How flat a flatter

[FlyingXS]

I acquired a few flatter heads yesterday and although quite rusted and a little pitted I think they probably have never been used.

my question is how flat should a flatter be?  When dressing the face do you just round of the edges or slightly crown the whole face, or just crown the outer 1/3 leaving a flat centre?

 

[arkie]

How flat do you want it to be?  Not being a smart aleck here, but most flatters are flat so that no gap is seen when placed on a flat surface such as a table, etc.  The edges do, however, need to have a radius to prevent leaving marks on your work.

[Frosty]

None of mine are crowned nor with broken edges. Being a top tool you aren't likely to accidentally let an edge of corner dig into the work, it's not like having a flat face and sharp edges on a hammer. I've never noticed marks from sharp edges from my flatters, even the first couple blows where you'd think the uneven surface would show an edge.

Of course there are situations where modifying a flatter would be in order, say you need to work into a shoulder and want the inside corner rounded. All you need do is radius one edge of the flatter though.

It'd be really impractical trying to crown even my small flatter, there isn't enough thickness on the edges to leave anything if crowned. My set hammer could be but I've never seen a need.

Frosty The Lucky.

[ThomasPowers]

So will you be using these with a 1000# Chambersburg  air hammer or a 4# hand powered sledge.   For some reason you assumed we'd know and I have been out of town and so missed that.

[FlyingXS]

I thought set hamers had "sharp" edges and flatters were crowned or radius edged so not to leave marks.  Apparently not the case from what you guys are saying?

These are top tools for hand use. Around 2" at a guess square on the face.   I also picked up a bunch of upsetting matrices for making them.  

[Alan Evans]

Most of my flatters are flat but have the edges relieved with a progressive curve...think one quarter of an ellipse profile. Maybe feathering 10mm (3/8") over the surface. By your description crowning about the the outer fifth of the surface. I have a few undressed ones, and will use one of those if I want to smooth right up to a shoulder, as a final pass having used the soft edge ones to do most of the work.

Because I use them to flatten an uneven surface (!) I found the as-manufactured sharp edges would leave a hard angle mark when it pushed half of a high spot down, the hard angle mark would still show when the rest of the high spot was knocked down with subsequent blows.

My set hammers have a much smaller plain radius edge, just a bit more than the wire edge off, and are smaller in surface area. They forge rather than smooth. I have one which is converted from a flatter by just cutting one flange off so it is flush and square with the shaft/body. This was made for forging a long tenon so I could focus the blow into the shoulder but take all the tenon down in one go.

I also have a few crowned top tools which I have made up (sometimes from flatters) for various projects that required a regulated concave surface.

Alan

[FlyingXS]

Just in case your interested here is the matrixes for I assume making flatters and top stages.