I made my knob since it was missing. I made kind of a rounded octagon shape from fir. what I did was embedded a nut in the knob with epoxy and imbeded a piece of redi rod so it screws on. In my case I need to be able remove the knob and I made the handrail and the pickets so it can come out using invisible shelf hooks. so I can unscrew the knob , pull up on the rail up and it comes out , then remove one part with the pickets and top and bottom rail. I needed to do that to be able to get furniture up to my attic. You'd never know by looking at it that it comes out so easily. Now and then I have kids over and they like to unscrew the knob .
In your case it's more preservative. I think you could fill the hole in the post and then just re drill the hole and insert a peg. any old bits of glue or remnants of the peg won't stop the drill but you'd have to be careful to keep the drill perpendicular. one way to stop it from wandering is to drill in steps from small to large. For that you;d need to use twist drills not forstner bits. You wont' see the hole anyway, so as long as it's a good fit to the peg you have on the knob and not crooked, it will be fine. one trick to drilling the hole square is to pre-drill a scrap of 2x4 on a drill press so it's square then put that on top of the post so when you drill the new hole you are just continuing the already plumb hole. I'd start with a small hole about 1/8th and just worry about getting it square and then increase the drill bit size slowly to your dowel size. You don't really need to put a larger dowel in and cut it off and redrill that but you can if you need to. either way I think it's easier to drill a new hole through wood , putty whatever glue is in there than to try to follow the existing hole.
The dowel is a bit short but as long as it fits the hole it should be ok. you can drill a new hole for the pin, Just be careful to get the alignment right for the two holes. make the larger dowel fit and then locate the smaller dowel.
drill one hole, than use a tool like this to dimple the other side. Just ignore the old location and pick a new spot for the small dowel if it's gone on the knob side. drill that side first. you can probably just make your own tool.but to describe what it looks like :
http://www.ebay.com/itm/Dowel-Centre-Po ... 1099360599I don't' understand how you'd use a band clamp other than maybe to hold the knob if you wanted to work on it. by band clamp did you mean a hose clamp?
that peg in the knob may have a slight taper. if it is and if the corresponding hole also has a matching slight taper then it would fit tight in the hole. you can check if it's tapered. even a slight taper on a fit like this will do the same as the pin is doing ( stop it from turning) as a comparison often machine bits have tapered shanks and when you insert them into each other they lock together. maybe a better example is a peg to hold a guitar or violin string at the correct tension. the tapered fit stops it from turning surprisingly well.
If you had to redrill the hole in the knob and insert a new pin it's possible but if not necessary I wouldn't work on that , just leave it. as long as the fit is ok then the glue will do the rest. that pin is probably turned with the knob and not a dowel. and if you tried to drill it out you could break the knob if you aren't careful, Its also harder to keep that square since the knob is round and hard to hold.
If anything goes wrong just save the splinters and glue them back with carpenters glue right away. If you need to fill gaps I'd use epoxy putty for filling wood. You can get those sticks where you cut off what you need and then knead it to mix it and then it sets up.
Don't use glue to fill gaps, thick blobs of glue don't' have strength unless its epoxy. you shouldn't have any issue drilling through the epoxy filler but where you can see a problem is when you drill a hole where one side of the bit is cutting through a harder material than the other side of the bit.
sometimes if you drill a screw hole and then find you want to move it over just slightly, and find you can't do that because the screw will want to follow the previous hole, you can fill the screw hole with tooth picks or shards of wood that are wet with glue and then you can cut that off flush and then predrill the screw hole exactly where you wanted it to be.
If you wanted to you could just slather it with epoxy and reinstall it and that would be strong but I think Al suggested you to use hide glue because it's reversible. If you use epoxy glue it'll break the wood before you split the joint should you ever want to take it apart again but Its not really that likely you will need to , its just good practice when working on antiques. If you fixed an old chair with epoxy than it would be pretty well impossible to work on it again but if you used hide glue you could still work on the chair and maybe use steam to undo your joints. so the epoxy isn't as good from a restoration perspective.
as long as the knob is straight you probably won't ever want to remove it and if you did it could still be cut off and replaced. on a dry fit you'll see if the knob is crooked or anything. one of the properties of epoxy glue ( like 5 minute epoxy) it will fill gaps and still make a strong bond. carpenters glue or hide glue is only strong in the form of it's bonding strength. If you build it up to fill a gap it won't have much strength at all with most glues, but epoxy can fill gaps and still have strength. It can't be steamed apart though , it's permanent. with something like a chair you can have many joints that depend on each other and if some guy comes along and repairs one with epoxy it can make really difficult for a future restorer to work on so for this reason it's sometimes not the best option for antiques. it also wont' take a finish like wood will so if you get epoxy all over something it can make a real mess for someone doing refinishing..
in some cases epoxy is still ok in my book. as an example at home I have a victorian chair from the 1800s , it has nicely carved features.part of the arm sticks out through the cloth covered section . at some point someone broke the arm off. its a really irregular shaped break and the wood where the break is is hidden by the upholstery. I think splinters have been lost. what I will probably do is drill little holes and use little metal or wood rods to locate the two parts as perfectly as possible. I may drill some external holes where the cloth parts hold it and use pins to locate the parts exactly where I want. once I had my locating pins working then I might use epoxy to glue the arm back on and fill any voids because of the lost splinters.
the other little issue you could see is if you fill the hole with glue and try to insert the peg and you could have a situation where the glue has no where to ooze out. sometimes dowels have a split on one side and if not you cna cut little slots with a hacksaw blade to give the glue a place to exit to prevent the situation of hydraulics from not allowing the peg to go into the hole.
