Cutting radius on the mill

This topic has 23 replies, 16 voices, and was last updated 21 September 2016 at 11:09 by Eric Cox.

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20 September 2016 at 15:53 #256961
Eric Cox
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@ericcox50497
When cutting a radius on the end of a connecting rod I put the connecting rod on a spigot in the vice and turn the rod against the end mill as per the photo.

The photo shows the rod at 3o'clock.

When I turn the rod from 3 to 6 o'clock there is no problem. However when I turn the rod from 6 to 9 o'clock vibration sets in and the rod rises on the spigot.

Any idea why.
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20 September 2016 at 15:53 #24745
Eric Cox
Participant
@ericcox50497
20 September 2016 at 16:02 #256964
KWIL
Participant
@kwil
I would suggest that your vertical bearing rod is not vertical and you will be changing the cutting angle as you rotate the con rod end. Also the rod end would be better lower as the vertical would vibrate less.

Edited By KWIL on 20/09/2016 16:03:28
20 September 2016 at 16:32 #256966
Dennis D
Participant
@dennisd
I think that once you get past the 6 o'clock position you are climb milling and the cutter is pulling into the rod causing it to ride up the flutes.

I seem to recall seeing a video of someone cutting a larger radius on the mill but in that set up the spigot was horizontal and a end mill used .

Would it not be easier to make some filing buttons.
20 September 2016 at 16:38 #256967
daveb
Participant
@daveb17630
It needs more support. The mounting post is too tall, the workpiece needs to be as close to the point of support as possible, also a collar with a set screw on the post above the workpiece to hold it down. Very light cuts only, turn the workpiece against the cutter rotation.
20 September 2016 at 17:05 #256972
Martin Connelly
Participant
@martinconnelly55370
I agree with KWIL, too high on a slender pin.

Martin
20 September 2016 at 18:25 #256979
John Reese
Participant
@johnreese12848
I agree with DaveB. In addition I would want the pin clamped in V jaws. If you still have a problem try cutting half the depth first, then lower the cuttrer and clean up the entire radius.
20 September 2016 at 18:43 #256984
Tim Stevens
Participant
@timstevens64731
It seems impossible to me to change from up to down milling (or vice versa) as the workpiece is rotated around the spindle. So, I don't understand the posting from Den24171. Is he right?

I would suggest making a forked or slotted holder for the spindle, and holding that in the vice. The spindle could be a loose pin or bolt, and there would be much reduced tendency to bend the attachment (and so, less tendency for the cutter to dig in as the spindle bent under load, and to wind the workpiece up the teeth).

Cheers, Tim
20 September 2016 at 18:51 #256986
Howi
Participant
@howi
Yes! Den24171 is correct. Draw a line through the centre of the workpiece and line that up st 90 degrees to the cutter. When you rotate anticlockwise you get conventional milling, when you rotate clockwise past the centrer point you get climb milling.
20 September 2016 at 18:51 #256987
KWIL
Participant
@kwil
The whole work is climb milling since he is feeding the work into the cutter, rotating as it does from 3 to 9 oclock.
20 September 2016 at 18:53 #256989
Tony Pratt 1
Participant
@tonypratt1
Tim,

You are correct & are conventional milling at all times, Den24171 is in error but your set up is much too flimsy.

Tony
20 September 2016 at 18:55 #256990
Tony Pratt 1
Participant
@tonypratt1
Kwil,

Just read your post & I don't agree, Tim is turning the part against the cutter rotation[I think]

Tony
20 September 2016 at 19:01 #256993
JasonB
Moderator
@jasonb
All conventional milling.

Shorter pivot pin with a nut or drilled and tapped for a screw and washer. Stick a Vee block between moving jaw and base of pivot to grip it true and firmer
20 September 2016 at 19:03 #256995
Tim Stevens
Participant
@timstevens64731
I was indeed thinking that the part turned against the cutter rotation, ie from 3pm to 9pm looking down on the work. My concern was not that it was one or the other type of milling, but that it could not change as the part was rotated. I saw nothing in the OP message to suggest that he was doing half and then going backwards to do the other half.

Cheers, Tim
20 September 2016 at 19:04 #256996
Boiler Bri
Participant
@boilerbri
Do you still have all your fingers?
20 September 2016 at 19:06 #256998
Anonymous
Posted by Tim Stevens on 20/09/2016 18:43:31:

It seems impossible to me to change from up to down milling (or vice versa) as the workpiece is rotated around the spindle. So, I don't understand the posting from Den24171. Is he right?

No he isn't right, it's conventional milling throughtout the whole 180º.

Andrew
20 September 2016 at 20:10 #257006
Chris Evans 6
Participant
@chrisevans6
Time to invest in a rotary table, that looks like a dodgy set up to me.
20 September 2016 at 20:12 #257007
DMB
Participant
@dmb
JasonB,

You said "stick a V block between moving jaw and base of pivot"

Would a vise with mirror – vee s machined in the jaws be OK? Promise not to be offended if you say i`m nuts or whatever – I simply cannot decide if that would work just as well.

While i`m posting, FWIW, I dont believe in hand held work in machines. I have managed to preserve 5 digits on both hands in perfect condition for nearly 7 decades and have no plans to change this!

John
20 September 2016 at 20:20 #257010
JasonB
Moderator
@jasonb
Yes vice with V jaws would work fine. I was assuming Eric only had the one milling vice and hopefully a set of vee blocks.

I also tend to use the rotary table or good old filing buttons.

J
20 September 2016 at 20:42 #257012
RICHARD GREEN 2
Participant
@richardgreen2
A connecting rod for a Gardner gas engine
20 September 2016 at 22:07 #257026
JohnF
Participant
@johnf59703
I am with Eric and Boiler Bri on this — please please refrain form dodgy inappropriate setups. This operation should be done on a rotary table with appropriate tooling or for small pieces use filing buttons.

Never sacrifice safety in the workshop or you risk injury or worse.
21 September 2016 at 09:28 #257053
Eric Cox
Participant
@ericcox50497
The photo was a quick set up to clarify the description. Normally the spigot is held in a block which is held in the vice and the rod held with Mole Grips so fingers are well out of the way.

No nearer to finding out why vibration sets in when moved from 6 to 9
21 September 2016 at 09:49 #257058
Tim Stevens
Participant
@timstevens64731
One thing that might clarify the situation is the positioning of your clock face. I guess that 6 o'clock means with the rod pointing towards the camera?

Tim
21 September 2016 at 11:09 #257074
Eric Cox
Participant
@ericcox50497
Yes, the photo shows the rod at 3 o'clock, 6 o'clock towards the camera and 9 o'clock to the left.
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