Thursday, August 5, 2010

On the Level--Part 1

There are so many projects in the very early stages around here that have languished far too long simply due to lack of current interest or inability to mentally work through the details. Often there's the hope that something complicated will have an easier solution given enough additional thought.

The project that I was interested in starting this morning hit a roadblock when I didn't have a piece of suitable material. I need a piece of steel tubing about 0.325"(+) OD with a 0.225(-)ID approximately 6" long. Putting half a foot of daylight in a piece of steel rod just isn't that appealing. If I don't find something suitable, maybe I'll bore out a spare 0.177 cal barrel--a .22 cal might even work.

In the mean time, there was another project that I wanted to try to make. I've always made scope levels that attach to the scope tube using an old ring. I've seen the B-Square (well, I've seen the pictures) that attaches to the dovetail and I thought that was an interesting idea. I don't know how they keep the mount from rocking upward from the clamping bolts on a 3/8" or 11mm dovetail.

I was interested in making the clamping mechanism for the dovetail attachment so it could be adjusted for level across the top of the gun. We'll see if it works. As I write part one, I truly don't know.

Half inch by half inch.

Chucked in the 4-jaw, roughly centered, then cut off hoping to get a relatively square end.

Ended up using a dial indicator to center the piece. It was actually fairly easy to center using the flats.

I'd purchased a cheap level at Harbor Freight a while back just for the bubble inserts. Took the level apart and have three of these. 3/8" diameter.

Spotted, then drilled 3/8" approximately 0.500" deep.

A small boring bar finished the bottom of the hole.

Set up the Taig lathe horizontal milling attachment. That's a 60 degree dovetail cutter. Small, delicate, expensive things. I almost destroyed this one the first time I used it. Resharpened it and it's still good to go. Played with the cutting speeds and it does better when run faster.

Used a lot of cutting fluid. The fluid lets the tool run at lower temperatures and prevents chips from binding to the edge of the cutter. A better finish results.

Tried a new (to me) cutting fluid. Cool Tool 2--worked fine, but it kinda smells like vinegar.

Bubble test fit is a go.

The dovetail is too narrow. I went back to the mill and made it wider.

It was far too long.

Milled the just-cut end.

A little layout fluid to mark some holes. It'll get drilled as one piece for alignment then cut.

A couple quick passes of a file flattened the base.

A few more steps later...


Paul said...

Derrick -

First, I want to say I am fascinated by the projects on which you and Nick work. I am no machinist, but I have aspirations of pursuing that as a hobby someday. I do have, however, an extensive amount of experience in woodworking, and I'd like to offer a tip that is used in that craft that might have an application to the work you describe here.

You made a comment about the fragility of the dovetail cutters. Woodworkers, when cutting a long dovetail slot, will often make the first pass with a straight router bit to hog out a majority of the material. They then follow up with the dovetail bit on a final pass. I'm wondering if you could follow the same process here - make the first cut with an end mill to remove most of the metal, and finish up with the dovetail cutter.

derrick38 said...

Yep, you're right on the money. I should have made (or at least made mention to) such a cut exactly as you've described. I was too lazy to make the cut--largely, because the dovetail cutter was already damaged and I have a brand new spare. Didn't feel like I had much to lose.