bolt lug lapping compound

User00003

Well-Known Member
struggling to find 500 or 600 grit lapping compound for lapping the back of bolt lugs. most advertised stuff says 500grit, but actually it's 500GRAM! not GRIT!..very poor advertising via google.

anyhow, found 'some' from the US but it's in massive (expensive) batches, when in all actuality I need a teaspoonful:rolleyes: or about 10 pence worth.

is 220 grit such as the 'fine' paste part on chemico's double ended product too much? ie, will it take off too much and leave scoring, or will is do just fine,,no pun intended?

thanks for your input.

P
 
Valve lapping paste, usually comes in double ended tin. One end coarse, one end fine.


Perfect for lapping, bear in mind that you will alter Headspace if you use lapping without doing anything else.....


Depends how far the lugs are out of true of coarse, but its worth thinking about.


Most times I true actions, I find that the lugs are .001" to .004" out - I machine them on the lathe then polish with fine lapping paste after cutting the lug abuttments in the action to true concentricty.
 
be aware that valve lapping compounds are designed to take a considerable (in engineering terms) amount of material away to cut into valve and valve seat.
would have thought removing a similar amount from a bolt lug would be detrimental.

why do they need lapping?
 
that's why I was thinking 600 grit or finer would be the best to use. I put some blue markup blue on the back of the bolt lugs and they show a high degree of contact, but a minor amount of lapping would see them completely trued, in fact, it would be very very little so I don't think the headspace would really be altered, just a fine-tuning exercise that no, is not 'really' necessary:rolleyes:
 
The finest of those pastes on that link I pasted is 25000 - buy a tube of that and you can polish to your hearts content without affecting the headspace...:)
 
you shouldnt be messing with lapping compound unless you have access to head space gauges ,and it wont correct untrue bolt lugs they need to be cut in the lathe to true them up then lapped for full contact along with the action lugs
 
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