# RF-40 'round post' downfeed improvements



## calgaryguy (Mar 29, 2022)

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









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

Gear Head Bench Type Milling Drilling Machine - RF-40




					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.






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?


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## calgaryguy (Mar 29, 2022)

This is the worm gear I am talking about (shown as part of/already installed in the side housing)









						FINE FEED ASSEMBLY at Grizzly.com
					






					www.grizzly.com
				




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









						FINE FEED CLUTCH ASSY at 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).


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## whydontu (Mar 29, 2022)

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.

Mt wife and I have been talking about a new business, dedicated to mediocre service. We’re going to call it The Good Enough Group. Started out with Good Enough Housecleaning -  slogan is “We‘re Cheap, But You Get What You Pay For”

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”


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## Tom O (Mar 29, 2022)

Couldn’t you cut your own worm gear with a tap?


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## YYCHM (Mar 29, 2022)

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.


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## turner (Mar 29, 2022)

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 =$$$.


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## YYCHM (Mar 29, 2022)

DIGITAL REMOTE READOUT 0 6IN. IN AND METRIC
					

Busy Bee Tools is Canada's largest Woodworking & Metalworking retailer. Find power tools, woodworking tools & metalworking tools at factory direct prices.




					www.busybeetools.com


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## calgaryguy (Mar 29, 2022)

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.


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## YYCHM (Mar 29, 2022)

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.



Mini-mills have the same arrangement and the same issue on top of the head drop problems.


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## calgaryguy (Mar 29, 2022)

YYCHM said:


> Mini-mills have the same arrangement and the same issue on top of the head drop problems.


Do the higher end square post like a PM-932/940 have the same issues?


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## YYCHM (Mar 29, 2022)

calgaryguy said:


> Do the higher end square post like a PM-932/940 have the same issues?



I don't think so, but I can't say for sure.


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## PeterT (Mar 29, 2022)

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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