Advise needed

H

Hillbilly

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I have a M/C primary cover , ally 5mm thick . I want to cut a hole in it 160mm dia .
I have a boring head [ never used it ] with an 18mm arm that takes a 6mm HSS cutter .
I am thinking to cut the hole either with the boring head and an appropriate shaped cutter, plunging down, or an end mill freehand & Finnish with the boring head .
I have a medium size knee mill . I am very inexperienced .
Can anyone foresee any problem I may encounter or offer any advice .
 
I agree with Parlo. I will add that trying to freehand a circle with an endmill (even just for roughing) is a recipe for disaster. It will be much easier to enlarge a smooth hole than trying to clean up a rough one.

GsT
 
machPete99 said:
Is that dimension correct? 160mm = 6.299", a pretty big hole... Might be a good choice for a rotary table and an end mill to cut.
Click to expand...
Yes correct , and yes may be doable with what I have .
I have a universal dividing head , not sure if I have the room to spin the part .
 
Thanks Gene , the hole I am cutting replaces 4 rough drilled holes , so a smooth hole to start may be difficult .
I am trying to make something nicer from a butchered part .
That is why I was thinking trepanning [ learnt a new term ] .
 
Trepanning might be possible. Grind the HSS cutter with enough relief to clear the inner and outer diameter of the cut, For a clean hole, grind an angle the bottom of the cutter slightly towards the outside dimeter. You will need to get the mill down to its slowest speed, below 100 RPM. Use power down-feed on its slowest advance if you have it. Lots of cutting fluid, (Kerosine, WD40 mix works great). Make sure the set-up is very solid.
 
Eddyde said:
Trepanning might be possible. Grind the HSS cutter with enough relief to clear the inner and outer diameter of the cut, For a clean hole, grind an angle the bottom of the cutter slightly towards the outside dimeter. You will need to get the mill down to its slowest speed, below 100 RPM. Use power down-feed on its slowest advance if you have it. Lots of cutting fluid, (Kerosine, WD40 mix works great). Make sure the set-up is very solid.
Click to expand...
I would strongly suggest locking the quill and moving the knee up by hand, especially as you may have an interrupted cut.
 
Trepanning is not much fun, at least in steel. This hole tapered, larger to the bottom. I assume it was due to the angle on the end of the cutter.

 
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