Saturday, July 18, 2020

The Importance of Power

No, not political power.   Milling power.

I have been machining an adapter to hold my 0x finder on my big telescope.   All the dimensions are right (after a number of math errors but all the extra holes are hidden) but even made of acetal,  the extra weight at the top of the telescope creates a balance problem, so I decided to fenestrate the bigger parts.   But running an end mill through 2" of acetal with the power of a Sherline mill is very slow.  So I am having it mark the holes by cutting .2" deep, then I will use the drill press with the 7/16" end mill to cut through.

At some point I will build a shop so that I can get a more powerful (and certainly) larger CNC mill.

Downside of more power: for the first time in years, the acetal melted around the Forstner bit, requiring me to mill the plastic away from the bit to break it loose.  This is a pretty delicate operation.  But I figured out how to make a lighter part to do the same function.  No need to fenestrate.

Other than gasping for air once freed from its acetaliferous grave, the Forstner bit came out unscathed.  The 7/16" smoothing mill, however, has gobs of metal acetal.  I was reluctant to try and clean it out with a file or sandpaper so I pulled out a small magnifier and tried to burn it off. In spite of being a hydrocarbom, acetal does not burn.  /it melts and drips.  The magnifier is so small that it would take forever.  A cigarette lighter worked although evem slower.  Somewhere I have a 5" Sherlock Holmes size magnifying glass.  I will find it and finish melting the acetal off.

UPDATE: Acetal does burn; you need an overhead Sun, and more glass.  In this case a 6" diameter 34" F.L. lens that I received as part of a collection of throwaway parts from an aerospace company.  Yes, it burns very well with a much larger focused burning disc.  But I can't stand under that direct Sun very long, so this will be in several steps.  The good news is that don't need to hold both lens and end mill at the same time.  I put the end mill on a glass table and stood above it.  I wonder if I could put the end mill under the table and lens on top?

1 comment:

  1. I think that even if I'd bought a bigger lathe and a bigger mill, I would still want both tools to be even larger.
    I'm sure that there were things that even the huge machine tools the shipyard's machine shop just couldn't chuck.

    Sometimes an errant hole can be tapped for a fastener.
    If it has a fastener in it, it must be there for a reason.