[mr_cool]

Thought this would be the best place to help me with this question when refering to metalwork hand fitting.

How do you produce a sliding or mating fit using filing, scraping and lapping
techniques?

cheers

[JC.]

What job are you working on exactly and in what material?

Filing generally leaves you with a rough finish but is useful for removing a lot of material quickly

Scraping goes one step further than filing. Essentually a scraper is a blade with the edge folded over and will give a finish not too dissimilar to wet n dry paper.

Lapping is essentially a very fine surface finishing process. your goal would be to remove any machine marks or, in the case of something like a valve, creating a close as possible fit between two surfaces eg valve head and seat.
It's so fine that, if done propperly, will actually make a perfect seal.

Anyway, as I said, what's your project?

[Lara C.]

JC's your man :P

[mr_cool]

Cheers,

Im doing a engineering skills course which invloves making various things generally with mild steel by machining and by hand. The questions I were answering were all based on general hand fitting skills.

I was not sure what it meant really by produce a sliding or mating fit - can you do this by filing.

Cheers

[JC.]

Think back to the example I gave you of the valve in a cylinder head.

Once it's all assembled then the polished surface between valve head and seat IS a mating fit.

You would use all three techniques turning raw MS into the finished product if you had to start from scratch.

Have a word with your tutor. Find out the sort of thing he wants you to produce.

[mr_cool]

Ah I see what you mean now. I was not thinking along the lines of doing one after another to produce the finish.

Cheers

[JC.]

No probs.

I often wish I'd done an engineering degree instead of a music degree now.

-JC