Author Topic: questions around BCA jig borers and fixing the RT  (Read 1665 times)

Offline Mcgyver

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questions around BCA jig borers and fixing the RT
« on: February 15, 2018, 04:34:44 PM »
On and off I've been doing various mods to my BCA jig borer/mill.  I've replace the Z carriage with a scraped cast iron one with T slots, so a variety of heads can be mounting including a new ER spindle I am 1/2 way through and I have also replaced the motor with a DC motor.

I've also started on my version of a Kurt vise but with 2" jaws.  That got me thinking.....has anyone come up a way to pin the RT at zero and also register the vise so its easy to set it on and have its jaws aligned to the X axis without messing about.

Anyone come up with a good spot for a pin?  Other ideas?  Any good ideas on repeatable tooling placement?  (with the three radial T slots its not like keying a vise to a mill table)

thanks
« Last Edit: February 16, 2018, 12:56:21 PM by Mcgyver »

Offline PJPickard

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Re: questions around BCA jig borers and fixing the the RT
« Reply #1 on: February 15, 2018, 05:29:51 PM »
Sorry no answer to your specific question but I'm interested in the spindle(s) you are making. I'd love one with a quill on it!

Offline Mcgyver

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Re: questions around BCA jig borers and fixing the the RT
« Reply #2 on: February 15, 2018, 05:49:06 PM »
A work in progress.....a few shots to make it more interesting.  I hadn't thought to bother with a quill....but maybe, its a good idea and it would be handy. 

Shaft is ground and P4 AC bearings bought.  Grinding is to a tenth, as determined with an indicating mic and blocks - pulling out all the stops to get a great spindle!  The shaft is drilled through but the internal taper hasn't be cut.  Its all from heat treated 4140.

 I went to grind the housing ID and was getting too much vibration (housing being done with a TPG, shaft was a on T&CG).  So pushed the project aside and starting making a soft bearing dynamic balancer (sigh, more down rabbit hole make a tool to make a tool nonsense)

The T slot block is scraped into the existing casting.  The idea is all sorts of heads could be mounted to it - slotting, horizontal, adapter for my UPT bits and pieces and so on









« Last Edit: February 17, 2018, 04:31:54 PM by Mcgyver »

Offline PJPickard

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Re: questions around BCA jig borers and fixing the the RT
« Reply #3 on: February 16, 2018, 12:48:33 AM »
Ahh you are doing it proper and all. Nice work.I think a quill would be really nice to have. True not as dead nuts accurate but very handy.

Thanks for the pics.

Offline Mcgyver

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Re: questions around BCA jig borers and fixing the RT
« Reply #4 on: July 24, 2018, 02:44:43 AM »
A little progress.  I still have to do the tapered bore and make the pulley.  The final seat for the collet will be ground in situ.  I've some nice SKF P4 matched bearings and there cool little laybrinth seals so we'll see how that goes.  Its all from HT chrome moly.

I'm also going to fix an encoder on it with the view that it could be an electronic hobber - as developed the late John Stevenson and the late Texas Tornado.

I've been making a soft bearing dynamic balancer in the interim which delayed things.  Its mostly done and I'm thinking set the whole thing up with bearings and pulley and dynamically balance before installing in the housing.  We'll see how that goes :)


Offline PJPickard

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Re: questions around BCA jig borers and fixing the RT
« Reply #5 on: July 24, 2018, 11:18:03 AM »
Very nice work! Please keep us updated.

Offline steamer

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Re: questions around BCA jig borers and fixing the RT
« Reply #6 on: July 24, 2018, 11:23:30 AM »
Nice indeed!    Nice piece of kit that centertype grinder!   What brand and model?

Dave
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Damned ijjit!

Offline Steam Haulage

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Re: questions around BCA jig borers and fixing the RT
« Reply #7 on: July 24, 2018, 11:26:06 AM »
Could you post a pic and some info on your dynamic balancer. I know nothing at all about these. :noidea:

Jerry
Dogs look up to you, cats look down on you, pigs treat you as equal.

Offline Mcgyver

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Re: questions around BCA jig borers and fixing the RT
« Reply #8 on: July 24, 2018, 02:52:49 PM »
Thanks

Steamer, the grinder is a Chevalier knock off of a KO Lee, so its really a T&CG with a motorized workhead vs a full fledged cylindrical grinder.  I put a lot of work into that machine, everything scraped, as I wanted a light but accurate cylindrical grinder.  Scraping is to .0002 overall, the table alignment to .0001".  The whole project appeared in Home Shop Machinist as part of a serialized article I did on scraping

While it is a real luxury have that kind of accuracy, it that accuracy comes from basic techniques and hand tools done by yours truly.  Feeling nostalgic on the project....here's some photos.

Jerry, The soft bearing balancer is basically a way way to hold a rotating part and minimize forces constraining it, so small imbalances can make the thing move easily as it rotates.  You revolve it at comparatively low speeds and accelerometers can pick up imbalance and (hopefully) fire a strobe so you can see where the imbalance is.   No photos yet, I want to see if it works first :)


















« Last Edit: July 24, 2018, 04:55:07 PM by Mcgyver »

Offline steamer

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Re: questions around BCA jig borers and fixing the RT
« Reply #9 on: July 24, 2018, 07:05:23 PM »
Yup     I remember the articles...

http://www.modelenginemaker.com/index.php/topic,369.0.html

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline pgp001

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Re: questions around BCA jig borers and fixing the RT
« Reply #10 on: July 24, 2018, 09:44:29 PM »
In answer to your original question of how people install a vice with repeatability, this is my setup.
There are dowels either side of the vice on the sub-plate and also beneath it onto the machine's rotary table which is generally left locked at zero for most jobs.
It is very easy to slacken of the three tee nuts and slide them out, then the whole thing just lifts off.




Or a vice within a vice for really titchy jobs.



I have similar sub plates for mounting other accessories such as chucks.





The larger ones having four as well as three slots so they fit my Hoffmann rotary table as well.





I also made an adapter so I can use my Pultra lathe head and tailstock as miniature dividing head.




Just a few ideas for you.
Phil

Offline Mcgyver

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Re: questions around BCA jig borers and fixing the RT
« Reply #11 on: July 24, 2018, 10:25:08 PM »
Thanks Phil....when you say the subplate registers with dowels into the table, did you bore holes or is that into the T slot?

Offline pgp001

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Re: questions around BCA jig borers and fixing the RT
« Reply #12 on: July 24, 2018, 11:27:19 PM »
Hi

I use the centre hole and the front tee slot for the twin dowel locations on the vice and Pultra sub-plates. And just the centre hole when the chuck sub-plates are fitted.

Drilling holes in a Boley/BCA table would be a hanging offence  :ThumbsDown:

Phil

Offline Mcgyver

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Re: questions around BCA jig borers and fixing the RT
« Reply #13 on: July 29, 2018, 12:43:39 PM »
more progress.  things are assembled and ready for balancing.  When I came up with this scheme, I hadn't thought that the outer races of the AC's wouldn't be loaded, but I don't think it will matter too much.

Broaching the 1/8 keyway was a a bit of a nail biter.  Trying to broach long sections put a lot force on the cutter, I tried to mitigate this by making a number of thinner shims so i broached it on four passes, each one cutting a fraction of the usual.  Keyway done and not a busted broach in sight :)

Next is balancing before final assembly then its grinding the collet seat






« Last Edit: August 01, 2018, 05:25:25 PM by Mcgyver »

Offline Mcgyver

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Re: questions around BCA jig borers and fixing the RT
« Reply #14 on: September 02, 2018, 07:02:34 PM »
What has been keeping me busy.......a lathe rebuild and some more BCA progress.   probably like many I bounce from thing to thing, taking apart and painting a 10ee ('42 round dial) got in the way of the spindle.  The 10ee is in a million pieces while I figure out all the bearings I want to replace.  Anyway, got back to the BCA and have been working on the pedestals for the housing.  The seem like a simple enough thing, but man, they were a lot of work!.  Anyway, here are some shots the interruption (10ee) and the pedestals

various feed sub assemblies from the feed gearbox, its a real puzzle to get apart....hopefully I took enough pics to get it back together again










Pedestals on the Z carrier



a real rube goldberg drilling setup.  I put the tap drill holes in the pedestals in the mill, clamped the hole thing together using the Z carrier as a frame, then used the tap drill holes in the pedestal as a drill guide for the tap drill in the house.  Still all clamped together, I tapped the house then took it apart and drill through the clearance holes in the housing



The second side as a an easier set up.  An adjustable parallel is used to set the pedestals at 45 degrees



Assembly, a few clean up ops left but the basic idea is there.  The 3/4" bar is an support arm, as the BCA Z axis so conveniently tilts, I want to be able hob with it so this support will let me run a horizontal mill style cutter arbor supporting a hob.  Not yet procured is an encoder and timing pulleys to facilitate the eventual hob set up

The final task will be to grind or scrape the bottoms of the pedestals into perfect alignment with the housing











« Last Edit: September 02, 2018, 07:23:54 PM by Mcgyver »