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Any possible risks with using a Makita 9820 for lapping?

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Forum topic by SirTonka posted 08-20-2013 03:16 AM 1257 views 0 times favorited 10 replies Add to Favorites Watch
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SirTonka

67 posts in 1225 days


08-20-2013 03:16 AM

Topic tags/keywords: jig chisel plane sharpening

This weekend I picked up a Makita 9820 from a seasoned woodworker thinning out his shop.
Had the unit going asap and started work on a few vintage chisels. After the primary bevels I took off the attachments and started lapping. While skating the backs across the 120 grit stone I imagined a corner catching on the spinning stone and the possibility of a chisel being thrown off with a good bit of force.

Does anyone have experience with using a Makite 9820 for lapping, and have you had any issues or injuries from using the unit in this way?


10 replies so far

View TCCcabinetmaker's profile

TCCcabinetmaker

930 posts in 1815 days


#1 posted 08-20-2013 03:23 AM

Well if there is any wear on the stones, your lapping won’t be flat. And while it may be faster to do this kind of thing with a grinder type machine, I think most people would agree it’s best to lap by hand.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

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SirTonka

67 posts in 1225 days


#2 posted 08-20-2013 06:27 PM

The vintage chisels needed so much material removed I went with the power option to make much better use of my time, finished off by hand lapping on a coarse diamond stone. It works for me, want to double check with long time Makita owners to find out if there are any dangers using this unit for power lapping.

View MrRon's profile

MrRon

3926 posts in 2704 days


#3 posted 08-20-2013 06:38 PM

Lapping should be done on a flat slow turning platen. An aluminum disc with a sheet of 3000 grit paper can be used. WD40 is used to secure the paper to the disc and to lubricate the lapping surface. I learned this in sharpening school.

View PurpLev's profile

PurpLev

8523 posts in 3109 days


#4 posted 08-20-2013 06:45 PM

lap on the side of the wheel that is turning AWAY from you, so that the wheel is ‘pulling’ on the iron and not ‘pushing’ on it – that way you won’t catch any corners into the stones. start with the chisel back slightly tilted upwards away from you, make contact with the wheel and lower the entire back of the chisel to make full contact with the wheel, that way you also protect against rounding off the edges.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View Loren's profile

Loren

8295 posts in 3108 days


#5 posted 08-20-2013 06:56 PM

I flatten chisel backs with it. I use a lot of water, usually feeding
it from a sponge in my hand. The drip feed is too slow and the stone
glazes. I use a nagura stone often. It is messy too. The stone
can get grooved easily by narrow chisels if you are not careful.
With adequate water I have found the stone wears to a
consistent plane when used on backs. Using the jig also
helps flatten the stone and removes ridges. I’ve only used
the jig on planer blades.

View Don W's profile

Don W

17958 posts in 2028 days


#6 posted 08-20-2013 06:58 PM

I will get it 98% with power then finish by hand.

-- Master hand plane hoarder. - http://timetestedtools.net

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SirTonka

67 posts in 1225 days


#7 posted 08-20-2013 07:39 PM

MrRon, would you happen to remember the rpm range?

PurpLev, ended up using that same technique. In order to work the entire surface on a larger chisel after starting off downhill I slowly swing around to nearly 180, ground with pushing force in this position. Only way I was able to reach around the handle to get at the other side. Would be of great benefit if I could reverse the direction of rotation.

Loren, Thanks for sharing your experience and good tips, have you seen david smith’s write up of shop made sharpening jigs here?

Don W, was hoping the Makita would be my silver bullet, a wonderful machine for flat primary bevels, though to speed up the final lapping I will need to pick up an EE coarse DMT stone or the like.

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Don W

17958 posts in 2028 days


#8 posted 08-20-2013 07:51 PM

I’ve got that Makita as well. I like it for planer and jointer blades, but that’s about it for me.

-- Master hand plane hoarder. - http://timetestedtools.net

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PurpLev

8523 posts in 3109 days


#9 posted 08-20-2013 07:54 PM

I see no reason to flatten the entire back of the chisel all the way to the handle – a waste of energy, time, and stone grit. I only flatten and lap the leading edge of the blade where it needs to be flat to produce a cutting edge:

http://lumberjocks.com/PurpLev/blog/37128

there really is no benefit for having the entire back lapped flat. it’s ok to have low spots where “it doesn’t matter” (as in away from the cutting edge area)

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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SirTonka

67 posts in 1225 days


#10 posted 08-20-2013 08:25 PM

PurpLev, read your sharpening write up, will watch out for rounding the side edges now. I intend to use the Makita for only lapping tools that have never been properly tuned, once I cycled through the backlog the follow up back lapping I will be done using the DMTs.

General question, would the electric motor work just as well with the current reversed? Interested in modifying the Makita by adding a switch to change the spin direction.

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