Making a level Part 2 .. Found a block of Invar.. scraping

[w1vlf]

Hey Folks,

Thanks everyone for your comments on the material I should use for my homemade level.
While on the hunt for a suitable cast base for my 98-6 vial, Steve from Connecticut piped up and mentioned he had a Starrett 98-8 level available for a more than reasonable price. Thank you Steve.

I remembered that I had some Invar pieces that were used in an electronics components where thermal characteristics were of paramount importance. The bar is about 8" long by 3" x 2" and it weighs a few lbs.

The bar has 5 holes bored into the 3" axis that go completely through.
So I guess that I would like to know if would I be better off mounting the vial to the on top of the 3" axis, or the on top of the 2" axis which has a flat top and bottom.

On another front I milled the top and bottom of the Invar block and proceeded to see how flat it was using my surface block.

The good news is that I finally got to do some scraping. After bluing the plate I slide the Invar block across the surface plate and found I had several high spots, so just like the videos I have watched I scraped off the high spots. Low and behold the next bluing revealed many more blue spots, repeat over and over, till finally the whole Invar block was blue, even with a very thin coat on the surface plate.

Repeat for the other side. When I was done I could slide the block across the plate with a dial indicator only about .0005 difference across the block.

This seems too optimistic to me I am I averaging the reading because of the size of the block??/
Seems to good tobe true

Any ideas folks?

Thank you
PauLC
W1VLF

[wsippola]

Well I haven't done any scraping, but from what I've read, it certainly sounds like you're on the right track.

I don't how large your vial is, but I expect it would fit inside your block of invar. Mill a deep slot on the 2" face, deep enough to bury the vial in. Mill a crosswise slot at the depth of the vial, which would leave the vial visible from both sides and the top, while providing a reasonable amount of protection to it.

Wayne

[Conrad_R_Hoffman]

You're doing good. Scraping can get you even better with enough patience. BTW, don't ask what the Invar piece is worth- it cost a bit more than you're average high nickel alloy. Since you didn't complain about machining it, it's probably Invar 36FC (FC=free cut).

[Comstock-Friend]

On my Starrett 98, the main vial is mounted on pads cast on the top of the cast bar. The vial in not fitted inside a slot.

There is also a V-groove machined longitudinally along the lower surface to allow the level to be mounted on round stock. And there is a small level vial at right angles to the main vial, probably to allow the bar to be approximately leveled when using the level on round stock.

http://www.starrett.com/metrology/produ ... il?k=98-12

John Friend