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To Lap or Not: That is the Scope question
- Thread starter TXAZ
- Start date
If you do choose to lap the rings,I'll give you a tip.
Your grit size is part of the equation in the resulting size of the ring id.
To say it another way,if you use a true 1.000 bar and apply a lapping compound,it won't cut a 1.000 hole.
Grit size,say 320 grit,is a screen size.The rocks will be about 1/320th of an inch,or .003125.As they cut on both sides of the rod,the effect on the diameter of the cut might be estimated at about .006.
As a general rule in lapping,the grit will embed to a degree in the softer material.It then becomes like the tooth of a file,and is driven by being embedded in the softer material.
A 400 grit we can estimate will approach cutting .0025 per side,or .005 on the diameter.
A former employer had a Swiss turning machine.The bar stock is fed in through bushings,an so the bar stock they would use would be precision OD ground .005 under nominal size.So,the 1 in stock was .995.30 mm nominal size is approx. 1.181,and there was stock about 1.176.
I was able to save myself some bar ends for lapping rings.
If 400 grit was a little tight,320 would work.
An important concept,if we are lapping in a fit,the traditional idea of working coarse to fine grits does not work so well.
Whether lapping a slide or firelapping a bore,the coarsest grit will create the most clearance.
If you want a close running fit,don't start with 240 planning to work down through 800 grit..The 800 grit cannot put steel back on.
If ,for example,you want about .001 running clearance frame to slide,try a 1000 or 800grit,as your first and only grit.
Your grit size is part of the equation in the resulting size of the ring id.
To say it another way,if you use a true 1.000 bar and apply a lapping compound,it won't cut a 1.000 hole.
Grit size,say 320 grit,is a screen size.The rocks will be about 1/320th of an inch,or .003125.As they cut on both sides of the rod,the effect on the diameter of the cut might be estimated at about .006.
As a general rule in lapping,the grit will embed to a degree in the softer material.It then becomes like the tooth of a file,and is driven by being embedded in the softer material.
A 400 grit we can estimate will approach cutting .0025 per side,or .005 on the diameter.
A former employer had a Swiss turning machine.The bar stock is fed in through bushings,an so the bar stock they would use would be precision OD ground .005 under nominal size.So,the 1 in stock was .995.30 mm nominal size is approx. 1.181,and there was stock about 1.176.
I was able to save myself some bar ends for lapping rings.
If 400 grit was a little tight,320 would work.
An important concept,if we are lapping in a fit,the traditional idea of working coarse to fine grits does not work so well.
Whether lapping a slide or firelapping a bore,the coarsest grit will create the most clearance.
If you want a close running fit,don't start with 240 planning to work down through 800 grit..The 800 grit cannot put steel back on.
If ,for example,you want about .001 running clearance frame to slide,try a 1000 or 800grit,as your first and only grit.