[t-head]

PART 2 Machining you own valve guides.

Before I start I might add that this is not the only way to do this but it is a way that I have found over the years to work out well. You end up with a new guide in which the OD of the guide is perfectly parallel to the the bore of the guide which is important so that it ends up concentric with the valve seat.

To do this right you are going to need a good lathe with an adjustable chuck or precision collets so when you flip the guide over to drill the other side you can set up the guide to run true again with .001.

You are also going to need a good set of centers that run dead true for the head and tail stocks. Check them with an indicator to make sure as the area of the OD of the guide that registers in the head gets machined off of centers which if you take your time and do it correctly will result it perfect alignment.

I first set up and turn the OD of the stock straight and true to give me a good set up that I can check with a dial indicator for each operation on each end of the guide.

Then I cut them to length in the lathe. Next set up a blank and indicate the OD and get it true then face off the end (this is the point the photos start at). Then center drill it carefully with a good center drill, photo 1. Next I use an undersize screw machine drill because they are shorter and will walk or deflect less than a standard length drill, photo 2. Drill in a little more than half the length you need and stop. Do one side of all the guides this way and take your time and don't force the drill and make sure it is sharpened correctly or buy high quality news ones which should drill fairly straight.

Then turn the guides around, indicate them and get then + - .001 and face the second end then repeat the procedure from the first side. After drilling thru and meeting the other side in the same set up drill all the way thru with a drill that is larger than the short drill but about .010 smaller than your reamer size, photo 3. By doing it this way if you were careful with all your set ups and used correctly sharpened drills you should end up with a good straight hole. Then in the same set up ream to your finish size or smaller if you are going to hone them, photo 4.

The OD of both ends and the middle can then be machined in a good chuck or collet but leave the area where the guide registers in the head oversized about .020.

After you have the ends machined to the shape that you need, put good centers in the head and tail stocks and indicate them to make sure they are true. Then set your guide between centers and finish off the .020 you left to clean up before on this area and you will end up with a very nice and true guide.

Photo 5 shows an old valve guide on a Sunnen honing machine to show you how the machine works. Its gives a much better finish than can be done with a reamer and the last photo shows the mandrel and stone which does the finishing in an oil bath.