Fly Cutter Set Screw

[brucevoelkerding]

I was given a lightly-used Fly Cutter which is 2-1/2" OD with an integral R8 Spindle. The Set screws which clamp the Tool Bit are shot. A hex Wrench will not tighten the Screws before twisting in the hex Socket. Note I am in the USA. It is typical for a Chinese Tool like this to have the correct inch size tapped hole in the R8 Spindle, but you are never sure what the Threads would be for the Toll Bit clamping Screws. The Tool Bit clamping Set Screws measure 0.157 - I would think they are M4. However, at the Hardware Store, no M4 will fit in any of the qty 3 tapped Holes. I have checked with a US standard #6 (.138 OD) Screw which is way too loose. I have checked with a US standard #8 (.164 OD) Screw which will not fit. I have also tried both the coarse and fine #8 Tap in the Holes and they will not go.

When I hold the existing Set Screws up to my collection of Screws, they seem to be close to 32 tpi which is very close to 0.8 pitch. Is there such a thing as an M4-0.8 thread used for Set Screws ? They sure don't seem available in the US.

[springcrocus]

Try 5/32" BSW which is 32 tpi.

Regards, Steve

[jem]

Can you drill them out, and retap at a slightly bigger size?

Jem

[jo479]

Maybe 4 BA, but I would think 4 mm

[SteveW]

Bruce,

I think all of my economy "High Quality Chineses" sourced bits use metric threads.

It could be that if the sockets are stuffed the threads could also have pulled. Perhaps re-cut the threads using your antiquated local thread choices.

[jasonb]

If you have had it a few years then Whitworth is quite likely on older far eastern (including india) tooling, certainly is on some of mine. More recent tends to be metric