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m10 draw bar torque for threaded 30 taper?

Beauvais

Aluminum
Joined
May 15, 2022
I have just converted my Bridgeport to a 30 taper spindle. I have a haimer probe and height gauge along with a 3 axis dro so I can quickly change out tooling and set my z to zero with ease, along with the poor runout of the r8 spindle original to the machine are a couple reasons I have done this conversion.

I have a test bar and upon first test I was getting roughly 6μm of runout at around 190mm down from the bar, nearer to the top the needle barely moves.

Does anyone know what ft/lbs the draw bar should be torqued to? I have read around 25, some less. Should the tool fall out the spindle when you undo the draw bar or will it be slightly pressed in?

I just want to make sure I do things 'by the book', as I've spent some time getting things setup and am very happy with the results so far, I dont want to break a draw bar or damage the tooling or spindle..

Thanks,
Zach
 
To update, I found that 26 ft/lb gave me the most consistent runout as less gave inconsistent results. A couple of my holders came loose without needing to be tapped out but some dont, but so far Im very happy with the consistency. This was after multiple tightening and loosening, same result every time.

 
First your conversion makes no sense to me. 30 taper tooling is much more expensive than R8 with no or little benefit. That said, draw bar torque is NOT what holds the the tool to the spindle. It is the taper. The draw bar simply provides safety insurance, so just snug is plenty good enough.
 
First your conversion makes no sense to me. 30 taper tooling is much more expensive than R8 with no or little benefit. That said, draw bar torque is NOT what holds the the tool to the spindle. It is the taper. The draw bar simply provides safety insurance, so just snug is plenty good enough.

Having far less runout in the spindle makes no sense to you? Also since torquing the draw bar correctly I have even less runout at the test bar and my tool holders, is this not a benefit?
 
I'm happy for you that you like the conversion, but a 30 taper BP is no more accurate, stiffer or more powerful than an R8 BP. It is the same machine. If you had an issue with the R8 spindle, you should have just fixed it. You would have saved yourself a lot of money.
 
I'm happy for you that you like the conversion, but a 30 taper BP is no more accurate, stiffer or more powerful than an R8 BP. It is the same machine. If you had an issue with the R8 spindle, you should have just fixed it. You would have saved yourself a lot of money.

I'm not sure how would I would have fixed it? Buying a spindle+vfd to re grind the taper? Buying a new r8 spindle? The cost is no difference really. And in regard to the bt30 tooling, there are far more options out there for which I need to do certain jobs I have lined up. I appreciate the comments but bare in mind the bt30 tooling is also a future proofing for a 30 taper cnc mill such as a xyz 2 op.

Also, its quite satisfying (and a relief) doing the work and seeing the accuracy after 😄
 








 
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