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CX605 Down Feed Tune Up

#1
Finally got fed up with the sloppy down feed and head drop issues on my CX605 and decided to do something about it.

RACK.JPG

Apparently the head drop issue has to do with the poor mesh between the column rack and up/down feed gear as well as the sprung head support system.

I tackled the mesh issue by shimming the rack out 0.02". I tried 0.013 first and that was fine, then I tried 0.026 and that was too much, so I settled on 0.02. There is still a wee bit of backlash between the gear and rack still. I may attempt to shim some more ...… will see.

I'll look at replacing the head support system if the head drop issue persists.

Note the key way in the shaft. The key for that is a major contributor to the down feel slop.

MESH.JPG

The slack in the mesh between the helical gear and handle seat is a big contributor to the fine fee slop. To resolve this I decided to try powder coating the teeth. It worked well and remove all of the slack when engaged. Only time will tell as to how long it lasts. I also powder coated the key for the rack gear shaft (see key way in first image). There was a lot of slop there. 3 PC applications made it fit nice and snug.

OVEN.JPG

If you're interested in trying powder coating, this is my setup. Pretty simple eh. 10min at 375F.

JOINT.JPG

Now I need to shim the slop out of this dumb a.. arrangement. Why this joint was necessary in the first place is beyond me.

Further updates as I piece it back together and test it out.

Later.
 
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Bofobo

Well-Known Member
#2
Finally got fed up with the sloppy down feed and head drop issues on my CX605 and decided to do something about it.

View attachment 4470

Apparently the head drop issue has to do with the poor mesh between the column rack and up/down feed gear as well as the sprung head support system.

I tackled the mesh issue by shimming the rack out 0.02". I tried 0.013 first and that was fine, then I tried 0.026 and that was too much, so I settled on 0.02. There is still a wee bit of backlash between the gear and rack still. I may attempt to shim some more ...… will see.

I'll look at replacing the head support system if the head drop issue persists.

Note the key way in the shaft. The key for that is a major contributor to the down feel slop.

View attachment 4472

The slack in the mesh between the helical gear and handle seat is a big contributor to the fine fee slop. To resolve this I decided to try powder coating the teeth. It worked well and remove all of the slack when engaged. Only time will tell as to how long it lasts. I also powder coated the key for the rack gear shaft (see key way in first image). There was a lot of slop there. 3 PC applications made it fit nice and snug.

View attachment 4474

If you're interested in trying powder coating, this is my setup. Pretty simple eh. 10min at 375F.

View attachment 4475

Now I need to shim the slop out of this dumb a.. arrangement. Why this joint was necessary in the first place is beyond me.

Further updates as I piece it back together and test it out.

Later.
My thoughts on the fine feed shaft is much the same as yours, i shimmed the joints as a temporary fix but i plan on a straight shaft, it should work.
 
#4
I put the little “air shock” mode on mine that I ordered from little machine shop and it head drop problem resolved..... of course still a limit to depth of cut but much better
 
#5
I shimmed the joints in that articulated hand wheel down feed shaft. I can't believe how much slop that eliminated between the helical gear and the hand wheel. She's tight now.

SHIMS.JPG

I'll wrap the union (name per parts list?) with electrical tape for good measure.

Powder coating the adjustable union (piece in the middle) would have been another option.
 
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PeterT

Ultra Member
Premium Member
#6
That is a curious application for a universal joint. You would think there is enough latitude in the bolt up assembly to accommodate any misalignment that a straight shaft would work? Interesting.
 
#7
That is a curious application for a universal joint. You would think there is enough latitude in the bolt up assembly to accommodate any misalignment that a straight shaft would work? Interesting.
No kidding! A internet blurb warns not to replace it with a solid shaft to. Makes me wonder if it's a work around for faulty dimensioning of the wheel support block and the down feed gear support block?
 

Bofobo

Well-Known Member
#8
I put the little “air shock” mode on mine that I ordered from little machine shop and it head drop problem resolved..... of course still a limit to depth of cut but much better
No kidding! A internet blurb warns not to replace it with a solid shaft to. Makes me wonder if it's a work around for faulty dimensioning of the wheel support block and the down feed gear support block?
so ... possibly some slots for the dial mount could allign that? Where was that blurb?
 
#9
so ... possibly some slots for the dial mount could allign that? Where was that blurb?
That blurb is here..

http://www.machinistblog.com/the-mini-mill-head-drop-problem/

It may simply be one of those "don't believe everything you read on the internet" situations. Dunno.

More on z-axis backlash here.

http://www.machinistblog.com/an-easy-way-to-reduce-the-mini-mills-z-axis-backlash/

Another thing suggested is to slot the screw holes on the fine feed worm gear mounting block as a means of improving the mesh between the fine feed worm gear and the down feed shaft.

I don't think I'll attempt that mod, I'm pretty happy with the improvement gained so far.
 
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#10
I shimmed the joints in that articulated hand wheel down feed shaft. I can't believe how much slop that eliminated between the helical gear and the hand wheel. She's tight now.

View attachment 4481

I'll wrap the union (name per parts list?) with electrical tape for good measure.

Powder coating the adjustable union (piece in the middle) would have been another option.
What did you use to shim that joint? I can't tell in the pictures. I was going to make a straight rod, but, now I'm going to look at the links you put up. I'm also curious as to why that joint is there.
 
#11
What did you use to shim that joint? I can't tell in the pictures. I was going to make a straight rod, but, now I'm going to look at the links you put up. I'm also curious as to why that joint is there.
I just used some .008 aluminum sheet stock I had. Cut little U shaped pieces out and jammed them in the hinge points to take up the slack.
 

Bofobo

Well-Known Member
#13
I like how this mounts, did you loose any travel? This same space is where i mounted my dro scale so the concept will not work for me but it is much more low profile than the MLMS.com version (theirs sticks out the top) but theirs extends the overall head travel allowing for bigger material or heavier tooling. My rack was shimmed with the steel banding that my mill was shipped with, and if i remember correctly an additional piece of shim stock
 
#17
Hmmm... the only PA strut that looks like it would work is 17 3/4" long and supports 47#. The stroke is 3/4" too short and 47# is a little over kill. The LMS version is 35#.
 
#18
I looked and it doesn't have a number on it. I just walked through the section in the store and picked one I thought would work. I don't recall what the rating was on it