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- Jun 24, 2010
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Thus far for finishing flats I have been an amateur wet-o-dry paper attached to glass plate kind of guy. I've been Googling lapping plates more out of curiosity, plus I will be receiving some lapping compounds for my cylinder trials & experiments shortly anyway.
I think I understand the basics - cast iron is preferred because its inert + can be trued + re-surfaced + has a surface type that accepts the lapping compound + relief groves can me machined in etc. Here is smaller example maybe catering to woodworking world.
http://www.leevalley.com/en/wood/page.aspx?cat=1,43072&p=59752
What I don't understand is:
- why the relatively deep recess grooves? I would think after only a few lapping circuits, 99% of the compound slurry will just reside in the valley not up on the flats where the cutting action is? Is there maybe a suction principle with the work piece that slurry gets sucked out & re-introduced to the top flats? If the plate had no grooves, wouldn't the excess compound just be pushed off on the side of the motion footprint?
- when vendors talk about oil/petroleum based lapping compound, either pre-mix or adding oil to dry grit, I can visualize the cleaning & re-charging with petroleum based solvent & you are good to go. So is water as a slurry carrier a no-no on the cast iron for obvious (rust) reasons? Maybe water based lapping is only for glass plates & ceramics surfacing for example?
- I also hear diamond compound is kind of specialized & be careful, because its so hard & sharp it can embed in both lap & part even when they are both steel & not easily removed. I've read where ultrasonic cleaners are required. So is diamond a non-no for CI lapping plate?
-because over time a (baseline quality 0.001") plate would wear into a dish or undulation, could a home shop guy ever hope to re-surface it to good original condition himself?
- what about this business of charging a lapping plate? I've heard you should roll it on. I can understand this mechanism for a softer lapping tool like brass or copper, but what kind of roller could be expected to 'press' this into hard CI?
- if you lapped yourself a nice flat surface A, now you simply want a lapped squared surface B, is there something like a 'fence' or datum that can be attached? I've only seen this truing action on scraping operations & even that is a different procedure. So is this getting outside the scope of a lapping plate?
I think I understand the basics - cast iron is preferred because its inert + can be trued + re-surfaced + has a surface type that accepts the lapping compound + relief groves can me machined in etc. Here is smaller example maybe catering to woodworking world.
http://www.leevalley.com/en/wood/page.aspx?cat=1,43072&p=59752
What I don't understand is:
- why the relatively deep recess grooves? I would think after only a few lapping circuits, 99% of the compound slurry will just reside in the valley not up on the flats where the cutting action is? Is there maybe a suction principle with the work piece that slurry gets sucked out & re-introduced to the top flats? If the plate had no grooves, wouldn't the excess compound just be pushed off on the side of the motion footprint?
- when vendors talk about oil/petroleum based lapping compound, either pre-mix or adding oil to dry grit, I can visualize the cleaning & re-charging with petroleum based solvent & you are good to go. So is water as a slurry carrier a no-no on the cast iron for obvious (rust) reasons? Maybe water based lapping is only for glass plates & ceramics surfacing for example?
- I also hear diamond compound is kind of specialized & be careful, because its so hard & sharp it can embed in both lap & part even when they are both steel & not easily removed. I've read where ultrasonic cleaners are required. So is diamond a non-no for CI lapping plate?
-because over time a (baseline quality 0.001") plate would wear into a dish or undulation, could a home shop guy ever hope to re-surface it to good original condition himself?
- what about this business of charging a lapping plate? I've heard you should roll it on. I can understand this mechanism for a softer lapping tool like brass or copper, but what kind of roller could be expected to 'press' this into hard CI?
- if you lapped yourself a nice flat surface A, now you simply want a lapped squared surface B, is there something like a 'fence' or datum that can be attached? I've only seen this truing action on scraping operations & even that is a different procedure. So is this getting outside the scope of a lapping plate?