Sunday, May 27, 2018

Today's Machining Lesson

I have long run into the problem that cutting small pieces of material is dangerous and scary on the chop saw and my vertical band saw has trouble with straight lines in aluminum.  I have built several jigs over the years to hold round, rectangular, and square material safely for the chop saw.  These are usually square or rectangular tube with 3/8"-16 bolts locking the material down, with a C-clamp holding the tube to the fence.  But once you get down to 3" long or less, or flats that are too wide to fit into my existing collection of such cutting jigs, you are entering the odd and somewhat scary use of C-clamps to hold everything down for cutting.

One of the pieces that I needed to cut for today's project was 1.654" x 1.336", too small for any jig, clamp, or other "keep the fingers attached" approach.  Some months back, I observed that at a low enough feed rate. I am sure this Sherline could slice through a battleship.  So why not use it as the world's most complicated chop saw?

The chop saw gets the material to a size that fits into the mill vise (or rather the hackery that I am using to hold pieces more than 2" wide).  If I feed fairly slowly, the 1/4" endmill produces a very ugly slice which I then clean up with another pass using the 3/4" endmill which makes a very nice finish.  (I think the finish difference is that they have different numbers of cutting edges; one better suited to aluminum.)

I still have not received the replacement fuse so Y axis is still handpowered, but the adjustment to match the needed feed rate is intuitive.

3 comments:

Will said...

One of the techniques I use with a chopsaw for small parts is to sacrifice a longer piece of wood. I clamp that in the saw to stabilize the small part. Sometimes I sandwich the part with two pieces of soft wood (like pine) to get a better grip on it.

B said...

Believe it or not, if it is flat, you can use a carbide blade in a table saw. (I also use this method for small square tubing. Keep your feedrate low and don't get the blade too hot or it will warp, with much merriment if that happens.

Or as has been discussed above, sacrifice pieces of thin wood (or plywood, or paneling) to hold your parts in a chop saw.

Mauser said...

Remember when cutting metal the key is "Surface Feet per minute". Cutting too slowly can also produce bad results much like cutting too fast. The 3/4" end mill (I'm assuming you're cutting with the side) Basically is running 9 x faster at the surface than the 1/4". All other things being equal, try speeding up the RPMs on the 1/4" cutter.