Fitting Align Power Feed on Z-Axis - Gate PBM2000

[Twizseven]

I bought an Align Z-Axis power feed several months ago to fit to my Gate PBM-2000 milling machine.  This is a Taiwanese copy of a Bridgeport mill.  As is normal the fitting instructions for these leave a little to be desired.  The booklet covers fitting all thee axis's.  The page for Z-Axis is just a series of small schematics with some notes.

Picture 1 - shows instruction sheet

Start by removing the castellated assembly on the end of the shaft.  This requires some leverage, I unscrewed the knurled locknut on the graduated dial and this move it off far enough for me to tap off the rest of the way.

Then removed the graduated dial and its associated shims and them the bearing retaining flange (three M6 caphead bolts).  The sleeve it is fitted to is on a standard right hard thread on the knee feedscew.  Would it come undone.  Not a cat in hells chance.  In the end had to resort to using the old and new knurled nuts locked together as a pair using to pairs of stillsons and then judicious use of small nozzle on the oxyacetylene welding kit to warm it up and hopefully expand it enough to remove.  Had to keep the two knurled nuts together with two pairs of stillsons and hit the rear pair of stillsons with copper mallet firmly.  Hurrah it finally cracked loose.

Picture 2 - shows the sleeve minus the graduated dial and castellated nut.  The bearing retainer is the new one.  This was reassembled just for this photo.

When cooled down fitted the new extension shaft to the feedscrew running it right up against the bearing tightened it up using the castellated nut and knee winding handle and copper mallet to tap it tight.  Fitted the bearing flange ensuring the two tapped holes to mount the power feed were uppermost.

Picture 3 - Bearing Retaining Flange Fitted

Picture 4 - Shims located on shaft

Picture 5 - Extension shaft being tightened into place

Picture 6 - Power Feed unit bolted into place

Bolted the Power Feed unit to the flange and then slid the brass gear on the shaft.  Played around with a couple of shims to get backlash between the two gears to suitable state and then did up the castellated nut.  It all locked up solid.  As the castellated nut was being done up it pushed the gear and any shims that were being used again the  roller bearing and then the main casting of the power feed.  This obviously locked everything all up solid.  On further investigation it transpired that the shoulder on the extension shaft (that the gear/shims) should butt up against was not protruding out of the roller bearing far enough to stop the brass gear pushing in too far.

I needed to move the extension shaft a very small amount away from the  bearings in pushed against.  The only way I could see to do this was to take several of the shims which would normally be used between the gear and shoulder and put them on the main feedscrew and then refit the extension shaft.  After a number of attempted with different shim thicknesses, 46 thou of shim was enough to get the should on the extension shaft to protrude out of the roller bearing enough that when brass gear and castellated nut refitted it would not lockup solid and still had a tiny amount of backlash.

This took a number of iterations to get to this point.  Each time the extension shaft had to be locked firmly in place, then the whole thing assembled and the castellated nut done up firmly.  Doing it up was the easy bit, undoing it again was a real pain in the ass.  The only way I could hold the extension shaft firmly enough to crack the castellated nut and then the extension shaft of the feedscrew was to wrap the end on the shaft with gaffer tape and then hold in mole grips, followed by sharp tap of the copper mallet.

Picture 7 - Gear fitted and done up ready to test backlash and ease of movement.

I think I am happy with the amount of backlash but before I drill the castellated nut, extension shaft and feedscrew for the 5mm rollpin which locks it all together I wanted to see if anyone on this forum could see a better way or any issue with what I have done. 

Colin

[Alyn Foundry]

Ah, the joys....

I fitted more than I can count Colin. Obviously the machines I worked on were brand new and hadn't got to the tightness that you've encountered. I seem to remember they supplied a couple of tubular packers to help extend the drive shaft but that was well over 16 years ago.

I never used the " Roll pin " but cleaned the male and female threads to use Loctite 638 as the final fit. I didn't like the idea of weakening the drive shaft further.

My own claim to fame was the fitting up of Chester's 626 mill with Align power feeds, this caused quite a stir at the time. Non of the competitors knew about my " mod " and Chester did quite well on sales that year. Needless to say my idea was adopted by all and the manufacturers were soon making the new leadscrew with my extension fitted as standard. I even did a Z axis mod for a disabled chap once.

From your description I'd say you've got it " sussed " and it will be a great lower back stress reliever!! 

Cheers Graham.

[Muzzer]

Looks about right.
Here's my installation: https://mightyshiz.blogspot.com/2019/03/align-power-feed-for-bridgeport-knee.html

Not forgetting the limit switches: https://mightyshiz.blogspot.com/2019/04/align-knee-power-feed-fitting-limit.html

Go on - drill it!! If the worst comes to the worst, you can weld it up and machine it down again.

[Twizseven]

Graham, Muzzer,

Thanks for your replies.  Think will connect up the power to the controller and check the movement up and down is okay and more to the point sounds okay.  Remove the castellated nut and get the initial hole centered and drilled through one side before refitting and drilling through both shafts.

Think will have to look out for a simple single standalone read head for a DRO for the knee.  Up to know I have wound down 50 turns and counted back up again if want to check a bore or suchlike.  The power feed will save this chore but need to know am back at the same location.

Colin

[Mike Bondarczuk]

Hi Graham,

I have two of the Chester 626 mills and one of them has the drive system already fitted so may be one of your installations as the unit is not in its first flush of youth, as per the attached picture.

For the second Chester 626 mill I made my own drive system using a 240v AC down to variable 40v DC power supply, Chineses circuitry, Mercedes wiper motor and drive interface by my own hand and can go a lot slower than the Aligh system.

Mike

[Alyn Foundry]

Hi Mike.

Your 626 might be " getting on " a little but it's definitely much younger than my time.   

The manufacturers took to my idea readily and rapidly, within a couple of months a batch of modified leadscrews appeard at the works which could be changed to suit the customers requirements. Before this happened it was my job to extend the leadscrew to suit the Align power feed unit, a job that was both tedious and time consuming.

Cheers Graham.

[Twizseven]

Well its all in and working.  My long term engineer colleague recommended not using the 5mm roll pin to secure the feed screw shaft, extension shaft and the castellated nut together, but to use a taper pin.  Several reasons for this.  The difficulty in removing roll pins especially if they have sheared in place and secondary reason is they are a damn sight easier to remove if need to make alterations.  He had suitable taper pin and reamer, and in fact gave me the reamer and another slightly bigger diameter one.  Very careful drilling out the base diameter 2.5mm and reamed and tested and reamed and tested till pin went into the required depth.

Next couple of tasks will be to fit a digital scale type DRO to the quill, and in fact was given a homebrewed Bridgeport Mitutoyo version with the machine.  Just needs some modifications.

Will also fit a knee DRO to keep track of raising and lowering the knee.

Colin

[Muzzer]

I've got glass DRO scales on the knee as well as the quill (on the other side of the knee from the power feed limit switches), so I can swap over if required, by unplugging the connector and swapping over. Having said that, I have rarely used the knee scale. I guess you might be able to combine the quadrature signals with some logic gates but that's not about to happen for me any time soon.

As long as the roll pin doesn't end up with loads of slop and thus cause the hole to become enlarged / damaged , I can't see how the job is terribly critical. There's no precision to the power feed and the leadscrew itself can't be controlled with any great finesse.

[Twizseven]

Having fitted the Z-Power feed i decided to a quill and knee dro.

I had been given the brackets for a quill DRO of sorts when I purchased my mill. It was a bit Heath Robinson and I could not see a neat way to fit it to my machine and put it to one side. It had a good Mitutoyo scale with it.

I looked at the Mill Star quill DRO sold by Machine-DRO and had a chat with them and was able to purchase just the bracket off them and made up the remaining bits I needed.  The most awkward bit being the expanding spigot which fixes the read head to the quill to move it up and down

I trimmed the original scale and refitted it and was able to set it correctly on zero.

Quite pleased with how it works. Just have to remember to switch it off.

Next job is to fit DRO to the knee.

Colin

[Twizseven]

Now fitted the knee DRO to Gates PBM-200 mill.

Used the kit from Machine-DRO

Fitting the vertical mounting bar on the main body of the mill was quite a long task. It only had three fixing screws but 12 jacking screws to get the bar both vertical in both axes and square with the knee travel. Took several hours but in the end i manage to get it within 3 thou from top to bottom. The scale support profile was then fitted and set vertical.

Mounted the display below the main DRO display. I used to have a bracket with the R8 collets hanging below the display but decided the knee display was better here and the collets have moved to a shelf on a trolley.

With the power feed and the knee DRO winding the handle will no longer be a painful chore.

Having the power feed is great,so I then decided to modify the knee handle on my small Cowells mill to a simple power feed. The previous owner had added a handle to the winding know to make things easier. It works very well but when sitting at the desk and operating the handle I can hear and feel my shoulder creaking painfully.

Turned down a 10mm piece of silver steel and threaded it M8. Fitted three washers to replicate the handle and then tightened up a M8 nut onto the thread. Faced this off to produce a thin locking nut. Mounted the handle in mill and found center and then drilled and tapped M8. Fitted adaptor with some washers to space out above the center fixing screw.

Motive power is provided by an old Powercraft 1/4" electric screwdriver.

Works a dream

Colin