negative rake scrapers

[Random Orbital Bob]

Never used one. Any opinions, comments, value judgements from people that have tried them please?

 

[woodfarmer]

I have a confession to make. I often use my skew chisel as a straight scraper.

It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.

I really haven't yet got the knack of using it as a skew chisel.

 

[Wybrook]

I have a confession to make. I often use my skew chisel as a straight scraper.

It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.

I really haven't yet got the knack of using it as a skew chisel.

Oh good. I am not alone

 

[-Matt-]

I have a confession to make. I often use my skew chisel as a straight scraper.

It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.

I really haven't yet got the knack of using it as a skew chisel.

Oh good. I am not alone

Seconded! Though I sometimes tend to make things out of wood in a "components" sort of fashion so a clean vernier'd step is easy to get with a skew.

 

[Paul Hannaby]

I have a couple I used for different things. Both are scrapers I have reground myself. The negative rake makes the scraper less "grabby" because unless you really try hard not to, the edge is presented in a trailing manner.

One down side I have found when using negative rake scrapers is that when using them inside a box, hollow form etc. you can't see where the edge is cutting so it is more difficult to find the exact centre to remove a pip.

 

[RogerP]

For small stuff (which is all I really do on the wood lathe) I use one of these HSS Square Lathe Tool Bit Boring Bar Fly Cutters http://tinyurl.com/qcld37w

They come in all sorts of sizes and banged into a handle work very well. Of course they are easily ground, with the correct wheel, to any shape or rake and also the sides can cut well.

Make a nice tight square hole in a wooden handle and you can swap them end to end with different faces on each. Being HSS they hold an edge very well.

 

[Grahamshed]

If you are talking about a second, face, bevel on an ordinary scraper then no, not yet, but Ihave just been watching Mike Waldt's youtube vid about them. They look 'interesting'

 

[Spindle]

Hi

I've yet to experience the need for one - I've never had a problem with a normally ground scraper - the harder the wood the easier it is to get a good finish.

Regards Mick

 

[Dalboy]

Hi

I've yet to experience the need for one - I've never had a problem with a normally ground scraper - the harder the wood the easier it is to get a good finish.

Regards Mick

Like you on the whole have no problem except with one scraper Ask SteveF when he came over I will beat it though

 

[chipmunk]

One of the nicest applications of a negative rake scraper is when finishing the continuous curve on the inside of a bowl.

If you try to track a standard neutral rake scraper round the inside curve with a consistent downward tilt on a straight toolrest it's actually quite tough to do. A negative rake french curve scraper flat and level on the toolrest turns this into a breeze.

So, I have one negative rake scraper like this one on top which is a reshaped long and strong 1" skew....

The cross-section is here...

HTH
Jon

 

[Vic Perrin]

I have a confession to make. I often use my skew chisel as a straight scraper.

It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.

I really haven't yet got the knack of using it as a skew chisel.

Looks like one or two of us use the Skew in this mode
:lol: Vic :lol:

 

[Spindle]

Hi Chipmunk

Is that technically a negative rake scraper? From your description of it in use it seems to be being used as a normal scraper, your relief of the upper surface allowing you to raise the cutting edge to the centre line and thus improve visual reference but still acting as a normal scraper in it's cutting action.

I understand negative rake scrapers to be used bevel rubbing and have an angle between the upper face and the bevel to be in excess of 90 degrees.

http://www.robert-sorby.co.uk/pdf/hardw ... craper.pdf

Regards Mick

 

[Phil Pascoe]

Would that be ground upside down to leave a burr? Would it cut otherwise with an obtuse angle?

 

[Spindle]

Hi

See the link - but yes an obtuse angle, (within reason), will continue to cut. Sorby recommends sharpening by honing the upper surface.

Regards Mick

 

[chipmunk]

Hi Chipmunk

Is that technically a negative rake scraper? From your description of it in use it seems to be being used as a normal scraper, your relief of the upper surface allowing you to raise the cutting edge to the centre line and thus improve visual reference but still acting as a normal scraper in it's cutting action.

I understand negative rake scrapers to be used bevel rubbing and have an angle between the upper face and the bevel to be in excess of 90 degrees.

Hi Mick,
I think it is (obviously ;-))because according to my understanding it has nothing to do with the relationship between the traditional bevel and the material being cut but the rake angle relates to the relationship between the leading edge and the material being cut...

A skew held flat on the toolrest is effectively a negative rake scraper because the top edge slopes down if held on-centre.
Jon

 

[Phil Pascoe]

Yes, I looked at the link but it showed it in use, not being ground. I suppose its being honed on the top would preclude its being ground with a burr. It's just something I've never come across.

 

[Spindle]

Hi Jon

You're at variance with the link I posted and plenty of other info on the web in that case - for instance:

http://www.docgreenwoodturner.com/scrapers2.html

http://www.woodturningdesign.com/askdale/8/8.shtml

http://www.woodturningvideosplus.com/double-bevels.html

Regards Mick

 

[chipmunk]

Well Mick I think the definitions are new to me although I guess according to that definition its the same as the top-relieved scraper in your picture. I think the problem I would have with these is that the presentation seems to affect the definition which is a bit weird.

If I rub the bevel with a conventional scraper I think it probably changes its type to something not listed in your pictures? Bert Marsh was a proponent of this and it works pretty well.

The rake angle IMHO is simply the angle, measured from 90 degrees, between the cutting edge and the material being cut. Like this...

Jon

 

[Grahamshed]

The video I was watching about it https://www.youtube.com/watch?v=tdXxkr1hEPE is showing a negative rake scraper as being an ordinary scraper with a 70 degree bevel with a top, or face, bevel bevel of 30 degrees added. To my mind this addition turns the tool into a kind of skew though it is used in a different way.
The results seemed good though.

 

[Spindle]

The rake angle IMHO is simply the angle, measured from 90 degrees, between the cutting edge and the material being cut. Like this...

Hi Jon

I know this is bordering dangerously close to semantics but I believe the rake can only be applied to the tool which is frequently demonstrated in metal working tools such as you have illustrated or negative rake applied to twist drills for drilling brass etc.

I've always regarded the type of presentation used when scraping as the tool is in the trail.

Anyhow, terminology doesn't affect how we turn and if it works it's fine :wink:

Regards Mick