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A sloppy RF-45 mill/drill

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I bought a RF-45 that had been CNCed , and I put it back to manual use. After milling some slots of a motor mount, I'm getting little tired of the drama. The combination of a powerful motor and a gearhead exposes the center wear on the X-axis . No belts to slip. I've adjusted the gib so it's tight, almost too tight at the ends. I bought it used with a lathe for good deal. Since this is not a Bridgeport, I won't end up with a $20,000 machine, even if I get it perfect. Nor could I afford the tooling to arrive at that point. Nor am I looking for perfection, it's a used mill/drill for heaven's sake .I'm a retired miilwright, on a budget, but not unhandy. So my question , what tools can get away with and where to find them. I have a cheap BusyBee (Canadian Grizzly) granite 12x18 surfaceplate used for layout and a couple of babbit bearing scrapers.
 

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What do you mean by 'center wear'. Could it be the leadscrew + anti-backlash nut combination in the middle range of travel or some dimensional issue relating to the table or...? Dumb question but has the original manual lead screw been re-installed or you have the cnc ballscrew assembly in there?
 
The RF-45 or it's clones are pretty much ideal for space limited garages .The RF-45 is fair bit more substantial than the clones. Even a 8x30 baby Grizzly bridgeport is over $7000 Canadian landed. Yes, I would have loved a Excello, but any used machine would have involved a much greater rebuild and cost twice as much to start with. I even know where a Richmond #4 with an optional head is. They are an excellent British milling machine. It fills his garage and he can't unload it.

Speaking of rebuild, when I got it, the X-axis screw wasn't even fixed at one end, no dials on either x or y, and there was a hole in the top of the column which to me suggested CNC. Hey, he was a cabinetmaker not a machinist. When I pulled the table , I found all the adjustment was taken up on the nuts. I 'll have to at least replace the nuts, may be the screws as well. But with all that backlash, I don't think that's my problem.
 
I owned a Taiwan made '97 RF-45 until just recently, so am somewhat familiar with the machine. There are some issues that, lets just say come with the price point. I would say running wise they all are not exactly quiet & you wont plough a 1/2" end mill through steel at full depth. That should not come as any surprise though. But in terms of overall accuracy, column squareness, table X&Y movement, dovetail fit, gib adjustability... I had no issues there. It was actually a very accurate machine. The current version of this is like this PM. So if that does not meet the 'decent' criteria, next step up is a baby Bridgeport for about 2X the cost depending on country of origon. There really isn't much in between, new at least.
https://www.precisionmatthews.com/shop/pm-833t/

It sounds maybe yours got molested somewhere between CNC conversion or re-assembly. Or maybe was a Chinese version of an RF-45 which have been known to be a bit more problematic even when new. But I'm still confused as to what is your specific problem. If you are saying the gibs feel tight, but only on the ends, that kind of infers dovetail wear or warpage in the middle section. So with the table off, how do the surfaces look & how does the geometry measure? Can you twist or displace the table in the middle travel & measure with DTI but not on the ends? Are all the components that hold the screw, end bearing castings all tight? Is the leadscrew straight or bowed slightly?

If you have the OEM lead screw & bronze nut, both are in good shape & grub screw acting against the nut's slit has been properly adjusted, you should have minimal backlash & the table should move silky smooth. Mine still had about 0.005" backlash with plenty of use. And it would repeat to within a thou over most any travel against DRO. The anti-backlash adjustment is a bit hokey but also no different that 99% of Asian mills & lathes out there. OTOH if the nut threads are buggered or lead screw warped... something has to be wrong in order to exhibit problems, so its a bit of detective work unfortunately.
 

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Mine is Taiwanese '01, that I've had for 4 years. It and the DF1224g lathe ($1750)were one of my first purchases after retirement. We had one at work that was only ever abused as a drill press., we never had any endmills after the first batch. But I was impressed enough with it to pickup a used one. The local ones are labeled Advance, house brand for Thomas Skinner. When I needed parts I went to them ,but they didn't handle them anymore but had contact at Rong Fu. So dropped over the line and got parts from Grizzly. They fit but weren't nearly as nice. And yes ,one of the gears are nosier than the others.

I have over .020 " backlash all the way along, I can't see a brass nut wearing the lead screw that much. But the nuts have no adjustment left,. They are kinda simple aren't they. I'm not looking for perfection, or even good, just acceptable . I was milling slots for a electric motor base, I was hogging them out with a 3/8" 2 flute slot drill with .020 depth cut. On a motor base I didn't need precision ,just adjustability. Enough with the drama queen, time to fix.
 
If it is loose just in the middle, then you need to scrape it in to get it even again, adjusting gibs wont help because they pinch on the ends. Its not a horrible project, just a time consuming one. If it is scrapped in descent, then you have a good mill that will last for years with a little lube. Tim
 
Mine is Taiwanese '01, that I've had for 4 years. It and the DF1224g lathe ($1750)were one of my first purchases after retirement. We had one at work that was only ever abused as a drill press., we never had any endmills after the first batch. But I was impressed enough with it to pickup a used one. The local ones are labeled Advance, house brand for Thomas Skinner. When I needed parts I went to them ,but they didn't handle them anymore but had contact at Rong Fu. So dropped over the line and got parts from Grizzly. They fit but weren't nearly as nice. And yes ,one of the gears are nosier than the others.

I have over .020 " backlash all the way along, I can't see a brass nut wearing the lead screw that much. But the nuts have no adjustment left,. They are kinda simple aren't they. I'm not looking for perfection, or even good, just acceptable . I was milling slots for a electric motor base, I was hogging them out with a 3/8" 2 flute slot drill with .020 depth cut. On a motor base I didn't need precision ,just adjustability. Enough with the drama queen, time to fix.
The brass nut won't wear the lead screw much but the leadscrew can wear the brass nut.

Can you find a replacement brass nut(s)? Maybe the Grizzly ones would fit or fit with some modification?

Or do a ball screw conversion. No more backlash. There may be a kit to do it for that machine.
 
I contacted Thomas Skinner again, and ordered the lead screws and nuts. They do mostly industrial CNC, now., They have to order from Rong FU in Taiwan. Maybe some day I'll see them. I've had some long waits for parts from Grizzly, before. This could be a couple months or more.

Even if I only have a improvement of a couple thou from the new lead screws overall, any will help. This still will leave the dovetails on the Drama Queen to scrape. So back to the question of what will I need at the minimum and where to find the tools.

Oh, BTW, that was very good idea about the ball screw conversion, I never thought of that.

When I was in Grizzly show room Thursday , I did look, drool, at the mills. But a baby Bridgeport, same capacity, is $8000 landed here in Canada.
 
Look at the way scraping section on the forum. Most people would need a small granite plate, a camelback, a scraper...and lots of time...
Oh and a ballscrew wont hold if you are cutting, it will want to rotate, that is why manual mills are typically acme screw. Tim
 
https://www.surpluscenter.com/Power-Transmission/ACME-Thread-Lead-Screw-Nuts/

I'm in Australia, and you blokes over there at the top, have this bunch in your backyard. Yes, bought a bit of stuff from them. Even with freight, is a good proposition.
(Star note, what ever I did, don't do it again, it posted before I was finished) enter. tab ...something????
Buy, 2 nuts, to set up your own "adjustable backlash remover". I did it some years ago, on the Z axis, still adjustable and as good as a Ball Screw. Which, I have since done for X, ball Screws from Aliexpress.
More than 1 way to screw a cat.
Mark Needham
 
You can have one fixed nut and another that is seperated with a spring washer to remove the backlash, but i would make it out of brass, use a split nut, creating 2 nuts in one, then use 2 pins to keep the 2 nuts from rotating and the washer puts pressure on them to remove the slack, crap, I wish I had a pic
 
All Rong FU does for backlash adjustment is cut a slot in the nut block and have a bolt ( allen head cap screw) that you can tighten to take up the wear. Crude . Mine are all the way in ! Nothing left. I have a shop built 6" shaper that will get a version of the two nut backlash adjustment when I change over from 1/2"-13 UNC to 1/2"-10 Acme. Using an off the shelf acme rod, I think I'll need something like that.
 
All Rong FU does for backlash adjustment is cut a slot in the nut block and have a bolt ( allen head cap screw) that you can tighten to take up the wear. Crude . Mine are all the way in ! Nothing left. I have a shop built 6" shaper that will get a version of the two nut backlash adjustment when I change over from 1/2"-13 UNC to 1/2"-10 Acme. Using an off the shelf acme rod, I think I'll need something like that.
Make the slot larger?
Mark Needham
 
If you happen to find a source of nuts corresponding to your lead screw selection, possibly something like this principle could be adapted. Looks like he employed it on a CNC type machine. Other ABL nut assemblies I've seen are adjusted like a screw within a screw rotational adjustment but I'm not sure about how accessible it would be on the RF-45. It would be nice to be able to adjust them from the end without a major disassembly. Cant help you on ball screws. I asked that question elsewhere & the consensus seemed to be divided. The yes camp said it will work as long as you lock your table before every single cut (which is good practice). The no camp says that's different than electrically holding the leadscrew position like via a stepper motor. Above my pay grade. I guess try & find someone who has a working example.

There is no guarantee a Grizzly part will fit your machine. I guess if its cheap enough, not much harm in trying & maybe it can be adapted.

 
That looks interesting, but knowing my skill level, I think I'll end with something cruder for the shaper.

Tomorrow, I'll Email Jesse at Thomas Skinner a Happy New Year. It's only been a month. But that should remind him of the order. There is a warning there about imported machinery.

To put it in service, I did buy Grizzly parts. There is a considerable difference in finish quality between Chinese Grizzly and Taiwanese Rong Fu .

Lately , I've been working on some lapidary equipment for the wife. Just finishing a Frantom grinder/polisher as a Christmas present. . I'm guessing this one is from the '60s or '70s. Nothing more than an arbor that I'm mounting 50k and 14k 8"diamond wheels on. Tom and Fran , a husband and wife team,made them, that's where the name came from, kinda cute. The next project is used 24" rock slab saw. A millwright made this one. The feed was from a floor polisher, remember those, that packed it in. I got a 60/1 small Radicon for it, break that, to get the 2 or 3 rpm needed. But I'm always surprised more rockhounds aren't electrocuted . They are a bit stone age when it comes to electricity.

To get an idea of rock saws, here's a commercial one. https://www.kingsleynorth.com/skshop/product.php?id=94916&catID=842
 
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The spring loaded lead screw nuts will remove backlash and will compensate for varying wear of the lead screw as long as the applied forces don't exceed the spring force.
I use a similar concept on my Atlas/Craftsman 6 x 18 lathe. It works there because in virtually all of my use, the reactant force is outward. If I were performing operations like counterboring where the work will be pushing inward, any significant reactionary force by the work will defeat the preload.
On the other hand, a mill is run in both directions. Moreover, climb cutting will tend to pull the work into the cutter. A stiffer spring can be used to reduce the effect but with a stiffer spring comes increased wear on the lead screw and the nuts.
 
All the force in one direction is on the three little pins. An antibacklash would have to be able to take full load that the nut takes. This discussion is good, I have shop built shaper project.

I got a reply back, tomorrow I'll get the price. He has to figure it out.
 
That's a good point RJ, I was wondering that myself. Do you think this spring method is confined to benchtop CNC or is it also present in big boy machines (with appropriate spring sizing).

Downwind, I think the role of the pins is to allow the 2 nuts to float axially but not allow rotation between then, which would defeat the anti-backlash setting. Its kind of the same principle as the slit nut concept with jack screws to open the one nut side up relative to the other. But in that mode they share a common base where the slit doesn't separate them completely. Technically I think they open up with an axial component but also a bit of hinged action to it (not in a perpendicular plane to leadscrew if that makes sense). A little bit cheesy but they are used extensively in the imports.
 
I got a reply back, tomorrow I'll get the price. He has to figure it out.
I hope the price & delivery works out for you. Sounds like it is a newer machine than my ex RF-45. That vintage is getting to be slim pickins in the parts department. Modern Tool in Calgary did me a huge favor & located some parts for my same vintage 14x40 lathe. And it was significantly lower cost than another vendor. Might have something to do with their ongoing business with Taiwan or contacts. Not sure but just an FYI.
 
Anything machinery related is expensive, so the price did take some sweet talking of the chief financial officer. I'm a retired millwright, so I can't just work more OT. Air freight added $150. Delivery is the beginning of February.

It's an '01 . It does get a few bit of use, I can say up to this point it's almost paid for itself. I just don't have a believing audience for that one. But now it's going to have to do some pretty major work.
 
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