[smallplanes]

I want to know if someone could tell me how to hand scrape the dovetail of a brigeport mill back to good use? It's very free in middle of table and on ends it locks up(X Axis).


Thanks for any help.
smallplanes

[TinkerDJ]

Check out the yahoo groups for Gingery, his books all include scraping of home made stuff, plus in the group i have run across posts were guys have really made there lathe work better by rescraping the ways. I use a good quality 1" wood chisel to scrape with, i have found that a good oil paint and a piece of glass works well, I usually have to resharpen the chisel as i scrape. I just have my shaprening stone next to my work and when the chisel starts to dull i give it a few swipes on the stone. Worked well for my lathe bed and a few other parts.

Hope this helps. Some posts of scraping.
http://www.geocities.com/plybench/scrape_posts.html

[widgitmaster]

Machinists hand scrapers are available in many shapes and types of steel, the one I would use for cast iron or cast steel would have replaceable carbide inserts. The inserts have a slight negative angle ground on a slight radius, they are usually 3/4 to 1" wide! The handle resembles that of a file handle. The objective in scraping is to have low spots for oil, and high spots wide enough to maintain good even contact. Thus a precision ground surface has the least amount of oil, and the most amount of surface!

the scraping is laborious, but the ability to check for flatness is the difficult task, especially if the casting has a twist in it! If you have access to a large flat surface plate, the task is much easier! A precision straight knife-edge will help get things flat, when combined with high spot blue ink. (very messy)

the carbide scrapers will allow metal to be removed with more control, and less effort from the elbow!


Machinist Scrapers at Enco
http://www.use-enco.com/CGI/INSRAR?PMSECT=0000000562

More info:
http://machinerepair.com/scrapers.html

Eric

[mxtras]

There are many, many threads on this site. How about doing a quick search real fast - there's enough to keep you busy reading for literally hours.

Scraping is a lesson in patience and resolve - that's for sure.

Scott

[Mcgyver]

I tried to describe the basic process in posts 26&34

http://www.cnczone.com/forums/showth...4&page=2&pp=15

and buy this book

http://www.powells.com/cgi-bin/bibli...4-1114266612-0

scraping is imo fundemental workshop skill, like filing or taping. lots of uses once you realize its no big deal. i just requires a bit of knowledge and an methodical approach

[sendkeys]

http://technicalvideorental.com/rental_16.html

has two dvd's on scraping i havn't tryed them but might be something. it's 10 dollars to rent for 1 week. they pay shipping.

[smallplanes]

Is the book that good its $92? About how long does it take some of you to resurface a milling machine? Will i have to buy or make a new brass gib after resurfaceing?


Thanks for the help guys your great
smallplanes

[xyzcnc]

Machine Tool Reconditioning and Applications of Hand Scraping. Originally published in 1955 is THE BEST BOOK EVER WRITTEN on the subject. Well worth the $92.70. It will methodically explain how to rescrape and test just about any machine tool.

[Stevie]

If it's a real bridgeport and not a clone; this will be impossible; the ways are hard chromed
I just completed a re-build of a Bridgeport
I had to use an angle grinder with a hard backed sticky pad (went through almost 50 discs)
This chroming is really hard; the nice thing is once done it would (should) last as long as the home guy would ever need
You'll need a long shaft on the pad to get to the dovetail ways; then a pencil grinder with mounted points to get the spots you cannot reach
Clones are not as well built as real Bridgeports; I also just finished a Toledo mill; it was not chromed

[smallplanes]

Yes it is a real brigeport and i also thought the ways were chromed. I guess it will be a lot harder than i thought. I might go ahead and get the book to see what they have to say about hand scraping.

Thanks for the help guys
smallplanes

[Mcgyver]

lots of bports are without chromed ways, I don't know if it was an option or based on when they were made. I've also seen chrome on china clones. don't need it though imo, its the oil that is the first line of defence against wear, not the hardness.

[smallplanes]

Do any of you have a Wells Index mill? I picked one up the other day and i see that it does not have the table locks for the X axis on it. I thought it might be like my bport but its not the same. If some one could point me in another good direction i would apreshate it.

Thanks
smallplanes

[wizard]

A couple of things to consider:

Hand scraping is a lot of work there is no way around that. If the unit has seen significant wear it would be advantageous to take it to a machine tool builder and have it ground to restore the table. Yeah this costs money but you do trade alot fo time. You still end up scraping for days on end but hopefully the table will be done straight and parallel.

Obviously not all of us can afford the machine tool build route. so complete hand rebuild becomes a reality. The thing to be aware of is that this is not cheap either if you don't have the tools for the job. For a bridgeport this means cranes and other heavy material handling equipment. It also means having a set of standards to work with also known as humpbacks or straight edges. Ideally you would find a set to borrow or rent. Otherwise you need to find and maintain your own. Scrapping isn't as bad as some make it out to be, but it is work and at times work that requires assitance.

The poeple that publish the Gingery series also have books on hand scrapping. At the moment that info is out in the shop, but do look into them.

Don't forget that Cabin Fever is coming up in the middle of next month. This is a good place to pick up books and materials related to scrapping. You may also run into people with experience there.

Thanks
dave