Steel lapping plate

[pompon44]

Hi,

Any user of a steel lapping plate for back of plane and chisel blades ?

I've bought the lapping kit of Axminster, and I now realize I'm not so sure how to properly use it

For instance, I started a (low quality) western like chisel with grit 90, then rinced the plate, went to grit 120 and it seemed to leave bigger scratchs than the end of the 90... (which I would explain by the fact the 90 grits were broken in smaller pieces by the lapping action). Am I completely wrong or what ?

With which grit should I start ? Any special way of rincing between two grits ? Well, in fact, a step by step instruction would be most welcome ;-)

Regards,

 

[Anonymous]

I think you need Alf on this one

 

[Alf]

'Fraid I've never used one and I'm not at all sure of the "proper" procedure. I would agree with your thoughts about the grit breaking down though, so giving a polish greater than the grit would suggest, but I think there may well be grit contamination there. No idea what the received wisdom is on an answer though.

Cheers, Alf

 

[David C]

The grits do wear down as you use them so a bigger drop in grit selected might have been desireable.

I think they are silicone carbide which breaks down faster than AlOx.

Breakdown may also be a function of time spent.

Eventually the mild steel plate will wear as well and need re flattening.

Surface grinding recommended.

David C

 

[pompon44]

Hi David,

Thanks for the answer. I'm afraid I'm grit-challenged ;-) Could you quantify "bigger drop" ? (or do I just have to test, which is probably just fine too ;-) )

I spent quite a time, as abrasive was almost dry before I changed.

Also, and please forgive my ignorance, what's "surface grinding" ? And do you recommend it to reflatten the plate and for the blade (instead of using the plate) ?

Regards,

 

[MarcW]

(which I would explain by the fact the 90 grits were broken in smaller pieces by the lapping action). Am I completely wrong or what ?

With which grit should I start ? Any special way of rincing between two grits ? Well, in fact, a step by step instruction would be most welcome ;-)

Regards,

Hey Pompon44,

Well seen, you grind the grit. I normally start with 50 grit silicium carbid and continue with grit 150. Passing from one grit to the other, you have to brush and wash off the resident silicium carbid off the plate. Don't forget some drops of water on the powder. Then you start polishing with no powder at all on the plate. It gives a well polished look on japanese chisel backs and costs half the time of flattening on waterstones. Just try it, you will be amazed. It is possible in this stage to add camelia oil instead of water. I never tried it, water works fine for me.

Check the blade as always at each level of grit before changing to a finer level. The whole surface must be finely scratched, no shadows left. So three grits (50, 150, none) work fine for me. Often it is no good spending to much time on one grit. Maybe this happened to you.

Maybe you use a longer batten you lay on the chisel so you comfortably grip at both ends with both hands. A nail head in the side of the batten can prevent the chisel from slipping under the batten. ( I can post a pic later on, if you wish to) The ends chamfered allow an easy grip needed because you have to give firm pressure down on the blade. Be sure your working surface is low, not to high.

Regards, Marc

 

[pompon44]

Hi Marc,

Thanks for the tips.

BTW, any order of magnitude for the time it takes per grit ? (assuming a somewhat badly out of flat blade ?)

Would like to see the pictures, if you don't mind.

Regards,

 

[MarcW]

Hey,

Ok, here's the pic. No magic just a nail. The head of the nail works as a catch so the blade won't slip out under the batten. The pic is for demo, so my left hand was on the camera and normally the edge of the plane should be at the left side of the plate.

Time? Hugh, difficult to say, but you go much more faster as with waterstones. It takes minutes rather than whole cup of coffees or Guinness :wink:

Regards, Marc

 

[David C]

Surface grinder does what it says on the box.

Engineer's machine grinder for producing flat surfaces.

David C