Friday, 14 September 2012

CNC: Building a DIY Trend T5 or Kress 43mm CNC Spindle Holder Mount without a CNC



I looked at a few 43mm spindle mounts, but non seemed to fit the bill.Armed with a chunk of 20mm aluminium plate and a hole saw I decided to have a go myself.

Basic Tools






M6 Tap (long)

Home Made Tap Guide (black rectangle with a hole in the middle).This will aid in starting the thread square to the work piece)

Light Machine Oil or Cutting Oil,
Toothbrush (For cleaning the Tap threads)
6mm Allen/Hex Key
43mm Hole saw (I chose a Starrett and a A2 Arbour)
Assorted Metal drills (4.8mm or 5mm for the M6 Tap Hole)
Hammer, Centre Punch (I used an optical centre punch)
Engineers Reference Square (Important,Or something that is known to be perfectly square)
Engineers Metal Ruler
Digital Callipers (Optional)
Craft Knife (For precise marking)


Parts

A Chunk of 19 or 20mm 6020 aluminium plate 112mm x 84mm
3x M6 Bolts and washers (2x45mm 1x40mm)

Power Tools

Table Saw (Non Ferrous Blade)
Pillar Drill



The Design






I'm quite a big fan of printing templates to scale, using double sided tape to stick the design to the material , meticulously cutting the sides of the template perfectly square with a very sharp craft knife.
I then form a corner using some waste material and align one of the square sides of the template to the form.
This method for me at least saves a lot of time marking , I doubt that I could mark any more accurately than a modern printer can!

A word of warning here! after setting your printer to "Print to Scale" in the printer preferences, do a test print and double check with a ruler or digital callipers that a few of the lines are of the correct measurement, I usually check from one drill centre hole to another.



Cutting the aluminium setting up the saw





In the following pictures, the different between a Non Ferrous Blade (Top) and a normal wood saw blade (Bottom) can be seen by looking at the difference in tooth profiles.

Non Ferrous blade (notice the chamfered teeth ,also the angle on the normal teeth is reduced)





Normal Wood Blade



Drilling


Notes on setting up the pillar drill for square

Before we can start using the pillar drill, we need to check the table to ensure it is square to the incoming tool.Using a reference square and a long shaft fixed in the chuck check for everything is parallel on at least 2 sides of the table.



If any adjustment of the table is needed it can be performed underneath.Using a combination of slackening  and tightening the large centre bolt and grub screw everything can be brought in to line so that the reference square is perfectly square with the shaft.
Every so often I like to run the drill and let it come to a halt in-between checking to allow for any backlash of the pillar drill.





 Here the grub screw is adjusted to tilt the table.





After Punching all the centres of the drill holes we can now use the hole saw to removes the centre material.


You may have noticed I have drilled a large hole off centre of the main circle.This has two purposes  its main  use is to remove more material to allow the opposite clamping side to flex more when tightening the Allen bolt as the spindle is installed.The second is to allow the chips from the cutting process to escape.This will dramatically enhance the quality and cutting speed of the hole with the aid of some machine oil.This will come apparent in the video below.

Its always a good idea to include an escape hole for cuttings when using a hole saw,the cutter tends to get bogged down and sometimes stall or jam otherwise. The hole could also have been on the inside of the circle touching the edge line, but in this instance its a feature of the finished piece.










Lets see how square we got it! Here I checked the slug from the hole for the squareness of its sides.This will give you an indicating of just how square your pillar drill table is to the drill bit over a distance.The deeper the hole the more square the pillar drill/Table needs to be.





The 13.5mm side holes are there to give a nice radial edge after the sides have been cut.



I then went back to the table saw to cut the excess from the sides of the part.A word of warning here! due to the the arc of the saw blade you have to stop short of the drill hole on the top side of the part ,otherwise you will catch the underside with the lower part of the saw blade. I then finished the cut with a hacksaw and file.

Drill the fixing holes



Using clamps and a couple of right angled scraps we can hold the mount in an upright position for drilling the tap hole.The piece is then rotated to drill the mounting holes.
Starting with the correct size drill for the tap hole ,drill the full length of the hole,then using a 6.5mm drill  the depth to the cut line on the side of the mount.This will save time and ease tapping.






Cutting the slot

(If you notice the slot is off centre to the middle compared to my 3D model. This was done as I had  a limitation, the length of tap I had to reach the opposite side!)







Tapping the treads

Here you can see how we can use the home made guide block to start the tread perfectly parallel to the hole with some light machine oil.





After we have cut five or six threads we can remove the guide block






The finished Spindle holder




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