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Abrasives with Screwhead Polisher

sstakoff

By sstakoff
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sstakoff WRT Addict

sstakoff

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Recently acquired a beautiful screwhead polisher:

polisher.thumb.jpg.bb6be4d0960084a0ff6208fe28d1a449.jpg

 

The polisher came with two jars of abrasive powder. One is carborundum and the other diamantine. I am looking for some guidance as to which abrasive gets used on which lap and advice on how to charge the lap. There is a steel lap, a brass one and finally a wooden one.  Thanks in advance!

 

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nickelsilver Distinguished Member

nickelsilver

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Diamantine and carborundum come in different grit sizes, you'd naturally want coarsest on the steel, medium on the bronze, and finest on the wood. 800 grit for coarse, 1200 or so for the middle, and to finish I like 1 micron diamond paste (about 14000 grit) would be my recommendation. Maybe even a little coarser for the steel if you want. Seems like a big jump at the end but in my experience works well. When I frequently used my similar tool I made up a tin lap to replace the wood. Now I use a tripod tool with 12 micron paper on glass to flatten, and 1 micron diamond on a tin lap. I find it's much faster than the above tool.

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sstakoff WRT Addict

sstakoff

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1 minute ago, nickelsilver said:

Diamantine and carborundum come in different grit sizes, you'd naturally want coarsest on the steel, medium on the bronze, and finest on the wood. 800 grit for coarse, 1200 or so for the middle, and to finish I like 1 micron diamond paste (about 14000 grit) would be my recommendation. Maybe even a little coarser for the steel if you want. Seems like a big jump at the end but in my experience works well. When I frequently used my similar tool I made up a tin lap to replace the wood. Now I use a tripod tool with 12 micron paper on glass to flatten, and 1 micron diamond on a tin lap. I find it's much faster than the above tool.

Thank you. I will check the grit sizes when I get home tonight. Assume you mix the powder with oil -  If so, any recommendations o=n type of oil?

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nickelsilver Distinguished Member

nickelsilver

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I've never heard the reason behind it but knowledgeable and experienced polishers have always told me it's better to use a good vegetable oil than a mineral oil. Colza is a good one. Nothing disastrous is going to happen if you use a thin machine oil though.

On the coarse laps the oil/abrasive can be rather wet, but on the final lap you want to rub it on and in with a clean finger or cloth, leaving a distinct layer but it should almost be dry. If it's wet the abrasive will clump together and ball up giving fine scratches along with the polish.

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vinn3 Distinguished Member

vinn3

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2 hours ago, sstakoff said:

Recently acquired a beautiful screwhead polisher:

polisher.thumb.jpg.bb6be4d0960084a0ff6208fe28d1a449.jpg

 

The polisher came with two jars of abrasive powder. One is carborundum and the other diamantine. I am looking for some guidance as to which abrasive gets used on which lap and advice on how to charge the lap. There is a steel lap, a brass one and finally a wooden one.  Thanks in advance!

 

    Very good!    what do you do if the screw slot is buggered up?

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vinn3 Distinguished Member

vinn3

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1 hour ago, nickelsilver said:

I've never heard the reason behind it but knowledgeable and experienced polishers have always told me it's better to use a good vegetable oil than a mineral oil. Colza is a good one. Nothing disastrous is going to happen if you use a thin machine oil though.

On the coarse laps the oil/abrasive can be rather wet, but on the final lap you want to rub it on and in with a clean finger or cloth, leaving a distinct layer but it should almost be dry. If it's wet the abrasive will clump together and ball up giving fine scratches along with the polish.

   I use synthinic (sp) oil,   veg. oil can mold.   the viscosity to use is the real question.  vin

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nickelsilver Distinguished Member

nickelsilver

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When you get to using it you have to make 110% sure you've cleaned the screw perfectly when going from one lap to the next. Otherwise you'll contaminate the lap and it will need to be resurfaced. Artist's gum eraser and old rodico do pretty well, finish with pithwood and a friendly solvent like isopropyl alcohol. It's tedious but less tedious than redoing the lap.

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nickelsilver Distinguished Member

nickelsilver

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    Very good!    what do you do if the screw slot is buggered up?
Depends, if the slot isn't beveled then simply polishing the head takes care of any raised burrs and makes the head look tidy again. You could run a screwhead file through it if really going for perfection.

On beveled heads a very fine cut square escapement file works well. Like a 6 cut or 8 cut if you have it. The file finish blends visually with the polished head and looks polished. A square degussit stone can also work but they often are too rounded at the corners. To keep the file centered in the slot leave the screw in the polishing tool, it will rotate slightly as needed keeping the file on track. If not using the lathe type polisher you can rest the screw in a bench block so it's supported by the head and the screw will align itself with the file.
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vinn3 Distinguished Member

vinn3

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8 minutes ago, nickelsilver said:

Depends, if the slot isn't beveled then simply polishing the head takes care of any raised burrs and makes the head look tidy again. You could run a screwhead file through it if really going for perfection.

On beveled heads a very fine cut square escapement file works well. Like a 6 cut or 8 cut if you have it. The file finish blends visually with the polished head and looks polished. A square degussit stone can also work but they often are too rounded at the corners. To keep the file centered in the slot leave the screw in the polishing tool, it will rotate slightly as needed keeping the file on track. If not using the lathe type polisher you can rest the screw in a bench block so it's supported by the head and the screw will align itself with the file.

   good show;  to de burr the slot.  I use a hone stone.  they are available in small triangle  or  small flat,  course or fine .  oil,  water or dry  vin.

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