Author Topic: How much polish for back of plane blades and chisels  (Read 897 times)

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Offline jussi

  • Posts: 399
How much polish for back of plane blades and chisels
« on: June 05, 2021, 11:03 PM »
What kind of polish do you get on the back of your irons.  Do you get it as shiny as the bevel side.  Reason I ask is no matter how hard I try I can't seem to get the same mirror polish on the back.  At least not consistently.  Parts of it will be shiny but not all of the parts I'm working.  Is it just a matter of a much larger surface area.  Do you guys get the same mirror polish on the back as you do on the front?

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Offline mattgam

  • Posts: 21
Re: How much polish for back of plane blades and chisels
« Reply #1 on: June 06, 2021, 12:08 AM »
Disclaimer I have a antique handplane addiction so all comments should be treated as coming from a crack addict.

Plane blades and chisel blades are very different in the amount of polish needed on the back.  Keeping it simple and ignoring the whole space of hollow grinding, a plane blade back only needs to have the very end mirror polished.   A chisel needs the time invested to have the whole back polished.  Rex Kruger, Wood by Wright, Rob Cossman and Paul Sellers all have excellent videos on this topic.  Pay attention to the ruler trick for plane back polishing.

I use the scary sharp system and crimson custom guitar has a fantastic video on it   For hard to flatten blades I go super aggressive and do back in bevels progressively from 40grit to 18000grit and the worst rust pitted nightmare blade was shaving transparently thin shavings in under an hour.  Taytools sells all the lapping films and float glass.  Eventually I may give in and move to diamond stones but things have worked great for 40+ planes so I can't complain.

Offline derekcohen

  • Posts: 569
    • In The Woodshop
Re: How much polish for back of plane blades and chisels
« Reply #2 on: June 06, 2021, 02:02 AM »
What kind of polish do you get on the back of your irons.  Do you get it as shiny as the bevel side.  Reason I ask is no matter how hard I try I can't seem to get the same mirror polish on the back.  At least not consistently.  Parts of it will be shiny but not all of the parts I'm working.  Is it just a matter of a much larger surface area.  Do you guys get the same mirror polish on the back as you do on the front?

Before you can get everything uniformly shiny, the surface needs to be uniformly flat. If you only have parts shiny, then these are high spots. You need to flatten the back of the blade. I recommend that the full length - flattening, that is, not polishing. Only the first inch needs to be polished.

The face and the back of the bench (or the two intersecting sides) need to be honed to the same final level (e.g. 8000 or 13000 waterstone). Once the back is done, it should not be touched by a lower grit medium.

A Ruler Trick backbevel (2/3 degree) is helpful on plane blades for novices, but one you are proficient, it becomes just an unnecessary extra step. The point of the RT is to ensure that the back is polished and flat where it counts. I find this unnecessary, and easier to run the blade by hand on the stone. The RT is only for plane blades and never for chisels.

Note that shiny, per se, is not the aim. Some media do not leave a shine but instead a matt finish. Just go to the highest grit you have.
If you want a shine, finish on Lee Valley green compound rubbed on flat hardwood.

There are more sharpening methods that one can shake a stick at, so every man and his dog wants to tell you what works. I've been doing this for 35+ years, and this is my system:  http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp.html

Regards from Perth

Derek
Visit www.inthewoodshop.com for tutorials on joinery, hand tools, and my trials and tribulations with furniture builds.