Sandpaper as a part is easy to make in bulk due to affix double faced tape to backside of the sandpaper and punch through by a punch. That's copy of someone's page. However it's unsuitable to peel off and paste for exchange the sandpaper. That's bother and a paper peeled off at once could not used.

With that, I tried to make an attachment for sandpaper which desired to be quick released.

In this case, I tried to look various items due to cruise many shops.



As it looked, tried to explain

to fix a seating to the head pulled out brush, which desired to bear with a high impact.

to fix a silicon wafer to the seating which could not be fixed by normal bond but denatured one, which would make high friction.

to grind convex side of a cap to be flat, and fix a mirror button to that with bond beared with a high impact.
It's okay to use a polished disk instead of a mirror button, which could be a seating for sandpaper.

I made five seating caps for use five types of sandpaper.

for #120, 180, 320, 600, 1000, 1500



It's working well. I felt it's only electric tool that could grind easy as a first impression. It seemed to have a high torque with two AA batteries.

It's easy to delete a parting line, to polish surface and so on. It might be used to grind soldering of high frequency circuit, to polish a LED and a collimator lenz. Anyway, an electric tool could do such tasks like a dream in short time.
It took kinda long time to use fine sandpapers. For that, I expected a variable voltage power supply to adjust.



I would sway confidence for purposeful behavior due to have such a tool.

-- Buffalos caused a growth of the horn to gore, or learned to gore cause the horn was grown? As that classic question, even if neodarwinism has no answer. This maybe get somewhere around Haeckel's unitarism.

Like that, I would consider about relation a spin grinder and the evolution.

What could it use for a power source?
It's dangerous to use AC source for home use, and that's needed a trans and a bridge which are relatively large parts, and it would be difficult to inmount them to the spin brush and it would be heavy. With that, it's better to use an AC adaptor for its weight.

An appropriate one of AC adaptors on desk use could be used, which has voltages around 12 ~ 5V, that's enough for a power source of the spin grinder.
A variable voltage power supply has wide allowable range.



As for a variable voltage power supply used three terminal regulator, it could used LM338, 335, 317, which could lead 5.0A, 3.0A, 1.5A in order, which all are enough.
The circuit would be inmounted to the cap for exchange batteries.

I used 1000uF for C1 condenser side of V-in, which could be allowed for power source which is not so smooth. Case with a trans and a bridge, it would be more large capacity.
As a diode, it might be no need though, for prevent spike current.

Voltage for output would be determined by R and VR, which range is 1.25V ~ 9.2V as theory value which upper value is Vin - 1.5V.






A hole of the cap bottom is let into driver which could control the output voltage.
It's better to use VR as encapsulated type though.



I thought it's easy to exchange the motor due to be inmounted all of circuit to the cap. The motor would be heat slightly after endurance test one hour running with 8.0V.

kinda density.
There is no space for mounting a jack connector, which was pulled out with a connector wired.













If there were large difference in potential between V-in and V-out the regulator would have a fever and need a cooling body.
In use few voltage as difference in potential, a cooling body might be no need.

I would make holes on the shell as exhaust heat holes.



As a variable voltage power supply, I made an external output terminals.





Two copper pipes were mounted as terminals for output which inner diameter was 2mm as a standard pin terminal.



However,











make it this far,

It was better to make a general purposed variable voltage power supply, separately from the spin grinder, and use it for power supply for the spin grinder and others.

what's ideal?

variable voltage as 1.25V ~ 24.0V.
with a voltmeter and an ammeter.
power source as AC powered for home use with a trans and a bridge, large capacity condenser.

A bird cries too late when it is taken.

with cooling body for the regulator.



Finished

The shell is very tough made by ABS regin which is hard to think its cheap price.
And the motor which was concerned has high torque and high voltage resistance.

Unexpected weak point exposed due to continuous running test one hour with 8.0V.
That's the fragility of a shaft bush.

Practical use is ranged 3.0V ~ 5.0V though, some day it would be broken.
It's better to add strength during into creating.



reserve brushes



As for the part of a shaft bush, it lost the accuracy at once that would progress as law of diminishing return.

It's a link mechanism.
A front edge of shaft is shaped as 'S' and it would make a head oscillating due to shaft rotation. Therefor the part of shaft bush became stressed.

However, the part of ABS resin is thin.



added strength.

to fix a washer which has a hole as same diameter of shaft to the part due to reeve the shaft to its hole.
with superglue with crashproof.











I bought one more.



This is a must have tool for modelers.