Scraping in a straight edge

[rabler]

I have a few lathes where I want to clean up the cross slide and compound, so I figured I start by making a straight edge. Got this casting from dgfoster a couple years ago. Just getting around to this, milled the faces, and just started scraping. Of course it would be nice if I had a suitable surface grinder that worked, but that's another restoration project yet to be tackled. The bottom was milled on the horizontal part of my Grizzly horizontal/vertical mill. The angle face was milled on the K&T 3k vertical with a 6" face mill. The K&T definitely left a flatter face.

I suppose if I'm going to a lot of this I'll have to invest in a power scraper. Obviously the biax are the only real name in the game but I can see trying out a demolition saw conversion before dropping the $2k+ on a biax. That way I'll appreciate the real thing But the surface grinder would probably be a better start! (And thus, he heads further down the rabbit hole)

 

[benmychree]

From what I understand, the demo saw conversion has little to recommend it, very clumsy to use for one thing, I suspect that you will hear from Rich King for more details. Having used the Biax, I heartily endorse it. I had an earlier unit that was single speed and used a Variac to slow it down, it was much cheaper and worked well, finally I was given a new model Biax from the estate of an old friend, and it works even better!

 

[rabler]

From what I understand, the demo saw conversion has little to recommend it, very clumsy to use for one thing, I suspect that you will hear from Rich King for more details. Having used the Biax, I heartily endorse it. I had an earlier unit that was single speed and used a Variac to slow it down, it was much cheaper and worked well, finally I was given a new model Biax from the estate of an old friend, and it works even better!

That's pretty much what I've heard. I'll probably end up with a Biax at some point. But I'll finish this one by hand.

 

[FOMOGO]

I always wince at the the price too, but right tool for the job and all that. I have enough jobs for one to justify it, but still hoping to trip over one for a low ball price. Mike

 

[Richard King 2]

I just saw this and will write tomorrow as I have 2 meetings today and tonight. Is your surface plate on 3 rubber pads? Have you watched any You Tube shows ? Like Stefan Gottswinter or Jan sverre Haugjord Adam Booth? They all are students and have good shows. Jan has a lot more showing scraping and rebuilding. He is in Norway and has taken 6 classes, 1 here in the states and the others in Europe.

 

[rabler]

I just saw this and will write tomorrow as I have 2 meetings today and tonight. Is your surface plate on 3 rubber pads? Have you watched any You Tube shows ? Like Stefan Gottswinter or Jan sverre Haugjord Adam Booth? They all are students and have good shows. Jan has a lot more showing scraping and rebuilding. He is in Norway and has taken 6 classes, 1 here in the states and the others in Europe.

Yes on YouTube videos from several of your students. Stefan Gotteswinter, Keith Rucker, Abom79, a few others that have taken your classes. I would really like to attend one of your classes myself but health issues make travel very challenging. I’ll check out Jan’s content. Thanks!

 

[Richard King 2]

Please take a photo of the scraper blade side and top. Did you sharpen the blade, do you have a grinding or lapping machine. What radius is the blade? Take your bathroom scale out to you scraping table; lay a red rag on it and hold your scraper handle and push down until you get 8 pounds pressure and if you measure the depth of the scrape mark it should be a min of .0002" to .001" deep. That's how hard you have to push down all the time when your scraping. You should have a blade radius of 60mm or 2.4" to a 90mm to 2.5" . The scraper blades usually come to flat or 140 mm / 5.5" and that is to flat to get a consistent scrape mark. I have seen those hand scrapers in Germany too.

 

[vtcnc]

(And thus, he heads further down the rabbit hole)

View attachment 423258View attachment 423257

You got me here!

 

[Uglydog]

rabler,
My rebuilding/scraping mentor and several machinist mentors are old school.
They were rather insistent that you learn hand wheels and hand feed with HSS before you use carbide, DRO or powerfeed.
Same with scraping learn high speed steel and Andersons before you pick up a carbide Sandvick or Dapra.
Yes, I have a Biax and they make life easier. And yes, if you are going to do alot of scraping you will want to source one. However, there are situations which are still best done by hand.
Do you have Connellys book on machine tool rebuilding? It's a worthy investment, and there are chapters on straight edges as well as the methodology and sequence for rebuilds.

Daryl
MN

 

[rabler]

@Richard King 2 - I have a low speed diamond lapper, I’ve ground a radius on the carbide scraper blade but haven’t measured it, and a smaller radius (2-3mm) on the corners to keep them from digging. I sharpened the carbide at a 5 degree negative angle so I can flip it before need to resharpen. Hand scraping is tough work.