As a follow-up to one of my recent posts, I received this question...
Matt
My Response
Regarding the screw - Most screw manufacturers will recommend that you use an outside micrometer. Since the flights do not match up, you should lay a block gauge block across a couple flights on one side of the screw and deduct the thickness of that block from the overall measurement. For consistency, you should note the distance, from the end of the screw, that the micrometer contacts the screw. As a result you should have a table with lengths and corresponding diameters.
Regarding the barrel - Using an inside micrometer, most companies will follow a similar procedure as with the screw. The diameters should be take at specific distances down the barrel and be listed in a table of lengths and diameters.
Additional Thoughts
You should avoid using a surface plate with a height gauge to measure the screw wear... This will often mask the areas of the screw with high wear.
-Andy
Andy,
Don't you mean an inside micrometer to measure barrel wear?
Keep on Molding! Keep on blogging and training too!
Brent
Thank You Brent,
I have made the correction.
-Andy
Hello Andy.
Does the new screw have to same diameter in front, middle and back?
Milan
Milan,
Typically... yes, though I will blog on this in more detail next week.
-Andy
Andy,
I measured diameter of screw today, but more wear was on metering zone than on feed zone, why?
Is it normal?
Milan
Milan,
This is normal due to the higher amount of material passing over the flights in this region.
-Andy