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RF-40 'round post' downfeed improvements

C

calgaryguy

Chris
My neighbour has a RF-40 round post mill. Looks identical to this

rongfu.com

Gear Head Bench Type Milling Drilling Machine - RF-40 - RongFu

Gear Head Bench Type Milling Drilling Machine - RF-40
rongfu.com rongfu.com

The downfeed has a massive amount of backlash in it. Its atrocious - and its not consistent - sometimes it will be - .020-.025 and others its .035+. The downfeed mechanism looks exactly like the ones on a RF-30 round post mill, eg is below.

1648583261075.png


I removed the entire downfeed assembly on my neighbours mill via the two capscrews that hold it to the main body, cleaned and inspected it to see if there was a way to improve the backlash. I couldnt see any means for improving backlash, but was struck by how poor the worm gear attached to the front round fine adjust dial mated with the gear thats part of the side downfeed mechanism.

I'll be using his mill from time to time until i *maybe* get my own, and wouldnt mind trying to improve this aspect of his machine.

Does anyone know of any methods, resources, or common approaches for improving backlash in this downfeed mechanism?
 
Last edited:
This is the worm gear I am talking about (shown as part of/already installed in the side housing)

www.grizzly.com

FINE FEED ASSEMBLY - Grizzly Industrial

Grizzly P1006333A - FINE FEED ASSEMBLY
www.grizzly.com www.grizzly.com

And this is the main downfeed gear I'm talking about

www.grizzly.com

FINE FEED CLUTCH ASSY - Grizzly Industrial

Grizzly P1006332A - FINE FEED CLUTCH ASSY
www.grizzly.com www.grizzly.com

The worm gear in my neighbours machine shows only wear on about half (ie: 180 degrees) of it. I'm not sure if the shaft is bent slightly (it spins freely and doesnt seem bent) or if the center on the worm gear was bored offset (ie: bad quality).
 
I use one of these at my side gig. Never been able to get rid of the slop. My guess is the worm gear is bored offset.

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Then Adequate Auto Repair “It Should Get You To Kamloops”

And now we’re going to add Bodgers Tool & Die “A Few Thou Won’t Make A Difference”
 
My RF30 clone has the exact same mechanism and the same issue. A quill DRO makes the problem redundant. You could sacrifice a 6" digital caliper and cobble together a quill DRO.
 
I have a RF30, Back lash would drive me crazy, and required a more than talented hand to hit a given target. I put a simple Digital read out on the front, game changer, you actually know where you are now. I compensate for the backlash now by just a slight bit of quill lock drag/on. Nothing expensive, similar to a digital caliper mod, but you do not have to look at the numbers side ways ( Hobby Metrics $84 freight in ) not sure if they are still available/in business. There is something similar available for the Bridgeport's = Mitutoyo =$$$.
 
Crazy that such a bad design has propagated for soo long. I see the same type of downfeed mechanism on some precision matthews mill/drills.
 
calgaryguy said:
Crazy that such a bad design has propagated for soo long. I see the same type of downfeed mechanism on some precision matthews mill/drills.
Click to expand...

Mini-mills have the same arrangement and the same issue on top of the head drop problems.
 
I don't recall backlash being much of a huge issue on my prior RF-45 (Taiwan dovetail) mill. It felt about the same as a decent drill press. I do remember the graduated scale was a bit of inside joke. It wasn't inch or metric. Somehow the gear department wasn't meeting regularly with the dial department. But I had a quill DRO mounted which could be pre-zeroed with the tool loaded so that takes care of accurate depth & backlash simultaneously. For milling you must lock quill of course but I left the DRO on to see if the quill drifted. Generally it stayed pretty good. Sorry no experience with the round column style.
 
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