should I convert these?

Possibly they jam due to insufficient chip clearance, try drilling a couple of through holes inside (meeting) the saw's cut to allow the chips out? If you use the saws to 'scribe' the work lightly it'll show you where to drill :)

Dave H. (the other one)
 
Make an R8 arbor with a threaded stub to receive the saw(s). Maybe you can adapt/modify a commercially available R8 shank. That's where I'd start looking. What is the thread size for the shank/pilot?

Me thinks those type of hole saws are always going to have the problem of trying to lift the work piece and grab at breakthrough. If your work piece isn't rigid, cover with a clamp plate (MDF w/ a pre-drilled clearance hole) and lots of hold downs.

By the way, I have same looking cutters but only up to about 1.5". I think they're designed to be used in hand held power tools but on aluminum material (think aircraft). I wonder if the tooth geometry of your cutters is intended for mild steel?
 
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To me those look like they're made for wood (coarse teeth). I've used a Starrett saw in steel and it worked good but I think it had much finer teeth than your picture.
 
Thanks for the ideas guys, I like the idea of making a R8 Arbor with a threaded stub. I dont think they are for wood (i could be wrong of course) but the guy I got them from was a machinist for 40+ years and selling all his items. Wish I would have bought more at the time :-(
 
I dont see any "set" to the teeth.
How far into the cut do you get before they start binding?

Cheers Phil
 
I,d say you have 2 problems here, one is to find or make an R8 arbor for those cutters, the other is your lubrication. tap & die fluid is probably too thin, maybe you'd get a better performance if you use some paste or solid stick type that's used for annular cutters.
I would load up the teeth with the wax before cutting,see if that helps.
https://www.emisupply.com/catalog/w...nt-105oz-solid-stick-p-2306.html#.WL1QUTsrKLw
 
From the original design it does not seem like these hole saws were intended for a lot of torque.
To use on a mill with an R8 threaded arbor would solve the slipping problem but then would those small threads stand up to the torque they might encounter?

What about threading and drilling the hole saw cups to fit a common hole saw arbor like this?
The shank is hex and the keying mechanism takes all the torque so the threads don't take a beating.
IMG_0115.JPG
 
Drill a hole or two the width of the saw blade through the part at the center of the circles where the blade will cut, this will allow the chips to fall through, a good deal of the binding is the result of chip binding in the cut.

Holding such a tool in an R8 collet is difficult at best.
 
These appear to be trepanning tools made for aluminum or wood. The teeth will load up with chips so you are going to have to "peck drill." Unless your pilot hole wallows out, the Bridgeport should be enough mill. What do the arbors mike? Are they undersize?
 
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