January’s theme seems to be the setup of the RF-45 milling machine. After it got mounted on its stand last weekend it was time to take a closer look at it. I knew that when I had decided to buy a clone there were going to be issues. I considered my purchase of the machine simply as a starting point on the road to getting a useable machine. The assembly of the machine is, in my opinion, terrible. I don’t think the clone I got is any worse then other clones it’s just that you get what you pay for. The most noticeable issue was how poorly the x axis and the y axis move. Some sections of the lead screws were tight and choppy, others loose and chattering. The backlash in the lead screws also seemed to be excessive. I consider the machine unusable out of the crate. I decided to spend some quality time with the machine and get to know it from the inside out.
Before I continue on with what I really have to say I thought I would give an opportunity for a short 3 minute break. Some visitors to this blog have no idea what a milling machine is, many of you do. If you are one of those that keep scratching their head every time you hear the words milling machine then scratch no further. I have posted a video made by Glacern Machine Tools that is a very basic intro to what a milling machine is capable of doing; it also clears up the whole x,y,z mystery. If you are one of those that know what the equipment is used for then just skip the video and carry on.
My main focus was to get the x and y tables to move smooth and precise. I started by removing both the cross feed and the table feed off the base of the machine. The removal process was fairly straight forward and logical with the exception of the tapered pins that center the lead screw end bearing plates. It took a 4mm x .70 screw and a slide hammer to pop them out however once removed the rest came apart easy.
Once I had the table dissected on the bench some of the main issues became evident. The ways and the lead screws were all lubed using a heavy, thick grease. I have no idea what kind of grease it was that was used but it resembled something close to Silly Putty. Every moving component had this grease on it making it impossible for tight clearances to move smoothly as well as makes fine adjustments of the ways and lead screw nuts impossible. The precision ground ways looked to be in good shape except for the holes where the gib locks were drilled. The bore of the holes that contact the gibs had burrs, once again, making proper gib adjustment impossible.
I had no idea how backlash was adjusted on the leadscrew nuts until I actually got my eyes on the nuts. The nuts have got a slot cut half way through the nut that runs parallel with the threads of the nut. There is then an Allen head adjustment screw that allows you to vary the pitch of the lead screw nut thereby adjusting the backlash out. Without changing the adjustment of the leadscrew nuts I cleaned the grease from them and the leadscrew. With all components spotless I inspected the factory backlash adjustment of the nuts. Not even close! Granted it was next to impossible to adjust with all the thick grease gooped in the threads.
Up till this point it was looking like all that was needed to improve the movement of the tables was a good cleaning, lubing, and a few adjustments. That is until I looked at the lubrication points, what I meant to say was the lack of lubrication points. The ways and the leadscrews had no convenient way of regularly lubing the contact points. Some machines come from the factory with one-shot lube systems and others can be retrofitted. One-shot lube is simply a way to lube all the required points of a machine from one central oil pump. If you’re interested in seeing the conversion done on a similar RF-45 clone you can visit the CNC Cookbooks website. I chose not to go to the degree of installing a one-shot system however I was prepared to start drilling and tapping the ways and lead screw nuts for the installation of hydraulic oil fittings.
So the game plan was this; clean all components, de-burr any rough holes that come into contact with the ways, drill and install oil fittings, and then reassemble and perform adjustments.
A trip to a local industrial parts supplier got me an Ultra Cut Gold Hi-Tungsten and Hi-Molybdenum ¼-28 tap, a heavy duty cobalt 135 degree split point 7/32 drill bit, and a 25 pack of Alemite 8000 psi hydraulic oil fittings. I was unsure just how well the cast iron of the milling machine would drill and tap. Clamping the milling table to the drill press, setting my cutting speed to 340 rpm allowed me to drill through the casting like it was butter. It reinforces, in my mind, just how drastic the difference in quality is when working with good cutting tools. I needed to install a total of 10 fittings, 8 for the ways and 1 in each lead screw nut. All fittings would be accessible with an oiling gun except for the lead screw nuts. I choose to install some 3/16” oil resistance vinyl tubing to the lead screw nuts that have oil fittings with the check balls removed. I then built a remote mounted oil fitting console that will allow me to get oil to the leadscrew nuts. On 2 of the ways the gibs also needed to be drilled to allow the oil to reach the lube points.
Drilling and tapping for oil fittings was only half the job. Since both the cross feed and table feed are supported on 2 planes the lube points had to be doubled. I ended up cross drilling into all the holes I had previously drilled. This way both the horizontal and vertical planes for all the ways can be lubed from 1 oil fitting.
I used my electric ¼ sheet sander to remove some of the factory paint. I cleaned off all the paint from the x table as well I cleaned the base of the machine just under where the cross feed sits. I prefer a clean metal surface near all the “business ends” of the machine. Since some of the blue paint on the lead screw end plates got chipped upon disassembly I opted to sandblast and paint them Tremclad grey.
Once all the cleaning and surgery was complete it was time for reassembly. All components were pre-oiled using straight weight 30 motor oil. The assembly started with installing the cross feed and adjusting the gibs. Then the cross feed lead screw nut got bolted in and the backlash adjusted properly. Next came the table feed and gib adjustment along with the backlash adjustment on the table feed lead screw nut. The table feed end plates got installed along with the gear for the power feed.
Time for a test drive. Wow! What a difference. The movement of both cranks for the x and y tables were smooth and precise. I ended up just standing and spinning handles for awhile, it felt like butter. I was concerned that I had the gibs adjusted on both tables a bit tight however the movement of the lead screws show no indication of over tightening. Needless to say the machine feels very useable at this point.
The fix took a week of my time but I would say it was effort well spent. As for what is next, I am still working on setting up the tooling. No chips will be flying just yet. Perhaps I will focus my attention back onto the coolant splash shield while I await my tooling orders to arrive.