# Is the Air Spring conversion for mini mills worth it?



## tmuir (Apr 4, 2009)

The OZ dollar is finally starting to climb back up against the US dollar so after waiting 5 months it looks like I may be able to afford the belt conversion kit got my minimill from LittleMachineShop.
I am also thinking about ordering the Air Spring Conversion kit.
http://littlemachineshop.com/products/product_view.php?ProductID=2258&category=879658189

Has anyone else purchased this kit and is it worth getting?

Thanks


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## rake60 (Apr 4, 2009)

I put the air spring on my X2 about the same time I did the belt drive conversion.







I really like it!
The original torsion spring would get tighter at the full down position and want to
push the head up while cutting. In the full up position it barely had enough force
to hold the head from dropping. With the air spring the pressure is constant no matter
where the head is. I'd recommend it.

Rick


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## tmuir (Apr 4, 2009)

Thanks for that.
AS long as the OZ dollar doesn't dip against the US dollar I will order it on Monday.


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## Tin Falcon (Apr 4, 2009)

I have love recommend the belt drive. the air spring conversion is on my wish/shopping list. 
Tin


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## websterz (Apr 5, 2009)

Go the really cheap route and build your own belt drive conversion...simple machining if you have a mill and a lathe. I did my own from plans I found online. I will be removing the torsion spring and installing a counterweight soon, all that will cost me is the price of a longer Z axis rack gear...about $30 US. The pulleys I will make, the steel cable I already have. So much more gratifying to make it yourself.


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## Speedy (Apr 18, 2009)

the air spring work if you convert to CNC?
I think its much neater then a counterweight.


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## websterz (Apr 19, 2009)

Speedy  said:
			
		

> the air spring work if you convert to CNC?
> I think its much neater then a counterweight.



If you are going to convert the machine to CNC you'll want to remove the rack and pinion arrangement altogether and go with a ballscrew. There is too much play, even in a tight fitting R/P gear, for precision CNC control. With zero backlash in the ballscrew there is no need to offset the weight of the head. On the contrary, the weight will actually improve performance by dampening vibration.


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## BobWarfield (Apr 19, 2009)

Some folks like to add an air spring or counterweight to increase the performance of the Z-axis for CNC. Many/most commercial vertical machining centers also do this. 

The point about the backlash is a relevant one for a manual mill. If you are successful with your counterweight, be sure you lock the gibs when cutting. You will have greatly reduced the force needed to make the head "push up" in the range of backlash. I don't know that this will affect accuracy, but I would think it could affect surface finish.

Cheers,

BW


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