Question 1

Can I use this for a feeding ramp on a 1911 45 acp?

Accepted Answer

Technically, you cannot polish a metal surface w/o removing metal. As a machinist, the amount of metal you remove may not need to be more than .00001", (one ten millionth of an inch). However, that's to be very 'technically literal'. Gauge blocks or pin-gauges, in mold & tool making instances would be very concerned about .00001". Still, my point is that, in metal materials, one must remove a certain amount of that metallic surface in order for it to be polished.

The ramp of a 1911 would likely polish up easily providing the gun maker didn't leave tool marks deeper than .0001" (one, one ten thousandth of an inch). The American measurement system in machine shop and manufacturing in general, has always made it hard to explain to someone who would typically note "one tenth of an inch" like this: 0.100.

In fact, in a machine shop, if you said something like "face-off one tenth", the machinist would remove only this much material: 0.0001, which is extremely small.

An average human hair is about .005". One tenth of a human hair is .0005". Therefore, "one ten thousandth of one inch is .0001", which is 5 times smaller than .0005" and about 1/50th of a human hair...

I guess this is why they're trying to convert to the metric system. I retired almost 20 years ago and even then, there was a lot of resistance to converting to the metric system because the measure tools, cutting tools, blueprints, and the general machining references would all have to change.

Just the machinist's standard set of measuring tools that each experienced machinist of 5 to 6 years or more, owned, would have cost well over $500 in 1980, and over $1100 in 1987.

Very few of the tools purchased before 1985 included a metric scale and many still don't. I owned an advanced set of hand tools purchased over a 25+ year time span. In 1992, I was contracted to a small tool-making machine shop, which was broken into and all the tools were robbed.

The company's insurance would only pay 80% of each man's replacement tool costs. I received a $4200 check and I was not very happy about it...

So you can see why many American machinist don't want to switch to the metric system. It could potentially be very expensive and that's just one aspect of at least five conversion points, which the complete conversion could cost.
FWIW

Question 2

can you use this as a final polish on agate?

Accepted Answer

Thank you for asking your question.  Our polishing compound is 400 grit and not something you would use for a finishing compound. We would recommend you get a jewelers rouge with a higher grit to do the final polish on agate.

Question 3

It is suitable for polishing glass..?

Accepted Answer

No, Dremel 421 polishing compound will not polish glass.

Question 4

Can anyone say with authority what the grit size is and what material the grit is?  Is it diamond or quartz/sand or something else?

Accepted Answer

Hello,

The compound is 400 grit.  It is 76% silicon carbide and 24% vitrified bond.  It is not classified hazardous.

Manufacturer	Dremel
Part number	421
Item Weight	27.2 g
Product Dimensions	10.48 x 0.43 x 10.48 cm; 27.22 g
Item model number	421
Size	Pack of 1
Color	Silver
Material	Solid Compound
Item Package Quantity	1
Grit Rating	421
Grit Description	Light
Included components	household-polish
Batteries Included?	No
Batteries Required?	No

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Dremel 421 Polishing Compound

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