# mini mill gas strut



## John Rudd (Mar 5, 2012)

Any mini mill owners out there with the air spring kit from LMS?

Could some one please tell me the diameter of the gas strut rod?

I think it is 8mm but not sure...

and could you also confirm the length of the body please?


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## Ken I (Mar 5, 2012)

I don't know if mine is the same but my gas spring is a 22mm bore x 10mm rod and exerts a force of ±8kgf

I used to make these things and that is a very small force for a 10mm rod gas spring (it is capable of 110kgf at max. pressure)

Stroke is 265mm, body length 322mm - it is equipped with the same ball & stud fittings at either end.

Centre to centre distance for the balls is 625mm extended.

It is installed rod down in my machine - this helps keep the gas in - there is a small quantiy of lubricating oil inside - keeping the seal wet improves life (oil leaks a lot slower than gas - nitrogen or CO2).








Hope this helps.

Now I have to put the damn thing back - doubt its going to be as easy as getting it out.

Regards,
       Ken


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## moanaman (Mar 5, 2012)

I have the air spring from LMS also bought their belt drive . Best money I have spent. The mill no longer makes loud grinding noise in your ears and the head stays where you put it with the air spring.

Barry G


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## rake60 (Mar 5, 2012)

I have the LMS air spring on my X2.






If you are referring to the rod that connects the top of the air spring to the head,
it is 12mm with a M10 thread on both ends.

Rick


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## purpleknif (Mar 6, 2012)

I have the air spring but I had to modify the mounting for my mill. Mine has ribs inside the column so I had to extend the mounts and go behind it. Still works pretty good though. The extended rack didn't fit either. Anybody need one?


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## rake60 (Mar 6, 2012)

purpleknif  said:
			
		

> I have the air spring but I had to modify the mounting for my mill. Mine has ribs inside the column so I had to extend the mounts and go behind it. Still works pretty good though. The extended rack didn't fit either. Anybody need one?



That reminds me of something I had forgotten about.

I bought the extended rack for my X2 before I bought the air spring conversion kit, which comes with
an extended rack.

If anyone needs an extended rack for their X2, I have one still in the original plastic wrap and dragon
grease. It isn't doing me any good. I already had one.

I'll ship it out FREE to the first person who requests it.

Rick


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## gmac (Mar 6, 2012)

Rick;
Hand up for the X2 mill extended rack - if you don't mind shipping to west coast Canada!
Cheers Garry


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## John Rudd (Mar 7, 2012)

gmac  said:
			
		

> Rick;
> Hand up for the X2 mill extended rack - if you don't mind shipping to west coast Canada!
> Cheers Garry



Bu**er you got in there before me....damn time zone difference...

Waiting for the courier to deliver my new strut..
My column is solid and doesnt have the cover mentioned in the LMS kit...
So a bit of trickery will be needed to install the strut.


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## Ken I (Mar 7, 2012)

Are you sure its solid - mine is a hollow extrusion - I presume the "cover" is an end cap.

Ken


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## rake60 (Mar 7, 2012)

gmac  said:
			
		

> Rick;
> Hand up for the X2 mill extended rack - if you don't mind shipping to west coast Canada!
> Cheers Garry



I sent you a PM Garry.

Rick


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## purpleknif (Mar 7, 2012)

I still have the extended rack. Pay the shipping and its yours.


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## gmac (Mar 7, 2012)

Rick;
PM returned . Thanks again!
Sorry John!!

Cheers Garry


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## rake60 (Mar 7, 2012)

This is the original column cap off of my X2.






It took a hammer and chisel to get it off. It was a little on the stubborn side.
The Scottish temper kicked in and one last good rap knocked it loose.
_And then_, I had to re-tram the column to the table. :

Rick


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## rleete (Mar 7, 2012)

That'll show ya! 

Funny, mine popped right off. Hardly had to do more than threaten it.


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## petertha (Mar 8, 2012)

I keep this link handy because the mill is similar to my RF-45 & it looked like a nice installation. Cranking the handle gets to be a pain & mine is in an awkward position high up vs down near the base like his.

http://homepage3.nifty.com/amigos/60_Gas Spring/GasSpring-e.htm


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## Swede (Mar 10, 2012)

I added a gas spring to my homemade bench CNC mill to support the very heavy Z, and these things work very well. One thing good to know is that there are ADJUSTABLE gas springs out there... they are shipped very heavily charged, and there is a set screw that lets you bleed gas off until the spring is at a strength appropriate for the task.

Of course, you cannot ADD gas, so one must be careful not to bleed too much off, but they are not too expensive, and a worthy addition to a small mill.


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## gmac (Mar 25, 2012)

Karma point for Rick's generosity - X2 rack arrived! Thanks Rick!!
Cheers
Garry


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## miner49r (Mar 25, 2012)

I'm late for the party again. This is the one I copied for my X2 recently. It doesn't reach into the clouds and leaves room for DROs. The struts came off an old truck tool box and are rated @ 55 lbs each.
Alan

http://www.rysium.com/projects/189-mini-mill-modifications


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## Swede (Mar 26, 2012)

You've got a nice web site there, Miner... I live on an airpark in the Ft. Worth area, a neighborhood of pilots. We've got a 3000' grass strip, and everyone, more or less, is into aircraft, flying, and machining as vintage aircraft are restored and flown. I can't count the number of parts I've helped make for my buddies, especially bronze bushes and other simple parts. Several guys are into machine tools to support the hobby.

I love the mini-mill for the vast number of add-ons, improvements, and the like, that have been offered over the years. And the gas strut mod is definitely a good one.


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## miner49r (Mar 26, 2012)

Swede,
  Maybe I wasn't clear. That is not my website. I copied the cable lift from RysiuM. I'm sure he would be flattered by your compliments.
Alan


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## Brass_Machine (Mar 26, 2012)

miner49r  said:
			
		

> Swede,
> Maybe I wasn't clear. That is not my website. I copied the cable lift from RysiuM. I'm sure he would be flattered by your compliments.
> Alan



Hey Alan...

Do you have pictures of your version? I am curious to know how it works as well? Did you use the same gas springs?

Eric


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## miner49r (Mar 26, 2012)

Eric,
  Pictures are forthcoming. I have the mill torn down for mantenance. Should be back together tonight. Tram .
tomorrow.
Alan

As Promissed. My clone of the Rysium Compound Cable Lift.


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## miner49r (Mar 26, 2012)

Two more.


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## Brass_Machine (Mar 26, 2012)

Thanks!

I like that design. I think I am going to try to imitate it? I saw that rysium used gas springs with six inches of travel. Is that what you used? Do you find it limiting? Also, did you make your pulleys?

Eric


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## tomrux (Mar 27, 2012)

two ropes holding the weight means 6 inches of ram travel will be doubled to 12 inches of head travel.

Tom R


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## Brass_Machine (Mar 27, 2012)

tomrux  said:
			
		

> two ropes holding the weight means 6 inches of ram travel will be doubled to 12 inches of head travel.
> 
> Tom R



Derp! You are correct. Wasn't thinking about that.


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## techonehundred (Mar 27, 2012)

Your installation is looking really good. To me this brings up a question, So if you have two struts @ 55 #'s, even with the weight cut in half by the travel, will that be too much for the head since it only weighs 30#s? I am asking because I found a 50# strut with a 14" strokeat a local surplus store and was wondering if it was too much. 
 I also mounted my rack so that it sticks up about 3" above the column. It really does make a difference when trying to install 1/2" drill bits above the vice and work.


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## miner49r (Mar 27, 2012)

Eric,
  With the Z-rack extended above the column the head has a full 12" of travel. The gas springs I used have a seven inch travel allowing me to be preload them. You can see the 3/8" eye bolt and threaded coupler I used for loading the springs.
  My original thoughts were to use to dual rate springs when RysiuM showed me his setup. The gas springs made it a "no brainer". As RysiuM mentioned in his notes, there is a slight delay in the gas springs where the cable goes slack. (it is slight, yet noticeable) Maybe a combination of springs and gas springs would overcome this.
Alan


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## miner49r (Mar 27, 2012)

Tech100,
  There is quite a bit of lifting force. The #55 struts were salvaged from an old truck tool box and were my favorite price. Is a positive lift better than a floating balanced head? I don't have the answer to that. At this point "head drop" is no longer a worry. Your milage may vary.
Alan


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## petertha (Mar 27, 2012)

I was wondering the same thing. I suspect part of the issue is how they rate them. Is it's analagous to a spring, one would think it must be a function of their compressed % or position? Maybe maximum?

I would thing you would want the head it 'almost balanced' so it still wants to come down on its own but still makes for easy up-cranking assist within the typical range of the head, no? Floating up like a balloon after releasing the locks would be weird. 

Here is some sizing/terminology info I found, maybe helpful. 

http://www.mcmaster.com/#about-gas-struts/=guo2ju


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## Ken I (Mar 28, 2012)

The rate of pressure rise is proportional to the square of the diameter ratios (for a quick and dirty calculation).

For a 10mm rod, 22mm bore gas strut this wil be (10/22)^2 = 0.206

or a 20% increace in force over its stroke (guestimate).

More correctly for a proper V1 / V2 calculation if you start with a volume of 1.00 then less the 0.206 rod volume entering = 0.794

 1 / 0.794 = 1.259 or 26% increace in pressure

ie :-  1 / ( 1 - {[d/D]^2})

Normally there is a small quantity of oil for wetting and lubrication which will not significantly affect this - but some applications contain a lot of oil either as an end of stroke damper or to deliberately ramp up this rate.
Some are made with a large redundant volume (the rod is a lot shorter than the tube) to reduce the rate.

Ken


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## Blue_Rock (Mar 28, 2012)

Very nice mod Alan.


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## miner49r (Mar 28, 2012)

Thanks Simon,
  The credit really goes to RysiuM at the GrizHFMininill group. If I had to change anything I would put #40 struts instead of the #55 ones. I would have to buy them.
Alan


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## Max762 (Feb 20, 2013)

I just received my air spring kit from LMS and am about to install. I read somewhere while researching this mod that the LMS instructions where incorrect as far as where to drill the hole for the lower end of the strut. But, now I can not find that post again. 
Can anybody shed any light on this before I go ahead and drill the hole?


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## rleete (Feb 20, 2013)

That was my post over on Machinistblog.com.  http://www.machinistblog.com/forum/mini-lathes-mini-mills/lms-gas-spring-conversion/#p311


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## Max762 (Feb 21, 2013)

That's the one I was looking for, thank you. 
Good news is that they must have updated the instructions. The ones I received  say to place the hole 15" down from the top, which is  much closer to your number than the 12" figure they gave You.

Thanks again for your reply.


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## rleete (Feb 21, 2013)

I had emailed them back when I made that post.  Nice to see they are paying attention.  That kind of customer service is what keeps me buying from them.


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## ZipSnipe (Mar 3, 2013)

I know this post is old but I would like to ask Alan if he finds the stronger springs better for drilling operations?


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## zoltan (Jun 18, 2013)

I installed my gas spring not too long ago, but instead of drilling another hole in my column, I made a mount for the bottom which allows it to rest on the base. It seems to work fine:
http://benchtopmachineshop.blogspot.com/2013/06/mill-gas-spring-installation.html


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