Introduction: 3d Printed Lathe Toolpost Drill for Myford ML10
This 3d printed toolpost drill is accurate and very useful, but not high precision. It is very suitable for drilling holes in collars for grub screws, using a slitting saw, drilling radial holes in the face of a turned part, etc. It can either be used perpendicular to the lathe's centre-line or parallel. It is automatically 'on-centre' without height adjustment.
In use, putting a dial indicator on a drill in the chuck holder produces a maximum sideways movement of 0.1mm when the electric drill is pushed firmly from side-to-side.
The Myford ML10 is a small lathe (3¼" centre height and 13" between centres) so using a 3d print as the basis for the drill does produce a very useful accessory.
This is based on a cheap (£7 in 2020) "Silver Precision Metal C10 ER16A 100L Straight Shank CNC Collet Chuck Holder". It is used in conjunction with a set of small ER16 collets (£11 in 2020) which I already owned (I use them in an MT2 tapered collet chuck holder [£10 in 2020], which fits in both the tailstock and main spindle).
The chuck holder is held by two precision bearings which enables it to produce reasonably accurate results.
"Silver Precision Metal C10 ER16A 100L Straight Shank CNC Collet Chuck Holder" (Banggood)
"61900 zz [6900 zz] 10x22x6mm Thin Section HIGH PERFORMANCE BEARING" x 2 (eBay)
"R16 10Pcs Spring Collet Set For CNC Milling Lathe Tool" (Banggood)
Step 1: Design and 3D Modelling
The 3d model is simple. It is based on a 61mm square body, which fits exactly on the lathe's toolpost. The chuck holder is held in a 32mm wide side-extension.
The critical dimension is the height. The lathe's centre line is 13.7mm above the toolpost platform, so if the height of the 3d print is 27.4mm (2 x 13.7mm), and the chuck holder's axis is at the centre, then the toolpost drill can be flipped upside-down for use perpendicularly and axially.
The model was created in Sketchup, exported as an STL, layered in Cura and printed on a JGaurora 3D printer in black PLA. Support has to be used and a 20% fill has worked well.
The final thickness of the print was almost exactly 27.4mm as designed, but the bearing housings came out undersized by around 0.5mm which was thought to be too tight to risk pressing in the bearings. The bearings were 10x22x6 (22mm outside diameter, 6mm thick and 10mm hole for the shaft). In addition, the removal of the plastic support material left an uneven finish inside the bearing housings. To get around this, an aluminium blank was turned down to 22.0mm, heated in an oven to 200°C and eased into the bearing housings. To line it up, a 11.5mm drill bit was pushed right through the model where the chuck holder's shaft would later sit, and the drill bit was used to guide the heated aluminium blank squarely into the bearing housing. The bearings fitted perfectly and were held with a small amount of 5-minute epoxy.
Step 2: Assembly
Assembly is pretty straightforward.
A retaining collar was turned up to keep the chuck holder in place. This had an inside diameter of 10mm and an M5 grub screw. In use, a tiny square of thin copper was dropped into the hole to avoid the grub screw from damaging the chuck holder's precision-ground shaft. This collar is pretty redundant as the 10mm shaft does not slide easily inside the bearings (see next step) and the operator is holding the electric drill anyway! However, it does avoid any possibility of the chuck holder being pulled/pushed out-of or into the 3d print.
A large washer was initially slipped on between the chuck and the front bearing, but was swapped for a much narrower spacer, parted off from some scrap steel tube (which bizarrely was covered in copper!) The large washer is unsuitable, because it could rub on the stationary part of the bearing; the small spacer just touches the rotating centre of the bearing and rotates properly with the chuck holder without rubbing on anything.
Step 3: In Use
Once assembled, the toolpost drill can be placed on to the toolpost and tightened down using a large circular or square spreading plate and the regular toolpost nut, as seen in the photos.
Some sort of spreader is needed to avoid crushing the plastic. When a spreader is used, the nut can be heavily tightened (much more than is necessary) without a problem.
An electric drill is coupled to the shaft and the drill can be held and operated, while the cross slide is advanced.
It operates on both axes of the lathe. For use along the axis of the lathe, the electric drill shown in the photos required the tailstock to be removed so that the electric drill could be attached. As it turned out, the 100mm long shaft of the chuck holder was vital, because the electric drill's chuck would have fouled the cross slide if the shaft had been a short one (see the close-up photo).
The whole affair feels solid. It seems ideal for small diameter drills. The collet set shown can accommodate drills up to 10mm diameter, however this would surely be too big for this device to handle - especially into steel or brass.
Be warned, that the length of the drill bit which can be accommodated is limited by the movement of the cross-slide and the diameter of the part being drilled. In the photos, there is not much more travel available for the cross slide to move towards the operator, so a long drill bit or big-diameter part could not be accommodated. A set of stubby drills might prove handy! (A tweak to the 3d print design could move the drill chuck closer to the operator if needed - see the design showing a 30mm set-back).
It might be nice if the collar could be left off and the electric drill then be simply pushed by hand to carry out the drilling process (without using the cross slide leadscrew to progress the drill bit). However, the 10mm precision bearings are a non-sliding fit on the 10mm precision ground chuck holder, so this would not work. To achieve this, the steel bearings could be omitted and a long plain brass or bronze bearing could be made and reamed to 10mm (see diagram). This would enable the electric drill to be pushed, so that the chuck holder/drill bit was forced into the part being drilled.
Step 4: Various Files
These files may form a basis for others wishing to produce something similar.
Lathe toolpost drill 04.skp = the toolpost drill featured in this Instructable
Lathe toolpost drill 05.skp = the same toolpost with a 30mm offset to accommodate longer drills
Lathe toolpost drill 06.skp = the toolpost with a brass/bronze bushing instead of steel bearings
Lathe toolpost drill 02.stl = toolpost drill featured in this Instructable
Lathe toolpost drill 02 with bearings.gcode = toolpost drill featured in this Instructable