Thread: Scraping Projects

Originally Posted by Greg Q

PDW you are welcome to collect yours on the way back south,

I have cause to go to Greg’s place, in the next week or so, with the trailer. Your welcome to stow that here, until you’re heading south. As you know you are virtually coming past on your way back to the ferry. I promise not to use it much.

Phil.

Petes, both of your plates are now at Phil's. We figured that it'd be closer for you, PDW, to call in there on your way to the Hume. Plus he has a better lifting rig than mine. I'll still meet you for lunch though.

Greg

Originally Posted by Greg Q

Petes, both of your plates are now at Phil's. We figured that it'd be closer for you, PDW, to call in there on your way to the Hume. Plus he has a better lifting rig than mine. I'll still meet you for lunch though.

Greg

Cool, that works for me. Thanks to both of you.

PDW

Just a quick pic to show scraping is not all for machine tools....

Here is an exhaust manifold that I repaired... My mill did not have enough X travel to do it all in one movement, so I scraped it to get it flat... It does butt up against gaskets so flatness is not 100% critical, but it is good practice...

Yes, but did you scrape in the side of the block to get a proper seat?



Michael

Originally Posted by Michael G

Yes, but did you scrape in the side of the block to get a proper seat?

What he said plus one. Did you eliminate the gasket. And go metal to metal? Kind of serious within the joke. Different industry to mine, but they talk of “oil tight” scraping for things like that, valve seats in big globe valves etc. Never seen it, just aware there’s a field the uses the technique for things other than machine ways.

I’m sure there’s a Vlad or Boris somewhere in Russia, that are half handy at scraping, but mostly on valve seats.

I’ve always wondered. People spend big money on race engines. Scraping the block and head faces must have some merit, but no one does it.

Phil.

Steam engine cylinder covers are normally scraped so a gasket isn't required.

Phil

Originally Posted by Machtool

Scraping the block and head faces must have some merit, but no one does it.

Hi Phil,

It certainly used to be done. Sometimes with a small groove around each cylinder to take a copper(?) wire.(ok technically ones I know of were lapped).

Maybe Hylomar is good enough and cheap enough these days?(if hylomar is still the in thing, its been a while since I was playing with cars that much)

Stuart

finally got around to finishing the bottom of the shaper ram
Attachment 212038
Attachment 212039
Attachment 212040
I also received an ebay bargain so i started scraping that as well
Attachment 212041
its 5"x8"x12" and weighs around 20kg
should be good for a master square for scraping once its finished
cleaning the rust off
i use the flat edge of the sandvik carbide to clean the surface rust off works realy well
Attachment 212042
first spotting
Attachment 212043
8 passes lots more to go
Attachment 212044
Attachment 212045
I have to travel to the US for work this week so will have to wait till i get back before I do any more

cheers
Harty

May I chime in?

You forgot about roughing. I see, that you are already attacking spots. That's way too early. Think in areas, not spots.
I highlighted the areas of your picture (8th pass) with the number of passes I would do within those areas:
Attachment 212051
Make those passed "blind". Means DO NOT blue in between. The spots you got outside of these areas are in fact strips (coming from your initial roughing where you had no overlap; thats a normal "error"). Those strips would get one pass.

After that, spotting blue. Two passes that correct errors due to the "blind" scraping with spotting in between and then "blind" scraping again depending on how much I was off with my guess.

The problem with scraping is, that you often waste A LOT of time in the beginning, because you fear to ruin something that is already bad.

After two to 3 or maybe 4 passes right from the start, you should get (have) a feel how much the surface is off. You see that by observing how quick your area of contact is spreading. If it is spreading slowly, the rest is way off. If it's spreading quickly, you are already close.

HTH,
Nick

Originally Posted by RayG

Must be getting close to having a surface plate stand show and tell..

That gets a big from me

Hi nick

Thanks for the info the ripples are from the original machining and you are right on being to light handed i will give it a go blind for a few passes as described and see how i go

Cheers harty

Hi Harty,
Looking great. Hows the arm?

Stuart

Originally Posted by Stustoys

Hi Harty,
Looking great. Hows the arm?

Stuart

Hi stuart

i am starting to feel like a single man again

cheers
Harty