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CX605 Down Feed Tune Up

YYCHM

YYCHM

(Craig)
Premium Member
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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YYCHobbyMachinist said:
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.
Click to expand...
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.
 
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
 
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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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.
 
PeterT said:
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.
Click to expand...

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?
 
Bfb123 said:
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
Click to expand...
YYCHobbyMachinist said:
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?
Click to expand...
so ... possibly some slots for the dial mount could allign that? Where was that blurb?
 
Bofobo said:
so ... possibly some slots for the dial mount could allign that? Where was that blurb?
Click to expand...

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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YYCHobbyMachinist said:
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.
Click to expand...

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.
 
Brian H said:
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.
Click to expand...

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.
 
Brian H said:
Here are a couple pictures of the setup I made
View attachment 4687View attachment 4688View attachment 4689
Click to expand...
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
 
I'll have to look at doing this mod. According to Brian H that spring strut is a $15 item at PA. I can't find anything like that listed on the PA website?
 
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#.
 
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
 
Made a significant discovery today.

I thought this screw was there to simply hold the down travel pointer onto the head.

SCREW.JPG


Upon closer inspection it occurred to me that it looked suspiciously like a gib adjustment screw, so I tightened it up and re-locked it.

Well...…. the whole down feed mechanism tightened up and shed a LOT of slop. The analog down feed dial now indicates very close to my Z-Axis DRO. It was nonsense before.

It would appear that the screw has a lot to do with stabilizing the down feed pinion shaft (name?) and holding the pinion gear close to the column gear rack.

No where in the users manual is the purpose of this screw mentioned.
 
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YYCHobbyMachinist said:
Made a significant discovery today.

I thought this screw was there to simply hold the down travel pointer onto the head.

View attachment 5432

Upon closer inspection it occurred to me that it looked suspiciously like a gib adjustment screw, so I tightened it up and re-locked it.

Well...…. the whole down feed mechanism tightened up and shed a LOT of slop. The analog down feed dial now indicates very close to my Z-Axis DRO. It was nonsense before.

It would appear that the screw has a lot to do with stabilizing the down feed pinion shaft (name?) and holding the pinion gear close to the column gear rack.

No where in the users manual is the purpose of this screw mentioned.
Click to expand...
Sounds par for a Craftex manual.
 
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