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Author Topic: Bridgeport Knee Mill Conversion?  (Read 158951 times)

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Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #740 on: February 17, 2018, 02:39:53 PM »
I was surprised too, seems the critical temperature is 125c no more, i also blew air down the spindle to try keeping it cooler.

No damage, no sweat and all parts reusable.

To reassemble, I borrowed a baking tray from the cook room ;) wrapped the bearings in tinfoil, set my powder-coat oven to 120c, put a lump of 1/4" scrap steel on the tray, bearings on top and gave it 20 minutes.

I mounted the spindle vertically in the vise, gripping on the drive dogs, donned a pair of welding gloves and the bearings just fell on, no hint of pressure needed. I realigned the little "o" marks on the inner and outer races and also between top/bottom bearings, tightened the locking ring and left to cool, retightened and lock-tabbed it.

These were original bearings, specially ground and marked with codes, the tubes were measured and both were equal.

Spindle feels very smooth and is now wrapped in cling-film awaiting fitting.

I need to make a drawbar - one piece or two joined ?? Its a hell of a lot of turning if one piece ;)

Anyone know what thread is in a BT30 holder??
« Last Edit: February 17, 2018, 02:41:50 PM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Bridgeport Knee Mill Conversion?
« Reply #741 on: February 17, 2018, 08:46:54 PM »
Have done bearings before it is sometimes amazing how much a bearing will expand (without damage) with some heat being applied. And just how strong a shrink fit can be.
IIRC "BT" holders are metric and CAT are imperial. The drawbar in my BTC-1 is two piece. If drawbar is being activated by an impact gun I am not sure you could get away with a two piece unit.

My son just made a drawbar for his M-head mill and he made it out of one piece. His is shorter than what you need. It fit on the Monarch CK-12 no problem.

Dave, you said you were not going to grease the bearings this time you were going to oil them IIRC. How are you going to supply them with oil on an ongoing basis??

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #742 on: February 18, 2018, 03:13:24 AM »
The head on my mill is the original style with oil cups - one for the bearings via a pipe cleaner drip-feed and the other was for the quill feed mechanism.

It's a total loss system - oil goes in, oil comes out but at least they get oil.

If i fit new bearings then they will likely be greased for life but you still need oil in there for the quill sleeve or it will seize - you cant mix oil and grease so just fitting greased bearings is not the end - you need to redirect the drip-feed to the quill sleeve or cap it off and use the down-feed oiler to lube the quill. To do this right needs a head strip IMHO.

I won't be using an impact wrench - this is BT30 tool-hoding so there is less need to rack the drawbar up mega-tight, when i get going on the power drawbar it will likely be a geared stepper motor system.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #743 on: February 20, 2018, 01:26:23 PM »
A box full of very nice tool holders turned up yesterday, on special from my tool supplier :)

Also made the drawbar for the new spindle.

Now i just have to make a gap to pull the head apart....
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Bridgeport Knee Mill Conversion?
« Reply #744 on: February 20, 2018, 08:45:26 PM »
Looking good.
Can't wait to see it in operation.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #745 on: February 23, 2018, 07:02:08 AM »
QC30 spindle and BT30 drawbar fitted :)

Pretty easy task after all. Whether the bearings will hold up i don't know but they sound ok and did not get hot after 30mins of variable speed idling.

Of course, some idiot ordered the wrong tool holders and didn't notice, ER16 instead of ER20 :(
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Tweakie.CNC

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Re: Bridgeport Knee Mill Conversion?
« Reply #746 on: February 23, 2018, 07:46:44 AM »
Quote
Of course, some idiot ordered the wrong tool holders and didn't notice, ER16 instead of ER20

There is no answer to that Dave - just keep taking the medication (in my case Beer - and lots of it  ;D )

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #747 on: February 23, 2018, 07:50:55 AM »
Turns out there was a reason for my insanity - the supplier does not do an ER20 :) Their range goes ER16-ER25-ER32 so i just ordered ER32 and the next one down :)

My stuff is ER20 & ER32

Easy fix is to order some ER25 chucks and ER16/ER25 collets - sorted.



If anyone is interested I will have a lot of nice R8 stuff for sale soon, will pop it in the forum section before it goes to the 'bay.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #748 on: February 25, 2018, 08:22:16 AM »
Assessing spindle runout...

Yes we all know zero is nice but in the real world, on an old Bridgeport we also know that's not going to happen ;)

Measuring inside the QC30 spindle socket, I get these TIR figures...

Near mouth = <0.005mm
Half way up = <0.01mm
Near top = 0.01mm

Measuring an ER32 collet holder....

Near mouth = 0.04mm
Mid way = 0.01mm
Near top = <0.005mm

Seem ok??

This is not taking into account the collet/tool yet, this is with budget tooling.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #749 on: March 30, 2018, 12:05:40 PM »
Still working on this :)

I have most of the parts for a power drawbar assembled now.

My idea is to let gravity do the down stroke - the theory is that it will make installing tools easier if the drawbar can lift a bit when the tool is loaded. If not then i can either use an air downstroke with air lift, or air downstroke with spring lift.

No ideas about control yet, I have various tiny PLC's on the shelf - would make it easy possibly to add the ATC later or i can add to my CSMIO setup. First off will just be a button or two and solenoid valves.

I'm using two valves - i want the wrench to drop first, then the power to be applied. The wrench can stay down until the next tool is fitted i think.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives