Cutting a cam with radiused flanks

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Apr 2, 2020
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Sunderland , UK.
Gb. I agree you are right. I was admitting my Human frailty... (lazyness), and what is sometimes necessity.
My spindle is No 3 MT, and I have limited headroom above the top of the machine, I usually have to lower and raise the Machine Head to make headroom to get the chuck retaining drawbar from the top of the spindle, it takes a good 5 mins of muscle and grunt to change from Drill chuck to collet chuck or back. Bench to ceiling is less than the height of the machine plus drawbar length...

I have to slacken the head clamp -bolts, crank the head lower - to about 1in from the machine vice, but to one side of the vice, slacken and remove the drawbar, slip the chuck out and fit the other one, refit the drawbar, raise the head and re-clamp. As the pillar is round, this is impractical if using concentric drilling and end milling for spot facing or countersinking, as the alignment of the reset head is never exactly where ir was before. so NOT changing from the drill chuck is sometimes a necessity. But due care IS necessary as drill chucks are not as precise, nor clamp as well as proper collect chucks.
I'm aware of the limitations of the machine and work accordingly.
I have 2 rules.
1: Not being safe HURTS!
2: Not machining within the strength, stiffness, and security of the machine, tool bit and workpiece will probably destroy either the workpiece (wasting all the previous effort), or the tool bit (COST £, $, etc.). And tears may flow...

So, for any SMALL milling jobs using a dia 1/4" or less, with a light cut, I have never had a problem with the retention of tool in my drill chuck. But I use collets for 1/4" up to 30mm as I have a large range of tools I have acquired... The largest collet I have is 3/4" and it gets used for a 3/4" dia boring bar, and a 3/4" milling cutter. My smallest collets take a 1/4" shank.

Obviously Brian has the expertise to manage when using a drill chuck instead of a collet chuck.
So I agree your point wholeheartedly, yet have exceptions in my life that I manage.
I agree this forum should always explain the "proper way" to all, especially beginners who do not know when and how "exceptions can be manged.


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Mar 30, 2008
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Surrey, UK
Why don't you change the drill chuck arbor to one with the same thread as your collet chuck? that way you don't need to remove the drawbar

And/or use an ER collet chuck and you can hold drill bits in that as well as milling cutters. That is what I tend to do and only changing to the drill chuck for sizes that require the collets closing down a lot which I try to avoid. Bonus is collet chucks are generally shorter than drill chucks particularly keyless ones so you gain some head room.
Mar 24, 2011
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UK, Warwickshire
Steamchick, what are the threads on your drawbars?

My mill has a 30-int taper. Tooling can come tapped for 3/8" or 1/2" Whit or M12 drawbars. I just make bushes, sort of home-made helicoils, to bring everything to 3/8".

For milling cutters I much prefer my Clarkson Autolock to my ER chuck, which is only used when I have to. And of course, quick, light jobs sometimes get done with the drill chuck.

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