should bolt right in place. My guess is that this is an off the shelf Chinese design from a spindle factory and the Shopmaster factory probably buys them there as well. The only difference I see is that the Skyfire uses unsealed bearings with the seals installed in the cartridge- do they run grease or oil bath? The flanges on the pulleys will prevent the belts from walking off, but unless the alignment is spot-on, you will get wear on the belt edge and that irritating whining sound, especially at 7500 rpm.

  11. #11
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Quote Originally Posted by BIGBLOCK1965 View Post
    Interesting, it looks like an identical cartridge to the Shopmaster, right down to the mounting holes- it should bolt right in place. My guess is that this is an off the shelf Chinese design from a spindle factory and the Shopmaster factory probably buys them there as well. The only difference I see is that the Skyfire uses unsealed bearings with the seals installed in the cartridge- do they run grease or oil bath? The flanges on the pulleys will prevent the belts from walking off, but unless the alignment is spot-on, you will get wear on the belt edge and that irritating whining sound, especially at 7500 rpm.
    It's actually a slight modification of Skyfire's R8-80 spindle that's been designed as a drop-in replacement for the Mill-Turn spindle using external measurements I took off my defective spindle. I asked them to include the flats on the face of the spindle so it can be tightened/loosened with a wrench so the PDB/QTC isn't required.

  12. #12
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    Re: Fix for Noisy/Hot Mill-Turn Spindle (& other upgrades)

    Quote Originally Posted by n1tr0 View Post
    It's actually a slight modification of Skyfire's R8-80 spindle that's been designed as a drop-in replacement for the Mill-Turn spindle using external measurements I took off my spindle. I asked them to include the flats on the face of the spindle so it can be tightened/loosened with a wrench so the PDB/QTC isn't required.
    That would be a great upgrade for mill turn owners- having a 10,000 rpm spindle available off the shelf that would bolt right in. Swapping out the spindle only takes a few minutes, so it could even be a way to change back and forth from the heavier milling to high speed operations. What is the price for the spindle?

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