In this Instructable I will show how you can make traditional door knobs that can be fitted to a standard threaded spindle. You can also use this method to repair or upcycle old plain-spindle knobs that have lost their fixings. In case you’re wondering what I mean, don’t worry, I will provide a proper explanation shortly.
Parts needed for one pair of knobs:
- Two door knobs (see later);
- One standard threaded spindle. I buy mine from www.inbrass.co.uk;
- Two threaded inserts for wood, with the same thread as the spindle. I use M10 x 13mm type-D inserts (I have also used M10 x 25mm before). I buy them on eBay;
- Two grub screws. I recommend M4 x 8mm, hex. I buy them on eBay;
- Hand tap to match grub screw;
- Drills and basic hand tools.
Step 1: How Door Knobs Work
Old style / British knobs used a 19/64” spindle, now standardised to 7.6mm (sometimes a thin metal sleeve is also added to increase the size to 8mm for some latches). The knobs have a metal insert with a square hole to accept the spindle. A grub screw, also called a set screw, passes through the neck of the knob and insert, and locates in a hole in the spindle. Several holes are provided so you can adjust the position of the knob to suit different door thicknesses. The trouble with this method is that it puts all the twisting and pulling force on the grub screw and insert, which is often thin, cast brass. Over time the grub screw works loose and falls out, or the insert cracks and become useless. It is also hard for the DIYer to make an insert with a square hole. There is a much better system which has been common in America for a long time, and is now found elsewhere.
The American system again uses a 7.6mm square spindle, but the ends have an M10 thread.* The metal insert in the knob therefore does not need to have an awkward square hole, but a round hole with an M10 thread. A grub screw again passes through the neck of the knob and locates in a groove on the spindle, as shown in the graphic. This system is much better than the one described above, because it allows you to adjust the position of the knob with finer precision (in quarter turn increments), and when you pull the knob the force is on the insert and spindle, not on the grub screw. This is the system used in this Instrictable.
*In Europe the threads are M10 but in America they might not be metric -I don't know. No matter, simply buy whatever threaded parts are appropriate for the spindles in your country.
Another system common with modern, metal door knobs is to have the knob integrated with or ‘trapped’ by the rose plate. The rose plate is then screwed to the door and takes all the pulling force, with none on the spindle. The spindle is a plain, square type and is not physically attached to the knobs at all. I mention this for completeness only; it would not be easy to make a DIY knob this way.
Step 2: The Knobs
OK, first you need some knobs. Exactly where you get them is up to you. I got a friend to turn some walnut knobs on a lathe, but you could also upcycle some antique knobs where the original square metal insert has broken or fallen out (see photo). Other ways to make your own knobs might be to carve them by hand out of wood, 3D print them, or cast them in resin. However, whatever material you use must be able to be drilled and tapped.
You will probably want rose plates too. These protect the face of the door from the endless wear of turning the knob. Again, mine were turned on a lathe. Traditionally the rose plates are screwed to the door, but I don’t recommend this. With years of use and changes in atmosphere, the thin wood tends split and the rose falls off. I don’t bother to fix mine to the door, they just sit on the spindle. If you do want them fixed, I suggest using double sided tape instead of screws.
Step 3: Fitting the Inserts
Drill a hole through the centre of each rose plate, big enough for the spindle to fit through. I worked my way up to an 11mm drill. If you want to screw your rose plates to the door then you should drill and countersink two smaller holes either side of the central hole, for the screws to pass through.
Drill a hole into the centre of the neck of each knob. The hole needs to be large enough to accept the threaded insert -mine required a 12mm hole. Drill it deep enough for the spindle to enter a useful distance into the knob (e.g. 25mm), even if this is deeper than the insert itself.
Now screw the insert into the knob. The inserts I use require an Allen key (hex driver) to do this. Other types require you to screw a bolt into the insert, then use the head of the bolt to drive the insert into the wood.
NB: If you’re upcycling an old knob, drill into the existing square hole. If the hole is too big for the insert then you can glue it in using epoxy.
Step 4: Fitting the Grub Screws
Now drill a hole into the side of the neck each knob and into the metal insert. You must then tap a thread into this hole, to accept the grub screw. Since I’m using M4 grub screws I drilled a 3mm hole and used an M4 x .7 tap. Remember the rule for hand tapping: one turn forward, half a turn back.
Step 5: Finishing Off
After blowing off the dust and swarf the knob is now ready to be installed on the door! Simply pass the spindle through the door latch, then slip on the rose plates (screw or stick them to the door if you want to). Finally, wind the knobs onto the spindle until they begin to press gently against the rose plates, then tighten the grub screws.
Sometimes the spindle is too long. No problem, just saw a bit off the end until you can fit the knobs to the door. Tip: wind an M10 nut onto the spindle before sawing off the end. Then as you unscrew the nut it will automatically remove swarf and re-tap the sawn end.