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I want to make a series of porcelain door knobs.  At first, I thought I could slip cast a prototype -- but I'm having trouble figuring out how to fasten the knob to a spindle without glue.  Another option would be to reglaze plain white porcelain knobs from Home Depot.  

Does anyone have experience with making ceramic door knobs?  I've seen lots of threaded inserts for making cabinet knobs accept screws, but only one source for door knobs and it's $15 for just one piece!   I looked into all kinds of hardware but can't find anything to match a door knob spindle, which is normally 9/32" with 20 threads per inch.

If I try reglazing the commercial knobs, would it help to rough them up with sandpaper first?  I understand that reglazing is unpredictable, but it sounds like a cone 4 - cone 6 would be safe.

My last resort would be to use Pebeo paints and forgo glazing altogether -- but I much prefer the look and durability of ceramics glazes....



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Could you glue a nut instead of a spindle?

I don't know about refiring something like that with mounted hardware, feels like something may go "off".  The commercial knobs are probably made using a process unavailable to us if the hardware is embedded directly.

Edited by liambesaw
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Make the knob and leave room to epoxy the spindle/nut into. The tough thing is figuring the shrinkage -its best to have the space be larger and fill with epoxy like JB weld(if you live in the US??) .If you need a side hole for the screw you can make that as well.

Just make it big enough to fit when shrunk after firing.I have made ceramic faucet handles that fit over brass fixtures and had to figure the hole sizes and firing with about 99% area glazed-its all a learning curve

I have made sinks for specific hardware as well-same deal need to know the shrinkage rates..I made big game =ceramic headed fishing lures with a specific hole size. same deal.

If you reglaze a commercial piece the only way to find out what will happen is do it and see.Testing its whats need -either way you will learn a lot from doing it.You do not know what temperature the commercial stuff is fired to so that also will be learning curve-what if its low fire or high fire and you are doing cone 6?Only way is to try it.

Good luck with the quest

Let us know how this turns out so we all can learn from your experiment.

Edited by Mark C.
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I just noticed that the Home Depot knobs are actually metal, not porcelain -- oops!   Most porcelain knobs cost $25+ per pair if new; vintage is cheaper but then they'll all be different and reglazing would get even crazier....

I'd love to just epoxy my own knobs onto the spindle, but then they'd never come off and that seems like it might cause problems someday...?

Mark C, you mentioned making a side hole for the screw: I assume you mean when the spindles have holes drilled in them, which can be aligned with side holes in the knob using a set screw.  That would be great, as long as it doesn't put too much stress on the porcelain -- do you have any idea how thick the walls would need to be?

Thanks for your help!

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I make a couple hundred door pulls/knobs per year.

I used to glue in a threaded nut which was made to be pressed into manufactured wood materials (MDF etc); the "nut" had barbed projections, and was about 3/8" long. I chose this because I wanted the barbs to help hold the glued nut into place. What I found that the method of gluing any type of fastener into the clay piece led to less than desirable results. If you make your hole too large (too allow for shrinkage and "play" to get it perpendicular to the pull/plumb), then as you glue the nut inside, you need some sort of method for hold the nut in place while the glue dries, otherwise it will shift out of plumb as it hardens, which looks mighty sad when stuck onto a cabinet at an angle. For a while I tried using a small ball of a two part, kneadable putty, stuck to the bottom of the nut so It would stay in the position I set it in, and then would come back with a two part epoxy and fill the rest of the cavity in. It was all too much hassle, and left a poor looking job.

What I do now, is I make my hole larger than my finished threaded portion, fill the cavity after its fired with a machinable steel impregnated two part resin. The resin becomes extremely hard, and is easily drilled and tapped for whatever size screw I want. I use the product Plastic Steel, sold as a liquid, not a putty (two options). The stuff is relatively expensive, about $50 of material will do about 70 or so pulls depending on how big your hole is that you have to fill. I drill/tap my screws to a 1/4" x 20 thread as its the most common size machine screw your going to find at a hardware store; your customers are going to have a range of thicknesses in their cabinetry, and a 1" screw you supply will work for some, but not all. 3/16" is a more common drawer pull screw size, but is not a standard. If your pulls are flat on the top, you can use a drill press to get the holes drilled about as perfectly perpendicular as you can; there are also machinists drill guides which will help if you dont have a drill press, or cant use one with your design. A decent drill bit and tap set will run you less than $10, and is much quicker than my previous method. Doing it this way I can "pour" them in one day, allow to cure for 24-48 hours, and drill/tap 100 or so in about two hours or less. Use the tap in you drill's chuck to make it easier. A note about tapping them though; while the resin is very hard, you can strip your threads out but continuing to turn once your tap bottoms out on the clay piece. If you do, just refill the hole and redo.

I sell my pulls for $14/piece; those folks who are shopping for handmade pulls have no complaints buying them at this price. If they are buying 20 or more at a time I will discount them by a buck or two per piece. Lots of folks like the idea, but shy away from the price. Remind them that they can go to HD/Lowes/Etc and spend $6+ per each stainless/brushed nickel/chrome/antique bronze pull they find there, or they can spend a little more and get a quality handmade pull from an artist. Ive had customers who have done each cabinet in their kitchen with a different shaped, different color glazed pull which ends up providing a unique look and personality to each cabinet.

A last note about the pulls; dont make them more than 1.5-2" wide; on a cabinet with double doors, the pulls will bang into each other if they are installed in the "original" pull holes. I throw each from a ball of clay a little smaller than a golf ball. Use a cordless drill with drill bit when they are leather hard to drill out the base. Use a sanding block when bone dry to get a perfectly flat bottom.

Edited by hitchmss
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11 minutes ago, Mark C. said:

Great info on door pulls/knobs

I think the Op is making entry door knobs (the larger ones) but your info should help  a lot for any knob makers.

Ah, I must have mis read the OP! I always call my pulls, "pulls", as lots of folks say door handles......it aint no handle! Ive been asked if I could make a ceramic "handle" style pull (like the side view of a mug handle), and havent attempted this yet; Dont see why it couldnt be done, but Id want it to be purty thick to avoid being too delicate.

Unrelated....kind of. There is an artist that I see at some shows; does sculpted bronze entry door knobs/handles and lockset mechs. Everything from sculpted animals, humans, random shapes etc...SUPER cool ideas. The choice on what portion of the sculpture becomes the "mech" is the fun to me...tongue of a dogs mouth, tail of the mermiad...

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