Adding A Column Riser To A Solid Column Mini-mill: Lots Of Questions

Alright, wall of text time:
First things first, in facing off the cast iron with my homebrew fly cutter I noticed i kept getting these weird flakes as I was cutting. I just kept taking 0.007" passes until I found a plane that was clean so NBD really. Still weird though.

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Once I got done, I took the column+head off and saw what a packing grease and cast-iron-chip-filled mess it was so I decided to do a full teardown of the machine and give it the good cleaning and TLC it never got when I first bought it. I washed the dovetailed ways, gibs, leadscrews and everything else out with acetone, took off the saddle and the nuts that ride on the screws and cleaned out the threads. Then I painted everything in fresh lithium grease and reassembled.

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I also took the opportunity to install the DRO kit I've had laying around forever. I put the column back on to test the fitment of the blocks I made. Turns out the M8 bolts I ordered were too short so I rethreaded the holes in the base as 5/16" and got some 6" bolts from THD.

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The additional height made a HUGE difference. To make the most of it, I took the old z-axis rack from before I installed the air spring conversion and added it below the new one.
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I also bumped the current one up one screw hole so that extends above the top of the column casting. the head will come more than half off the dovetail before the rack flexes back enough for the pinion gear to start slipping. I backed off 3/4" from that point and installed a stop so that I couldn't go above that and strip the gear over time.


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I had a problem though: I realized with the 11" air spring I would not be able to get the head far enough down use small endmills on short workpieces. So I bought an M10 tap and made an extension for the rod that supports the head from some 3/4" delrin I had laying around. (I actually had to reassemble the mill most of the way so I could use it to get everything lined up and drill a straight hole through the rod. Oops :p)

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I had another problem though, with the extension in place I couldn't raise the head up high enough before the spring hit max extension to make use of my extra tall column. This is where the real inspiration struck. I replaced the lug that connects the bottom of the air spring to the back of the column casting with a tube that has a conical plug in the bottom.

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This way, when the air spring extends to its max length, it simply lifts off the bottom of the cone instead of binding. When you lower it back down, the cone shape centers the tip of the spring rod back to the same place in the center of the tube to avoid any side load that would ruin the seals on it. There is no support once it lifts off so you need to be careful to use the gib lock or fine feed clutch to hold it in place above that point. I also don't have a lot of confidence in the rigidity of the machine when the Z is maxed out like this but it's great for trying to get long drill bits into the drill chuck when you're near the limits of the work envelope.

The result of all this is pretty impressive. I now have a gigantic Z space to work in which should make my life a lot easier when working on the sides of my molds.This is the max height
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And the minimum. This is dictated by the height where the top connector of the air spring touches the top of the rack

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Once I got everything back together I tested the tram and the X axis is pretty much dead on but the the column was tilted a little forward in the Y axis. WIth a dial indicator in the spindle, the front edge of the table was reading about 2.5 thou higher than the back so I put a single 0.001" shim under both of the front column bolts and tightened everything back down. now there's about about 8 tenths between the front and back of the table (~4") and about 15 tenths left to right (~16") which I'm pretty satisfied with.
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My original fear about the riser killing what little rigidity this small machine has appears to be unfounded. I can still take a 0.030" cut with a 5/8" roughing endmill without any chatter so I'm pretty satisfied.

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I've already put the thing into use making this totally stupid and pointless wooden pistol grip stock for my mossberg 500.

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Also, here's a picture of the vertical stand I made for my portable band saw that I've been too lazy to make a thread about.

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Happy hacking!

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M2X7qZ4.jpg

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7JrgclC.jpg

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PUPta2g.jpg

qH96nca.jpg

qH96nca.jpg

UekdKAp.jpg

UekdKAp.jpg

7lgTcoe.jpg

7lgTcoe.jpg

eL4us8X.png

eL4us8X.png

MZ3NQBq.jpg

MZ3NQBq.jpg

NxDZson.jpg

NxDZson.jpg

WlpEW0S.jpg

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v5WFKXF.jpg

Neujbbe.jpg

Neujbbe.jpg

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Not sure why some of the pictures are huge. Anyone know how to fix that?
 
BTT because I'd really love to get some feedback on my work so I know what I can do better
 
Nice work TIGL, must do something similar to my mill someday:rolleyes:. Is that orange thing on the left in the second last picture the detachable power feed as I have a similar model?.
John.
 
Is that orange thing on the left in the second last picture the detachable power feed as I have a similar model?.
John.

That's the one! it makes tramming and vice squaring much less of a pain
 
Nice mod, I've been thinking of doing the same. What did you use for / where did you get the blocks? have you done anything else to stiffen the column?
sorry if I missed the answers in the OP.
 
Hi, Nice work , I have LMS3900 cnced mill.
Id like to mod onto colum base.
Can I get dimension of the riser?
 
The hole spacing is 135mmx50mm. I'd post the diagram I got from chris at LMS but he specifically asked me not to distribute it since apparently they're working on a factory riser.
 
The hole spacing is 135mmx50mm. I'd post the diagram I got from chris at LMS but he specifically asked me not to distribute it since apparently they're working on a factory riser.
They now carry a 2" riser.

Tom
 
Well, I read this thread so I could tell you LMS has a 2" riser. Lol. Old news I guess. I've got the solid column conversion kit on its way, along with the 2" riser. Wondering if anyone has doubled up and used 2 risers? I'm also glad to read you feel added stiffening isn't needed. I've got a stiffener on my tilting X2, and it made a huge difference. It's already got the 3900 oversized table, with powerfeed on both X and Y (the latter I designed myself) so it will be a lot like a 3900 once this kit is installed. You did a nice job! And I was wondering about the issues with the air spring lift, so I liked reading how you dealt with that. Well done! :)
 
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