What kind of Plastic for Lapping Plane Soles

[David Weaver]

Good morning -

I have seen several people lapping the soles of planes on plate glass with SC grit on top of some sort of thin layer of plastic.

I have the glass, the grit, and I have SC paper, but I can't find information on what type of plastic it is that's cemented to plate glass for lapping.

LV has plastic laminate with a PSA backing, but it's too small for what I'm doing. Sandpaper is a bit slow where the bottoms are out of whack, and I seem to go through a lot of it.

Can anyone tell me what type of plastic to use - that'll be durable enough to stand up to the grit, but not so thick that the grit doesn't bite?

My glass is about 14x20 inches, so it needs to be at least that large.

Thanks -

[Mike Henderson]

I put sandpaper on a flat surface, such as my table saw top, and use that to flatten a plane sole. I "attach" the paper to the surface with one or two clamps on the edges of the paper.

I use a sheet of sandpaper which is about 8x10.

Mike

[David Weaver]

Mike - I have been fixing sandpaper to the surface of my plate with just the tension of water, which works OK. Two sheets fit on it easily, so that's what I've been using.

I have a #8 to lap - that is out about 0.002" at the mouth, so I'm just trying to ease the burden a little. It'll already be difficult to do it because it's longer than the glass I think the diagonals were about 22 inches or so - so I may be wrong about the measurements of the glass in my previous post.

I can see this plane taking 3 or 4 hours to lap if I use the plate and the SC paper I have. I don't like to use the grit on the paper because it gets between the sheets and dings up the glass.

I'd use the TS if that was an option, but mine is hollow 8 thousandths in the depth - just too much to lap a jointer.

[Eddie Darby]

I just finished going through the same thing a month ago because my previously flattened planes had changed over the years, and I too found sandpaper to be slow, so I poured SC on the top of the sandpaper, and sprayed it with water. I thought this helped a lot, just make sure to watch that you don't go through the sandpaper.

[Mike Henderson]

Mike - I have been fixing sandpaper to the surface of my plate with just the tension of water, which works OK. Two sheets fit on it easily, so that's what I've been using.

I have a #8 to lap - that is out about 0.002" at the mouth, so I'm just trying to ease the burden a little. It'll already be difficult to do it because it's longer than the glass I think the diagonals were about 22 inches or so - so I may be wrong about the measurements of the glass in my previous post.

I can see this plane taking 3 or 4 hours to lap if I use the plate and the SC paper I have. I don't like to use the grit on the paper because it gets between the sheets and dings up the glass.

I'd use the TS if that was an option, but mine is hollow 8 thousandths in the depth - just too much to lap a jointer.
Yep, I can see the problem with lapping a #8. One thing I'd say, however, is that it's not as important to have a jointer exactly flat as it is to have a smoother flat.

I guess I'd try one of two things.

1. Get some sandpaper in a roll so that I have a long enough surface to do the lapping - but you still need a long flat surface like a flat table saw or jointer.

2. Send the plane to a machine shop and have them grind it flat. Around here, they charge about $25 to grind the sole of a plane (but I never asked about grinding a #8).

Good luck!

Mike

[Scott Loven]

I have seen people use a sheet of phenolic plastic for this type of work, is that what you are looking for?

Scott

[David Weaver]

I have seen people use a sheet of phenolic plastic for this type of work, is that what you are looking for?

Scott

Generally, yes. I just need to know what I'm getting before I get it, to make sure the plastic is going to be durable enough to withstand the grit passing back and forth over it, and that the type will be porous enough so that it can be glued to the glass with contact cement.

[John Schreiber]

I'm not sure what the purpose of the plastic is?

I have a glass plate about the size of yours and I use rubber cement sprayed on the back of the sandpaper to attach it to the glass. Then I use that for lapping. I'm sure you could add SC abrasive over that when the sandpaper runs out, I just change to new sandpaper.

[David Weaver]

The purpose of the plastic is to keep the glass from getting marked up by wayward SC grit. Two sheets of sand paper won't cover the entire glass, so I'm trying to avoid that.

The suggestion of aerosol rubber cement is helpful, though. I have 50 sheets of 60 grit paper, so it won't be the end of the world if I have to go that route. I'll just have to mark the glass to make sure I only screw up one side of it (the other is used for sharpening and lapping water stones). I know in reality, it won't be too big of a deal to scratch it, but I'm just trying to preserve it some since it was almost $100 for the glass.

[Pam Niedermayer]

First, it's a good idea to try to use the plane before flattening, which may not even be needed, as Mike said. Second, I think scraping may be a better option than sandpaper in this case.

Pam

[David Weaver]

As in scraping with a Sandvik carbide scraper?

[John Goodridge]

I have not tried this before; but it was my understanding that the purpose of the plastic was to allow the grit to embed into it slightly so that the grit would not slide around as much and cut better.

[Eddie Darby]

Ran across this:

https://home.comcast.net/~rexmill/sharpening/super_charge/super_charge.htm

[Pam Niedermayer]

As in scraping with a Sandvik carbide scraper?

No, more like the blunt end of a file.

Pam

[Gary Herrmann]

If you have a glass shop nearby ask them to make you a piece for lapping long planes. I asked the local place and they made me a 6"x36" piece of 1/2" float glass for $20.

[Ray Sheley]

I've been curious about hand scraping a plane sole for a while. I think that I have the basics, Prussian blue a truly flat surface, press the plane into the blue, lift it, then scrape the spots that are blue, keep going until it is all blue.
I can see the sense in scraping in the beginning where theoretically only 3 points will make contact, but how tough is it when the plane approaches flat? And what are the odds that this is a self teach, get it right the first time project? I'd like to try it, but this has to be tougher than a "dive in and do it" project.
Do you think that a safe approach would be to scrape in the early stage, then lap to finish for us Newbies?

[Pam Niedermayer]

Ray, I've only played around with scraping metal planes, mainly because I sold almost all my metal bench planes a few years ago. But in the situation where a long plane needs serious flattening, as in the plane doesn't work properly without flattening, it seems easier to me than sanding. I scrape my wooden planes, but the difference is that a scraper plane is prefered to a metal scraper.

Pam

[James Carmichael]

No, more like the blunt end of a file.

Pam

An HSS scraper for turning wood works well scraping iron. I might want something with a wider radius for working the sole of a plane, though. There are HSS and carbide machinists scrapers, but I don't think that's the Sandvik he's referring to.

I'm with Pam, flattening isn't always necessary. If the toe, mouth, and heel are coplanar, you should be fine. Layout fluid and scraping the high spots may be a lot less work, especially on that #8:eek:

[David Weaver]

Too late - i got a 42" long piece of plate glass for it yesterday :eek:

Since I probably only lap something once a month at this point, I'll struggle through it - and if it doesn't work, then I'll look for alternate routes.

I backed off on the type of plastic needed as I found that it's easier just to follow the suggestion of someone else on here and use contact adheisive to fix the paper to the glass - it stays on well enough, and comes off easily enough.

I emailed Ernie Conover to see if he'd enlighten me about the plastic used in his video, but no response, and I don't feel like jumping through the hoops to try to get a hold of him.

Thanks for the suggestions. I'll keep the machinist scrapers in mind - especially if I can't get the #8 to look flat along a starrett edge. I expect it's going to take several hours to lap it.

[Walt Quadrato]

I have to agree with Pam..try it first..scraping is an option but if you're not familiar with the technique I would recommend testing on a junker first..another option to sandpaper is drywall screen..it's very coarse and should be used for the initial flattening, then go up to progressively finer grits...but to "hog" off a lot it works well..

think co-planer...toe, mouth and heel...that's the trick


walt Q