More work on copper laps

pmace

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Thread starter #1
I use Lindsay templates with 1/16" copper practice plates built up to 1/2" as lapping plates. Plates are sanded in a cross hatch pattern with 400 grit emery paper then finished with a 40 micron diamond hand pad to get rid of burs and any residual abrasive.

Diamond paste cut with whatever extender the vendor sells works great. The problem is it's messy and expensive. I use powder. I've found you need something to suspend the abrasive. Oil based products work but are messy. I find that for me a 50/50 combination of water and propylene glycol (RV antifreeze) along with one drop of Jet-Dry dishwasher rinse agent works in a 30 ml squeeze bottle (I stole this idea from the lapidary guys).

The smaller mesh diamond powders (14,000 and 50,000 mesh in my case) need cleaned before using. They may start out as the stated mesh size but by the time you get them they have clumps that will leave scratches. I put some powder in a juice glass, add some water and a drop of Jet-Dry and try and smash out the lumps with my finger. Stir it up and suck out the dirty water with a plastic pipette and put it in your dispensing bottle. Throw away the black stuff left in the bottom of the glass. The dirty water is your clean abrasive slurry. If you want you can let that settle out and decant some of the clear water on top. Add the PG and you are ready to go.

Two drops of slurry on a lapping plate is all you need. 30 seconds each of 14,000 and 50,000 do the face and heels if the tip is ok. If not then add 30 seconds to a minute with 3,000 to get the face repaired.
The journey continues. Next step is to sacrifice a piece of cast iron and see what happens.
 

John B.

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#2
Paul.
Try using the small diameter cast iron frying pan from Harbor Freight.
Cut the handle off and drill and bush a center hole and it can rotate on a power hone or even a slow turning small drill press with a mandrel.
 

monk

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hmmm. i'm wondering if a cheap imported, diamond impregnated disc could be used. the ones i have are absolutely flat. could one not just turn the disk over and charge it with the grit of choice. i have a 120 that i've never used. i just may give that a try. i'll mention my results after i try it. the things go for around $11 to 13 bucks. not enough to break anybodys' bank. i just use wd40 and a toothbrush to clean them overtop a trash can.
 

monk

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I use Lindsay templates with 1/16" copper practice plates built up to 1/2" as lapping plates. Plates are sanded in a cross hatch pattern with 400 grit emery paper then finished with a 40 micron diamond hand pad to get rid of burs and any residual abrasive.

Diamond paste cut with whatever extender the vendor sells works great. The problem is it's messy and expensive. I use powder. I've found you need something to suspend the abrasive. Oil based products work but are messy. I find that for me a 50/50 combination of water and propylene glycol (RV antifreeze) along with one drop of Jet-Dry dishwasher rinse agent works in a 30 ml squeeze bottle (I stole this idea from the lapidary guys).

The smaller mesh diamond powders (14,000 and 50,000 mesh in my case) need cleaned before using. They may start out as the stated mesh size but by the time you get them they have clumps that will leave scratches. I put some powder in a juice glass, add some water and a drop of Jet-Dry and try and smash out the lumps with my finger. Stir it up and suck out the dirty water with a plastic pipette and put it in your dispensing bottle. Throw away the black stuff left in the bottom of the glass. The dirty water is your clean abrasive slurry. If you want you can let that settle out and decant some of the clear water on top. Add the PG and you are ready to go.

Two drops of slurry on a lapping plate is all you need. 30 seconds each of 14,000 and 50,000 do the face and heels if the tip is ok. If not then add 30 seconds to a minute with 3,000 to get the face repaired.
The journey continues. Next step is to sacrifice a piece of cast iron and see what happens.
if you took a brand new graver and wo®ked it up, at what grit level would you change over
tot he powder ? just curious.
 

DanM

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#5
I use Lindsay templates with 1/16" copper practice plates built up to 1/2" as lapping plates. Plates are sanded in a cross hatch pattern with 400 grit emery paper then finished with a 40 micron diamond hand pad to get rid of burs and any residual abrasive.

Diamond paste cut with whatever extender the vendor sells works great. The problem is it's messy and expensive. I use powder. I've found you need something to suspend the abrasive. Oil based products work but are messy. I find that for me a 50/50 combination of water and propylene glycol (RV antifreeze) along with one drop of Jet-Dry dishwasher rinse agent works in a 30 ml squeeze bottle (I stole this idea from the lapidary guys).

The smaller mesh diamond powders (14,000 and 50,000 mesh in my case) need cleaned before using. They may start out as the stated mesh size but by the time you get them they have clumps that will leave scratches. I put some powder in a juice glass, add some water and a drop of Jet-Dry and try and smash out the lumps with my finger. Stir it up and suck out the dirty water with a plastic pipette and put it in your dispensing bottle. Throw away the black stuff left in the bottom of the glass. The dirty water is your clean abrasive slurry. If you want you can let that settle out and decant some of the clear water on top. Add the PG and you are ready to go.

Two drops of slurry on a lapping plate is all you need. 30 seconds each of 14,000 and 50,000 do the face and heels if the tip is ok. If not then add 30 seconds to a minute with 3,000 to get the face repaired.
The journey continues. Next step is to sacrifice a piece of cast iron and see what happens.
Cast iron lap instructions.............. http://www.gemworld.com/CastIronLapPrep.asp
 

gcleaker

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#6
hmmm. i'm wondering if a cheap imported, diamond impregnated disc could be used. the ones i have are absolutely flat. could one not just turn the disk over and charge it with the grit of choice. i have a 120 that i've never used. i just may give that a try. i'll mention my results after i try it. the things go for around $11 to 13 bucks. not enough to break anybodys' bank. i just use wd40 and a toothbrush to clean them overtop a trash can.
The problem with turning the disk over is cross contamination before it is all said and done you will have a mix of 14k and 50k on both sides. Not what you want. Dedicated lap for each grit.
 

monk

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The problem with turning the disk over is cross contamination before it is all said and done you will have a mix of 14k and 50k on both sides. Not what you want. Dedicated lap for each grit.
tyvm 4 that. i'm well known for not thinking things out.
 

monk

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ok, here goes. i took one of my discs, totally cleaned it with wd40. followed with a couple rinses in 91% alcohol. after sterilization, charged it with a bit of diamond, 50k grit. ran the dc motor at maybe 40-50 rpm. left a polish as good as i would ever need. btw, i used the back or bottom side to do this. other techniques may be better, but this way would work for me.
 

pmace

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Thread starter #11
From what I understand on the internet the finer grits work by rolling around between the lap and the work. Coarser grits are charged into the lap surface and more or less stay put. Using a harder lap like steel or ceramic works on finer grits but not on coarser grits. You can charge 600 and 1200 into a copper lap and it acts just like an electroplated diamond stone.

I don't have a power hone so everything is by hand with templates. I have a bench grinder with diamond plates for rough shaping but final shaping, sharpening and polishing are by hand. 600 grit takes metal off pretty quickly once you've got the basic shape.

I tried a piece of cast iron and wasn't impressed. Maybe on a power hone it works but it doesn't seem to work as well by hand as the copper. Plus the copper is free because I'm using the back side of some used practice plates.

The only pain in the neck is washing the finer diamond powders. I've tried two different vendors (Kingsley North and Tech Diamond Tools) and both need washed. Granted they are 1/3 the price of GRS and others so I guess you get what you pay for. That's why my slurry is water-based where if you use more refined powder you can use something like WD-40.

It's an interesting experiment and saved me from having to buy a new set of electroplated diamond plates. As soon as I get another practice plate to work with I'm going to try 325 grit and see if that for faster shaping.
 
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