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The Finished Part Blog

The Finished Part Blog

Wednesday, June 10, 2015

Mesh vs Grit

There is often confusion about the differences between the terms mesh, grit, sieve size, micron, micro-inches and others. These are all terms used to describe physical particle sizes. With regard to abrasive blasting and other applications that use that type of media, these terms - especially grit and mesh - (while technically different) are used interchangeably.

A more detailed article is available on our website HERE.

Tuesday, May 5, 2015

Black Acrylic Polishing

Polishing Black Acrylic
We have written a number of posts about polishing acrylic (here, here and here and more). The 4-step dry tumbling process with Hardwood Media and the Finishing Creams previous written about and detailed in this article has proven itself with multiple types of acrylic parts and with multiple colors.

Black can be a particularly challenging color as every imperfection in the surface will seem to stand out. The before and after parts above show that even with black parts, the parts can shine like glass.

Tuesday, April 14, 2015

Wood Part Tumbling

Cleaning Wood Tumbled Parts
A common process for removing machining marks, hairs and rounding edges on wood parts is barrel tumbling with Hardwood Media and White Aluminum Oxide Grit. This will eliminate the need for a series of hand sanding steps but can leave White Aluminum Oxide Grit lightly embedded in the surface of the wood pores (see part on left above). This leaves the wood with a white discoloration and makes it more difficult for additional finishing.

This issue can be resolved (especially with harder woods) by tumbling the part in a Walnut Shell Grit. The part pictured on the right was barrel tumbled with a Walnut Shell Grit - 12/20 Medium for 30 minutes. The white grit was removed and the wood color was restored. The part is now ready for further processing like stain, paint or wax.

Tuesday, March 24, 2015

Cleaning Routered Wood

Routered Wood Parts
When wood blocks are routered  or machined to a specific geometry, there are always rough surfaces and wood burrs or hairs where the router enters or leaves the part. The part pictured on the left shows this condition very clearly.

Removing these burrs and achieving a smooth finish is a relatively simple process. Barrel tumbling the parts with a Hardwood Media and White Aluminum Oxide Grit will clean up the part and leave it smooth and ready for further processing. The cycle time to accomplish this task will depend on how rough the raw part is, what grit size of abrasive is being used and how much edge rounding is desired.

Barrel tumbling is a better process than vibratory tumbling for this application. The barrel will force the entire load (media, abrasive and parts) to stay mixed and performing optimally. A vibratory process will likely tumble the media and parts but the abrasive will often not stay uniformly mixed.

Tuesday, March 3, 2015

Polishing Stainless Steel

Stainless Steel Polishing
Machined stainless steel parts typically have sharp edges, burrs and a matte surface finish. Vibratory tumbling can be used to get a polished finish sometimes even down to just a few Ra surface profile. This is often a multi-step process.

The part on the left is the 'raw' part ready for deburring and polishing. The first step is to deburr and round the edges. This was accomplished using a KM general purpose Ceramic Media. This was a wet process using a solution of Kramco 1010 General Purpose Compound. The result at this point (not pictured) was a matte, tumbled finish with rounded edges.

The second step needed to get the pictured polish (on the right) involved tumbling with a Precision Ceramic Sphere and a solution of Kramco 2020 Burnishing Compound. Generally, a rounder media will produce a smoother finish than an angular media.

This part could be further polished with other tumbling media or hand buffed to a near-mirror finish.

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