Flattening plane blade backs

[Ern]

Recently I acquired 3 wooden Mujingfang planes - a real bargain in the world of new planes.

Each has a 1 3/4" HSS blade, with coarse machining marks on the back.  A sharp edge requires both bevel and back to be polished.

If I had a dime for every minute spent lapping blade backs on stones I'd be a millionaire, and buying premium planes ;-}

I read somewhere that this could be done on the side of the Tormek.  And practised with two chisel backs.  This was a bit hairy as landing them flat with the wheel turning takes some skill.

My son dropped over a few days ago and I enlisted him to control the on/off switch.  That allowed me to register the backs properly with the wheel stopped.  Side on the mounting bar and a finger on each corner of the blade pushing it against the wheel side.

Wow!  It took about a minute to get the machining marks out and leave something approaching a polished finish.  Magic.  Two blades done in short order.

Seeing that there was a good bit of steel grit in the wheel sides, I hit them with the coarse grading stone.

That dropped the cutting power big time when it was time for the 3rd.  In fact after 2 minutes there was still a lot of steel to be removed.

That sent me to read through posts on this forum and it seems that what may be required is to press hard with the corner of the grading stone.

Sound right?

I can see that some care will be needed to apply it flat and square to the wheel face.

[Jeff Farris]

Ern,

Since I rarely have someone to enlist as a switch-master, I'll share my method for getting the tool onto the stone flat.  What I do is rest the tool on the Universal Support (in the horizontal mount) and start moving it slowly toward the stone, playing a little game with myself.  I see how close I can get without actually touching the stone.  After a few seconds of creeping closer and closer without touching, you should be ready to apply it perfectly flat.

Grading the sidewall of the stone takes a bit of patience, and yes, it may speed up the process to use the corner of the grader.

[Ern]

Thanks for the tips Jeff.

Will try the 'creeping up' method when I'm fit again; recovering from a broken wrist ATM.

[Tony29]

My method for flattening the backs is to use the universal support as a guide like Jeff mentioned.  Then I do the hovering thing to get close.  Then I deliberately make the first contact with the wheel using the heel of the iron, then rotate the rest of the blade flat against the wheel. 

[Ken S]

I finally tried back flattening yesterday.  I was surprised with how simple it is.  I started with a spare old plane blade.  The wheel moves slowly; a little practice soon makes one comfortable. I did not use the universal support bar, although it seems like a good idea. The Tormek did as well as my 1000 grit waterstone, with less discomfort to my hands.  It was no faster.  In the future I will look into beginning with the 200 grit waterstone if much flattening is necessary.  I still prefer to finish with the 4000 or 8000 grit waterstone.

The Tormek did a nice job of flattening an old 3/8" Buck chisel with a belly in the blade.  Progress was slow, but very controlled.

[ionut]

Hi Ern,

Probably Jeff will kick me out after this but I hope not. Tormek is the perfect machine for a million things but one single thing, flattening the tools. First it was not build for this purpose and does not offer means of maintaining a true flat surface for flattening plane blades or chisels. Also when flattening in this manner, depending on how you set the blade, the speed of the grains in the wheel is depending on their distance from the center of the wheel creating more or less grinding effect  When I got my machine the seller included a couple of chisels with it as a promotion, the chisels were low to average quality so I have tried the flattening procedure. What happened was that I removed the original machine marks, but the surface left was far from  a true flat surface of the back suitable for a straight cutting edge. My stone was a bit wobbly from the beginning, and I have seen since then at least 4 more 220 stones and they were all a bit wobbly. That is not of an issue for the normal grinding surface but I have big doubts about the flatness by using the side of the Tormek stone on any tool.
   My suggestion would be to invest in a DMT diamond stone (220 or 325 mesh) and start the flattening on that stone and after that you can finish up to 8000 water stone or more if you want. The diamond stone is really fast and does not require heavy pressure. The most time I have spent flattening in this manner, a badly prepared face otherwise great steel blade, was 15 min. So I guess even if I would get paid 10$ for each minute spent flattening I would still be very poor.

Ionut

[Ern]

Hi Ionut,

Yep, I've spent a lot of time lapping using the std methods (diamond stones, PSA abrasives etc) and maybe I just got lucky with the side of the Tormek wheel.  After lapping I went to stones to complete the process and had no significant diff in flatness in the transition.

My Tormek wheel is a bit wobbly too but the blades followed it OK.

Course this was a 2 off only which is a shortcoming given the grading stone didn't work too well to clean the swarf.  Next step will be to try a dressing tool on the Jet side mount.

We're talking about HSS blades here which obviously demand more of an abrasive than HCS, but even with chisels in that it's taken me 1000 strokes to lap a good one like Marples or Titan.

[ionut]

Hi Ern,

1000 strokes should be around 10 minutes which in my opinion is not bad for one time flattening. I only have one HSS hand plane blade, which I really didn't have any troubles lapping on the diamond but I am not a metallurgist to be able to decide the quality of the blade by touch so I don't know how much harder it was. The rest in HSS are just few planer and jointer blades which don't seem to me to take much longer sharpening on the tormek than HCS but they are also thinner and have more acute angles.

Ionut

[Ern]

Well, that was only a 3/4" Marples firmer.  Then polishing out the scratch marks followed.  Yes, no sweat only if there's one but I rehab a few and lap to an inch back from the edge.

The Muji blades are exceptionally abrasion resistant, compared with Hock or Veritas even.