Bridgeport Power feed modification

[CarpenterRacing]

Hi guys,
I'm fairly new here so please forgive me in advance if I break any rules unintentionally.
I recently acquired an old 1970 Bridgeport 1J mill after our 1930s Rouchard finally died. It was fitted with the original Bridgeport geared power feed unit which was temperamental and has now died (motor finally failed) so I bought a new modern power feed unit to retrofit. The mill has been abused in its life but has cleaned up well. I've retrofitted a new 2hp motor as someone had fitted a small single phase 3/4hp foot mount motor at some point in its life which was slightly dodgy, and fitting a VFD to drive the new motor. Anyway, back to my reason for posting.
I did a little surfing on forums and saw that the general consensus was that the leadscrew is short and that there was an extension shaft pinned to the lead screw to drive the old power feed. To retrofit the new modern type power feed you simply needed an adaptor shaft available online to pin to the screw and extend it past the bed & drive the new motor.
This is where I have come unstuck. After stripping the old power feed I have a 1 piece long shaft with a pin which drives a sleeve which intern was feed by the original geared unit.
Is this a common lead screw? I'm a small single man engineer shop so have the means to turn down the adapter shaft (if I buy one) on my Gate Sturditurn lathe to fit the leadscrew (if I cut it short), but I'm curious if anyone had done a similar mod before? I'd machine an adapter up myself but I don't have the means to machine the key slots to drive the bevel gear as my mill is obviously now in pieces. Any advice or input would be appreciated.

 

[projectnut]

I have a 1972 Bridgeport that originally had the 6F power feed on the X axis. The power feed was originally pinned to the lead screw, however when I got the machine the power feed and coupling were long gone. Rather than try to recreate the original coupling I used a standard 3/4" ID, 2 piece Dayton coupler like this to secure a shaft extension to the lead screw:

https://www.grainger.com/product/3ZN70?gclid=EAIaIQobChMI3YeSrMyQ6wIVhYbACh3Ezw20EAYYAyABEgJ9xvD_BwE&cm_mmc=PPC:+Google+PLA&ef_id=EAIaIQobChMI3YeSrMyQ6wIVhYbACh3Ezw20EAYYAyABEgJ9xvD_BwE:G:s&s_kwcid=AL!2966!3!264955916366!!!g!630077959592

!

I bored the lead screw end to .812" and turned the end of a new shaft to .750". Rather than make woodruff keyways I milled a long standard keyway. I used a short key in the coupler end, and another longer one for the drive and handwheel.

As you mentioned there are premade shaft extensions available on eBay and other sites. The one on eBay comes with the pinned style coupling as part of the shaft:

Steel Shaft Extension with (2) 1179 Key for Elect Standard Power Feed Bridgeport | eBay

NEED PARTS FOR YOUR BRIDGEPORT?. for Bridgeport Mills. For Bridgeport Mills. Other parts available for Bridgeport Milling Machines. ID of Shaft Extension.815" fits over. 812" shaft. Steel Shaft Extension w/2 Keys for.

www.ebay.com

ON Edit: When removing the shaft from the gear box be sure to support or block the lead screw. Somehow my lead screw got slightly bent. With a double bearing plate and handwheel there was no noticeable problem. However when I removed the bearing plate and mounted the new drive it was obvious there was a problem. It took me the better part of an afternoon to shim the shaft so it wouldn't bind the gear when the lead screw was being powered.

I have 2 additional lead screws. I should check to see if either of them are straight and replace the current one when time allows.

 

[ttabbal]

So you had the original gearbox feed? I actually like mine, but I suspect I've got some issues in there, so I might have to switch it out. I'm curious to see how to adapt it if you do. I think I would make an extension shaft like the one above. But using the coupling looks like a good option as well.

 

[hwelecrepair]

Ttabbal has the right of it, that was an old gear driven powerfeed not a 6F or 8F. The gear driven feed lead screw went all the way through the unit while the 6F and 8F stopped under the table. If you had gotten the Servo unit for the proper feed, it would have come with an extension bracket that looks something alot like what is below.



For the most part, the hole patterns for most of the import powerfeeds and the Servo match up or are close enough to just modify the casting. This bracket is mounted to the table, and then the powerfeed mounted to it.

Jon

 

[hman]

Welcome to the forum! I can't help you with your power feed, but just wanted to say "Hello."

 

[CarpenterRacing]

Thanks for the replies guys.
I've managed to sort now so very happy I have power feed back on my bridgeport.
In the end I bought one of these -Bridgeport Powerfeed Shaft - and machined to fit.
I trimmed the extra long shaft down an inch from the tapered pin. Then I turned a 2" long sleeve to attach the new shaft to the existing screw with the OD the same as that needed for the needle bearing in the powerfeed unit.
I then fitted the new power feed motor and measured the distance from the tapered pin to the outer edge of the bearing in the power feed unit. The new shaft was then turned down to the same diameter as the original screw and parted so the shim surface was flush with the outer edge of the bearing so I could shim the bevel gear appropriately. I drilled the sleeve and pinned the new shaft and
Screw together so nice and tight. Shimmer the bevel gear onto the new shaft and refitted the handle etc. Now works a treat, easy to replace the power feed motor should anything happen in the future with another unit, and its all single phase now (thanks to my VFD controlled spindle motor) so gives me safer operation, greater flexibility in the future and full control of the speed rather than having to use the 4 stepped pulleys.
Thanks again everyone for your input.
I will sort out the old gearbox and fittings soon as I nolonger need them so will list them for sale if any one is interested. Motor is not much use obviously but the rest is pretty good for its age from the brief look it got while stripping. I know one of you has already messaged about bits which I will reply to as soon as I get it sorted.
I will also have an original old Heidenhain DRO for sale. The x axis got smashed before I got the mill (so will be retrofitting an ebay sourced modern unit) but the display and y axis works a treat and seems a shame to bin it.