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Okuma2540
05-18-2009, 10:43 AM
Thought I would say hi. I have been in the machining field for about 15 years and have been teaching it for about 8 of those. I have a Bridgeport mill that needs the head to be rebuilt and new ballscrews, gibs and most likely scraped. How hard is it to rebuild the head and put the ballscrews in myself? I will send it out to be scraped and the table ground. I was trying to save a little bit of money by doing the head and putting the ballscrews and gibs in myself. Just thought I would ask so better informed brethren about it first. Is it worth the hassle to show the students how it is done or should I just pay the extra money?

lakeside53
05-18-2009, 11:42 AM
Rebuild... that can mean many things. What is actually wrong with it?

It's always worth showing someone else how it's done...

The heads are very straight forward.. You'll need to take some care with the spindle and quill. There are a couple or excelent blogs on j-head rebuilding that will get you started. Apart from a couple of spanner wrenches and bearng pullers, you'll likely have the other tools required.

Be carefull with some aftermarket bearing suppliers - they do not suply the correct DB ground bearings for the pulley or the bullwheel support, and some sealed "spindle beariings" are not ABEC 7. Ask for the exact bearing numbers they provide and do your own research (or ask here).

Okuma2540
05-18-2009, 12:34 PM
The head is making noises high pitched sqeals and it sounds like rocks are being crushed in it. The table has a lot of small end mill slots and some very small drill spots & somebody (aka the teacher before me) has taken the gibs and acme lead screws out of the x/y axis. I figure that if I am going to spend a lot of time and money I should try and make it as close to new as I can. Plus i think the students will enjoy working on the mill and painting it. I did look into sending the spindle out with the rest of the mill and having them put in the spindle/quill bearing for $400 dollars more i didn't think that was too bad considering the bearings alone are $295.
I will be getting my parts from a dealer here in state (Indiana) H&W Machine Repair & Rebuilding Inc. here is their website. http://www.machinerypartsdepot.com
They look like they know what they are doing and plus they are only a couple hours drive from where i am located.

Mark Hockett
05-18-2009, 02:47 PM
You mentioned putting ball screws in, are you converting it to CNC?

Okuma2540
05-18-2009, 06:25 PM
No I am not going to convert to CNC.

doctor demo
05-18-2009, 08:39 PM
If You are not converting to CNC, and it is going to be a mill that students use I would stick with acme screws.
I have a BP EZ Trak that has ball screws, and when runing in manual mode they are a pain.

Steve

lane
05-18-2009, 08:47 PM
I agree. You do not want ball screws in a manual mill.

gnm109
05-18-2009, 09:03 PM
I agree. You do not want ball screws in a manual mill.


My new to me Webb 4VH has ball screws since it was set up as a CNC machine by a former owner. I've been cleaning and adjustiing the machine since I got it. Some parts were missing due to the CNC conversion so that slowed me down a bit but I have all of the necessary parts now.

I've heard that ball screws are not ideal for a manual machine. I seriously doubt that I will be changing them however, due primarily to the cost of the parts which would be horrendous. I do plan on adding X and Y servo motors in the next year or two as well as a DRO.

In working with the machine after I received my manual from the Webb company who are very helpful folks by the way, I adjusted the gibs on both the X and Y axes. By minimally tightening the gibs which were adjusted fairly loosely when I got the machine, I discovered that there is enough drag to counteract some of the freedom of motion engendered by the ball screws. The saddle and table are quite heavy since the table is a 50" version. I think that makes a bit of difference in the feel.

So, while in general I would tend to agree with you that ball screws are not ideal for manual use, I will certainly be able to manage. Besides, who knows which direction I may go? I do still have two of the servo motors and drives for the Z and Y axes and with an X axis servo unit and associated computer gear, I could turn it back into a CNC. That may be a fun project for the next year or two as soon as I recover from the money drain that I have just undergone.

It's funny isn't it? When you have acme screws, you want ball screws and when you have ball screws, it seems that they are not ideal for your present use and you would be better off with acme screws. It's a strange world. :)

lakeside53
05-18-2009, 09:09 PM
The head is making noises high pitched sqeals and it sounds like rocks are being crushed in it. The table has a lot of small end mill slots and some very small drill spots & somebody (aka the teacher before me) has taken the gibs and acme lead screws out of the x/y axis. I figure that if I am going to spend a lot of time and money I should try and make it as close to new as I can. Plus i think the students will enjoy working on the mill and painting it. I did look into sending the spindle out with the rest of the mill and having them put in the spindle/quill bearing for $400 dollars more i didn't think that was too bad considering the bearings alone are $295.
I will be getting my parts from a dealer here in state (Indiana) H&W Machine Repair & Rebuilding Inc. here is their website. http://www.machinerypartsdepot.com
They look like they know what they are doing and plus they are only a couple hours drive from where i am located.


Well.. H&W is one of the suppliers that sells standard radial bearings where they should be DB ground... Pulley bearings are not 6207 - they are "7207" DB ground... and the main bull bear bearings are not 6208 - they are "7208" DB ground... Buyer beware... Confusion arises because on many machines BP uses specially selected and modified 62xx bearings. These were DB ground and simulated angular contact... but BP left the original bearing descriptors. Using standard $8 C3 radial bearings in place of preloaded precision angular thrust just isn't right. I've been there.

Spindle bearings... the originals are NOT sealed (many aftermarket are) -they are 2MM207widul (or several other equivalents). From time to time they appear on ebay for $80-$160. Sealed bearings offered are often 'aircraft magneto bearings", and most of these are not angular thrust but a variation on deep radial.

Ask H&W (or any aftermarket suppliers) for the exact bearing numbers they supply....

I can't comment on "squealing and rocks...". Might be be very simple.. might be bad.. You need to narrow it down.

Okuma2540
05-19-2009, 08:34 AM
Thanks for the info guys. I will be tearing into the mill this summer laying it out on the bench in the order it comes apart and will have the students start looking for part numbers and looking online to find replacement parts from different sources. That way they can learn how to ask questions and find the proper parts.

ckelloug
05-19-2009, 10:29 AM
Wells index offers a good deal on spindle rebuilds which includes bearings and touching up the taper via a light regrinding. I didn't have them do mine because I discovered it just had a bit of dirt in it and a misadjusted collet alignment screw inside the spindle.

cadwiz
05-19-2009, 06:46 PM
Take lots of pics as you tear down (detail before and during your tear down of each piece). It took me about 6 months to rebuild mine mostly on weekends. The pics come in handy when you get around to putting it back together as there are severeal intricate subassemblies and you're likely to have several people moving stuff around. Also watch out and be aware that just about everywhere you have to remove a set screw there's probably a second screw behind it.

Cadwiz

Okuma2540
05-20-2009, 04:49 PM
Thanks! I will take lots of pictures. Like I said I am a teacher so the more I can save on fixing equipment myself the better off I am. The way the economy is every dime I save just makes my program look good. I have a lot of equipment to maintain and students are not exactly easy on equipment. I have 9 Vertical mills, 1 Horizontal mill , 5 surface grinders, 10 lathes, 2 small cnc mills, 1 bench top cnc lathe, heat treat furnace and oil quench tank, 3 bandsaws, 1 14" evolution chop saw(love it), 1 drill press and several other pieces of equipment. And we pack it into a little shop only 30 x 80 so the shop is pretty full. But thanks again for responding and I probably will be picking your brains on other projects I will be starting soon.

doctor demo
05-20-2009, 07:05 PM
Okuma 2540, I failed to welcome You yesterday in My post.
Welcome !
Could You elaborate on what Your Students are, such as: High School, Trade School, etc.
It would be nice to hear that it is one of the few remaining Highschools with a machine shop , also if You would add a general location to Your profile so We can more easyly compare apples to apples instead of kiwi. Thanks.


Steve

Okuma2540
05-20-2009, 08:49 PM
I am high school teacher in Attica, Indiana. My school is part of a vocational co-op of 8 schools. My students are juniors and seniors from 4 local schools. We are in class 2hrs for juniors 3 hrs for seniors we make screw jacks , bench vise , grinding vise and a bunch of parts to maintain the schools equipment. We have made shafts for air handlers, front spindles for the little tractors around the various schools and too many others to list.

doctor demo
05-20-2009, 09:36 PM
I am high school teacher in Attica, Indiana. My school is part of a vocational co-op of 8 schools. My students are juniors and seniors from 4 local schools. We are in class 2hrs for juniors 3 hrs for seniors we make screw jacks , bench vise , grinding vise and a bunch of parts to maintain the schools equipment. We have made shafts for air handlers, front spindles for the little tractors around the various schools and too many others to list.
Machine shop class is alive and well in Attica Indiana !!

They still do a little welding and simple sheet metal stuff around here, but not much else. I'm going to tell everyone to move to Indiana if they have kids.
California is not going to have schools if the Govt. can't get their act together.

Steve

Okuma2540
05-20-2009, 10:06 PM
Yeah, there are several dozen schools like mine through out the state. We have several contest through out the year to see how our kids compare to each other.