How large of a thread can the original refill hole support

[headphonesman]

All of the foregoing involving screws , o rings , tape, clear sealant, etc. have their merits, they all work given its a bit fiddly.
My current method is using the little rubber bungs of various sizes provided with the reifill kits. these are of variable quality and robustness, and will soon need to be replaced by an alternative method. I was favoring the screw / o ring method to go forward.
I have also used previously a glue gun......but its a pain chipping the glue back off....and switching on and using the glue gun , switching back on again etc........but it works.

But in one of my re-fill kits was a small "eyelet" ? screw.....I think it was for hooking out the "plastic ball " (the one in the hole originally used by Canon to fill the cart , underneath the label). I thought if it could hook the ball out it might as well be used to put the ball back in.......again.!

I first scraped the label away exposing the ball, first attempt to start the screw in the ball failed....needed a "start" ....this was done by pressing the point of a Stanley Knife blade into it.......then screwing the eyelet screw gently but firmly into the ball (like a wine cork) untl it had enough purchase (about half in) and then lift...the ball comes out on the end of the screw , with a nice popping sound....(put to one side).Put the ink into the nice big hole. Take the screw , put the ball back in (nice popping sound), unscrew the screw from the ball, turn cart upside down and check no leakage from ball hole. Ball is ready to be unscrewed again provided care is taken not to overstress it. I currently have a half filled Cyan in the Garage that I am monitoring that i used this method on. I`m sure I have seen this method described before, correct me if you think I am wrong or the system is flawed...I shall probably be continuing with it when the bungs run out.
The eyelet screw is the smallest size that there is I think...?...about 1.5 cm long.

 

[Osage]

Interesting conjecture headphonesman,

As a machinist by training, I do have alot of faith in a screw thread in metal---and a lesser faith in a screw thread in plastic. But as one poster noted, we are somewhat obsessing--at least discussing a screw seal method---as long as it works is what counts---and best start small as someone else noted---you can always drill bigger if it ever strips--but unlike a rubber plug a screw seal won't back out over time---but could strip out with wear. But then the should be noticed--as one is tightening the screw it will simply keep turning rather than firmly building up pressure making further tightening more difficult.

Another thing to note----its the O-ring rather than the screw thread that provides the air tight seal. And any flaws in the sealing surface are forgiven by the plastic flowing nature of an O-ring--in short its a gasket. I also note rolls royce car engines have no head gaskets. Instead the mating metal pieces are laboriously handscrapped after machining--which gives a gas tight fit.-cheaper car engines use gaskets.
But best be carful with such a handscraped surface--any good nick or ding and the seal is no good. Easy to do when you are assembling heavy objects.

Which is what scares me about your plastic ball method----initially it may work well---but any damage or small nick to the seat or the ball could cause an air leak--and I also wonder if a steel ball bearing would do better. Maching wise, a special chuck could be made for such a steel bearing and a threaded hole could be drilled to allow holding--for easy insertion and removal---such a set up would be very expensive for a few but mass production could reduce the cost to near nothing---or a plastic mold could do the same thing for balls made of hard plastic.

 

[headphonesman]

Thank you Osage for your comments and further points. I acknowledge that the seal may become compromised with repeated use.....(as do some other methods).....but once the screw has been accomodated by the ball the first time it is relatively easy repeat the process again and again ( I did try that a few times to see if the ball was "up to it " ....I believe it is )....you just need the one eyelet screw, the ball is in the same position you left it. A side effect of the eyelet screw going in is that it slightly swells the ball (you have not drilled out a pilot hole, removing material) ....... The ball appears to be made of nylon type material which retains its new dimension making an even better fit in the hole.

The problem with this method is its apparent simplicity.............(its why I`m not using it full time....I`m a glutton for punishment.....)

It needs a few others to give it a whirl ...just for the hell of it.......(Just experiment with a few duff carts)
I didn`t think it would be very easy to do, but it was........the most difficult bit was getting the screw started...(small prick with a Stanley Knife point)...(no cracks please)...........once thats done its plain sailing.
I have re-read again and find:-
Trainman said:I removed the ball by drilling a hole into the ball with a small diameter drill in a pin vise. When I had drilled about half way into the ball I threaded a small self tapping screw (#2 or so) into the hole and pulled the ball out.

there you have it , if you dont want to buy screws, o-rings, rubber bungs, glue, use a drill, mastic, use a glue gun......use the little ball Canon put there in the first place........just ensure the seal is good.

 

[ocular]

One advantage of cutting my own thread is that I own a drill press, a handy vice,
a supply of taps, and can thus insure that the thread I cut is very close to perpendicular with the top plane of the cartridge------and have not figured out a method to hold a self tapping pan head screw to insure that same degree of perpendicular.

It is important that the self tapping screw is perpendicular so that the pan head seals the O ring against the flat cartridge face. The best success I have had is to to put the self tapping screw in the drill press chuck, so that the chuck holds the pan head and the point of the screw is down. Square up the screw in the chuck so that it is perpendicular and the pan head is just inside the chuck and tighten the chuck. Hold the cartridge horizontal under the drill press so the tip of the screw is in the hole. Turn the drill press chuck by hand whilst holding the cartridge by hand. Once the screw has bitten, you can take everything off the drill press and do the rest by hand.

This should ensure the Pan head + O ring seal adequately.

 

[fotofreek]

After reading your technique with the drill press, I guess I've just been lucky with my slipshod approach which is to heat a paperclip hot enough to start a hole and slightly enlarge it and then screw in the self tapping pan head screw with o-ring. No leaks with about 30 carts. You can "eyeball" vertical insertion of the screw by watching the angle of the screwdriver, and the o-ring compression will take care of the screw being not quite perpendicular to the surface of the cart.

 

[Osage]

To Fotofreak,

Since my hypothesis is that the real sealing is done by the bottom surface of the screw head against the top surface of the cartridg itself, it then becomes possible to calculate how big of an air gap remains.

Add that to the accepted principle that the human eyeball can't detect angles of less than 2 degrees off perpendicular--add a little trig--and one can calculate the air gap some sort of gasket material must be able to take care of.

So lets take a worse case senario---something like a .4" diameter button head rigid steel machine screw threaded 10-32 or 10-24.--at various angles off perpendicular.

At 2 degrees off perpendicular-------one end of the head is about .014" higher than the opposite side. at 5 degrees of this jumps to .035", and at 10 degrees off this is a whopping .0694". In the 2 degree case, its probable no gasket would be needed, the cartridge top could easily distort downwards enough, in the 5 degree case, an O-ring could easily take care of the gap, and the O-ring would probaly still be enough in the 10 degree case.

But the machinist making the hobbicolors mold is probably no more than a few hundreths of a degree off perpendicular.

And for what its worth, most of the time, I just eyeball the hole also---the pan head screw can even start a little off--slight screw driver pressure can correct it in process.

 

[fotofreek]

Osage - I think that your conclusion is correct - that the screw/o-ring would easly create a seal with as much as a 10 degree deviation, and I think a reasonably careful person can be closer to 5 degrees than 10 off a vertical insertion. Spliiting hairs, but an interesting exercise in determining how this system works! the #6 sheet metal screw shank diameter is about 3.2 mm. and the #005 O-ring I use on it is about 1.6 mm. (1/16th inch) thick when uncompressed. The seal actually occurs with the compression of the O-ring at 0.8 mm. from the surface of the screw shank (1/2 the diameter of the o-ring cross-section), give or take any distortion of the o-ring away from the surface of the screw shank and forgiving the slight cross-sectional thinning that occurs when stretching the tight fitting o-ring onto the screw. this translates to the seal occurring approximately 2.4 mm. from the central axis of the screw. The diameter of the head is only relevant as long as it is wide enought to prevent the compressed o-ring from bulging out beyond it. With some carts, of which HC is one, the hole is sufficiently large that I use a #8 sheet metal screw (shank diameter aobut 3.7 mm.) and a #006 o-ring, also with 1.6 mm cross section.

And now for the shoot-from-the-hip, unscientific evaluation - "whatever works!"

 

[kudos]

Guys Guys Guys I have rubber plugs that are used by refillers to plug the holes after you take the ball out. You can put a 14mm needle through the plug fill then pull out. Ink will not leak out and you will not need all that extra stuff. I refill 10 to 20 of these a day NO Problems! Email me if you want some I will have to charge for shipping of course but you can try them.

Peace

 

[fotofreek]

Kudos - nice offer! Computer Friends sells such a plug and it has a tab on it to make removal easier. Do the ones you are using have such a tab? Aftermarket carts don't have the same type of fill hole, and these are the ones that one needs to improvise with. Some come with a tiny rubber plug that is impossible to handle, and the hobbicolors carts come with a small nylon machine screw that is pretty small and difficult to align due to its blunt end. I replace these with the screw/0-ring combination, but I have also used the computer friends plugs on OEM carts successfully.

 

[drc023]

What would really be good on refillable cartridges is a plunger type snap cap which is hinged on one side. If shampoo and ketchup bottles can have such a cap, so could our beloved Canon cartridges. Since those don't exist at the present those of us stubborn enough to use screws and o-rings will continue to do so. I do agree a nice rubber or vinyl plug is probably better for those not interested in converting over to various screw / o-ring setups. I use 10-32 nylon screws for my cartridges. The screw shank is larger than the other screws mentioned, but the threads are finer. While I do use o-rings, they are there as insurance only. The actual sealing is not from the base of the screw cap, but from the threads. Even without tightening the screws enough for the bottom of the head to make contact a complete seal is already made just from the finer threads on the nylon screws that I use.