Cutting a cam with radiused flanks

[Steamchick]

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.
Thanks,
K2

 

[Jasonb]

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.

 

[Charles Lamont]

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.

 

[cuttergrinder]

I am late to the party but I am currently building a camshaft grinder. I machined a sample model cam lobe on a cnc mill to use to copy and produce a master lobe.

 

[Steamchick]

Hi Jason, - Call it laziness?! But different collet chucks and drill chucks have different lengths for the drawbars. M12, 3/8" and 1/2" !Ideally I should make a better workshop, but my missus won't move, and the ceiling can't be raised. I have drawbars also for holding the same tools in the lathe main-shaft - no 3 taper. It is worth the clart when I am using a larger milling cutter, - doing a lot of milling, etc. but often I am just counterboring or spot-facing a drilled hole with a milling cutter, and if a smallish size the drill chuck is perfectly adequate. I recently faced a casting about 1 inch square with a 1/4" end mill without any issues using the drill chuck to hold the cutter. Faces cleaned-up between 0.005" and 0.010" so I wasn't making much swarf... But to hold my 20mm boring bar in a collet means I must remove the drill chuck...
Hi Charles - an Obvious solution. Must get around to it one day... On the list of "improvements"! - I still have 3 lengths to contend with though.... and 1/2" is difficult to reduce to M12 - if they were the same length. The M12 and 3/8" may be commonised though.. Must check.
K2

 

[Charles Lamont]

If you standardise on 3/8", both 1/2" & M12 can be sleeved down. A long thread and nut at the top of the drawbar allows for different lengths.

 

[Steamchick]

Aye. Simple n effective. Thanks Charles.
I have made draw-bars from a bolt and some re-bar - cut and welded. I sense a "universal" draw-bar being added to the set.
But first, the drawing board! Or just chalk-board, or fag-packet, to optimise lengths...
Lots of fun.
A good reason to use this site. - clever guys plus experienced guys.
K2

 

[cuttergrinder]

I have never made a model engine but I have made a crankshaft for a pulling tractor. It weighed 800 lbs when I started.

Now I am working on making a camshaft. I have a guy that will design the lobes but he charges 88.00 per lobe. I seen where some of you were using a spreadsheet to calculate the lobe profile. Where can I download the spreadsheet. I have tried but all the links I find are dead.

 

[stevehuckss396]

I have never made a model engine but I have made a crankshaft for a pulling tractor. It weighed 800 lbs when I started.

Now I am working on making a camshaft. I have a guy that will design the lobes but he charges 88.00 per lobe. I seen where some of you were using a spreadsheet to calculate the lobe profile. Where can I download the spreadsheet. I have tried but all the links I find are dead.

That spreadsheet just calculates the height you cut for a given degree to form the lobes. You have to know the Base circle, nose radius and flank radius to use the spreadsheet.

 

[cuttergrinder]

That spreadsheet just calculates the height you cut for a given degree to form the lobes. You have to know the Base circle, nose radius and flank radius to use the spreadsheet.

Ok thanks. The guy I have designs the lobe and then gives me a table for the lift at every degree. He charges 88.00 each though which really isn't too bad. I then use his numbers and make a cad drawing and then use cam to program the cnc mill to cut the lobe.

 

[stevehuckss396]

Ok thanks. The guy I have designs the lobe and then gives me a table for the lift at every degree. He charges 88.00 each though which really isn't too bad. I then use his numbers and make a cad drawing and then use cam to program the cnc mill to cut the lobe.

If you are trying to make big power you might want to also see what existing cams measure. Lift, Duration, lobe seperation, all have an effect on performance. Is this guy also providing seperation numbers also? even advancing and retarding cam timing can have an effect on torque and HP. Hats off for doing it.

 

[cuttergrinder]

If you are trying to make big power you might want to also see what existing cams measure. Lift, Duration, lobe seperation, all have an effect on performance. Is this guy also providing seperation numbers also? even advancing and retarding cam timing can have an effect on torque and HP. Hats off for doing it.

He doesn't give lobe seperation. I'm on my own there. We have tried changing cam timing but its the best where its at. The tractor runs pretty good. Just would like to tweak it alittle to see if we could get more power. We won the points for the class on Saturday. So its doing pretty good.

 

[ShopShoe]

Steamchick,

I may be missing something in your description of your headroom and drawbar issue: My apologies if I am.

If you used a collet chuck and collet arrangement as "standard," could you use a drill chuck with a straight arbor to be retained in the collet? I think that would only need for you to loosen the drawbar without removing it to remove the drill chuck with its arbor and replace with whatever other collet and tool you wanted to use. Or is headrom so small there is not room to do even that?

I know that part of the problem may be that MT collets often are a bear to remove, so perhaps another taper system might work better.

Another idea: It may not be ideal, but perhaps making a shorter bench for your mill could help.

--ShopShoe

 

[Steamchick]

Thanks Shop Shoe. This isn't a major issue for me, I'm just not as fit strong and flexible as a few decades ago.... My lathe, bench and mill-drill only occupy about 6ft x 8ft. The mill-drill is on top of a heavy chest of drawers. Gives me a solid structure and good working height. But I haven't got need to swing a cat so manage everything standing on one spot. I'm only 6 inches or so shy of enough headroom for removing drawbars, but slackening the machine head, cranking down to change tooling the cranking up to fit the job for machining is avoided if I cheat sometimes by using the drill chuck - carefully - for milling or spot facing. Most of the time I am drilling, and when I need heavier milling I can manage. It just takes time and effort.
Thanks for the ideas, I'll probably optimise some aspects as and when.
Just now I have boilers to service and pre-test before certification this weekend.
Thanks for the suggestions.
K2