On Wed, 16 Nov 2016 11:50:14 -0800 (PST), robobass
wrote:

On Wednesday, November 16, 2016 at 7:24:41 PM UTC+1, Larry Jaques wrote:
On Wed, 16 Nov 2016 06:49:58 -0800 (PST), robobass
wrote:


Y'think? That's 51.6% faster than your ideal. Why didn't you slow
down the lathe? Or did that speed work best with the density of the
larger diameter brush?

Jawohl, Herr Jaques! I slowed down the lathe to 550 for the 10" wheel, and everything works perfectly now. This wheel should last for years, so I will stop fretting about finding 3" wheels that are real brass.

Great. Glad I could help. It's amazing the simple things we can
overlook, or perhaps, are too lazy/hesitant at the moment to change
things.

I don't know why I didn't try to match the surface speed when I got the big wheel. I guess 550 just seemed so slow!

I was going to mention that, but you said "everything works perfectly
now" so I let it alone. 705rpm is your ideal speed, unless the
density of the brush changes that.

Thanks for the calculation. I did it at one point, but have lost the data.

It is a simple formula. Pi x diameter in inches x rpm (or 2 Pi r).
You said that a 3" brush at 2350rpm was good, so 9.424778 is the
circumference and 22148.23ipm the speed. The 10" @ 1100 is 34557.52ipm
and @ 550rpm, it's 17248.76ipm. 705rpm brings it to the same as the
3", 22148.23, or 31.76fps. Something itchy in the back of my head
says that wire wheels are counted by the bristle rather than sfm.


With the belts on my lathe, it is quick to change between 550, 1100, and 2200, but a bit more involved to get other speeds. Yes, 550rpm works well for initial cleaning with tripoli. I think I will try a Tampico brush for the final finishing, as that is still a bit laborious. I use a super fine compound that is not rouge, and I use heavy sewing thread to clean it out of the machine threads. Yes, this is a process intensive operation, but my niche market seems to appreciate the effort. I'm still in business, anyway!

550 it is, then. What's the density diffenenc between the old 3" and
the new 10"? Most 3" wheels I've seen are pretty sparse, and large
wheels tend to be much more densely bristled. At 550rpm, you may
already have the same number of whiskers whisking per rpm as the 3".
I'll bet Tawm knows the actual term for that. snort And I know
from experience that faster and/or denser wheels are harder to get to
dig down to clean the root of the thread.

Just curious, did you ever try a die to remove the scale? I wonder if
that wouldn't clean it enough to simply polish the rest out. Seems
quicker, but would it leave a looser fit? Wire brushing can do that,
too. Six of one...

--
I have never understood why it is "greed" to want to keep the money you
have earned, but it is not greed to want take someone else's money.
--Thomas Sowell