Scraping a flat gib

[Braeden P]

Hello I want to scrape the gibs on my lathe but I want to know the proper PPI and the proper percent of coverage. So is it any different than scraping a tapered gib?

 

[benmychree]

A straight gib should be easier to scrape, because it will be easier to straighten if needed (likely); a tapered gib is harder to straighten due to its changing section thickness, which takes more force as the section thickness increases. I defer to Rich King on percentage of bearing.

 

[Ulma Doctor]

Richard mentioned 5ppi in a recent thread for gibs

 

[Richard King 2]

That's on the back positive side, not the wear side. Back side can be more percentage too.. You can stone it harder and get 50 to 80% POP (percentage of points) In a conventional lathe and depending on the size of the machine and your scraping experience think about 40 to 60 POP and 20 PPI. Remember you need oil pockets too, oil grooves, middle 40% aa few thousands low too. ....etc. What is it from? How about a photo.

 

[Braeden P]

It’s from my lathe about 3 inches long 1/2 inch wide 1/4 inch thick I’m eating right now so I will take a picture later.

 

[Richard King 2]

You know....I have confidence in you.. I have a SB compound with such a gib and if I got 10 to 15 PPI and 50 POP on the wear side I would stop. as you want a compound tight anyway. It's not going to be moving much.

 

[Braeden P]

Here’s the ways on my lathe. (The orange is a (highlighter?) so that I can see the high spots from the low spots).

 

[Braeden P]

The ends are high I think that is from the middle screw being to tight

 

[Braeden P]

Turns out the middle is low by two thou! Now time for some roughing.

 

[Braeden P]

Now it hinges properly and it one has a one thou dip in the middle third, it’s too hot out so I’m taking a break and if I use a fan the temperature change could make it warp or cause other problems.