Looking for an easier way to flatten the back of plane irons

[James Spangler]

In my hobby of restoring old bench planes, the hardest task for me is flattening the back of plane irons. I currently use an extra coarse DMT diamond hone which works quite well but can be time consuming (I follow this with a Trend 300/100 2-sided diamond hone and then extra-fine sandpaper). However, I have some arthritis in my fingers that makes grinding on the extra coarse hone for any length of time quite painful.

So, I have considered buying a “Work Sharp 3000” sharpening system for the flattening process, which uses a 6” flat tempered glass lapping plate with PSA sandpaper and runs at 580 rpm. I’m not sure if it would make flattening an iron any faster, but would hopefully be kinder to my fingers.
But really, I don’t need the other bells and whistles offered by the Work Shop machine – I’m happy using my CBN wheel to cut a hollow-ground bevel followed with several flat stones to cut a secondary bevel – not hard on my fingers. So, I’d like to avoid spending the $200 on the Work Shop machine if there’s another, cheaper way. (I know there’s also a Veritas MK machine out there, but that’s beyond my budget).

So, here’s one idea and a few questions:
- I have a benchtop drill press that I can adjust the speed down to 740 RPM. Would it be feasible to chuck one of the Work Shop tempered glass discs to my drill press and use that with the Work Sharp coarse sandpaper discs to flatten plane irons? (The glass disc is 5/8” thick and available as a Wood Sharp accessory for $20 + the cost for sandpaper discs).

- I’d need to get some kind of mandrel or arbor to adapt the glass disc to use in my drill press (does anyone know the hole size of that disc?). Would that mandrel/arbor need to be anything special to hold the glass disc (e.g., without cracking it and without adding wobble)?

- I assume my drill press speed of 740 RPM would be ok for flattening plane irons with coarse sandpaper on the glass disc. Am I correct?

- Is this just a bad idea (if so, why)?

- Alternatively, is there perhaps a completely different solution for easily flattening plane irons and avoiding painful fingers?

Thanks in advance for any comments and suggestions!

[Andrew Hughes]

Ya there is another way to use a diamond plate or a corse stone that can be kept flat.
Hold it like this.
Im use a piece of hard maple to bear down on plane iron.
Good Luck

[Jim Koepke]

Alternatively, is there perhaps a completely different solution for easily flattening plane irons and avoiding painful fingers?

Do you have a belt sander and a vise big enough to hold it upside down?

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Here a belt sander is being used to work on the bevel of a chisel.

When flattening the back of a plane iron only the first 1/4" really needs to be worked. Just enough to seat against the chip breaker. One could likely get by with even less than that. My preference for a 1/4" is after this each time the blade is sharpened a bit more of the back gets worked. With less than 1/4" you will have to work more of the back sooner.

jtk

[Ralph Boumenot]

I restore planes too and on hard to flatten irons I start with 60 or 80 sandpaper glued to a granite tile. I then sand my up back to the coarse diamond stone. I don't skip any grits and use 100, 120, 150, 180, 220, and 320. I usually go to the diamond stones after 320. I also use a block of wood like Andy suggested.

[Jim Koepke]

Here is another thought that came to mind when rereading and seeing:


However, I have some arthritis in my fingers that makes grinding on the extra coarse hone for any length of time quite painful.

For marking corners to be rounded a lot of circle templates have been made:

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This is only a few of them, they all have knobs or handles.

One of the small ones works great for applying pressure to a blade being worked without stressing the fingers:

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It could be just a scrap of wood or it could be a piece made for the sole purpose of working blades.

jtk

[James Spangler]

Ok, that would be easier on my fingers, but how do you prevent the iron secured to the underside of the piece of wood? Maybe hot-melt glue?

[Jim Koepke]

Ok, that would be easier on my fingers, but how do you prevent the iron secured to the underside of the piece of wood? Maybe hot-melt glue?

It isn't, my hands work in tandem.

If one wanted to make it more secure the underside could be made with a proud center to sit in the slot on the iron.

Mine is used on plane blades and chisels but was made primarily as a circle template. It has found an exta use.

jtk

[Stephen Rosenthal]

Let me preface this by saying that now that I’m in my 70s, some things neander are no longer labors of love but simply laborious and cause for discomfort. Similar to Jim’s suggestion, instead of a portable belt sander I use my 6x48 stationary belt/disc sander to flatten the backs of plane irons. If you have one, just make sure the platen is perfectly flat (it probably is) and use a 240 grit belt. Very light hand pressure makes quick work of an odious task and you can then move on to finish up with your stones. I wear leather gloves just in case of a slip, but I’ve never had one. Btw, I have one belt dedicated to this, so as not to contaminate wood with any metal particles.

[Eric Rathhaus]

David Weaver has a video on his youtube channel showing a simple jig he made to hold the iron. He uses rolls of sandpaper on a long glass sheet . Its seems efficient, easier because of the jig and cheap as he uses regular sand paper and a glass shelf.

[Thomas Wilson]

Fine Woodworking had a tip this month to attach a block of wood to the front of the blade with double stick tape. I have some chisels and plane blades that I need to flatten. I shall try it and report back.

[Frederick Skelly]

David Weaver has a video on his youtube channel showing a simple jig he made to hold the iron. He uses rolls of sandpaper on a long glass sheet . Its seems efficient, easier because of the jig and cheap as he uses regular sand paper and a glass shelf.

I have that jig, someplace! When I first started using handtools, David used to hang out here and recommended it to me. It works well for flattening by hand.

Couple thoughts on the OP's question:
* I have a Worksharp. It isnt as good for flattening plane irons as I'd hoped, but it works. I added a footswitch so I could position the iron before starting the machine. I use diamond lapidary disks instead of sandpaper.
* You might be able to do as well on your drill press. I'd be concerned about that glass disk breaking. You might want to attach it to an MDF disk or such.
* I just checked 2 of my Worksharp glass disks - the hole is 7/16" (may be a tad over).

* Harbor Fright sells 4x36" stationary belt sander for $79. That might be a better move.

Fred

[James Spangler]

Thanks everyone for the comments and suggestions.
Further investigation on the web uncovered a vendor (Woodcraft) that sells the tempered glass disks for the Work Shop.
In that description it says "650 maximum RPM."
So the answer to my main questions is "No, do not run it on your drill press at 740 RPM."

I will follow-up on some of your suggestions to continue to use the extra course diamond hone with some sort of aid attached to the iron to take the stress off my fingers.

Regarding the belt sander suggestions, I have an old Ryobi 3x21 portable belt sander that I bought back in the 80's that I love, because the top of it is flat and I can run it upside down clamped between bench dogs. I've tried using it to flatten a plane iron and the iron came out dished a bit in the middle. So I guess the platen is not flat. This thing is out of production and no one sells parts for it any more so I gave up trying to find a replacement platen.

And thank you Frederick for your comments about using the Work Sharp 3000 to flatten irons. I am still considering that option.

[steven c newman]

Easiest way for me.....to flatten the back of a plane iron.....IF it even needs it, to start with........turn my 6" grinder on....hold the back of the iron to the side of the spinning wheel....1..2..3..4...5...dunk...and check for flat...will check after each...rarely need to go the full 5 seconds.....

[Andrew Hughes]

Using the side of a grinding wheel is a lot like poking at a hornets nest.

[Barney Markunas]

I know it might be convenient and I imagine lost of folks have been doing it for ages but Andrew is absolutely on target - wheels are not designed for that kind of use. A wheel failure is likely to be catastrophic to more than just the wheel.

[Rafael Herrera]

Last night I cleaned up and restored a 2" iron for an Stanley jack plane. Although I've used the method suggested by David, with good results, this time I used a double sided fine/coarse crystolon bench oilstone. It didn't take very long to get a decent face. The bevel and edge squareness needs a little more work, though. I think it spent about half an hour to prepare the iron and the chipbreaker.

[Andrew Pitonyak]

I generally use a magnet when I want to flatten the back of a plane blade. Lookup Magswitch Magnetic Jigs

Works well to hold the blade so it is not hard on the fingers.

[steven c newman]

Ok.....Not sure how ham-fisted others are around their grinders. Do they press as hard as they can against a wheel.....hoping for a failure?

This is the grinder I have, and use...
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Still has the wheel it was sold with, BTW. The grip I use?
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I press DOWN on the rest....NOT against the wheel I want a light, vertical rubbing going on. In, back out, check...repeat until done....fingertips will also inform me IF things are getting too warm, and needs a quick dunk. The iron being flattened in this photo is a 2" wide Defiance iron.....

Results?
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Back is now flat, and ready to polish to whatever level one wants....in my case, that would be around 2500 grit.

Counting walking to the shop, setting up, flattening AND polishing....AND walking back to my computer.....time? 10 minutes.....YMMV.

Iron had a hollow centered in the middle, just behind the edge....Bevel is a single one, at 25 degrees. There is now a nice bald spot on my left forearm....

[Andrew Hughes]

Nobody doubts you use this method Steve. Others passing through might read your post and try it on a totally different grinder maybe with a defect. And lastly without the skills you have.
We have to consider others.
I stand by my post using the side of high speed grinder is a lot like poking at a hornets nest.

Good Luck

[J. Greg Jones]

For others passing through, and to support Andrew’s comment, grinding on the side of these wheels is highly discouraged by the manufacturers because of the risk of wheel breakage.

https://www.nortonabrasives.com/en-us/resources/expertise/dos-and-donts-bench-grinding-wheels

[Alan Schwabacher]

I've thought the CBN wheels with a wide swath of grit on the sides (Woodturner's Wonders mega square, for example) might be well suited to flattening plane iron backs, but I've not seen anyone who has one comment on that.

[Ray Bahr]

Hi All,

Couple of thoughts, and apologies if stating the obvious:

Keep the speed down, really really important to not get things hot
Don't flatten the entire back, no need to
I recently picked up a Worksharp 3000 and some diamond disks similar to what is use by jewlery folks, etc. I got some from https://www.ebay.com/b/Craft-Glass-Grinding-Supplies/116644/bn_16515001

Seem to work. I have also used DMT and sandpaper. There is no 'easy' way.

Ray

[Rob Luter]

Ok, that would be easier on my fingers, but how do you prevent the iron secured to the underside of the piece of wood? Maybe hot-melt glue?

Double backed tape. It works great.

[steven c newman]

Couple of items I should point out....just in case some can not read....

1) ALL pressure is down onto the tool rest. It is not like I am jamming the iron into the side of the wheel....

2) I slowly rotate the iron to the wheel, lightly touching. After all, what's the hurry? A light touch is all you need.....

3) Raise some sparks, pull the iron back out, check the progress...repeat as needful......process might take 5 minutes....if that....then go to your favourite stones, and polish as needed.

My left hand was running the camera for the photos....otherwise, it is the one rotating the iron to the wheel's side. The right hand's job is to keep the iron vertical, and pressed down on the tool rest. Fingertips to tell me when the iron is getting a bit warm, and needs a dunk in the cup of water.

I also have a disc/belt sander...that I can use for the same operation...however, not everyone out there has such a machine.....but, they usually will have a grinder. And IF they take care of that grinder, and have GOOD wheels on board. I suppose there are some out there that will get in a big hurry, jam that metal as hard as they can against the side of the wheel.....one, you WILL burn that steel, two, the grinder WILL throw the iron right back at you for doing such a stupid thing...way before the wheel would break.....unless the iron gets caught somewhere inside the grinder. Which is why the "Ham-fisted" remark....

That's ok, go back to those hours of sheer drudgery flattening the back of an iron on a stone.....Then complain because the stone is no longer flat.....


You could buy a 1" x 30" belt sander....make sure the table and platten are 90 degrees to each other....and go that route....it will work, IF you can also KEEP the iron at 90 degrees to the table. Too good a possibility of the iron leaning a bit in or out....I tried this ONCE....was not worth the effort.

[J. Greg Jones]

I can read, and comprehend, just fine. The manufacturer states one of the steps to avoid wheel breakage and injury is ‘Don’t grind on the side of the wheel.’ It doesn’t also say, ‘unless you grind on the side of the wheel like Steven does-then you will be fine.’ Grinding on the side of the wheel is an unsafe practice. If it works for you and you are ok with the level of risk, carry on. However, it is an unsafe practice and to promote it in a public forum without acknowledging the risks as stated by the manufacturer, is just irresponsible.

[Andrew Hughes]

Well said Greg. One problem with giving advice is we never know how far someone will take it. For instance developing a skill doing something that has grave consequences.
Don’t take it personally Steve. We all do stuff that not to be passed on.
I myself have practiced the safety squint too many times. When I’m too lazy to find my glasses.
I fully know and understand if you hang around the barbershop long enough your bound to get a haircut.
Are we cool?
Good Luck Always

[Jim Koepke]

Grinding on the side of the wheel is an unsafe practice. If it works for you and you are ok with the level of risk, carry on. However, it is an unsafe practice and to promote it in a public forum without acknowledging the risks as stated by the manufacturer, is just irresponsible.

People should be careful about mentioning procedures including practices to be deemed unsafe by conventional wisdom. There are many people new to the field who may not have learned safe practices or how to be careful in various situations.

At one time it was common for me to mention shaving arm hair to test a blade's sharpness. Another member brought up the point of how this can be very dangerous. Those of us who use or have used a straight razor to shave know the techniques involved to not draw blood.

Anyway due to the concerns of another over the safety involved in my method of sharpness testing it is now seldom mentioned.

Another point people would be surprised to learn is how many woodworkers do not have a grinder in their shop.

jtk

[J. Greg Jones]

People should be careful about mentioning procedures including practices to be deemed unsafe by conventional wisdom. There are many people new to the field who may not have learned safe practices or how to be careful in various situations.

At one time it was common for me to mention shaving arm hair to test a blade's sharpness. Another member brought up the point of how this can be very dangerous. Those of us who use or have used a straight razor to shave know the techniques involved to not draw blood.

Anyway due to the concerns of another over the safety involved in my method of sharpness testing it is now seldom mentioned.

Another point people would be surprised to learn is how many woodworkers do not have a grinder in their shop.

jtk
Jim, your analogy is seriously flawed. This is not about ‘technique’. Sure, people can shave arm hair successfully to test blade sharpness. People can also use a table saw without a blade guard or splitter and never have an injury as a consequence because they have developed a ‘technique’ that serves them well. There is no ‘technique’ that prevents a grinding wheel from flying apart if one ignores the manufacturer’s instructions to not grind on the side of a wheel not designed for that purpose. It happens. I’ve seen it. I had to file the worker’s comp report to get my employee’s injuries reimbursed. No amount of ‘technique’ is going to overcome some instances of ‘stupid’.

[lowell holmes]

I have diamond hones and use them to flatten and sharpen chisels and plane irons. I have three hones with progressive coarseness.

[James Spangler]

FYI, I did try Steven's suggestion yesterday. I have a Rikon slow-speed grinder with a 150 grit wheel and very gingerly used one side to lap an old plane iron. I ended up with the edges worn back more than the middle, and I was careful to put only slight pressure at the center of the blade. So dangerous or not, it does not work for me. I also checked the platen on my old belt sander and verified that is is indeed not flat across, so not worth revisiting it to flatten irons.

There is a Woodcraft store and a Rockler store within driving distance from me. If I happen to get a coupon from either, I may go there and buy a Work Sharp 3000. Not in a big hurry, but still a consideration.

Thanks again to everyone who responded.

[Jim Koepke]

Jim, your analogy is seriously flawed. This is not about ‘technique’. Sure, people can shave arm hair successfully to test blade sharpness. People can also use a table saw without a blade guard or splitter and never have an injury as a consequence because they have developed a ‘technique’ that serves them well. There is no ‘technique’ that prevents a grinding wheel from flying apart if one ignores the manufacturer’s instructions to not grind on the side of a wheel not designed for that purpose. It happens. I’ve seen it. I had to file the worker’s comp report to get my employee’s injuries reimbursed. No amount of ‘technique’ is going to overcome some instances of ‘stupid’.

You are right on this. My attempt was aimed more at discouraging others from recommending procedures deemed dangerous.

jtk

[steven c newman]

In the 40+ years of working with my grinders....have NEVER had an issue with any of the wheels I have used. Maybe because I tend to be more careful about how I use mine....than some on here.

I suppose one could jam an item as hard as they could against the side of the spinning wheel....then act surprised that the wheel broke. Then think everyone else will treat a grinding wheel the same way.

"Stupid"??? Respect for the tools I use.....I use a light touch, not out to burn away metal. Of course, IF one has a CHEAP, crappy wheel on their grinder......Get the good wheels, NOT the Harbor Freight/Borg ones..Had one of those break apart...just trying to dress the edge....that had just crumbled away.....

But, I suppose there are some out there, that buy the cheap wheels, slamma-jamma an item into the wheel...after all, don't have the time to carefully do the job.....maybe not so much the "Procedures" as it is the person using the "Procedures" that is at fault.

"Don't interrupt the man by telling him a job can not be done, until after he has completed the job"

Then, there are some, that go out of their way to prove a "technique" will fail.....

Had enough of this...stuff....go your own way, I'll go mine....see ya!

[Rafael Herrera]

Norton Abrasives is not a cheap manufacturer. Their dos and don'ts clearly specify not to use the side of the wheels. You're just fortunate you have not had an accident.

[J. Greg Jones]

You are right on this. My attempt was aimed more at discouraging others from recommending procedures deemed dangerous.

jtk
I went back and re-read your post and I see that now-sorry! At the time my comprehension wasn’t as good as I thought it was! :) Cheers.

[Andrew Pitonyak]

FYI, I did try Steven's suggestion yesterday. I have a Rikon slow-speed grinder with a 150 grit wheel and very gingerly used one side to lap an old plane iron. I ended up with the edges worn back more than the middle, and I was careful to put only slight pressure at the center of the blade. So dangerous or not, it does not work for me. I also checked the platen on my old belt sander and verified that is is indeed not flat across, so not worth revisiting it to flatten irons.

There is a Woodcraft store and a Rockler store within driving distance from me. If I happen to get a coupon from either, I may go there and buy a Work Sharp 3000. Not in a big hurry, but still a consideration.

Thanks again to everyone who responded.

I have a stone that specifically states that you can do this (Tormek), but boy am I bad at it. I will never try it again. I also would not try it on a stone that specifically warns against it.

I have seen Steven do things while fixing or sharpening that I simply am not capable of, but that is also why when I find something that I cannot make work I make the trek out to his shop. One example is using a belt sander on the bottom of a frog. Yeah, he fixed it and when he was done this "might as well throw it away" #4 plane was usable. I have not seen Steven flatten the back of a blade, but, with the warnings of a shattered stone, I would be very leery of doing this without something that said it was ok to do.

Also note that I was not able to flatten the back using a Worksharp and many here are able to easily do that.

[Thomas Wilson]

Fine Woodworking had a tip this month to attach a block of wood to the front of the blade with double stick tape. I have some chisels and plane blades that I need to flatten. I shall try it and report back.
I tried taping a block of wood to a new A2 plane blade using XFasten double-stick tape. The block was about 1 1/4” by 2 5/8”. The blade is 2 5/8”. I glued the block right next to bevel. It does give a much better grip. It stayed on until the block got pretty wet from the water used on the DMT diamond stones. I was about done when it came off. I had to work a long time on the blade so I think that is satisfactory.

My best grip was with finger tips on the bevel and thumbs behind the block. This position gives good pressure at the cutting edge. It works well for either forward/backward and side-to-side motion. I also tried placing my palm on top of the block and pressing down. This gives a good grip and works well for coarse grit. For finer polishing, it only polished under the block. I needed more pressure at the edge.

One further point about diamond stones, you can’t use a MagSwitch as a handle. The diamond plate is magnetic. Well, maybe you could if you are a gorilla. I couldn’t budge it.

[Todd Ulery]

I've had really good results with the Charlesworth ruler trick. If you watch any of Rob Cosman's videos on sharpening on YouTube, he demonstrates the technique. This saves needing the flatten the entire back, by putting a very slight back bevel on the edge. All it requires is a thin steel ruler (like 1/32") and you have everything you need.

[Jim Koepke]

I've had really good results with the Charlesworth ruler trick. If you watch any of Rob Cosman's videos on sharpening on YouTube, he demonstrates the technique. This saves needing the flatten the entire back, by putting a very slight back bevel on the edge. All it requires is a thin steel ruler (like 1/32") and you have everything you need.

Hi Todd and Welcome to the Creek.

One problem with this is if the back isn't flat the chip breaker may not mate up properly. This could become a real problem if the shavings start jamming.

jtk