holdrich style radius cutter that mounts in a quick change toolholder

[eweissman]

so, i just finished this fella tonight. kinda a crappy prototype of something i want to make a better version of some day.
cut the body of it from a piece of 1/2 aluminum on my crappy harbor freight horizontal / vertical bandsaw.
needs some work, i need to figure out a better sort of bearing for the hinge, was thinking maybe a bronze
bushing sleeve inside the arm rather than the bronze washer thing i tried this time.

i also need to figure out a better way to broach the arm, that was a pain. basically made a chisel out of a dull drill bit with my
bench grinder and used the quill on my mill to kinda roughly broach the hole for the hss toolbit.

anyhow, let me know what you think,
and i appreciate constructive criticism.

 

[chuckorlando]

Looks pretty good to me. Though I would have used steel for rigidity. Bronze bushing would work ok I would think

 

[markknx]

Next time for broaching try squaring up the end of the HSS bit and dishing out the center. think Ball shaped dremel grinding bit.

 

[eweissman]

would have used steel too, but i had a piece of aluminum on hand and i don't think my crappy little bandsaw would have handled 1/2 steel plate very well, if i had any.
was thinking of trying to use the cnc plasma cutter at work to make a better frame from steel for the next one.

 

[chuckorlando]

Plasma table would cut that pretty easy. Just one of the many tools I want. The alum might do just fine. You built it so might as well use it and see how she does. If nothing else it should work on softer materials. So if you find you do need a steel one then keep one with a bit for steel and one with a bit for alum.

 

[Bill Gruby]

You are only taking light cuts with the tool Chuck. The aluminum will ne more that substantial in rigidity. Yes steel is more rigid but not really needed. Nice job.

"Billy G"

 

[chuckorlando]

Good to know Bill. Admittedly I shy away from Alum more from ignorance then anything. If I aint sure I make it in steel.

I might even make my self one in Alum in this style. I made one from steel thats like Steve Bedairs. But I have seen the style in this thread with some really nice attachments and the ability to do some larger radius work

 

[eweissman]

it works ok, one change i would make to my design is to perhaps shorten the inner, moving frame. made it a little long and it doesnt seem to cut much smaller than a 1/2" radius without having to over extend the tool.
otherwise, i am happy with it. i just guessed on the dimensions based on some pictures i saw online, but it works ok. been wanting one for a while. i kinda want to make a rotary broach too, but the cutter bits for it are pretty pricey even if you do make the broach tool.
http://www.polygonsolutions.com/rotary-broaches/

 

[chuckorlando]

I would love to try some roto broaching. I worry my little lathe wont take it. Maybe on the mill?

 

[sinebar]

Nice job.
If you add some more pivot points along the moving frame, you will be able to adjust the radius more and even be able to do concave radii with the cutter extended past the pivot axis. Take a look at the sherline radius cutter for ideas. Their's cuts in the vertical plane but it works the same as yours only smaller.