• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
[4]

Bridgeport Ballscrew Dilemma?

January Project of the Month [3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

beeser

Iron
Registered Member
Joined
Mar 18, 2016
Messages
9
Likes
1
#1
I recently purchased a Bridgeport mill that was originally outfitted as a CNC by MillPWR. All of the CNC specific equipment, e.g. controls, servos, etc. were stripped from the machine, basically rendering it strictly manual. It does however have the original precision ground ballscrews for the X and Y axes. Although the screws have the advantage of minimal or no backlash the ends do not fit a normal handwheel setup without modification. It seems to me that I have 3 options;
1) Modifify the screws to accommodate handwheels. The Y axis screw would have to be cut down, a woodruff key added and the end threaded to accept the normal nut on the end of the handwheel. The X axis screw would have to be threaded on one end for the handwheel and possibly lengthened on the other with possibly an extension.
2) Purchase new precision ground ballscrews, optimistically without the nut to save cost. If that's not possible because of an incompatibility of existing nut to new screw, then purchase a new precision or rolled ballscrew retrofit kit.
3) Convert the screws to an ACME thread setup.

Any thoughts of suggestions?
 

4ssss

Active Member
Active Member
Joined
Apr 25, 2017
Messages
215
Likes
102
#2
I'd rework the screws. You already have them and it won't cost you a dime except the time you put into them, not to mention those screws are better than the Acme's in my opinion.
 

brino

Active User
H-M Supporter - Sustaining Member
Joined
Jan 2, 2014
Messages
2,985
Likes
2,830
#3
Although the screws have the advantage of minimal or no backlash the ends do not fit a normal handwheel setup without modification.
How about option 4) make some custom handwheels that fit the existing screw ends? (or an adapter from the screw to a handwheel)
What are they now?
Maybe you could modify some "off the shelf" handwheels.

-brino
 

dlane

Active User
H-M Supporter-Premium Member
Joined
Sep 27, 2014
Messages
2,376
Likes
967
#4
Wasn’t there an issue using ballscrews on a manual machine
 

MikeInOr

Active Member
Active Member
Joined
Jan 1, 2018
Messages
32
Likes
38
#5
I recall reading a thread on here about a manual mill with ballscrews. I recall a lot of negative comments about the TPI of the ball screws being MUCH too course for a manual mill. Turning the handwheels a few degrees moved the table much too far for precision work. I think they also said that because the threading on ball screws are so course that a milling operation that required any amount of force would actually move the other axis and index the handwheels... so you had to lock the table axis you weren't using. I.e. taking a long cut on the X axis would actually cause the Y axis and Y handwheel to move. So every time you index the Y axis you have to lock it down after indexing. Not a terminal condition but annoying.

Have you considered reworking the mill back into a CNC mill?

If you don't have any CNC aspirations for the mill it sounds like #3 - Convert back to Acme threads might be your best choice... But I am only going by what I read and have no direct experience myself.
 
Last edited:

cg285

Swarf
Registered Member
Joined
Jan 10, 2018
Messages
3
Likes
1
#6
a friend is the milling foreman at a large manufacturing co and, at one time, they were replacing some older bridgeports -in which case they always scrap old equipment. i stripped one for the ball screws for mine. i asked the same questions to him and he stated they have always had ball screws on the manual bridgeports with no issues. i can say i have not had a problem with mine after converted. the ball screws did not change the travel in mine.
 
[6]
[5] [7]