endmills/slot drills

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johnnyone
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endmills/slot drills

Post by johnnyone » Tue Nov 27, 2012 3:37 pm

hi
i've got a clarke cl500m 3 in 1 lathe mill with a mt3 style colett type on the quill. whats the bigget end mill i can fit into it? my supplier tells me its a 12mm endmill. can i go upto 16mm on this mill?

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SteveM
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Re: endmills/slot drills

Post by SteveM » Tue Nov 27, 2012 3:50 pm

I've never seen metric MT3 collets, but in inch size they go up to 3/4".

Steve

Torch
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Re: endmills/slot drills

Post by Torch » Tue Nov 27, 2012 8:09 pm

SteveM wrote:I've never seen metric MT3 collets, but in inch size they go up to 3/4".
... which is very close to 19mm.

It's really more of a question about can your machine handle it rather than if it will fit. Bigger mills need more power and greater rigidity. Obviously, how tough or soft the material being milled is will also be a factor. Aluminium is a lot more forgiving than steel.

Also, be aware that any tram error will be more pronounced with a larger endmill.

johnnyone
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Re: endmills/slot drills

Post by johnnyone » Wed Nov 28, 2012 2:32 pm

thanks for that. i'm looking to cut a 16mm slot in 12mm mild steel

Torch
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Re: endmills/slot drills

Post by Torch » Wed Nov 28, 2012 7:15 pm

To be honest, I think you would be better off to cut a narrower slot -- maybe 15mm, almost to depth, then widen it on each side. Depending on the depth, you might need to take several passes to do that too. Bring it to 0.01 or 0.02mm shy of the final dimension. If the dimension is really critical, let the part cool before making the final two passes to finish depth.

Make sure your column is clamped very tight and don't try to take big bites when slotting. The tool bit will want to torque the mill and can rotate the column if the motor power combined with reaction force can overcome the clamping force. Don't Ask Me How I Know This (tm). I would limit the depth of cut to 1mm or less per pass in steel.

johnnyone
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Re: endmills/slot drills

Post by johnnyone » Thu Nov 29, 2012 2:36 pm

thanks for that. i did'nt say earlier, but this will be a 16mm radius slot through 12mm mild steel.+45 deg to -45 deg on a rotary table.

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GlennW
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Re: endmills/slot drills

Post by GlennW » Thu Nov 29, 2012 2:59 pm

Bore a 16mm hole at the termination points of the slot, and then mill the arc making two much narrower slots to join the bores using a small end mill.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

johnnyone
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Re: endmills/slot drills

Post by johnnyone » Mon Dec 03, 2012 3:01 pm

the main problem that i've got with the cl500m is that i can't seem to get the mill head to stay put.

slotting out a hole, the damm thing either jumps to the side or wanders off line.

its not the job thats moving, its the mill head! any advice would be welcome.

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warmstrong1955
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Re: endmills/slot drills

Post by warmstrong1955 » Mon Dec 03, 2012 4:13 pm

johnnyone wrote:the main problem that i've got with the cl500m is that i can't seem to get the mill head to stay put.

slotting out a hole, the damm thing either jumps to the side or wanders off line.

its not the job thats moving, its the mill head! any advice would be welcome.
When I started started milling my Smithy 1340, I had the same problem. An easy fix, I just made a longer handle for the two capscrews that locked down the mill head to the column. The wrench thing that came with it was hardly enough to keep things from moving around.

You might start there....

Bill
Today's solutions are tomorrow's problems.

Harold_V
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Re: endmills/slot drills

Post by Harold_V » Mon Dec 03, 2012 4:50 pm

johnnyone wrote:the main problem that i've got with the cl500m is that i can't seem to get the mill head to stay put.

slotting out a hole, the damm thing either jumps to the side or wanders off line.

its not the job thats moving, its the mill head! any advice would be welcome.
If location or size is critical, don't cut slots with one pass. Use an undersized end mill, opening the slot with material remaining on both faces. You can then take independent cuts on each side, controlling location and size (as well as finish). This is true of heavy mills, too, not just light weight machines. It's just a matter of degree.

If you MUST make the cut with just one pass, do not use a four flute end mill. The leading flute will cause deflection of the tool (flexing of the machine) and cut the slot off location. A two flute limits the deflection, but it is not eliminated.

Harold
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Torch
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Re: endmills/slot drills

Post by Torch » Mon Dec 03, 2012 6:07 pm

johnnyone wrote:slotting out a hole, the damm thing either jumps to the side or wanders off line.

its not the job thats moving, its the mill head! any advice would be welcome.
That's exactly what I was talking about. Make sure the column is clamped tight (eg: use Bill's longer handle, a socket wrench, a cheater bar on the handle, whatever...) and limit your depth of cut, especially when using a large diameter endmill in hard material. Harold is also right-on (as usual) regarding the number of flutes. The idea here is to reduce the amount of force torquing the column and/ or increase the amount of force resisting torque at the column.

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