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Ball Nose Mill Cutter, did I break it?

Ball Nose Mill Cutter, did I break it?

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Aidan Browne21/04/2010 17:25:58
15 forum posts
Hi,
 
I have just started making a Stuart D10 stationary engine and I needed to make a 7/16 inch semi-circle on the bed of the engine for the crank carriers to sit on. My plan was to use a 7/16 inch ball nose cutter to do this.
 
I order one on Ebay with the description

7/16 INCH. BALLNOSE SLOTDRILL 2 FLUTE  HSS GRD  MADE IN ENGLAND      PLAIN SHANK 
 INDUSTRIAL STANDARD... 
 
it arrived and I set up the engine bed on the mill and gently plunged the cutter into the casting. It didn't sound like it was cutting well and removed it immediately only to see that the flutes had been worn away and the tool was overheated. It's only cast it's going into and none of my other cutters have had a problem. Did i get a dud or did I do something wrong.
 
 
David Clark 121/04/2010 17:34:42
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3357 forum posts
112 photos
10 articles
Hi There
Try a file on the cutter.
Then try a file on the cast iron.
The cutter should cut fine on cast iron.
I used a modified slot drill converted to a ball nose and had no trouble.
I did not go straight in to full depth but after aligning the cutter with the centre, went down 30 thou at a time. This is not because the cutter would not take that sort of cut but rather because the cutter would probably deflect.
Go down to aproximate depth and then widen slot a couple of thou at a time until bearing fits.
Finally ensure cutter is at full depth.
I went about 5 thou wider and deeper than required to allow for paint.
 
I cleaned up the sides and underside of the bearings before milling the slot.
I think I described this in Model Engineer a while back.
regards David
JasonB21/04/2010 17:37:56
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25215 forum posts
3105 photos
1 articles
Its possible your casting is "chilled" this happens when the casting is cooled to quickly and results in very hard metal. Try giving the area a couple of strokes with an old file, if that does not touch it come back and we can suggest a few options.
 
I have heard that quite a few of Stuarts castings are comming out chilled lately.
 
Jason
mgj21/04/2010 17:45:46
1017 forum posts
14 photos
What revs were you using.
 
At 500 rpm or so it should have walked through it. Cutting to D/2, with a reasonable mill and a proper milling chuck you could have taken that out in two passes plus a finishing cut.
 
Jason - you beat me to it. I hadn't heard of recent casting problems but they are fairly thin sections so that's a possibility, but he ought to have been OK. He might have bluntened it, but not knackered it, which is what seems to have happened.The file test is OK in so far as it goes, on a virgin casting, but you still have to get through the skin.
 
Still it doesn't sound as if the cutter is too grand.
 
Not often you find bargains with milling cutters, and the ones worth having tend to be expensive. Sorry, just one of those things.
 
(One of the reasons, said he having a dig generally, why I built a Quorn. In terms of resharpened milling cutters and the ability to operate without fear at reasonable cost at industrial feeds makes it well worth the effort)
 

Edited By mgj on 21/04/2010 17:56:24

Aidan Browne21/04/2010 22:19:13
15 forum posts
Thanks for the quick responses. I have milled the other side of the same casting flat with an end mill and it went through it like butter so I think the castings are OK. All the other castings I have worked in the kit have been OK also.
 
I was running the Ball nose slot drill at 600rpm approx. I think it's beyond a file it just deteriorated in a second and barely marked the casting. The flutes at either side have lost their correct width now, so I think they are useless.The edge on it was very sharp but obviously very soft. I don't know if this matters but there is an initial semi-circle in the casting and I'm just trying to enlarge it to the correct size.
 
I had trouble finding a ball nose drill  from any of the online shops. I have bought a lot of the stuff I needed from Chronos and they have been excellent but they do not have a Ball Nose slot Drill in the size I need.
 
As I said earlier I am very new to model making and could be going about this in completely the wrong way. I'm really enjoying it at the moment and it's very addictive. If there is a better way for me to carry out the job I need to do, I would be glad of your advice. 
mgj22/04/2010 07:04:46
1017 forum posts
14 photos
600 is a bit swift.500 is probably about as fast as you ought to go in a fairly rigid machine.
 
Sounds like a poor cutter.
 
Turn the casting through 90 deg and mill your half circle with the side of an endmill. Its not "better" it just saves having to buy a new cutter.
Chris B22/04/2010 18:01:59
34 forum posts
5 photos
When I did the bed for my 10H, I didn't bother with a ball nosed cutter, I just used a round file to give enough depth to let the bearings sit down and then tidied up the sides with a slot drill to give a snug fit to locate the bearings.
 
CB...
DMB22/04/2010 23:44:43
1585 forum posts
1 photos
Hi Aidan,
Try using a carbide cutter, which will not be blunted by chilled iron like HSS. Or use a small rotary grindstone as supplied with the hand held rotary tools.
If you can, get a proper Clarksons milling chuck and screwed shank cutters to fit. Trust me, their the "bees knees."!
John
Circlip24/04/2010 13:07:49
1723 forum posts
Awww don't tell them about Clarksons Mr Coleman, you're ruining the market for us oldies.
 
  Regards  Ian.
Aidan Browne26/04/2010 23:35:15
15 forum posts
Hi lads,
 
I'll try the file and slot drill method and let you know how I got on. I have a Clarkson milling chuck that came with the mill it's an Int 30 but I only had the 4 basic collets. I found it really good but I have started using the ER collets lately as they are so handy to change.
 
I'll let you know how I get on, and thanks for the advice. 
Stub Mandrel27/04/2010 21:03:38
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4318 forum posts
291 photos
1 articles
FWIW I used a round file when I built my 10V...
 
Neil
elanman28/04/2010 12:58:24
47 forum posts
4 photos
Hi,
I built a Stuart H10 a couple of years ago and found most of the castings had a very hard skin, the thinner parts being hard right through. I had to use TCT tools to machine most parts. I was not impressed!
Cheers
John
KWIL28/04/2010 16:07:10
3681 forum posts
70 photos
John,  Clarksons have only have 4 "basic" collets per imperial and 4 collets for metric unless you get a larger Clarkson. I would not use an ER on a milling cutter as they can pull out under use. The Clarkson principle stops all of that.
Versaboss28/04/2010 22:46:31
512 forum posts
77 photos

Hmm, KWIL, what do you think the ER system was invented for? These collets are used on umpteen thousands of professional machines. In theory you may be right, but in practice that never happens, when the collet nut is closed correctly and the cutter sits completely in the collet.

The danger of the pull-out is much higher in the 'one-sided' collets like the W-types or the C-types from the U.S. 

Greetings, Hansrudolf

KWIL29/04/2010 09:45:15
3681 forum posts
70 photos
Hansrudolf, I am aware of the ER attributes and that it was invented in CH by rego-fix, but we all cannot afford such expensive precision items.
Circlip29/04/2010 11:22:59
1723 forum posts
Leave it Kwil, more for thee an me
 
  Regards  Ian.

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