I am building a simple pvc whistle for my grandson. I had seen on youtube that you can use 1/2 inch pvc with a 1/2 inch dowel as the fipple plug. The only problem is that the plug needs to be sanded to fit and then the short piece of pvc that you cut to put on top does not fit completely around the fipple since you have to cut a pretty good size gap to have it spread over the top of the fipple. I will need to glue the plug in place but am wondering what do most of you use to seal the wooden dowel? Do you use polyurethane, bees wax or something else? I would like to buy some delrin rod. Can anyone tell me in the United States where most of you buy your supplies like this (delrin rod or tubes etc)? Thanks for any help or advice.
Scottie
Guido Gonzato’s site is always handy for tips.
We have a local farm/hardware/hillbilly type store that sells everything needed to make whistles. If you have a similar type shop there, then you’ll likely find all you need easily. Our store probably has every type of PVC imaginable!
If you haven’t yet, look up Guido Gonzato’s tutorial on making simple “low-tech” PVC whistles. He covers everything a first-time whistle maker would need to know to get started early on in whistle making, with a good bit of detail.
Edit: Gumby beat me to it!
Definitely a regularly mentioned website on here, and worth looking into. it might involve a bit of trial and error on some of the points, so it’s worth noting that it’s a good idea to make sure you have boughten a bit extra of supplies, in case you make a mistake or want to try something differently. It’s easy to get a bit obsessive over trying to improve upon your last one. Luckily, the supplies are all extremely cheap.
Mr Gumby beat me to Guido’s site http://www.ggwhistles.com/howto/
I seal the wooden fipples with super glue, just don’t glue your fingers together 
Yes, I have used his site and it does have some good tips. The videos on you tube are good but I think they make you think the dowels just fit very easily into the 1/2 cpvc tubes but it take quiet a bit of sanding. It would be good to have a lathe to turn them with a fine sandpaper to make sure they are perfectly round for sure. I can see light on the bottom side of this one which I will have to replace. As for as the basic sound on a tube without any holes the D note sounds pretty good up to two octaves. I will keep experimenting. I thought I read or head that some people seal the wooden plugs with cork grease which would also help to prevent moisture absorption.
For making high whistles, I’ve used 1/2" CTS (Copper Tubing Series) CPVC for the tube, 1/2" SCH40 PVC (which is a bit wider) for the fipple cap, and a standard 1/2" wood dowel for the fipple block. It seemed to fit pretty easily for me.
As for getting delrin or other plastic dowel rods for the block, the easiest place I’ve found is ordering online. Here’s a 1/2" delrin rod: http://www.amazon.com/dp/B000FN15OW/ref=biss_dp_t_asn
I haven’t ever bought or used that exact product, but I’ve gotten wider acetal rods for lower whistles, and they work just fine–if you can find a rod with a diameter that’s quite close to what you’ll need. Otherwise, delrin is a little harder to sand and shape than your standard hardware store dowel rod.
Guido’s instructions are very good, and I’ve learned a lot from what he has to say. However, if you want to design your own tone hole layout, with the sizes and spacings that you prefer, you can use this calculator: http://11wall-west.com/~ph_kosel/flutomat.html
Have fun building! Your grandson will think it’s great.
Let me offer some alternatives for you to consider.
Guido Gonzato’s site is great. He knows what he is doing but here in the US we do not have (easy) access to the materials he uses. And you have to re-calculate the dimensions for US pipe. Use the calculators I linked to in your last thread for that.
Stanton has listed what many folks use here is the US. His suggestions are very workable IME. So that’s one place to start but there are still alternate materials and methods you can utilize.
Here’s the rub, as you have already discovered. Nominal 1/2" CPVC pipe does not have a 1/2" inside diameter. The inside diameter actually varies (closer to .49" but still varies +/- a .001 or so.). The outside diameter is what is standardized. So you have to make a plug that actually fits. And that is a really big deal in terms of the finished whistle. If you use a plug that is too large it will stretch the CPVC around it and will not align properly with the floor of the blade. The results are whistles with unfocused and breathy tone that are hard to play. So you have to get the plug right for the inside diameter of the pipe.
There are ways to do this cheaply and simply. You have the dowel and if you like that idea you can turn it down to the right diameter. The best way people have done this is to mount a long piece of the dowel, maybe 3", in the chuck of an electric drill and wrap a piece of sand paper around the dowel to sand it down while it spins. This all assumes you have an electric drill with a 1/2" chuck. Clamp the drill down to a work surface. Lock the trigger to the on position. Be even with the pressure across the length of the dowel. This will take a while to get right. Patience is by far the most important tool in your toolbox. Once sanded coat the whistle with CA glue. It may swell - repeat the process if needed.
Delrin (or acetal polymer) does not come in a strict 1/2" diameter either - and certainly not a .489" diameter to fit inside a particular CPVC pipe. It comes in a plus 1 or oversized diameter varying by usually .001 or more than 1/2". That’s the industry’s standard for manufacture. It is intended to be machined. So you still have to size it to to your pipe. Delrin (or acetal) is harder to deal with than wood. Same with PVC or CPVC rod stock (which does a great job and is lots cheaper than delrin). You could try the dril/sandingl method with delrin, CPVC or PVC rod but a machine lathe is really necessary to use this stuff IMO. You can buy plastic rod (acetal, delrin, PVC, CPVC, Acrylic, ABS) on eBay from a few retailers in small quantities. Other plastics suppliers online may want a minimum order. McMaster-Carr is always a good place to start looking for materials. Check your Yellow Pages for local Plastics suppliers and make some calls if you find some locally.
If you do not have a drill I can offer two other alternatives. Poly clay is one and cast resin is the other. These are both easily molded to the size of your pipe.
Poly clay is a plastic clay used by artists to make sculptures and jewelry. It is sold in craft/hobby shops like Michaels, Joanns and Hobby Lobby. There are two major brands Fimo and Sculpey. The stuff is actually form-able PVC so the finished plug is the same type of material as the pipe. It comes in little bricks in many outrageous colors too. It has to be baked to harden. That’s the rub with this stuff. There are a couple ways of making a plug from this material. I’ll describe one. You can get imaginative with others if you try it and it does not work out for you. To make the plug you build a mold from a short piece of the same pipe as the one you are using for the whistle head. Slit the mold in half lengthwise. Line the inside with a wax or lubricant as a release agent. Stuff the clay inside the mold so that there are no voids. Wrap with wire to hold things in place. And then bake per the material’s instructions. I bake it in a toaster oven out-of-doors so that if there is enough material the off-gassing as it hardens does not build up inside the house. YMMV. Once baked let it stand a while to cool. Take off the wire and pop the plug out. File the nasties off where the two halves of the mold met. Test your fit.
Don’t want to bake? You can try “Better Living Through Chemistry”. Go to the craft/hobby store and look for casting resin. It comes in kits as well as separate components. The kit might have the resin, a catalyst, a release agent and coloring agents. You can get away with the resin and the catalyst. You can use home waxes or cooking oils for the release agent. The coloring agents are neat if you like that sort of thing. Kids sure do. Once again you cut a short piece of CPVC tube for a mold - make a few at a time for laughs. Swab the inside of the mold with your release agent of choice. Use transparent wrap and a rubber band to seal one end of each mold. Make sure the sealed end is smooth and flat. Mix the resin and catalyst according to the instructions. Pour into the molds and set aside while it hardens. You cake even mold stuff (pre-historic mosquito in amber, anyone?) into the plug if you like. I wait a week for the plugs to harden but I am a patient guy. Pop the plugs out and check the fit. Here are some examples of cast resin plugs.
For the outer mouthpiece you have alternatives. Stanton mentions using nominal 1/2" schedule 40 PVC. That’s a good suggestion. But it does not always fit over the 1/2" CTS CPVC for the same reasons that the inside diameter is not standardized. Try it, it is cheap, but if that does not work you can rely on the CTS sizing. The 1/2" CPVC pipe is 5/8" in diameter on the outside. You can use K&S telescoping brass tubing (eBay, online or hobby shops) as both a coupler (tuning-ish slide) and the outer mouthpiece. The 21/32" size is 5/8 inside diameter and fits round the pipe nicely. The cheaper and more common method is to use a 1/2" copper pipe coupler from Home Despot or Lowes. You can also use a CPVC pipe coupler for both the head and the joint if you like. I drill out the center of the connectors with a 5/8" forstner bit for a good fit over the head.
You do not have to glue the head. You can pin the pieces in place. That’s what I generally do - it is completely reversible and maintainable. But CA glue works well if you want to glue things. A little dab’l do ya - as they used to say. Don’t use a polyurethane glue. 
That glue is moisture seeking and it will wreck your head if you have any moisture in the structure before you glue it. And you will have moisture in the head after you test it by blowing into it to see if it plays before gluing. Oh, and delrin requires highly specialized glues.
Here are some of my Qando ( Can-do, or quick and dirty whistle, if you like) model whistles made for kids to look at as examples.
Hope that helps. Bet you can’t make just one! 
Feadoggie
As feadoggie points out:
Here’s the rub, as you have already discovered. Nominal 1/2" CPVC pipe does not have a 1/2" inside diameter. The inside diameter actually varies (closer to .49" but still varies +/- a .001 or so.). The outside diameter is what is standardized. So you have to make a plug that actually fits.
I find that the inside diameter varies by far more than +/- a 0.001, I have seen and used pipe from 0.470 to about 0.495 id. And this is to be expected: the outside diameter is always very close to 0.625" and needs to be in order that the glue fittings work well and there needs to be a minimum wall thickness to ensure the pressure rating of the pipe - the actual id of the pipe is not so important in its intended application. Look up the specs for the pipe, say this page: http://www.harvel.com/piping-systems/gf-harvel-flowguard-gold®-cts-plumbing-pipe/dimensions and you will note that the od is guaranteed to be 0.625 +/- 0.003 ( I have never measured it to be more than +/- 0.001 off which is probably straining the accuracy of my calipers. Do a little math and it seems their pipe id can vary from 0.425 to 0.505 - though as I say I’ve never seen those extremes.
A small lathe seems the way to go but I’ve things such as an electric drill and sand paper, just takes patience and the willingness to do it over!
Also note that if you are using wood dowels they are not usually very accurate in their dimensions, or even round!
I usually use super glue to seal/glue my wood dowels to the plastic pipe. I usually (actually to date always except once*) use wood fipples - mostly because I like the idea of a little wood in my whistles, and partly because I’ve never got around to order anything else to use.
I have also used brass tubing from KS (available in better hardware stores and hobby shops in the US) with an id of 0.625" this tubing is very precise and will reliably fit well over the top of the 1/2" cts pipe (as will various copper fittings - but these are a bit thick and chunky for the job). However in my opinion this gives a windway that is too tall but maybe it will work great for some.
- I know if I have once used some acrylic to make a fipple (to match the rest of the acrylic whistle - an experiment that I have not repeated as it was not worth the effort) then I should not say always but it is better than 99% true!