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Head lift mod
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I like playing with my Patriot, trying to improve the precision and feel of it. Eventually I will build some neat stuff thats not for my patriot, but for now thats all I can think about. I got it to make wood lathe tools, but my wood lathe has been gathering dust while I learn how to machine metal. I lika the metal chips, there's no dust involved.
My most recent thoughts on tuning the Patriot are to add some 1/2" thick steel plates to the front and back sides of the millhead lift to add rigidity to the 4 columns. I bought some 1" thick plates to replace the top 1/2" and bottom 3/4" plate to give me something thick to bolt into.
I'm still thinking about the best way to reinforce the forward and backward spindle motion at the lift joint, any ideas?
I think I should be able to push on the spindle from any direction with about 50Lbs of force and get a deflection of around 1 thousandths; is this reasonable, ridiculous, or should I shoot for more?
Also, I'd like to bolt the Patriot to a couple of 52" long pieces of 2" x 3" x 1/4" thick steel tubing. Does anyone see any problems with that? Thermal expansion warping the ways or something? It seems like as is the mill is not directly supported, so I feel like raising it 6" and supporting it better, but I don't know a lot about how these machines twist and warp...
Thanks,
Ira
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Check out this thread
Head lift mod
The machine in that thread was one of the early style units with the original mill head bolted into a fabricated lift box. My quadra-lift was the same. The newer machines have the mill head casting with the four column holes bored directly through them. Because my quadra lift did not have the 5th column support, I tried the same idea to add a plate to the rear connecting the top and bottom plates. All in all it did not seem to make a lot of difference. I bolted the plate in place, as I was afraid welding would warp the assembly. I think finding a set of linear bearings on E-bay and retrofitting them would be a more paractical use of your time and money.Originally Posted by dgapilot
Thanks dgapilot for the link I was thinking of possibly putting a slot in the plates to accept keystock bolted to the mill head, but I dont think it's necessary, depends on if I get to where I want to be. I could have a crazy complex of scafolding around this thing before it's all over, that would give you all a good chuckleAnd I will post pics
I don't think it will get that out of hand, I did a quick finite element analysis that showed the four columns held the weight of the mill fine (negligible deflection change from bottom to top position), but adding 100 pound forces pushed the spindle around quite a bit. The analysis showed the plates to add significant rigidity, of course assuming they were molecularly fused to the top and bottom plates
This all started when I was trying to tram the head, and I didn't like how much my indicator moved when I pushed on the spindle. Some of the tramming posts talked about the lift binding after shimming for tram, which suggests the 3/4" bottom plate is deflecting, which I guess it should unless all four bolts were shimmed precisely into one plane or tapered shims were used. So, I thought if I beefed up the bottom plate (1" 1018), it would help the deflection and let me drill some proper badass bolt holes to mount my front and back plates onto. I guess proper shimming would be the easier route, but this is way funer!
Alright, I'm thinking out loud, Fastlanecafe is right, the fifth column has tremendous leverage on the mill lift joint and gives it way more support than any plate at the joint could. But I want/need it to move. So, maybe a linear bearing and rod assembly or dovetail-column at the fifth column. A piece of angle iron would fix the forward backward motion. Possibly a second jack screw would be needed, like the synchronized servos on router mills or a chain system to link the two. Very cool.
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That's what I've been toying with. Change the flimsy fifth column to a dovetail. The main problem is that the lathe bed is attached to the table and the table is not a rigid as I would like. Perhaps set the lathe bed on a plate at both the headstock and tailstock end, extend the tailstock plate outto the extreme edge of the table in the back and attach the dove tail back there.
There have been a number of comments about the fifth column getting in the way when working on longer parts. That's whay I would want to move it as far as possible from centerline and as far as possible from the headstock. Another advantage of using a dovetail would be to eliminate having to lock it. That way a stepper could be used on the head lift and control that via Mach, giving much greater Z movement.
That's still a while off. I'm working on my tool post holder to hold a BXA size quick change. Next I need to install my G251 to control the rotary table, and change the stepper on the rotary. I baught 3 steppers, all the same. One will be for the rotary table (I couldn't get any more of the one that came with the rotary, so I needed to change it), one will be for the tailstock screw and the last for some future project. That way I can use the same drive (G251), just with a different profile. The mill profile will be set up for the rotary tabel, the lathe profile will be set up to use the tailstock.
Just a matter of switching cables between set ups (make sure you power down the controller before cable changes!)
[QUOTE=dgapilot;681189]That's what I've been toying with. Change the flimsy fifth column to a dovetail. The main problem is that the lathe bed is attached to the table and the table is not a rigid as I would like. Perhaps set the lathe bed on a plate at both the headstock and tailstock end, extend the tailstock plate outto the extreme edge of the table in the back and attach the dove tail back there.
There have been a number of comments about the fifth column getting in the way when working on longer parts. That's whay I would want to move it as far as possible from centerline and as far as possible from the headstock. Another advantage of using a dovetail would be to eliminate having to lock it. That way a stepper could be used on the head lift and control that via Mach, giving much greater Z movement.
QUOTE]
Remember the 5th column is strictly for vertical load, so its plenty strong for any milling forces on a machine this size. To add some horizontal strength, a simple tie rod from the top of the column to the corner of the bench would give it all the triangulation necessary. A dovetail would have to be free-floating with no leadscrew, and defeat the purpose. As far as interference in turning, I cannot imagine any object large enough to tangle with the column being supported by the 5" chuck.
QUOTE]
Remember the 5th column is strictly for vertical load, so its plenty strong for any milling forces on a machine this size. To add some horizontal strength, a simple tie rod from the top of the column to the corner of the bench would give it all the triangulation necessary. A dovetail would have to be free-floating with no leadscrew, and defeat the purpose. As far as interference in turning, I cannot imagine any object large enough to tangle with the column being supported by the 5" chuck.[/QUOTE]
What I'm envisoning is that the dovetail would be significantly long, say 10-12inches in length where it attaches to a rigid 5th column. This would stop the mill head from racking. Without racking, the spindle is constrained vertically. Of course things can't be perfect and it would be worth looking at how tight the dovetail would need to be to allow acceptable vertical spindle motion. If it's too tight, you might as well build another 4 column lift, link the two, and have the added feature of a shop press
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That's what I did. I added an additional two column support to the end. Ran a chain between the two to raise and lower each end together. Doesn't look the prettist but it sure it stout. Now if I could get rid of the quill slop and table flexing I would have it made.
I would like to see a picture of that chain drive system- I thought of that idea, but was afraid that a chain would not be precise enough to keep both lift screws running together to prevent racking and binding.
As far as the quill issue is concerned, you brought this up in a seperate post and I asked some questions about your setup in order to offer you some tips. However, you never responded- do you want to get the quill tightened up?
I'd like to see a picture of that! Sounds very nice. To stop the table from flexing, I'm going to lift the lathe off the table and bolt two pieces of 2 x 3 tube steel to the bottom off it spanning the length of the table. Two more pieces of 2 x3 will run front to back at the ends and in the middle to support the long 2x3's and carry the load through the existing legs down into the floor. The extra length on the ends should give me some places to bolt a 5th column assembly, but before I go that route I would like to use the quill motion for CNC.
I've had pretty good luck with the brass tipped set screws on the quill, quill slop/rocking of course I won't know much about accuracy untill I get CNC running and I can start cutting circles over grid patterns. There is a little backlash in the Patriot's Z movement (it,s pretty small), but I like it tight. JT sent me an extra Z-axis leadnut so I could setup double nut backlash compensation, thanks JT!
Back to quill rocking in the bored casting, does anyone know of a way, like melting babbit, lead or something to make a perfect fit? How did they make a matched pair in the old days, usually it's something dirty but wickedly clever. Those giants rocked and we are blessed to stand on their shoulders.
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Its really pretty simple- like a piston in a bore- you need some clearance in order for the quill to move. There are several possibilities-
1. quill is undersized, or bore oversized
Depending on the oversize and as long as there is no taper, you could knurl the quill to tighten up the clearance- old school engine builders do this on pistons
2. quill is tapered or bore is tapered.
If quill is tapered, you could turn it true and then knurl it to size.
If bore is tapered, then you would need to strip it down to the casting and have it re-bored. If boring would bring it beyond the capability of knurling the quill to fit, then press in a sleeve and bore it to fit.
Thanks smallblock, that's exactly the kind of knowledge I was looking for! Is checking for taper more complicated than measuring bore and diameter at both ends? I didn't think of taper.
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