Can't get bolsters flat

R

Runthemall

Joined
Jan 25, 2012
Messages
66
How do you get bolsters completely flat? No matter what I do, I end up with a high spot in the middle and they wobble. I've put them on the belt sander platen, which didn't work. So I tried hand sanding on a flat surface. No luck. It seems like the edges are getting sanded more than the middle.
 
I flatten the bolster and handles or tang on my surface grinder, some use a disc grinder. Have you checked, maybe its your handles or tang that is not flat.
 
How flat is your media? If the surface under your sandpaper is not dead flat, nor will the item you are trying to flatten end up flat. I have a piece of polished granite I snagged for free as a small cutoff from a fountain fabricator but counter guys will have them too.
 
You also need to sand in a figure 8 pattern if you're hand sanding on sandpaper on granite/glass/other flat surface. If you just use lateral movements the rocking pressure of your hand will cause the problem you're having. A figure 8 evens it out across the surface.
 
Make sure you glue down your sandpaper on your flat surface, if it shifts, it bunches up on the leading edge of your piece, making the center higher.
 
An added problem - if you already have a high spot, then you may not recover unless you change tactics. That is, when you put pressure down on a concave surface, it will tend to roll it towards an edge. In the end, you may just have a thinner concave item.

To fix this, you may want to clamp it into a fixture to make sure you are working relative to a known plane.

Another option is to use files. They may not be dead flat, but they can help eliminate/identify high spots.
 
Color it with a sharpie.

Then use a figure 8 motion on your flat surface with some 80 grit paper.

Look and see where the ink is worn away, adjust your grip turn the part around and do it again until flat.
 
The figure 8 motion is important.

TIP #1:
Another trick is to use a ball burr on a dremel or flexshaft and relieve the middle of the underside a tad. Leave an 1/8" around the edges unrelieved. That makes the sanding only affect the perimeter. Same method works great for handle scales. I do almost all scales and bolsters this way. You only need to relieve it a tiny amount for this to make a huge difference in ease of installation. It also makes getting a tight peen easier, as it allows a little place for expansion so the bolsters will pull down tight. It prevents the problem the following tip deals with.

TIP #2:
Another bolster installation tip is to make the holes through the tang slightly larger than the pins. I would say that 10-20% oversize would be good.
If the pin is snug fit on the holes here is what happens:
When you peen the pins they will expand.
If there is no room for expansion in the tang, it will make the pin bulge ( called upsetting) on each side of the tang.
This will raise the bolster up a little.
All the pounding in the world will not make the tiny gap close.
 
Stacy E. Apelt - Bladesmith said:
The figure 8 motion is important.

TIP #1:
Another trick is to use a ball burr on a dremel or flexshaft and relieve the middle of the underside a tad. Leave an 1/8" around the edges unrelieved. That makes the sanding only affect the perimeter. Same method works great for handle scales. I do almost all scales and bolsters this way. You only need to relieve it a tiny amount for this to make a huge difference in ease of installation. It also makes getting a tight peen easier, as it allows a little place for expansion so the bolsters will pull down tight. It prevents the problem the following tip deals with.
Click to expand...

:eek: That never crossed my mind for scales. I drill a load of holes but a full relief... :thumbup:
 
Stacy E. Apelt - Bladesmith said:
The figure 8 motion is important.

TIP #1:
Another trick is to use a ball burr on a dremel or flexshaft and relieve the middle of the underside a tad. Leave an 1/8" around the edges unrelieved. That makes the sanding only affect the perimeter. Same method works great for handle scales. I do almost all scales and bolsters this way. You only need to relieve it a tiny amount for this to make a huge difference in ease of installation. It also makes getting a tight peen easier, as it allows a little place for expansion so the bolsters will pull down tight. It prevents the problem the following tip deals with.

TIP #2:
Another bolster installation tip is to make the holes through the tang slightly larger than the pins. I would say that 10-20% oversize would be good.
If the pin is snug fit on the holes here is what happens:
When you peen the pins they will expand.
If there is no room for expansion in the tang, it will make the pin bulge ( called upsetting) on each side of the tang.
This will raise the bolster up a little.
All the pounding in the world will not make the tiny gap close.
Click to expand...


Great tips Stacy! I've never done bolsters but I'm sure I'll have much less trouble whenever I do decide to try them out. :)

I do the same thing on my scales as well, but I probably wouldn't have thought about doing that with bolsters :D :thumbup:

Ever since I first tried tapering a tang a few years ago and learned about creating a hollow in the tang before going to the platen
(in order to reduce surface area for less grinding), I've been doing the same thing on all of my non-tapered tang knives as well using the 3" idler on my platen. It really helps to make sure the tang is dead flat along with helping to avoid any epoxy starved joints, not to mention it reduces weight. I also drill some large lightening holes in the tang before grinding the hollows which also help with reducing the overall weight, as well as another insurance for a good bond with the scales (epoxy rivets).

~Paul
My YT Channel Lsubslimed
... (It's been a few years since my last upload)
 
Last edited:
Armin Drumm said:
Get them flat on the miling machine, or, if from steel on the surface grinder (magnetic platten)
Click to expand...

That works great in a full shop, but few hobby makers have either tool. Methods that work well in a small shop where most tasks are done by hand with simple equipment are often the most reliable and repeatable.
 
when I personally have tried using a figure 8 the surface I'm sanding stays closer to square with the rest of the sides but it seems to make the whole surface i'm sanding slightly rounded
so it's sanding the edges very evenly but the center not as much.

If I sand in 1 direction (usually only pushing the object away with the sandpaper on granite) the surface I'm sanding gets much flater though I need to be very very careful of how I'm holding it as the of the orientation to the other sides can be off very easily(and by a very noticeable amount) if I'm not.

It's entirely possible I'm doing something wrong. Has anyone else had a similar experience?

though stacy's 2 tricks kinda make the point moot as making to surfaces join up like[()] will be much much easier than trying to make it [||]
 
Here's a tip that saved me hours of "why the hell can't I get this flat!"... Take a hand file then clamp it to your work bench, and run the bolster over it with your hand. Saved me hours of frustration, and about the straightest bolster I've ever made.
 
Runthemall said:
How do you get bolsters completely flat? No matter what I do, I end up with a high spot in the middle and they wobble. I've put them on the belt sander platen, which didn't work. So I tried hand sanding on a flat surface. No luck. It seems like the edges are getting sanded more than the middle.
Click to expand...

Where are you at in Ohio?
I have a surface grinder and I'd be happy to flatten something for you.
By the way, I just bought it this year so I'm a beginner at it, but the offer still stands:D
 
I flatten my bolsters on a 9 inch disc grinder using leather gloves...easy and very flat. Larry


xVhXapOm.jpg
 
You must log in or register to reply here.
Back
Top