# HF mini mill Z axis power feed, or maybe just a larger fine feed dial?



## 62Scout (Sep 14, 2019)

I've found myself using the boring bar set up on my mini mill MUCH more frequently than I ever thought I would when I bought it.  Up until now though, I've been using it just to create holes larger than I could drill with the mill, as I've been without a drill press for a while, and none of them required any real precision... 0.050" was plenty close enough for what I was doing.  

My problem hasn't been so much one of holding a set diameter, but rather achieving a smooth enough feed to get a decent surface finish. Either I got an interrupted feed with the fine dial, or got a finish that looked like I ground it out with a coarse wheel on an angle grinder, using the coarse feed because it was difficult to feed it slowly enough while still applying proper pressure on the bit. Of course, this also has a tendency to chew up the edge on the cutter as well. 

Now I find myself with a project that will require a slight press fit of parts, so I need to come up with a better way of handling boring these holes. A z-axis power feed would be ideal here, and I've seen a few CNC kits that include Z axis control. But I don't want to go full blown CNC at this point, as I'd want to maintain the ability to manually machine parts. A large chunk of my use is machining existing parts, as opposed to making new parts from blank stock. All the CNC Z axis set ups I've been seeing are just computer controlled, period, and don't provide provisions for manual control. 

Barring that, would machining up a larger dial/fine feed handle, similar to the X/Y feed handles, be an appropriate solution here?


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## Cadillac STS (Sep 14, 2019)

Could you make a handle that could fasten on and off the fine feed?  Like a bar 6 inches or so long so you could make nice even swing and remove it when not boring?

Preferably with a swiveling handle so just turn it and the handle you grip can spin

If it could be removed then it could be longer and not in the way when not boring.

On my small lathe the cross slide has a small handle and if I need a smooth long cut I have a handle that goes over the small one that is long and makes a nice easy smooth swing. Then I remove the handle so it is out of the way most of the time.

If you machine a larger fine feed handle that stays on it would still likely be smaller if it is permanently on..


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## hman (Sep 15, 2019)

Talk about timing ... check out post #15 in








						setting up a LMS 3990
					

my 3990 arrived a few weeks ago,, been busy tramming and taking a slow learning curve.. cleaned it all up and mounted it on a welded stand that held a craftsmans jig saw for 45+ years (way over built for the saw) stand was cleaned up and painted, a 1.5" laminated top was mounted, new adjustable...




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homebrewed just posted it this morning!


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## Cadillac STS (Sep 15, 2019)

hman said:


> Talk about timing ... check out post #15 in
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Exactly!


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## DAT510 (Sep 15, 2019)

Stefan Gotteswinter has a nice YouTube series where he makes a powered quill feed, specifically for boring. Not quite the same, as I don’t believe the Mini mill has a quill feed, but only a whole head z axis feed. But it might give some ideas for use in combination with the postings above. 









						Project: Quill Powerfeed
					

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.




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## 62Scout (Sep 16, 2019)

hman said:


> Talk about timing ... check out post #15 in
> 
> 
> 
> ...



Thanks much!  That was more or less what I had in mind, just wasn't sure if it was going to work well like that.  Part of me was wondering if I was going to have to somehow come up with a way to gear that feed down even finer than it is now in order to run the head down slowly enough.  Though that post also explained why I never could corrolate dial markings to feed depth...completely forgot that these things ship with metric graduations, and I had replaced the X/Y feed screws and dials with LMS's inches kit a while back.  Like the other posters, I never really pay attention to the Z dial anymore either, but I don't have a DRO (yet), so it's always been a guessing game for how far the head is being fed.  Thankfully, I've gotten pretty good at guessing, lol.  

I'd still like to come up with a way to make it a powered feed as well, but I think the handle idea will work well enough for now.


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## hman (Sep 16, 2019)

I don't recall your mentioning what brand of mini you have, but I'd guess they're all pretty much the same.  The Z feed on my HF mini has a whole lot of linkages, including universal joints, all of which can contribute to slop or backlash.  Then there's the rack and pinion.  If the rack isn't well made or if a bit of foreign material gets behind it when it's installed, the backlash will be inconsistent along its length.  Finally, there's the counterweight system ... the original spring arm, an aftermarket air spring, or maybe an actual counterweight with a pulley system.  All of these can produce forces that vary with height.  The bottom line is that adjusting/setting the Z knob is, as you said, a guessing game.  

A good 3-axis DRO is indeed a pleasure to use.  But even if such a system is out of your reach for the moment, you might want to look at installing a single axis unit on Z.  They're not too expensive.  Here's one for $55:





						AccuRemote 6" Z-AXIS Vertical Super HIGH Accuracy Digital READOUT (DRO) Stainless Steel for Mill/Lathe: Digital Calipers: Amazon.com: Industrial & Scientific
					

AccuRemote 6" Z-AXIS Vertical Super HIGH Accuracy Digital READOUT (DRO) Stainless Steel for Mill/Lathe: Digital Calipers: Amazon.com: Industrial & Scientific



					www.amazon.com
				




Getting back to your original topic, smooth Z feed needed for a good finish when boring ...   I think a crank arm on the Z dial, along with partially tightening the gib lock on Z to add friction, would definitely help achieve your goal.


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## 62Scout (Sep 17, 2019)

hman said:


> A good 3-axis DRO is indeed a pleasure to use.  But even if such a system is out of your reach for the moment, you might want to look at installing a single axis unit on Z.  They're not too expensive.  Here's one for $55:
> 
> 
> 
> ...



It's not so much a cost thing, as it is a time thing.  Or more appropriately, a time management thing...I have ADHD, thus I also have about 30 projects in a stage of mid-completion.  Generally it results in me tearing something apart, making a couple small modifications, then finally getting it put back together about 3 years later, while starting 20 more projects in the mean time, lol.  Being that this is my only mill at the moment, and my lathe is currently one of those project victims....I don't want to start on the mill just yet.  

Also, I'm REALLY liking the Yuriy's setup based on using an Android tablet for the display.  I need to dig into it a bit more to make sure it'll work the way I want, but I'll probably start accumulating parts for it soon.


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