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25th Dec 2018, 08:08 PM #1.
- Join Date
- Nov 2008
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- Perth WA
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- 71
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- 6,458
All For Naught ( A Milling Mishap !! )
A while back I picked up a shell end mill arbor along with a saw arbor from Fiora Machinery that would have accompanied my mill but somehow were misplaced prior to my purchase of the 13. The shell end mill arbor suits a 3/4" bore cutter which was probably a fairly common size back in the early Sixties.
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Searching online revealed that they are now uncommon but I was able to purchase a Dormer 2 1/2" cutter in "excellent condition" from C-Tool on eBay. Turns out the excellent condition simply means not completely f....d. Every edge was chipped which was sad because the cutter had never been used.
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To install the cutter correctly on the arbor required the making of a spacer and a spanner. The spacer took two goes. The first attempt unravelled when a new Goliath 3/16" BSW tap snapped off while tapping the second hole.
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A trial cut with the chipped cutter provided unexpectedly good results so this moring I thought I would have a go at making a pair of boring bar holders for my boring head. A couple of years ago Michael G had sent me photos and dimensioned drawings of the accessories that accompanied his Kaiser Piccolo. I had made a left hand boring bar previously ( with Michael's help ) and realised the other day when working on the Douglas vice, that these bar holders would be a useful addition to the Kaiser's kit.
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My plan was to turn a spigot on each end of a 75mm long piece of 28mm diameter 4140 then use the shell end mill to cut the remainder of the bar 18mm square.
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Easy I thought to knock it off before the crowd arrived for lunch. 100 RPM with a 1mm depth of cut provided a neat finish. Then BANG !!!
Two horsepower will search out the Achilles's heel in any setup and the heal must have been the tightness of the three jaw on the 10mm spigot. The bar rotated and cutter tore the bar off the tailstock centre snapping the very end of the centre off. The cutter is pretty much useless with the face of one tooth sheared off and two other teeth badly chipped.
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A lot of work down the drain but it could have been worse.
I hope you all enjoy the remainder of Christmas day !!
BT
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25th Dec 2018, 09:25 PM #2Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
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- 6,541
Ouch Bob. I'll keep my eyes out for a 3/4" bore shell end mill. There might be one kicking around my second hand haunts. Plan B might be to square up the stock first then put the spigots on. More to hold onto.
Michael
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26th Dec 2018, 12:21 AM #3Most Valued Member
- Join Date
- Jul 2016
- Location
- Melbourne
- Age
- 35
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- 1,522
I also might have a shell mill lead I'll have a look at a friend's collection asap.
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26th Dec 2018, 07:16 AM #4Senior Member
- Join Date
- Dec 2013
- Location
- Sydney
- Posts
- 201
Oh, what a disappointment Bob. The good thing is that you're not reporting any damage to the indexing head, tail stock (apart from the centre) or the mill itself.
It's easy to comment in hindsight, but that cutter, with its big broad cutting edges needs very solid clamping of the part. Could it be held in a vice to square it up? That would be my approach, I'd put a small flat along the diameter keeping cutting forces low, then if I was still nervous I'd rotate it 90 degrees in the vice before finishing the first flat. That way the second cut won't rotate the part in the vice because the first small flat is locking it solid.
Graham.
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26th Dec 2018, 08:59 AM #5Diamond Member
- Join Date
- Mar 2011
- Location
- Dural NSW
- Age
- 82
- Posts
- 1,203
Bob
I think many of us have had these giant stuff ups, but just keep quiet & do not like admit it !
Well done on the revealing photos. Thanks.
Christmas is over, however I wish you & your family all the best for the new year.
Bruce
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26th Dec 2018, 10:23 AM #6
Ouch!
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26th Dec 2018, 03:24 PM #7.
- Join Date
- Nov 2008
- Location
- Perth WA
- Age
- 71
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- 6,458
I spent a bit of time this morning with my indicators and found that the table and the vertical head had been knocked out of alignment. The table had rotated both on the x and y axes and the head on the y. Easily made good. I also ran an indicator around the shell end mill arbor and there was about 0.0003” TIR. The shorter saw arbor shown in the first photo has a TIR of 0.0002” so I reckon the shell arbor hasn’t been bent.
I was wondering how I would hold the tail stock centre to regrind it’s damaged point. Wondering because Schaublin use a 2 degree taper not the more commonplace Morse. Turns out that the tailstock barrel is readily removable so I will centre the barrel in a four jaw mounted on the T and C’s workhead and grind the centre insitu.
Nearly ready to start the what I thought would be a quick simple project again.
Bob.
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26th Dec 2018, 05:27 PM #8The cutter is pretty much useless with the face of one tooth sheared off and two other teeth badly chipped.
"Pretty much useless"--- Wouldn't wanna see some of my stuff. Ground back damaged teeth and running with the good ones. Not ideal, but still good enough for a lot of what I do.Frisky wife, happy life. Then I woke up. Oh well it was fun while it lasted.From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".
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26th Dec 2018, 05:40 PM #9Member
- Join Date
- Oct 2012
- Location
- Mullaloo WA
- Posts
- 80
Bad Luck Bob hope it didn't spoil all your Christmas. As someone said most would have kept quiet about it.
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26th Dec 2018, 06:47 PM #10.
- Join Date
- Nov 2008
- Location
- Perth WA
- Age
- 71
- Posts
- 6,458
Saddled up and sounding like a five legged horse galloping, here's the finish at 150 rpm, 29 mm/min feed and about 0.7mm DOC. I certainly wasn't expecting this outcome. Looks like its hardly missing those three teeth!
IMG_20181226_151729546 (Large).jpg IMG_20181226_152014828 (Large).jpg
If broadcasting my misadventure prevents someone else from pushing their luck with insecure clamping then it will have been worthwhile .
Bob.
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26th Dec 2018, 07:31 PM #11
As an aside, I've had some very disappointing purchases from C-tool on eBay. Rusted, chipped and very worn - condition not obvious from photo or description. A few items that were listed as new, and still with the factory protective coating on them were fine. I thought maybe I just had some bad luck, but then I saw you had a similar experience.
Sent from my SM-G955F using Tapatalk
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26th Dec 2018, 08:09 PM #12Pink 10EE owner
- Join Date
- Aug 2008
- Location
- near Rockhampton
- Posts
- 6,216
Looks like a nice "feature" you have machined onto that cutter.
Gold, the colour of choice for the discerning person.
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26th Dec 2018, 09:47 PM #13.
- Join Date
- Nov 2008
- Location
- Perth WA
- Age
- 71
- Posts
- 6,458
The cutter was posted in an Australia Post satchel in this "gift" wrapping -
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C-Tool might be doing his bit for the environment by reusing old packing tape but a bit of secondhand bubble wrap wouldn't have gone astray!
Bob.
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27th Dec 2018, 10:00 AM #14Most Valued Member
- Join Date
- Jun 2011
- Location
- Australia east coast
- Age
- 71
- Posts
- 2,713
Yeah - some of the stuff I've bought from him has been like that. I have to say that overall my experience buying from him has been good, though. Often his gear - if new - is a bit on the high side but, shrug, he has it, nobody else does, so....
I needed a 7.5mm 2 flute centre cutting slot drill, he had a NOS one. I bought it, used it for one job, got me out of trouble. Could have ground down an 8mm one but for $20 (which was billable) I'm not going to bother.
WRT the shell mill if you grind back the matching teeth and reduce the feed rate accordingly it'll work as well as ever. Sounds like you don't need to bother, though.
I've a big diameter slitting saw someone completely pulled one tooth out of. I still use it, just make sure I'm not too aggressive with the feed rate so as not to break off the next tooth taking the bigger cut.
Couple years back I outbid c-tool on approx 50 kg of milling cutters, there was 4 of those shell mills in the batch I got, all NOS 1" bore. I've used one a fair bit machining straight edge castings, it leaves a lovely finish.
PDW
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27th Dec 2018, 08:59 PM #15
Not a bad surface finish there Bob. Just goes to show the cutter don't have to be perfect to produce the goods.
Wonder if C-tool pulls the stamps off packages and sticks em on with sticky tape to stuff to send out? Fathers favourite online site does this. Drives the chick at our local post office barmyFrisky wife, happy life. Then I woke up. Oh well it was fun while it lasted.From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".
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