Originally Posted by Mcgyver  I recall being told by an old hand that when finish scraping (ie light, small cuts) the depth of cut typically is in the neighborhood of a tenth, so that may be where it comes from
John thanks for the kind words - but i want to emphasize that old expression "the different between a layperson and expert is 5%". I happily share what i know but you'll get us both into trouble if you take it as being some deep expertise or authority on the matter. I'm no where near qualified to be the scraping expert....in fact by the time you finish the mill i think you're going to get to wear that hat around here  .
To your surface grinder vs scraping question, don't know if there is a big advantage once the job is done. Some even push back on the value of the oil reservoir benefit. still, its one big honking surface grinder to take the main castings of a mill - if you're not talking production, grinding might be precluded just because the equipment isn't available. I guess the other aspect is the nature of scraping mating parts. A is done to a reference and B is done A. for example, to surface grind dovetails that's going to take some careful work to keep the angles perfect so they mate. when scraping, we don't care, the exact angle doesn't matter, so long as the parts are the same. sort of like making model T's requires standardization and production but for onesy machine reconditioning the hand fit nature of scraping might be more efficient. |
I will probably have to buy the book that was mentioned in the other thread. It’s a shame to think out of 50,000 odd members none are skilled in scraping. For the sake of old mills/lathes needing re scraping and diy improvers with these Chinese mills it is a skill that should not be lost and more widely used imho. I’ve spent some time digging around on the net for information but it is thin on the ground to say the least.
Thanks any way for helping me getting started.
As for being an expert, is there any point? One thing for sure even with my very limited knowledge my cheap Chinese mill will be a far better machine for my efforts.
Regards,
John
If anyone reading this has the book (they will know which book I am talking about) it would be excellent if they can chip in here with some information.
EDIT :You threw me a bit there with your edit
One thing I would like to say about the scraped vs grinded surface. I have tested the effects of “sticktion” between the two and a scraped surface is far superior in eliminating/reducing this effect. END EDIT