Fitting Align Power Feed on Z-Axis – Gate PBM2000

[Colin HeseltineParticipant @colinheseltine48622]

A couple of issues – comments/thought appreciated

[Colin HeseltineParticipant @colinheseltine48622]

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.

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.

The picture above shows the sleeve minus the graduated dial and castellated nut. The bearing retainer is the new one. This was reassembed 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.

Bearing retaining flange fitted.

Shims located on shaft. (as discussed later)

Extension shaft being tightened into place.

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.

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

[Colin HeseltineParticipant @colinheseltine48622]

Surprised there were no comments or thoughts after 102 viewings.

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

[Chris Evans 6Participant @chrisevans6]

Colin, a knee mounted DRO is on my roundtuit list. I am looking at a standalone unit rather than fit full 3 axis kit because the Heidenhien 2 axis works well.

[clogsParticipant @clogs]

Colin,

well done, always fancied something like this for my Bridgeport……..

the last time I looked they / it was around the £400 mark and have other needy things to buy first……

I do have a couple of 1/4hp x 3phase motors going spare and had thought to use 1 of them with the right gearing…..

plus they'd be easy to reverse direction with the approp switch gear….

something to think about when u can't sleep…….!!!!!

alas, a job for another day……..

it's these little (or not so little) that make life so much more enjoyable…..

thanks for showing us ur work…..

[Colin HeseltineParticipant @colinheseltine48622]

Chris, I had quick look at machine-fro and they do a stand-alone single display head at around £90. Obviously need the read head and mag strip to go with this. So not exactly cheap. Hopefully I’ve just sold one of my flypresses which will pay for it.

you are welcome to come and have a look.

Clogs,

I have a somewhat suspect shoulder joint and this should save a lot of winding. Pleased with it and can recommend it.

colin

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