Saturday, December 22, 2018

Cutting Tools Must be Kept Sharp

Every time I replace a dull cutting tool, I am thrilled at how much easier the task becomes.  I recently replaced the 100 tooth blade on my chop saw, and wow: 1/8" wall aluminum tube cuts so much quicker and with less rough edges.  Once you are through the top and bottom, where you only have the side walls, it always goes quickly.

I made a very nice discovery the other day.  The side of this Alcoa tubing has printing on it identifies the alloy (6061) and various standards that it meets.  I have always tried to remove it by sanding, which can take a couple of minutes and then a couple of minutes to get the other three sides consistent.  It turns out this printing is just ink, and a small amount of acetone (or fingernail polish remover which is acetone with nicer smell) just wipes this off with very little rubbing.  I no longer need to sand the other three sides to get a consistent finish.  I only need to sand the ends and break the ends of the faces at each end.

Next steps in reducing labor and thus increasing profit margins:

1. Find a way to hold the inserts in the vise so that I can drill and tap the 1/2"-13 holes in one operation.  I mentioned some weeks back that I need taller vise jaws, but I have found a solution: the piece of acetal that I machined to hold the 30 degree angle inserts in place will be held by two 1/"2 thick aluminum of steel sheets that are bolted into the acetal.  (Countersunk holes in the aluminum so flat head screws won't run into the vise jaws.)  Then 3/8"-16 thumbscrews in the plates to lock down the insert.  I doubt that the side plates will get me to exactly level, but I will square them with that hope.  Right now I use a bubble level to get the hole into the insert as parallel to ground as I can.  I can still move this assembly in the vise to get to level.

2. The other labor reducing step involves cutting 4" tall shims of thicknesses from .020" to .065".  (These provide both a tighter fit between the bolts that lock the sleeves on to the legs and distribute stress to reduce cosmetic damage to the legs.)  The current battle is that trying to cut these 4' long pieces of sheet into 4" tall shims on the shop saw sends the pieces flying (where bend on impact) or under the saw's back fence (same result). 

On the bandsaw, the material is so thin it slides under the fence and often ends up with less than square shims.  My solution is an aluminum U of two 1/2" thick pieces held together by two 1/4"-20 bolts with through holes on the top piece and threaded on the bottom piece.  The U has an internal depth of 5".  Then, threaded 1/4"-20 holes on the top piece of legs of the U where 1/4"-20 thumb screws secure the sheet to the bottom leg of the U.  The combined height is a but more than 1" (a washer between the bolts holding U top and bottom together leaves room for all thicknesses of shim sheet).  That combined height will not slip under the bandsaw fence,  Each time I cut a 1.75" wide slice, I withdraw the fixture, loosen the thumbscrews, and push the sheet up against the bandsaw fence, retighten the thumbscrews and make another cut.  Making the U at least 4" wide  enables me to cut shims in all the widths that I need: 1.25", 1.5", 1.75" and 2.5".

1 comment:

Jim Dunmyer said...

If you're cutting aluminum shims, a shear would work well. Steel can also be sheared, but it'll take a more robust tool. I have on of those 3-in-1 machines (shear, brake, roll) that works great, but steel is limited to 20 gauge, about .020" thick. See: http://www.grizzly.com/products/Grizzly-30-Combination-3-in-1-Sheet-Metal-Machine/G4011 Mine is similar, but 40" wide and was much cheaper when I bought it 15-20 years ago.