A small tilting table for a mini proxxon mill.

[Kris Avonts]

Hello All,

 

This is my mini proxxon mill. It consists of a MB200 drill stand, a KT70 xy-table and a 230V ISB/E drill/grinder. I already added an extra z-control on top of the drill stand as you can observe in the next picture.

 

 

Milling small wooden (or aluminium) parts to precise dimensions is possible but you must take into account that total run-out at the end mill can be up to 0.2mm.

From time to time I need to do milling at an angle and I used to make small wedges to be placed under the workpiece. An example is shown next.

 

 

 

It requires some calculation of the wedge dimensions and precision sawing to get it right. The problem is that a next piece more often then not requires a different angle and a repeated effort to make the wedge.

That is the reason I want a small tilting table on this mini mill. Looking around on the internet, I could not find any suitable solution for such a small mill. So I started my CAD program and tried to design something that would support the MS4 machine vice at an angle. See below an animation of this design.

 

 

And here is a view with all parts made semi transparent.

 

 

So I started construction. First ordered some aluminium parts of different sections: 6x70 mm for a base- and the tilting-plate, 3x20 mm for the bearing-holders and 2x15 mm for the locking plates.

 

 

The base and tilting plate were sanded to make the surfaces clean and flat. Then some machining followed: threaded holes for M3 and M4, 10 mm holes for the MF105zz bearings and 4 mm holes for the cylinder pins that connect the tilting plate to the bearings. Here you see some finished parts.

 

 

These parts could be assembled and checked on the xy-table.

 

 

While the result was quit good (< 0.1 mm over a 50x50 mm area) I could see that when tilted the tilting plate moves different left compared to right. That is because the holes for the cylinder pins are not positioned equal at both sides (see next picture).

 

 

I already noticed that the 4 mm drill was wandering a bit to much at 1 side when making the hole.

Also drilling the 10mm holes in such small parts is not easy to keep them at the wanted position. I tried to fix things by enlarging the M3 holes to 3.5 mm in the bearing holders. It helped a little but not sufficient to meet my requirements. So it is time for a ‘plan B’ to fix this. But that is for a next update.

 

best regards,

   Kris

Edited February 13 by Kris Avonts
spelling correction

[Kris Avonts]

Hello All,

 

As announced work on the tilting table now concentrates on fixing the bad alignment of the pins that connect the tilting table to the bearings. The ‘plan B’ is presented in the next figure.

 

 

As you can see the 2 pins are replaced with 1 cylinder that is mounted to the tilting plate with a V-groove. The 1 cylinder will result in better alignment to the bearings. But that shifts the problem now to the fit of the cylinder in the V-groove. I have no equipment (larger mill) to make this accurate groove. So I will make it to the best of my abilities and use a clever interconnection technique to join cylinder to the tilting plate.

 

First things first: the V-groove. I first removed both steel pins and then cut off a small strip of the edge. This is to assure that the new cylinder which has a 6 mm diameter will be in the same position then the former pins.

 

 

Next is the V-groove that I will make with 2 saw cuts at 45°. For that I need a fixture to hold the tilting plate at 45°. The fixture is made of some scrap wood glued together and then sanded a bit. It is not perfect at 45° but will do.

 

 

 

Then the V-groove can be sawn.

 

 

The next close-up of the V-groove show that it is far from perfect. When the cylinder is pressed in the groove it shows small misalignment to the top or bottom of the tilting plate. Then I realise that gluing the 2 parts together can compensate for the misalignment on condition the I can position both correctly to one another.

 

 

So lets start, the next picture shows all parts involved before gluing. I have 3 dowel pins that are ground accurate at a diameter of 3 mm. That is exact the distance between base plate and tilting plate in horizontal position, see the picture below.

 

 

The 2 dowel pins under the cylinder will support both the cylinder and the tilting plate so that they are level. The 2 small plates at both sides of the base plate will align base and tilting plate. A weight on top covering part of the tilting plate and cylinder assures that everything stays in contact while the glue sets. As a last measure I put 2 calipers set at 73.1mm over tilting plate and cylinder at both sides. Now I hope I cancelled most sources of bad alignment. The whole setup is shown next.

 

 

Now its time to take a break and cross my fingers.

 

Best regards,

 

Kris

[Kris Avonts]

Hi All,

 

After the metal epoxy glue had set (24 hours), 2 bolts are added just to be sure it will withstand vibration and forces during milling operations.

 

 

Curious about the outcome of the glueing I measured the misalignment. As you can see in de following picture there is a small gap (0.1 mm) between the highest point of the cylinder and the tilting plate.

 

 

Next was again a check of the flat surface on the xy-table over a 50x50 mm area.

 

 

I was disappointed but the inclinometer showed it as ‘flat’, so I will accept the result and start making the last parts: the 2 plates that lock the tilted plate in position.

 

 

The tilt-locker plates have an arc at its top and a slit also in the form of an arc. All arcs have the same centre point. First I start with marking and drilling 3 holes as a reference.

 

 

To mill the arcs I will use a jig that I already made earlier and consists of a base plate with 5 positions, spaced 20 mm apart, that can hold a pin that will act as the rotation centre. The next picture shows it on the xy-table. For wooden parts I use a plate with some sandpaper glued on it and lots of holes that have an M4 nut at the back of the plate. A workpiece can then be fixed with some small clamps. For the metal tilt-locker parts I need firmer clamping, so I will construct a different plate from a scrap piece of MDF (shown bottom left in next picture).

 

 

It starts with marking 3 positions: 2 holes of the tilt-locker and the centre of the arcs.

 

 

For the arc slit, a number of holes along the arc are marked and drilled.

 

 

Next I use my mini saw to cut off some excess material of the plates.

 

 

Then both plates are fixed on the piece of scrap MDF.

 

 

Milling starts with positioning the base MDF plate: the centre pin is mounted in the proxxon mill and lowered to make a fit in the middle hole of the base plate. Then the base plate is fixed in place to the xy-table with the 2 sunken bolds at its sides.

 

 

The proxxon mill is brought up again and the centre pin replaced with a 2 mm end mill. The center pin is now placed in the lowest hole. That makes the distance from rotation centre to end mill centre exactly 40 mm. From there the y position can be set at the required position to start milling, see next picture.

 

 

The result of milling:

 

 

For the final shaping of the tilt-locker plates I convert my mini saw into a mini disc sander.

 

 

The finished parts are shown next (you can see that at least 1 hole was drilled a bit to much off centre).

 

 

And here is the tilting table, set at a 20° inclination. It can hold the MS4 machine vice as well as a small rotating table (if I ever need that extra degree of freedom for a workpiece).

 

 

 

 

As a last tip to set an inclination with good precision, you can use a long M4 bolt to make fine adjustments before tightening all 4 M3 bolts.

 

 

That ends the making of a small tilting table. Hope you enjoyed it and maybe you start making your own.

Best regards,

Kris

Edited February 13 by Kris Avonts

[wefalck]

Nice tour de force across some machining and alignment problems !

 

I have had the same vice for decades and due to its lack of accuracy relegated it really coarse work only a long time ago. I am now using so-called toolmaker insert vices instead. They are available down to 20 mm jaw width and cost around 40 EURO/USD/GBP only.

 

The more parts the greater the chance of accumulating manufacturing and alignment issues. Such sine-type tables are nice, but as you experienced need to be manufactured to close tolerances on all parts in order to ensure overall accuracy.

 

For my little toolmakers vice, I went a different route and made a tilting device from a solid piece of aluminium that has no moving parts per se and only two critical dimensions: the verticality of the sides of the slot into which the vice fits and the parallel alignment of the holes for the fixing bolt vs. the bottom surface. Both dimensions I could control reasonably well with my equipment:

 

[Kris Avonts]

Hi Wefalck,

 

You are right, it was a serious challenge but I'm glad I could make it to a usable tool.

In a 3D cad program it all seems very simple (no tolerance and no misalignment) but in the real world it requires some skills to get it done.

Your solution is indeed simpler and very robust. For me it comes a little too late.

I hope my tilting table will serve me well for upcoming ship projects.

 

best regards,

   Kris