What's new
  • Guest
    As per our long standing policy of not permitting medical advice on the forum - all threads concerning the Coronavirus will be locked.
    For more info on the coronavirus please see the link below:
    https://www.cdc.gov/coronavirus/2019-nCoV/summary.html

Balsa Strop Base Shape

I have at last sourced some good balsa for my balsa strops. The balsa is 900mm x 100mm x 10mm. It wasn't cheap at USD 15 but it is very good quality. From that, I will make three balsa strops each about 300mm x 100mm.

As the balsa is only 10mm thick, I will need to mount it on some 8mm thick marine plywood that I have. This will give an overall thickness of about 18mm.

The question is, do I made the plywood just about as big as the balsa strop or do I make the plywood longer giving me a handle by which to hold it?
 
Forget my last post. I just reread Slash's balsa strop topic. The balsa has to be attached to a really dloid flat substrata like marble. I will do that and not use plywood.
 
Acrylic works great too. Somewhere in Slash’s Balsa thread there is a link to Tap Plastics. 12x3 inch works great.
 
Or you could do what I did and get a bit of balsa that it’s 80mm thick if you could min was 80 x 100 x 300
 
Or you could do what I did and get a bit of balsa that it’s 80mm thick if you could min was 80 x 100 x 300
The thickest blocks of balsa that are available to me are 50 x 50 x 300. I am thinking of:

1. Gluing 3 thicknesses of 6mm acrylic together to make 18mm thick, or
2. Gluing 6mm acrylic to 6mm tile glued to 8mm marine plywood.

The 3 x 6mm layered acrylic is the most expensive at about USD 30 each. The acrylic/tile/plywood would be about USD 7 each but will be heavier and could break if dropped.
 
Okay here is what I would do.

You know that balsa without backing will warp. You also know that thick balsa, even with backing, will warp in your climate. You know that wood will warp.

What you might not realize is that perfect flatness is no requirement for the backing. Once the balsa is properly fixed to it, you then lap the balsa flat. So any sort of tile would work as long as it is big enough. Even a brick would work, as far as that goes.

The problem with tile is if it is thick, then it is heavy, and honing in hand will get tiresome, and you don't want to strop or hone on a bench or other unyielding, fixed object. So you want preferably something lighter, even if it is some composite you lay up yourself, as long as there is an element in it that will not flex or warp.

This is gonna take some ingenuity on your part, owing to the availability of materials. The one thing you have in abundance is local hardwood. So one way to tackle this is to build up a box structure, glue a piece of heavy glass to it, and glue the balsa to that. You could also use steel, if you stayed down around 1/8" thick. If the structure is all wood, it will probably warp.

Speaking of composites, you could lay up something in fiberglass or some other composite based on the same principle. It just has to be something that won't absorb water and is dimensionally stable. If it is not thick enough to hold without endangering your fingertips, then glue it to a box base.

You know what a box joint is, right? Similar to, and often improperly called, a dovetail joint. The ends of boards are cut with notches and fingers that fit into one another. It is intimidating until you see how simple it actually is. A box joint is an extremely useful bit of carpentry skill. Look it up on youtube. Dovetail joints, as well, though for this project the box joint is simpler and will work just fine. So you make up a box with no bottom or top using the box joint. Glue or otherwise attach a stable base layer for the balsa. Then glue a thin layer of balsa, maybe 1/4" thick, and lap it. End result is a thick but light structure that will not flex or warp appreciably, with your balsa on top and lapped and pasted.

Not sure how thick 6mm is, but since .22 caliber is 5.56mm I am guessing 6mm is just less than 1/4". Should be stable enough. You just need some height to it, and that's where your carpentry comes in. A solid board WILL warp. The box, not so much at all.
 
Thanks Slash. My thinking is that acrylic (smooth/fat) glued to 6mm ceramic tile ( non-warping) glued to painted marine plywood (for thickness) should reduce a good base for my 10mm thick balsa that I already have.

Lapping the balsa flat might take a mm or so off its thickness. Over time (future lapping) the balsa will get down to 4mm or 5mm thick before needing replacement.

I understand that this base needs to be warp proof, reasonable flat and provide enough thickness to protect my delicate fingers from that dragon edge.

I am looking to make similar bases for my lapping film.
 
You are way overthinking. You just need a solid and non flexing base and need enough to hold on to. You don’t need all this multiple layer stuff. And honestly the hand holding is not 100% necessary and you can do just fine on a bench with basic techniques. Just find something rigid like tile stone masonry thick-acrylic etc to glue it to and be done. Not plywood thin-acrylic or any multilayer stuff. Keep it simple and you stand better chance of success. Get creative after you learn what you are doing with a razor first.
 
You are way overthinking. You just need a solid and non flexing base and need enough to hold on to. You don’t need all this multiple layer stuff. And honestly the hand holding is not 100% necessary and you can do just fine on a bench with basic techniques. Just find something rigid like tile stone masonry thick-acrylic etc to glue it to and be done. Not plywood thin-acrylic or any multilayer stuff. Keep it simple and you stand better chance of success. Get creative after you learn what you are doing with a razor first.
Nearly all newbie failures can be attributed to bench honing or stropping. The media must yield to pressure, so that it balances out equally. Trust me on this. I have been doing this for a while now. Balsa stropping and honing in hand will give superior results, particularly while still learning.

Multiple layers and workarounds are only needed in this case due to the difficulty of getting 3/4" or 1" thick acrylic where the OP lives.

Just sit back and watch. OP is determined and resourceful. I think he is going to succeed and it is too bad you won't be there to experience his edge and compare it to your own edges formed under the same regional hardships.
 

RumpleBearskin

Contributor
For what it's worth I used aluminum bar stock as a base. Stable, relatively lightweight, relatively inexpensive.

If you need more thickness you could sandwich the aluminum between your plywood and the balsa as a stable core.

Just another option FWIW.
 
For what it's worth I used aluminum bar stock as a base. Stable, relatively lightweight, relatively inexpensive.

If you need more thickness you could sandwich the aluminum between your plywood and the balsa as a stable core.

Just another option FWIW.
Should work fine. Yeah, you could just glue 3/4" plywood to the underside of the aluminum, or MIG weld or braze aluminum side and end pieces to the plate. If you have a MIG machine you could add sides to the plate.
 
Weight of the balsa strop assembly has also been a consideration for me. Thick (>3mm) aluminum is not easy to source for me. What I was able to find was some 8mm (5/16") thick polyethersulfone (PES) structural foam manufactured by DIAB (Sweden).

My current thinking is to epoxy glue two pieces of PES together to make 16mm (5/8") thickness then expoxy glue some 6mm (1/4") thick smooth glazed ceramic tile on top to take the balsa.

My calculations show the the total mass (weight) should be about equal to 20mm (3/4") acrylic. The PES provides the thickness to protect my manicured fingers. The ceramic prevents warping and provides a flat surface for the balsa.

Of the foam proves too soft, I can later coat it in a thin layer of FRP.
 
I think your over thinking it a little use the k.i.s.s method steel plate cut to size epoxy its to the plate job done
 
i disagree with you. My stropping (and honing) is done hand-held. Mass of the balsa strop needs to be taken into consideration to decrease fatigue in use.

My PES/tile substrate came in at about 25% lighter than using the same in acrylic.
 
Last edited:
i disagree with you. My stropping (and honing) is done hand-held. Mass of the balsa strop needs to be taken into consideration to decrease fatigue in use.

My PES/tile substrate came in at about 25% lighter than using the same in acrylic.
That maybe so but a mild steel plate that is 50 mm wide but 200 long and 5 to 8 mm thick won’t weigh that much maybe 500 grams but even then you could just rest one end on a bench or table I do my honing while I’m siting and my stone siting in a plastic dinner plate and my balsa strop one ends on the ground an the other is leaning or pushed against my leg to half it in place really most people aren’t going to go I’ll get a balsa stropand travle with it weight shouldn’t be a big issue
 
Top