CHAIN, how to use chain tool to put on chain
When you join the ends of a chain with ANY chain tool, the place where you joined the ends will always be too tight and will not move freely until you get the tightness out. If you don't loosen the tight link, it could cause the chain to "jump" over a tooth on the rear freewheel while you are riding the bike, and this could be dangerous.
To loosen the tight link, you can use the chain tool (this tool will loosen tight links); or, you can act as if you are trying to bend the chain from side to side at that link, but don't press hard enough to actually bend it. Work the chain lightly from side to side at the tight link several times, and test it to see if it has worked loose. If links are tight because they have rusted, you cannot get the tightness out like this - you will have to oil the links and work them up and down (not side to side as described above) to work them loose.
If someone is injured because of using this chain tool or because of trying to follow my directions, I am not responsible. Chains can break and the ends can be joined improperly causing injury or death to the rider.
Some higher priced chains are not made to be joined with a chain tool because the rivets are "mushroomed" on the ends so they cannot pull out. You use a chain tool to take out the unwanted links in the expensive chain and you join the ends with a special link that is provided with the chain. When you take out a rivet from one of these expensive chains, the mushroomed end of the rivet is ruined. Also, the mushroomed end of the rivet will enlarge the hole in the link's side plate, and if you were to put that rivet back in the chain, the rivet would not fit tight enough on that end and could come out when you shift gears. The special link for joining the chain is supposed to prevent that problem. This is normal with expensive chains and does not hurt anything. This special link is not a regular master link - a regular master link would come off too easily. The special link is made by the chain manufacturer for a specific chain.
With cheaper chains, and with some expensive better quality chains, the ends of the rivets are not mushroomed so the rivet will still fit tight when you put the rivet back in. However, if you don't start the rivet exactly in the hole in the side plate, the edge of the rivet could shear off some metal making the hole in the side plate larger where it would not hold a rivet tightly, and that could cause the rivet to pull out while you are riding the bicycle. So, if it is too hard to turn the handle on the chain tool as you are just starting to push the end of the rivet through a side plate, the rivet is probably hitting the metal and is not going straight into the hole in the side plate. If you keep turning the handle, the rivet will shear off some metal which will make the hole too large to hold the rivet tightly. In this case, stop - move the chain slightly until you don't have to turn the handle very hard to make the rivet go in the hole in the side plate. It is supposed to be a little harder to turn the handle of the chain tool just as the rivet starts through the hole in the second side plate. That is why it is difficult to know whether the rivet is going straight into the hole or if it is a little off center and is shearing off some metal. If the side plates don't get hit by something while the rivet is out, knocking them out of alignment, the rivet will usually go into the hole straight without shearing off any metal.
You can buy the most expensive chain tool and you will still have these same problems. If you know how to handle the problems, they do not cause any trouble - and most people have no trouble even if the don't know how to handle problems, but they could have trouble.
As you can see in the picture, the piece that sticks up in the middle of the tool is used for loosening tight links. I have heard of that piece breaking sometimes. The main reasons why it sometimes breaks is that it is thin, it has no support, and people put more pressure on it that they should. You should not use it to try to loosen the links in a rusted chain (loosen them as described above) because that might put too much pressure on it and cause it to break. You should not use it to try to loosen tight links in a chain that has the rivets "mushroomed" or "peened" on the ends of the rivets to keep the rivets from coming out - that might put too much pressure on it and cause it to break because it is hard to push the mushroomed end of a rivet into a hole in the side plate when the end of the rivet is larger than the hole. You can take out a mushroomed rivet with a chain tool but you should not try to put it back in (see above) - that type of chain has a special link that comes with a new chain or is available from a bicycle shop to repair a chain. If that piece on the chain tool does break off, you can continue using the chain tool. I never use the tool to loosen tight links - I loosen them faster and easier by hand as described above.
>>PROBLEMS CAUSED BY A NEW CHAIN:
You can have the problem of "chain suck" with any new chain, and it is not caused by how you put on the chain. Also, any new chain can jump over a tooth on one of your freewheel cogs when you are riding the bike. The problems are caused by putting a new chain on a bicycle when the teeth on the front sprockets (chainwheels) or the teeth in the rear freewheel are worn too much.