Pull Scraper Geometry

After watching some videos on YouTube and seeing "this old tony" using the pull technique, I figured I should try it, so I machined up a blade holder and tig brazed a milling insert to the end. The surface in the picture was very rough when I started and the tool chattered really really bad. But after six or seven passes and it starting to flatten out, as well as me holding a better angle, the chatter is gone and the surface is looking pretty good. I'm not sure I have the geometry right, it looked like in his videos that the insert was almost square with the work, which I have to have mine at like 45 or so, the more square I make the cutting edge to the work, the worse the chatter gets.the blade holder installed in the handle is for getting into the tiny dovetails of my compound and cross slide.

We talked about this a while ago.
http://www.practicalmachinist.com/v...scraping-and-inspection/pull-scraping-303305/

First thing that's really obvious to me in your photo is that you have a curve in the cutting edge. Swiss pull scrapers have a dead straight cutting edge and scrape the full width in one go. Second thing is the angle is too flat - look at all the pictures and videos in the other thread Richard pointed to. The angle of the edge is in fact the same in both pulling and pushing: quite a negative rake. Looks like about 60 deg or so. On a pull scraper you get that angle by leaning the handle on your shoulder or chest. You can see that best in the French language video Richard listed.
I can't relly see that pull scraping is suitable to get into dovetail corners though.
Good luck!
I quite like pull sraping, mainly for the pattern it leaves, and to rest the muscles used in push scraping...
Cheers,
Joe

Sorry about the photo, the blade that is clamped is the push scraper, made to get into my dovetails, the other bent job is the pull scraper, I tig brazed a square milling insert on a bent piece of steel, and yes when using it the handle is on my shoulder, with both hands on the shank, and if I kind of rock my body for the actual power I can cover the surface pretty dang quick, and it looks nice, however it is much slower as mentioned in the linked thread

The pull scraper is dead flat on the cutting edge, zero radius

As Chevydyl mentioned the blade has no radius


My pull scraper insert are made with a lathe carbid inserts.
The tip is a Sandvik SEGN 12 03 08 in K10 / H10 carbid grade
In the background you can see the original one, which is based on HSS.



I also made some small versions of it.

For the lower one I used a Sandvik SPGN 09 03 08 tip with a carbid grad of K10 H1P
For the upper one I cutted a piece from an original Sandvik scraping blade.
The width for this blade is 6mm (0.23622") and 9mm (0.354") wide.


One important fact is that you need either a pull scraper where you can change the angle of the head or you need a bench vice with a lift.
In this way you can scrape in a comfort position with the right angle between the blade and the work piece.
When you watch the pull scraping video from Wyler, there you can see that they have a fixed head but they use a bench vice with a lift to setup the optimal height.

Cheers Juergen

Is that a Agathon pull scraper or did you make it? I wish I would be able to find one of those in the US. Thank you very much for posting this as I've been reading all the pull scraping Info I can find. I just bought a Maho MH800 and I would like to have a scraper just in case the vertical or x axis ways need to be scraped. What angle is the tool ground to?

Yes thats an Agathon like pullscraper from Urben+Kyburz.
One I bought directly from Urben+Kyburz and one I found on a picture of an advertised lathe on the online marketplace "ricardo" here in Switzerland.
I know they are not easy to find.

In the early days Agathon was a machine manufacture company in the city of Solothurn here in Switzerland.
They still exists. Later Urben+Kyburz was founded also in Solothurn. They started to manufacture the inserts for the agathon pull scraper.
Agathon later decided to stop producing such scraper and Urben+Kyburz started to manufacture them.
Unfortunately they stopped as well.
They still have some of the small ones in stock.
Here is a picture with prices (without 8% VAT) from Urben+Kyburz AG.

The short version and the HSS inserts are still available. Also the angled carbide blade
Mine is also a short version. I drilled a hole in the wooden handle and put a stainless steel rod in it.
It works great and when I need the short version again I can pull out the rod and change the angle of the head.

Be aware that you cannot take big amount of material with such a pull scraper.
It is very useful for fine work such as the gauge scraping from Wyler.

For the angle IMHO it should be around 80 degree.
I found some info about the angle in an old German mechanic book from 1954.

It only says the angle 'beta' (ß) should be less than 90 degree for pullscraping

More important is to get a really good edge.
Sharpening the blade by hand on a diamond grinding wheel is very hard.
I use my small universal grinding machine for sharpening the blade

At the moment I only use pull scraping to scrape patterns and to get into the corners of the dovetail.
For the rest I still use push scraping.

Best regards
Juergen

Just to clarify Juergen was the friend and student who emailed me the pull scraper info I attached in the other thread. He attened the first class I had at BIAX Germany a few years ago. So he has done both pull, push and power. I would consider him an expert on this subject. He lives in Switzerland too.

When I was teaching the class in Peurto Rico, in post 25 in the other thread they had copied and made one of these scrapers like Juergen bought and shows. They were so proud of it and to make a long story short after they learned to push and BIAX Power scrape it ended up laying in the tool box. I tried it, but I was not patient enough to test it long. It seemed so awkward.

I can see where it would be great scraping Turcite that is down in a VMC box way channel as my assistant teacher Ted showed in post 4 in the other thread. It's is part of scraping and if you like it and you can scrape and get mega PPI and an amazing appearance, so go for it and use it. Would work good on Hardinge lathe saddles. I believe Bebob shows his work in the what are you scraping on thread. I believe he learned to pull scrape from the SIP techs he works with when he rebuilds SIP Jig bores. In the last Boston class one of the students scraped 55 PPI with his BIAX Power Scraper so you know I will talk about pull scraping, show how to pull scrape Turcite in the classes, but I will stick to push, push and lift tap tap and BIAX Power scraping. Rich

I totally agree with Rich, pull scraping is not suitable for all projects.
It is worth to learn but it is not the holy grail of scraping.

Advantage of pull scraping:
- Very accurate
- Good looking
- You can reach places which cannot be reached by push scraper

Disadvantage
- Only one edge of the blade is usable
- Much slower comparing to push scraping
- You cannot remove so much material

Juergen

Looking at Juergen_M's photo of his pull-scraper handle, I'm thinking a mechanic's "hinge handle" (aka "breaker bar" or "pull bar") might just be close-enough cousin to provide a good start on a home-brewed pull-scraper handle.

The scraper isn't that complex.
There is the head which push into a pipe(tube) and the two wooden handle.
The head consists of two main parts. The rotatable blade holder and the head.
I will try to post soon some detail picture of the parts of the head.

I put a long handle on my Sandvik 20mm scraper and pull scrape rather well with it

Juergen_M said:

I totally agree with Rich, pull scraping is not suitable for all projects.
It is worth to learn but it is not the holy grail of scraping.

Advantage of pull scraping:
- Very accurate
- Good looking
- You can reach places which cannot be reached by push scraper

Disadvantage
- Only one edge of the blade is usable
- Much slower comparing to push scraping
- You cannot remove so much material

Juergen

Click to expand...

im quite surprised you say that. i sure can remove more material by pull scraping. (but then again i never tried hip scraping.)

I know Matt - MCritchley - has been working with a old retired German Scraper that learned pull scraping and rebuild machines long ago and he has been teaching Matt to pull scraping so he can give a good comparison as he is one my top 10% of my students. What is your opinion Matt?

dian said:

im quite surprised you say that. i sure can remove more material by pull scraping. (but then again i never tried hip scraping.)

Click to expand...

I'm not the expert in shoulder pull scraping.
I can only compare what I'm able to do.
I just stared early this year with pull scraping. I have more experience with push scraping.
And with my current level of scraping, I can remove more material with push scraping (standard scraping)

I do not practice hip scraping. That's to odd in my opinion.
I can see where the advantage of hip scraping is but there are a lot of disadvantages too.
But this is another topic.

Can you tell us more about your blade geometry, the angle between blade and work piece?

i do put a radius on the blade, btw.



0.k, i see, you were talking about the small scraper you show. it similar to this one:



thats for "finger pull scraping".

To get the pull scraped checkerboard look it is necessary to scrape the last passes at 45 degrees to the long axis of the work, but that's good practice anyway