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- Aug 16, 2013
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It’s been a while since I did any maintenance on my Craftex Mini Mill and things are starting to move in ways they just aren't supposed to. One of my biggest beefs on the mill has been the fine feed knob. I don’t know if this is common on all mini mills but on mine the fine feed has about 1 1/2 turns of backlash.
My grand plan was to put a thrust bearing behind the knob to take up the slack. All I would have to do is machine a recess in the back of the knob to accept the bearing and smack it back on, easy peasy. . . . .
Nope.
When so much of the stuff coming out of China suffers from poor fit and finish and at times questionable materials, why is this knob harder than the hubs of hell.
So a new knob was in order. I have a DRO on the mill and have never used the indicator ring because of the backlash so the ring was put on ignore. Chucked up a piece of 2 in aluminum in the lathe and brought it to (give or take) the same dimensions as the original. Knurled it and cut the recess in the back.
Quick tip. Sometimes when swapping the jaws on a chuck I’ll put a rubber band around them, rotate the jaws backwards until the number 1 jaw clicks then just spin them in. A little easier than the three point Kung Fu grip.
The fine feed shaft goes to a worm held in place with a pin. Between this and the 2 universals there is about 3mm of movement to be taken up when turning the knob.
I split the shaft so I could drill and tap the end 10-32 for a screw that I can use to pull the slack out of the shaft down onto the thrust bearing. Then lock the knob with the setscrew.
The thrust bearing I have are imperial and the shaft is metric so I had to make up a small bushing a bit shy of the thickness of the thrust bearing and washers.
Most times the knob is a bit of a pain to use so I added a short crank arm. Used the lazy man’s setup to dial it in on the mill. Chuck a piece of drill rod that fit the hole in the knob then tighten down the vice and milled a slot to fit the crank arm.
I cold blued the arm because . . . OK, no logical reason but I think it looks cool, and 3D printed a handle then mounted it up.
I am pleasantly surprised with the result. It’s down to maybe 5 degrees of backlash and with the extended crank a lot more comfortable to use.
My grand plan was to put a thrust bearing behind the knob to take up the slack. All I would have to do is machine a recess in the back of the knob to accept the bearing and smack it back on, easy peasy. . . . .
Nope.
When so much of the stuff coming out of China suffers from poor fit and finish and at times questionable materials, why is this knob harder than the hubs of hell.
So a new knob was in order. I have a DRO on the mill and have never used the indicator ring because of the backlash so the ring was put on ignore. Chucked up a piece of 2 in aluminum in the lathe and brought it to (give or take) the same dimensions as the original. Knurled it and cut the recess in the back.
Quick tip. Sometimes when swapping the jaws on a chuck I’ll put a rubber band around them, rotate the jaws backwards until the number 1 jaw clicks then just spin them in. A little easier than the three point Kung Fu grip.
The fine feed shaft goes to a worm held in place with a pin. Between this and the 2 universals there is about 3mm of movement to be taken up when turning the knob.
I split the shaft so I could drill and tap the end 10-32 for a screw that I can use to pull the slack out of the shaft down onto the thrust bearing. Then lock the knob with the setscrew.
The thrust bearing I have are imperial and the shaft is metric so I had to make up a small bushing a bit shy of the thickness of the thrust bearing and washers.
Most times the knob is a bit of a pain to use so I added a short crank arm. Used the lazy man’s setup to dial it in on the mill. Chuck a piece of drill rod that fit the hole in the knob then tighten down the vice and milled a slot to fit the crank arm.
I cold blued the arm because . . . OK, no logical reason but I think it looks cool, and 3D printed a handle then mounted it up.
I am pleasantly surprised with the result. It’s down to maybe 5 degrees of backlash and with the extended crank a lot more comfortable to use.
