New Project: Shop Made Flexbar Fly Cutter

[erikmannie]

So my budget is zero here, but I can do this.

I am going to make one of these:



My first concern is that I haven’t yet found a way to make the square holes. I don’t have a broach.

 

[erikmannie]

EDIT: I scaled down the dimensions below:

I have a 1-1/2” end mill holder that doesn’t get much use, so my initial plan is to have a 1-1/2” straight shank with a Weldon flat.

I have some 1” thick plate that is 10” in length. I can use this for the body.

I will turn the straight shank to 1.5000”, or whatever fits tightly in the EMH. Then I will drill/bore a hole of the same dimension so that the straight shank is perpendicular to the body. I will weld on the shank and then machine down the weld beads.

I have 3/4” square turning tool holders, so I just need to figure out how to get a .750” square hole in the 1” plate.

I will have set screws in order to secure the tool holders, *or* I could have slits on the ends so that the screws would clamp the body around the tool holder.

 

[erikmannie]

I could make two halves, where I would use end mills to make 3/4” wide slots, & then weld the two halves together. That is one way to make a square hole.

I would have to be careful not to warp/deform the slots when I welded it up. I could do it slightly undersized, & then finish it with a square file.

 

[erikmannie]

So my questions so far are:

(1) How would you make the square holes?

and

(2) Should I make slits on the sides so that the screws would *clamp in* the tool holder?

 

[erikmannie]

Now that I think about it, I would be better off having a 3/4” straight shank & put that in an R8 3/4” collet. No need for an EMH here.

In this case, I would use 3/8” brazed carbide tool bits. Same dimensions as in the drawing above.

I like these scaled down dimensions. I can see a rigid 5” lever set way down in an EMH abusing the head. If I am going to have some flex, I don’t want it to be on the machine.

 

[jwmelvin]

I’d mill a slot from the OD surface and then silver solder in a block to close it off.

 

[erikmannie]

I think that I will forego the slits, & have set screws tighten down on the tool bit.

 

[erikmannie]

I’d mill a slot from the OD surface and then silver solder in a block to close it off.

So mill a 3/8” wide slot (say) 5/8” in, and then silver solder (braze?) in a [3/8” X 1/4” X plate thickness] steel block? I had not considered that.

I would have to buy silver wire (and flux for silver brazing), as I only have bronze brazing rod here, & nobody thinks bronze is strong enough for this application.

I have done silver brazing (but not silver soldering) before (at a school). It is really strong!

I like the idea of brazing because warping is a non-issue.

EDIT: Now I see why you used the term “silver solder” rather than “silver braze”:

Silver Solder & Braze, the difference and what you need to know!

Silver Solder & Braze are both easy to do processes that can be an incredibly useful alternative to welding. This plain speaking article will help you understand the differences between Silver Solder & Braze.

www.thewelderswarehouse.com

(I’m not building a fillet in this application. Rather, I am using capillary action to fill a seam.)

 

[erikmannie]

Any opinions on how thick the plate should be (for the body)?

 

[francist]

Maybe even slot in from the ends and weld a tab across to close the hole to form the square?



As for body thickness if I were considering it I wouldn’t make it any thinner than twice the width of your cutter shank. So for 3/8” cutter make the plate 3/4” thick. If you scale the flex bar example it looks to be about that ratio as well, give or take a hair.