Here you can see the scales for x and y axes. We bought this mill because it came with a DRO. This tool can help improve efficiency and accuracy.
Next we removed the table, which moves along the x axis. The table is easily removed be sliding it off of the saddle onto some horses or another table. The knee(z axis) can be moved up and down to put the table at the right height. Loosening the table/saddle gib will also make it easier to remove the table. We used the steel table that came with the hand tapper. Before removing the table we had to remove the ball crank and power feed. This allows the table to travel right off the saddle without any parts interfering.
Keep in mind that you will need to support each side of the table around the feed screw. We used some scrap 2x4's which supported the table just fine. We estimate from two of us lifting the table that it weighs somewhere around 150 lbs. If the feed screw is not removed, it will need to be supported. Currently the feed screw is only supported by one bearing on the left side. This creates a cantilever and will create unnecessary stress. We used another scrap 2x4 to support the free end of the feed screw. The feed screw is a long screw that runs the entire length of the table.
Above you can see the saddle with the table removed, the saddle ways, the table/saddle gib, the feed nut bracket, and lots of nasty grease. We wish we would have known about the grease before buying this mill, but now it's something we have to deal with. Grease should have never been used to lubricate the ways on this machine; only way oil should have been used. Grease is good for lubrication, in the appropriate application, but here it only collects dirt, grit, and shavings. Over time the ways will wear prematurely, which is the case for us.
...and here is the reason why we think there is grease in our mill. You can see in the pictures above and below what look like fittings for a grease gun. There are a total of six zerks, for the six ways(two for each axis: x,y,z) on our mill. After doing some research I learned these fittings are called zerks. If I hadn't done any research I would have assumed that this mill required a grease gun, which I'm sure any novice would assume. This is probably what happened with our mill. The knowledge about these zerks was not passed down, and eventually the user kept putting grease in the mill. These zerks are actually a little bit smaller than the zerks that would be used with a grease gun. They are made to be used with an oil gun, which does commercially exist. We plan to remove all of these zerks and install a one shot lubrication system, that most mills now have.
Next up is the cross feed screw, which moves the saddle and table in the y axis. We removed the screws that hold the cross feed bearing bracket in place, which allows you to unscrew the assembly from the feed nut bracket.
Oh yeah! Show me more of that grease. This is the lower part of the feed nut bracket within the knee.
The feed nut bracket, which houses the feed nuts for the x and y feed screws, must be removed before the saddle can be removed.
Off comes the knee chip guard and the saddle shortly follows. Again, loosening the saddle/knee gib will make it easier to remove the saddle. All of the dovetail joints on the mill have gibs. The gib basically acts like a shim, removing any play in the dovetail joint, restricting the motion to one degree of freedom. The gibs are adjusted by a gib screw, which is how we loosened them.
We can see directly into the knee now. It's full of shavings, lots of shavings, which means this mill hasn't seen a good cleaning in a while. The knee has to come up to be removed. We started by cranking it up as far as it would go.
Before bringing the knee up we had to rotate the top of the mill so the head and ram would not be in the way. Then we cranked up the knee as far as it could go. We discovered later that cranking up the knee as high as it would go is not the best way to remove it. More on that later.
The elevating screw will only bring the knee so high, so we used some brute force to move it higher. Eventually we gave up and locked the knee in place with some wood. We estimate that the knee weighs around 300 lbs. We decided to continue the removal of the knee when we have a lift handy.
If we were to do this again, we would not crank the knee up all the way. Doing this actually damaged the threading on the elevating nut and screw. Above is the elevating nut with part of the first thread crushed by the weight of the knee pushing down through the elevating screw. The force of the weight also damaged the first thread on the elevating screw, which you can see below.
After discovering what we did, we were sorta upset with ourselves. We thought we knew what we we're doing, but it goes to show that eventually everyone makes mistakes here and there. This mistake would not be the end of the world so we were lucky. It's just part of the first threads that were damaged. This can be cleaned up and will not effect the operation of the mill whatsoever. If we had a second shot at this, we would remove the screws securing the elevating nut to the knee pedestal allowing the assembly to come apart all together. We figured since we made the mistake it was time to call it a day and take some time to prepare for the next part of the rebuild.
...to be continued.
For those going to remove the knee. Rotate the ram 180° and use the mounting hole on the rear of the ram to attach a come-a-long for lifting the knee. This makes it a one person operation and very controllable. My 2¢, for what it is worth.
ReplyDeleteThat's an incredible way to do it. I am a bit weary on how the ram can handle the weight, but would have prevented our problem. Can't be any worse than what we tried.
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