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a shopbuilt milling jig for Dremel rotary tool


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Hello, I thought this milling fixture for a Dremel tool might be of interest to builders.  I haven't built one and so I can't attest to its precision.    But if it were built with care it might be serviceable. The thin jam nuts on the lead screws should take up backlash.   One thing that might be an improvement is to make adjustable gibs for the ways, such as are found on Sherline mills.  Another possible improvement might be to install sintered bronze bushing/bearings or 8mm skatewheel bearings and threaded rod instead of the wooden bearing blocks, although the hard maple bearings should last a long time if they are soaked with oil.   

 

http://woodarchivist.com/1624-diy-milling-machine/

 

The rest of the site might be of interest to you as well.

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I checked into buying parts for that very article. After paying $45 for a half sheet of ply and then going on to locating and pricing the other parts I would have had several hundred dollars invested. Check out the Grainger catalog prices for those fancy knobs and left handed threads etc. Just not doable for me. Rather buy a premade mill for those prices. I have to admit I was smitten by the Idea that I might be able to build something like that though.

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On 3/24/2017 at 1:50 PM, reklein said:

I checked into buying parts for that very article. After paying $45 for a half sheet of ply and then going on to locating and pricing the other parts I would have had several hundred dollars invested. Check out the Grainger catalog prices for those fancy knobs and left handed threads etc. Just not doable for me. Rather buy a premade mill for those prices. I have to admit I was smitten by the Idea that I might be able to build something like that though.



Grainger is one of the most expensive places for buying anything if you don't have a high-volume corporate account.  I would shop elsewhere, e.g. McMaster-Carr (mcmaster.com) .  A casual search shows 3/8-16 LH thread rod at about $6.24 per 6 ft length.  (By the way, I would use 1/4-20 rod, because each full turn of the handwheel would be 0.050")  That said, I find it difficult to believe that the cost of the hardware parts would amount to several hundred dollars.  Most of them could be found in a hardware store or scavenged, and the knobs & handwheels could be shopmade easily.  MDF could be used for the base and arm, and likely would be better than plywood anyway because it is heavy, and at these dimensions it won't warp if varnished/shellaced.   A little ingenuity goes a long way.  

It would also be helpful to go to the Sherline website (sherline.com) and read through some of the thoughts about precision and manual & methods of setup of their tools.

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Overall, a good design.  I was just think of something like this for semi-automating block production.

 

One simple improvement would to add adjustable gibs on the dovetails slides.  With wood construction you can expect to see tightness of the slides change with the relative humidity.  I see that the rails of the dovetails are held down with counter-bored screws, so there is an ability to adjust the tightness, but this also creates a chance for them to slip.  I would insert a 1/8" hardwood gib, held in and adjusted by two 1/4" bolts.  This should eliminate a lot of frustration with chatter and unpredictable sizes.

 

Second point when building: make sure the axis of the rotary tool is parallel in both planes to the Z axis slide.  If this isn't done, then you'll be breaking drill bits, especially for the fine sizes.  If the case of the rotary tool is round and concentric, then the method described in the article will be fine, but expect to do a little shimming to get if right on.

 

As others have mentioned, other than the left hand threaded rod and nuts, there is nothing exotic here.  You could use right hand threads, but if you're used to full sized milling machines, like I am, you'll end up going in the wrong direction and wrecking parts. If you're not used to full size machines, you have no muscle memory to over-ride and you'll be fine.

 

What's needed next is the lathe, so you can make nice hand wheels...

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"

 

 

"  One simple improvement would to add adjustable gibs on the dovetails slides."    

So noted in the original post.  The gibs for the Sherline are a plastic, probably Delrin, and they're held in place with a simple "L" shaped pin and a setscrew.

To build a lathe, one could use 8mm I.D. x 22mm O.D. skate wheel bearings  for headstock bearings, and  8 mm drill rod could used for the spindle. As a matter of fact, the wheels themselves might do for the first handwheels.

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A Sherline lathe or mill with 20 TPI lead screws can achieve quite acceptable precision for small work - the handwheels are graduated in 0.001" or 0.01mm.  For this shopbuilt machine, the precision would be determined by the quality of the initial fitting of the parts and the wear over time due to friction and accumulation of dirt and chips.    If it is built with adjustable gibs and smooth bearing surfaces as discussed above, then compensation for wear is possible. I think the greatest problem for this machine would be the fixation and alignment of the rotary tool, and this is the part which I think needs improvement.  It would be better to have a screw-in socket for the tool than the cradle & clamp shown in the plans.  Finally, the mass of the machine and a secure fixation on a stable, level bench is necessary, just as it is for any precision tool.

What might be of greater interest is the precision of a completed model, which would depend upon the scale.  Commercial models of sailing ships are often scaled at 1/350, which may be expressed as 0.0028 inches per foot, and so 0.01" imprecision would translate to about 3.6 ft at scale.  Larger scale models would suffer less.

 

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Hmm, this has started me thinking about making the X-Y mechanism and fitting a toolpost for light duty metal turning on my midi-lathe.  Recently, I equipped my midi lathe with a 2HP DC motor from a treadmill.  Now the lathe can spin over a continuous speed range of ~50 to 2500 RPM and it can be reversed as well.  This would also be an excellent motor for small shopbuilt lathe.  If you wish to learn about configuring such a DC motor and electronic controller for tool use, I can offer some advice.   

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Sorry to sound so negative on that homebuilt milling machine. We have a pulp mill here in town and there are various suppliers of parts for such machines , but I'm afraid none of them were very helpful. I was thinking this might be a job that Gaetan or Michael Mott could undertake with success. The idea of building it had me excited for awhile.  You types with experience in machining might have a field day with this project and may even know how to use them when finished ;).

    I do have a the Dremel drill press accessory that allows one to turn the Dremel at different angles and that has been quite helpful. I also have a Harbor freight 3x12 lathe that I have used in a limited way. I actually had better success with my wood lathe for projects than anything.

   Kinda on a different subject, I have a small Ryobi 4V screwdriver I love for drilling styrene.. It has lots of torque,is two speed, and doesn't turn so fast as to melt the plastic I'm working with.I use a three jaw chuck with it to hold fine bits.

   Another handy tool is the Harbor freight hole punch set which is great for making discs in various sizes.

   So I hope I haven't given anyone the impression that this project is worthless.

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4 hours ago, reklein said:

"Sorry to sound so negative on that homebuilt milling machine.....So I hope I haven't given anyone the impression that this project is worthless."

No, there's no problem at all so far as I'm concerned. We're here to sort out ideas and find what's useful and what may not be useful, for oneself and for others.  

 

 

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  • 2 months later...
4 hours ago, ca.shipwright said:

Check out this X-Y table and others on ebay. Awesome and reasonable priced. Also fits the Dremel drill press stand.

s-l1600.jpg

Hi Michael,

 

That is almost certainly a Chinese knock off of the Proxxon KT 70. Looks almost identical even down to the colour,doubtful if it's anywhere near the same quality.

 

Dave :dancetl6:

 

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I am all for building machines and accessories myself - if they can do something a commercial product cannot do or cannot do with the desired precision. Wood has its (beautiful) uses, but makeing machine tools from it is one of its less desirable uses. When I saw the original post, I was thinking that there x-y-tables and drill-stands out there on the market in exactly the right dimensions that would cost just a bit more than the materials that go into such a home-grown machine. I would rather spend the time to tweak these into something reasonably precise - as one may need to do with these Chinese products.

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