[brian257]

I just finished installing my new Rockford Ball screws and new bearings in my Bridgeport and I have about .002" backlash. The Rockford ball screws have factory preloaded ball nuts that should have no backlash.

The bearings I used are NSK B20-147. In another post I found that these are the bearings made for this machine and they are hard to find. Rockford says to use 7204 type angular contact bearings with spacers because they are a little thinner than the original bearings.

I can't find any data at all on the B20-147 bearings so I am not sure if they are angular contact bearings or how precise they are. I asked the supplier how they get installed and was told that the sides without the grease seals face each other.

Before I go and buy new bearings can someone tell me if these are not precision enough or are not angular contact bearings? I want to be sure that the bearings are really the issue before I spend a lot of money on new ones.

[WALL-E]

Hi Brian,

Not sure on your NSK bearings, I found with bearings a simple Google search will not bring up the information you are asking about. I have had more success actually going through bearing suppliers website literature and finding it that way.

McMaster have a selection of precision bearing if this is any help. McMaster-Carr

Before you go ahead and purchase new bearings, are you able to adjust the back nut locking screw? Does Rockford supply instructions on how to do this? As this the the main reason for going with the Rockford's it should be published to the end user so it can be preformed as necessary.

I am also about to retrofit a Bridgeport series 1 2j and was reading your other posts when you were purchasing the Rockford ball screws.
Rockford would not reply to my emails regarding sales of the ball screws and after a second email they finally forward my email to a local distributor here in Australia (sesgroup.com.au). I will obtain a price from SESgroup soon and also H&W Machine as you recommended, As the ball screws have to come from the U.S either way it's always a good price check.

What did you end up paying for your ballscrews and also what did they get delivered in? do they come already preloaded on both axis. and you just drop them in. Did you get model ball screws to keep the power feed or not, your thoughts on this?

Regards Tristan

[brian257]

You can adjust the Rockford screw, but they come factory adjusted with a note to call the factory for instructions if they need to be changed. Since they feel good and stiff and both X and Y have the same backlash with the same set of bearings I am thinking it is probably the bearings, not the screws. I will call Rockford in a few hours and see what they say.

I did notice when going on their web site yesterday that they now also offer bearing sets with the spacers. I kind of like the idea of getting the screws and bearings from them so if you have problems you can go back to one source. Likely I will wind up getting their bearings and returning the others I got.

Can't find the receipt right now, but think it was around $1,300 for the screws.

I got the screws for the power feed. What you need depends on what you have on your machine. I have the factory Bridgeport power feed and with that you have no choice but to get the screw for the power feed. The screw is shorter on the end and does not have the turned down end for the handle and dial. Some of the retrofit power feeds are made to go on in place of the handle and dial so if you have one of those you need the screw for a machine that does not have a feed. I can post a picture if you would like.

The screws were delivered very well packed. I was worried about them being delivered with the ends beat up, but they use a heavy cardboard box that has wood blocks on ends so it is very hard for any shipper to damage them. As already said, they come preloaded.

Installation was easier than I expected it to be.

[brian257]

I was just on the H&W web site and looks like I remembered the price of the ball screws incorrectly or the price has gone down because they have the 12X48 set of screws on sale now for $862.50 here Leadscrew Assembly. Look at items 37 and 38. Note these are not the ones for the Bridgeport power feed.

if you look here you will see drawings for the X screw with and without the Bridgeport power feed. Bridgeport Kits - Rockford Ball Screw

[sudip]

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