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Thread: Deep hole drilling. MT5 - ER32
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12th Jul 2013, 12:38 AM #31Most Valued Member
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Wow, now thats some drill. Could have saved me some trouble. Thanks but its done.
MIG welded the drill into the collar as even though it was a hammer fit. I didnt want it coming loose 300mm into the bore. One thing to watch for anyone making one of these (thought I dont know it makes any difference) is twist drill taper towards the shank so you have to bore the hole and I assume make the collar the size of the "big" end. Was very happy when they collar was damn near air tight in the bore, meant I didnt have to pull it all to piece to take an other few thou off.
Took about 2 hours to drill the hole about 1.25mm at a time. The tailstock "DRO" was very handy. Biggest problem was heat really, burnt myself touching the left hand end.....thats a little to hot but of course I didnt do that until I was finished, I was paying more attention to the drill. It did get exciting one time when I was pushing the drill back in, some how it grabbed and started feeding itself at what I assume was the pitch of the flutes. That didnt do a lot for the finish and was happy to have a brake.
Quick check of run out, better than 0.06mm (I paid no attention to cosine error so it might be better than that)... pretty happy with that.
Stuart
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12th Jul 2013, 09:30 AM #32Distracted Member
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Great result Stu. Fortune favours the brave.
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12th Jul 2013, 10:22 AM #33Most Valued Member
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Nice job Stuart.
Rob
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12th Jul 2013, 10:50 AM #34Most Valued Member
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Next time (if there is a next time) make a clamp block for your QCTP and use the power feed to do the job.
You could shorten that free length right down to minimise any possible bending moment and get a more consistent feed rate.
Also I've always used the thickest extension I could to improve stiffness - pipe works - and brazed the joint.
PDW
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12th Jul 2013, 11:00 AM #35Most Valued Member
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12th Jul 2013, 02:47 PM #36Most Valued Member
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thanks guys
Hi Peter,
The small feed was more about heat than anything else. I could have gone deeper, I tried up to 2.5mm but things got hot fast as the amount of drag from the swarf went up. Might be the first time I've really needed coolant on the lathe. If I'd know how hot the adaptor was getting I would have done something about it. In hindsight "where was the heat going to go?" 90% of the adaptor is sealed inside the spindle )
I've been told using the carriage for drilling isn't such a great idea? The forces being much higher than boring or turning. I guess it depends on the size of the lathe as to what drill is "to big". I think winding the carriage in and out that many times would have set me around the twist. Though I did use the carriage as a depth stop.
My theory was I actually wanted it to bend. I figured if the headstock isn't aligned with the ways I wanted the drill shank to be able to bend so it could correct itself and not rub to much.(one hole hardly proves that lol and given how much misalignment there is in a lathe spindle you're likely correct and I'm making thinks up)
Brazing would have been nice but
1. I don't think I really have enough heat ATM, I might have been able to silver solder it.(hopefully that will change soon).
2. being a press fit blazing would only have been at the fillet..... do you think that would have been enough?(though thinking about it I could have bored the first 5mm or so a little oversize)
Stuart
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12th Jul 2013, 06:18 PM #37Most Valued Member
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12th Jul 2013, 09:03 PM #38Most Valued Member
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Brazing is heaps strong enough, I've done exactly this for a 1.25" drill bit extension. However the amount if heat is an issue, I used oxy-acetylene.
As for the carriage strength issue, people gun drilling do it this way so it seems to work. If you wanted the extension to flex, fair enough.
End of the day, as usual, many ways to skin a cat and yours worked fine, therefore it was a good way to do it.
PDW
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12th Jul 2013, 09:24 PM #39Member
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Well Done Stuart
... and what a bonus to see so many following this thread. A great education (again) for Daryl.
db
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15th Jul 2013, 11:15 PM #40Most Valued Member
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Well I was thinking my large LPG burner, But maybe that wont be enough? I've only ever used an oxy but that was a long long time ago.
Well it would have worked for my little drill then.
Well I'm still not sure I wanted it..... but it seemed like a good idea at the time lol
Whether is was a "good idea" or "I got away with it" I'm not so sure.
Checked the runout again, its between 2 and 3 thou.
Roughed then ground the taper. Blued it as was pretty happy.
Cut the thread(which I should have done first!)
Checked the runout, a bit over a thou
Seems my taper angle isnt as good as I thought.
Maybe I should first try boring out the centerso the small end of the collet isnt on the taper like the chuck(doubt that will fix anything though).
Also the thread is pretty tight, I wonder if thats a bad idea. Wouldnt a little slop let the nut centralize on the collet?
A few pictures of the Navara adaptor
Stuart
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15th Jul 2013, 11:30 PM #41Most Valued Member
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Did you bore it to the correct dimension for the choice of collet?
You don't appear to have faced the front edge or to have provided a chamfer/lead for the thread.
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16th Jul 2013, 12:16 AM #42Most Valued Member
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Hi PC,
Well I started, then changed my mind as I didnt think it would matter, but maybe it does, thats why I was asking. I didnt bore as I will one day need to bore the whole thing to 20mm and I figured more metal is always better(if it doesnt screw things up)
Its faced, but only rougly, no camfer as yet.
Stuart
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16th Jul 2013, 08:14 AM #43Most Valued Member
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For the ease of it I would bore at least to 23.5mm ID for 34 mm length.
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16th Jul 2013, 11:17 AM #44Most Valued Member
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16th Jul 2013, 11:54 AM #45Most Valued Member
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When I make mine I off set the compound and advance it up to around .6mm or there abouts and trial the nut from there.
I try for a free fit for the nut, not sure of the technical term, but I don't want the nut firm/tight on the thread.
Not really sure if giving extra clearance for the nut on the thread would serve any real benefit as the collet is fairly free to move in the retaining ring of the nut and is centred more so by the taper.
Could be totally wrong in my opinion of this, but it is what I have found.
the main problem I find is getting everything running true or near to it, thats why I believe it would be safer runout wise for people to be able to finish their own taper off after installing it on their machine.
I can generally get the ones I make down to about .0005" to .001" runout at the chuck end but sometimes it can be greater.
In regards to running long slender material inside your spindle bore (say under 1/2") I wouldn't like to have more than 150mm to 200mm out of the rear of the spindle at any great speed, unless a support was used.