# Mini mill screeching sound



## homebrewed (Jun 22, 2022)

The X axis on my mini mill has had this problem, intermittently making loud screeching sounds when I turn the handwheel.  The sound emanated from the bearing block (also called the retainer block) on the right hand side of the table.  I usually could get it to stop -- temporarily -- by greasing every part of the bearing block -- but lately it's seemed that this "fix" only lasts a few days.  The last straw was a few days ago when it made that noise immediately after grease was re-applied.  Enough already!

Carefully disassembling the bearing block, I noticed that the portion of the feed screw which passes through the bore of the block was bare of grease, despite being well-greased the last time I went through the exercise.  Getting suspicious, I measured the OD of the shaft and compared it to the ID of the bearing block, and they were darned near the same.  That axis has groove-type thrust bearings so it's not at all necessary to have a close-fitting relationship between the shaft and bearing block.  It ain't a bushng, just a hole for the shaft to go through.  I opened the hole up by about .010" and the annoying screeching sound disappeared!  Hopefully it stays away!


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## markba633csi (Jun 22, 2022)

Typical import machine- perfect fit when you don't need one, and the opposite when you do
LOL


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## Road_Clam (Jun 24, 2022)

Can you post up detailed pics ? Pretty sure we can figure this out.


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## addertooth (Jul 1, 2022)

For screeching to occur, it means metal is moving.  I would suggest tightening it if it is possible.  A tuning fork only makes noise, because the tines can move.


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## homebrewed (Jul 2, 2022)

addertooth said:


> For screeching to occur, it means metal is moving.  I would suggest tightening it if it is possible.  A tuning fork only makes noise, because the tines can move.


It was coming from the portion of lead screw shaft passing through the bearing bracket.  Tightening it up would mean that the lead screw wouldn't turn.  That would indeed stop the noise but there would be a serious downside


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## Jeff.64 (Jul 2, 2022)

I had the same problem several years ago.  Went through the replacement of thrust bearing and relubing the lead screw.  A little better, but still present.  Pulled the table off and noticed slop in the tombstone shaped lead screw nut.  Took a hack saw and made a cut from the bottom (square end) of the nut through to the threaded section (// to and centered to the bore).  Cross drilled and tapped the split section 10-32 or 14-20 (clearance on one half and threaded on the other side of the slit), I don't remember.  Used a SHCS long enough to have room for a lock nut to be installed on the SHCS protrusion after the nut was appropriately fitting (SHCS slightly closing the nut) around the lead screw.  The screeching went away.  Backlash much better.  Bought a properly sized acme 16 tpi internal threading tool and a chunk of brass to make a new nut.  Because the "fix" continues to work great, the new threading tool and brass bar are collecting dust.  You know, I have and had more "important" things to do.  Until I saw your post, I kinda forgot about making a new nut for the mini mill.

Hope This Helps,
Jeff


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## homebrewed (Jul 6, 2022)

Jeff.64 said:


> I had the same problem several years ago.  Went through the replacement of thrust bearing and relubing the lead screw.  A little better, but still present.  Pulled the table off and noticed slop in the tombstone shaped lead screw nut.  Took a hack saw and made a cut from the bottom (square end) of the nut through to the threaded section (// to and centered to the bore).  Cross drilled and tapped the split section 10-32 or 14-20 (clearance on one half and threaded on the other side of the slit), I don't remember.  Used a SHCS long enough to have room for a lock nut to be installed on the SHCS protrusion after the nut was appropriately fitting (SHCS slightly closing the nut) around the lead screw.  The screeching went away.  Backlash much better.  Bought a properly sized acme 16 tpi internal threading tool and a chunk of brass to make a new nut.  Because the "fix" continues to work great, the new threading tool and brass bar are collecting dust.  You know, I have and had more "important" things to do.  Until I saw your post, I kinda forgot about making a new nut for the mini mill.
> 
> Hope This Helps,
> Jeff


I took a slightly different approach to reducing backlash on my machine, making something very similar in action to what Sherline uses .  It's an external nut, snugged down to take care of the backlash then fixed in place.  The advantage of this approach is that when the backlash starts to go back up due to wear, I don't have to take the table apart to tighten things back down.  However, I did have to drill and tap a couple of holes on the end of the X-axis table to install a plate for the external nut to bear on, so your approach is less intrusive.

It also is interesting that it was your nut that was the apparent source of the noise.  Not so for me, guess it illustrates how many ways these little machines can go sideways.


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