As anyone who has ever worked on a ReedJet engine knows, the factory installs (2) 7mm dowel pins in the top deck of the case which are used to align the cylinder.

If the deck of the case happens to not be perfectly parallel to the crank centerline, the pins must be removed in order to remachine the deck.

The problem is... those 2 dowel pins are installed with so much interference, they simply can not be removed without using extraordinary methods. Adding to the problem, the dowel pins used are a full "through hardened" dowel pin that checks 62Rc (about the same hardness as rollers or balls in a bearing).

In the past, I've tried grinding flats on the pins and rotating them (only to have them seize even more), TIG welding a bolt to the top and using a slide hammer (no luck), grinding a "dovetail" into the exposed part of the pin and using a mating piece on a slidehammer (broke off the top of the pin), and finally resorted to drilling them out using a carbide drill (a lengthy process!).

A logical alternative would be a sinker EDM, but I don't own one.

If you've never seen a ReedJet engine apart, this is where the pins are located:

So... my solution was to come up with a tool to machine them out without doing any damage to the deck.

The tool...

Here's what I came up with (and I admit; the first one I made didn't work very well, so you're looking at the second design):

In a nutshell, it's nothing more than a tiny little holesaw. The ID of the cutter is .001 larger than the OD of the dowel pin (about .277"), and the OD at the front is about .330". The first .200 or so has about a 5ｰ taper (for relief behind the cutting edge), and then it's straight the rest of the way. The shank of this cutter is very thin wall... probably around .017" or so. I made the back of the tool .500" in diameter so it would be convenient to hold in a collet in the mill.

I gave the cutter 3 teeth, and machined in the gullet of the teeth using a .080" diameter endmill. The cutting edge has a 10ｰ positive rake, and the front face of the cutter was machined to give a 5ｰ relief angle to the cutting edge.

The image above is my CAD model so I could envision what it was I was making.

Here's how the real cutter turned out:

The discoloration is from the "tempering" I did after heat-treating.
I made the cutter out of some tool steel that I had. I heat treated it, then polished it (to be able to see color temperature) and drew it back to around 60Rc.

How does it work?

It works remarkably well!

I just held the cutter in a 1/2" collet in my Bridgeport. Since the ID of the cutter is essentially the same as the OD of the dowel pin, it's easy to line things up. I then clamped the case down to the table of the mill, and started cutting.

I don't have any "action" photos (while I was actually using the tool), but it cut surprisingly well. It's definitely something where I had to "go easy", mainly because there is so little room for chips to clear out of the hole. It wants to "pack up" with chips if you try to just keep cutting, so some caution was in order. "Pecking" about .010" or .015" at a time, and using an air nozzle to keep the chips cleared away worked very well.

(I was also a bit paranoid about breaking my cool little cutter that I had just spent an hour or two making!)

When I was just about to the depth of the dowel, I just noticed that all of a sudden the dowel pin came out in the cutter.

Finishing the job

The particular set of cases in these photos was getting a full blueprint job (sleeve, linebore, square deck), so after the deck was squared I still needed to reinstall the pins.

Since there is absolutely no reason that the pins need to be pressed in like the factory does it, I decided to make some Delrin "sleeves" to take up the space I had machined away (the hole for the pin was now about .055 oversize).

I just machined up two little "tubes" that were about "net fit" in the holes in the cases, and had a tiny bit of interference on the ID for the pins.

I just pushed the little Delrin tubes into the case with my finger.

Here is the case with the Delrin tubes installed:

I then just tapped the dowel pins back in using a plastic hammer. The pins are quite snug, but can still be pulled out using a pair of ViceGrips.

Here's the finished product.

The beauty of this "system" is that the hole I machined is perfectly concentric with the original factory hole. Since the cutter is essentially "piloting" on the dowel pin, there's no way that it can "wander" or cut off-center.

Once I pushed the pins back into my plastic sleeves, I did a quick check on position and spacing, and the pins were dead-on where they had originally been.