Spotting drill spindle for QCTP?

[PekkaNF]

Hello,

My first question here ever.

I have been toying with the idea of buying a QCTP and works for two lathes. I'll do that AFTER I have succesfully copleted this project:

I need some advice on spotting drill spindle design. I haven't build it yet, I have some material lying around, but I need to confirm few parameters.

Basic design considerations:
* Simple, no need to use for general drilling/milling with added complexity/weight/setup. I want it's spindle centre to lathe centre height and leave it there.
* Would be nice to able to use commercial QCTP boring bar holder. Most of the commercial tool blocks for my needs have about 1" hole.
* Therefore would be nice if I could fit spinle cartridge into 1" hole, least most of it. Then again I suppose I could bucher up one and machine it to acept slightly bigger bearings or build the whole tool block.
* Drills would be 3 mm or 6 mm (7 mm for M6 camfer) something like 95% of time. Drill Chuck or ER-collet? I have sope ER11 collets and they are neat. Chuck would be more versatile, but much bigger.
* I probably could aim to 6000-9000 rpm spindle speed, but I don't want to go very much over (motor/gearing/seals). Do I get away with only one spindle speed?
* I think I would get away with only one speed, maybe 3000rpm and 120w or 180w induction AC motor (I like it quiet)?
* I'd like to be able to mount it axially and radially to TP.

Spindle design (the major self made part):
* I have this one book about spindles, but I'm not completely happy with designs. Spindles (Workshop Practice Series No 27) by Harpit Sandhu.

* Closest of the design I like I have found is one with anglular contact ball bearings in this book: Lathework a Complete Course, number 34. ISBN 1-85486-230-8
Same design is also on MEW #80
MODEL ENGINEERS’ WORKSHOP
http://www.homews-mew-index.co.uk/index.html
 80   12   LATHE PROJECTS FOR BEGINNERS14   MILL/DRILL SPINDLE               C   HALL
 81   12   LATHE PROJECTS FOR BEGINNERS15   MILL/DRILL SPINDLE 81            C   HALL
Not completely happy with this one either. I don't "get" the need for the first nut on the primary bearing. Bearing clearance is adjusted yet another nut and the thing is just a little of LLP design. (Lot of Little Parts). But I't closest I can get.

* I'd rather start with a good design than overly simple or fiddly. I'm allergic to ball bearings all over, I rather would but a small taper roll bearing, but they would kill small motor and would need additional shiels/seals. Should get away with angular contact ballbearings. Then again I don't want to go overly expensive/sensitive/accurate bearings, because of my track record: I probably blow up few before I learn my lessons.

Also I don't want build to a lesser standards you could buy from the shop...

Am I missing something obivious here?

PekkaNF

[Trion]

Hi, I am currently thinking about the same as you, only I aim a bit bigger. Mine is going to be used both to hold a boring head, so that I can use it as a ball turner, and should have an MT2 taper so that I can fit other tooling for my lathe. I haven't got too far, as I need a QCTP for dimensions, and some shaper tooling to be able to make the dovetails. I also need a small boring bar, a boring head and a MT2 reamer + the motor, so don't hold your breath You can find what I´ve done on the "My Slager 12x36" lathe" topic.

I don't know much about rpms etc, but I reckon you have a problem when you say you´d like to be able to use it axially and radially, because the drill bit is going to end up pointing away from the workpiece in one of the situations, unless you are able to flip the holder over.
Good luck on your build!

[PekkaNF]

Hi, I am currently thinking about the same as you, only I aim a bit bigger. Mine is going to be used both to hold a boring head, so that I can use it as a ball turner, and should have an MT2 taper so that I can fit other tooling for my lathe. I haven't got too far, as I need a QCTP for dimensions, and some shaper tooling to be able to make the dovetails. I also need a small boring bar, a boring head and a MT2 reamer + the motor, so don't hold your breath You can find what I´ve done on the "My Slager 12x36" lathe" topic.

I don't know much about rpms etc, but I reckon you have a problem when you say you´d like to be able to use it axially and radially, because the drill bit is going to end up pointing away from the workpiece in one of the situations, unless you are able to flip the holder over.
Good luck on your build!

Thanks.

You just described the reason I want to keep my build simple: I have a greater change succeeding when I design tool to make only one thing, but I aim to do it well. Most of the time versatile tools are pain to adjust and even more so to design. It takes considerable amount of gumption and knowledge. I consider it character building exercise.

* I do want to use it both radially and axially, therefore my first aim is to fit it in an ordinary boring bar holder - If I can attach from either end, this would avoid the need for turning something over? Then again the hole on the toolholder might not be very true, leading on furher comlications.
* If I had to build from scratch I probably would make dovetails on both sides of the tool block, to prevet the need for flipping. Two set of dovetails would make it unnecessary wide and might compromise it's accuracy (I probably would machine it for axial direction....for an obivius reason).
* Then again I just could design the holder to be flipped and allow the motor to be flipped too. This probably would be the least painful excercise on the long run. How hard it could be remove original height adjustement and make two separate features (such as stop screws) for individual height adjustement?

I toyed a little with the idea of attaching the motor rotor at the end of long spindle. With a small motor this would be viable for my needs (no need to consider tail stock), BUT I have no idea if AC squirel gage motor rotor can be removed from the original shaft and mounted succesfully to a new shaft. I have reservations and therefore I dropped this avenue.

PekkaNF

[PekkaNF]

Didn't go as planned - and I'm not even off the drawing board.

Basically got caught on wishfull thinkking....I tought I could be able to use ready made part to avoid machining a nasty part...


FIRST FAULT: Wishfull thinking
I have read that often people complain "import" collet sraight shanks being too "tight". This would have been ideal for me: I was planning to press 12 mm ID bearing to nominally 12 mm straight shank.

I got two ER11 collet straight-shanks
http://www.ctctools.biz/servlet/the-334/ER11-12MM-STRAIGHT-SHANK/Detail

It looked promissing, but only tail of the shank was tight, collet end was way too loose (miked something like 11,97 - 11,98 mm). BLIZNAK!

THE BUMMER:
I rather avoided making the spidle shaft, now I have to decide:
* Ordering one oversize ER11 collet straight-shank 1/2" for 12 mm bearing ID or chopping one 16mm shank for 15 mm bearing ID. Problem: how to center (ready shanks have about 7 mm hole straight trough? Collet end could be located, but probably would need a steady for the other end.
* Fabricating one with ER 11 cavity and M13*0,75mm thread. Never tried this sort of taper turning excercise. Does not look overly easy.
* Could make spindle shaft for JT2 or B12 taper drill chuck, this I believe could be doable.
* Could make spindle shaft 1/2" 20 tpi (or chuch) drill chuck. Never tried imperial threads. Should be even easier and better chance for immediate success, providing I have gears for this thread and the thread angle is 60 decrees, I don't have 55 decree threading tools.

I talked to one design engineer who is well versed with bearings. He gave me some pointers and chucked me one SKF manual that should be great for self defence: It weights least four kilos. I got the drift:
* I can have it with few parts (but fiddly to adjust) or I can go bomb sure, but higher count of parts and more features to machine. I think I'll play it safe.
* I might be better off without thinking formal fits and geometrical form IT6 etc. Just have to do as good as I can and hope its tight under load where it should be and close to sliding fit at the free bearing end...
* Have to prepared to build it over few times....

I have to muse little over this one...Using a drill chuck over collet has pretty fundamental impact on the design. Even smalles chuck makes it impossible to insert trough a 1" hole on the boring bar holder....I could then ditch the whole spindle cartridge idea and machine straight into holder... making it pretty heavy modifications - flipping et.al.

PekkaNF

Wonder where all the pictures are going to go....

[PekkaNF]

Hello again,

I'm wondering when I should start a new thread on "Project Logs"?

Then again - I think I might be better here wallowing over things until I'll get over this hiatus ans start building this spotting drill with dire intention. Even few botched spindles qualify as an design phase, don't they? I call it feasibility study. If I can't make it, its not feasible for me.

I'm still not overly confident about my ability over the spindle structure. Do I choose the one that is under size or do I try to make one that is clearly above my skill level?

1A) I have this 12 mm ER11 straight-shank collet holder, that is just a tad too much under size something like 11,97 - 11,98 mm
http://www.ctctools.biz/servlet/the-334/ER11-12MM-STRAIGHT-SHANK/Detail

It's too loose for a proper bearing fit, but I just might get way on this low loaded application on bearing glue. I'll try this if everyting else fails. I can google many people going this route, but I haven't found details or proof of longevity.


2B) DIY. Not very convinced I have the skill to get there. I roughed out some blanks: One to practice, one for ER11 collet and one for drill chuck.

* I have one unused Rhöm half decent drill chuck that has markking 1/2"-20. It's thread chuck.  I spent some time trying to figure out it's thread form. Optimisticly I'm assuming that it is UNF i.e. 60 decree angle. IF SOMEONE KNOWS, please tell before I go amok. I have Tubal Cains book (of tables and other engineerins stuff) it has even chapter devoted to drill chuck threads, but it only says "caveat".

* Steel I have now is pretty much limited to tempering steel and silver steel (drill rod). Not very happy turning.

I made the spidle blanks from tempering steel. OD 16 mm 700 something rpm 0,12 mm/r feed, chips looks file. Somewhat rough finnish. Probably I have to go up with the speed or sharpen HSS finishing tool.

This tempering steel is 34CrNiMo6 to me, these are other names for same stuff (or close)
4340
817M40
En24

This steel seems to need rough turning and then some rest before final turning, othervice I'll get bananas. I don't like it, but it is something I have to live with. Other choice would be a mysterysteel from the hardwaresore or junk yard and sometimes there is a reason why someone has abandoned good looking steel: Inclusions and other tool eating nasties and mechanical strength somewhere chicken crap and chewing gum. You never know.

Any advice? Free cutting steel is no option. I simply can't buy any small quantity here, even few hundered kilograms per size it way below minimum order!

Thanks,
PekkaNF

[andyf]

Hi Pekka,

It's a bit late to mention this, but if you only want a spindle for light drilling, have you thought of improving a commercial flexible drive and adding a mounting so it will fit in the toolpost?

Here is an example:
http://mikesworkshop.weebly.com/toolpost-drill.html

Andy

[PekkaNF]

Hi Pekka,

It's a bit late to mention this, but if you only want a spindle for light drilling, have you thought of improving a commercial flexible drive and adding a mounting so it will fit in the toolpost?

Here is an example:
http://mikesworkshop.weebly.com/toolpost-drill.html

Andy

Saw it and other similar. Clear benefit is to get the motor out of the toolpost. Drawback is the "flexible drive". I'd like to have something more substantial. Let's see if this ever flies.

PekkaNF

[PekkaNF]

Bliznak! Tempering steel spindles had gone bananas. Lucily I had them much oversize, but I definately have to turn them between centres. I'm sidetracked in making fixed steady. If it does not fly, I'll probably have to buy one. For my lathe CQ9325, this guy has similar 130 mm centre height.
http://users.picknowl.com.au/~gloaming_agnet/cq9325rev.html

I gues I finaly need one!

Pekka

[PekkaNF]

OK. Steady rest down, now I only have to learn turn between centres. Searching this site as I go. Then I have to figure out how much speed and power I need. It's dawning to me that ideal would be AC servo close to 240 VAC that I could drive with VFD...I even don't need any feedback. Have to bug my frieds if anybody would have a 100-200w or so servo. Maybe I shoud experiment before comintments.

Pekka