I have had my Bridgeport Series I mill for about a year and a half now. This is my first CNC mill and I am at the point where I think I finally have it all figured out and have been making some nice parts for friends. With the exception of some backlash and runout issues I am pleased with this machine.

I contacted a local Bridgeport service tech to give it a once over about 6 months ago and he showed me how to adjust the backlash and since then I am seeing improvements in my parts (squares are now square and holes are circles). But I am not happy with the spindle runout I have and the poor finish it leaves. The tech said my runout was within tolerance (if there is any such thing) but I am not happy about it. I am seriously thinking about getting some new bearings installed on the spindle and having the spindle taper reground while it is mounted in the machine. I hve found a place that will regrind the taper at their shop, but you need to remove the quill assembly and ship it to them also - I would rather not have to disassemble part of the machine to have the spindle reground. I have read a few threads on the topic but am not sure I correctly understand what bearings I need (and the best place to get them from) and where to see about getting the spindle reground. I have found a few places but haven't checked yet to see if they will travel (I am currently in Southern California but will be moving to Idaho in a month).

Also, I am having a hard time identifying the model head on the machine - I have had several people tell me different model designations. The machine is a Series I Rigid Ram with the 2HP motor Boss 3 (replaced with Centroid controls). Serial number on the knee is CNC 4331 and I couldn't find any numbers on the ram or head (but the numbers 5849 and 5812 are engraved into one of the trim plates on the side of the ram). I know this machine was rebuilt with parts from a few different machines. I do have a manual dated 1978 but it really isn't much help in figuring out what the model of the head is. Any help on this would be appreciated.

About the spindle. The spindle in the machine now is the Erickson QC30 spindle without a through hole for the drawbar. But I do have an extra spindle that came with the machine that does have the hole. Would it be better to swap out the spindles so I can eventually use a drawbar or rebuild the one in the machine now? I am not looking for ultra precision, but would like to not resort to sanding every part I make. Eventually I may look at getting a full rebuild with some premium ballscrews or just step up to a newer VMC machine.

I am also thinking about getting some leveling mounts since the new shop floor is a bit out of level where I want to put this machine. What would be some good leveling pads to get for a Bridgeport?

If anyone can help me out or offer advice, I would greatly appreciate it.

http://www.orbitalmachining.com/assets/images/100_2977.jpg
http://www.orbitalmachining.com/assets/images/100_2985.jpg

Nobody has any advice?

Hello there to remove the spindle and replace the bearings as far as I am aware it is reasonably straightforward you undo the 1/4" grub screw at the rear of the quill lower the knee down remove the locking ring put a wood block on the bed to catch and save the spindle end from damage tap the spindle out from the top and it should come out complete with the bearings. If you have a maintenance manual I think it describes this you can then send off to one of the re-furbishing company's and get the bore of the spindle re-ground and have new bearing's replaced on it. Here in the UK Braithwaite Machines charge approximately £250.00 for this service (about $500.) hope this helps Cheers Colin

I do have a manual that details how to remove the spindle and replace bearings, but they basically say you need to replace the spindle as a complete unit and not change bearings. Also, I'd rather not have to remove the entire quill and send it and the spindle in for grinding unless I absolutely have to. The down time would most likey be more than the cost to have someone out to regrind the taper. I am still at a loss as to what bearings to order. I dug the old spindle out of storage today and will post the numbers I find on the bearings (if I find any) tomorrow.

Hello again I think you got the wrong end of the stick you don't have to remove and send the whole quill only the spindle and the old bearings with the spacer's so you would not have to disturb the quill at all. Cheers Colin

Ace are you certain that the finish problem is caused by the machine, or possibly the wrong feeds speeds,tool type, coolant for the material you are cutting????

When was the last time you trammed in the spindle to bed?

(;-) TP

Ace are you certain that the finish problem is caused by the machine, or possibly the wrong feeds speeds,tool type, coolant for the material you are cutting????

When was the last time you trammed in the spindle to bed?

(;-) TP

Fairly sure the finish problem lies with the spindle. I mostly cut aluminum and use 4 flute HSS or carbide end mills. I use OneCNC CAM and let the software tell me the correct speeds and feeds and I use flood coolant. Have tried 2 flute and 6 flute end mills and no coolant too when I was experimenting and always had the finish problem. Not sure about tramming the head. The machine is a Rigid Ram so the head does not swivel. I have heard there is a way to adjust the head but have never checked to see if it was off or not. I know there is a rather nice sized gouge in the taper but it has been cleaned so the only thing you can feel is the groove. One thing I have noticed is when I run fast finish speeds, the finish is more rough than if I run slow finish speeds. If I run very slow finish speeds, the finish is better, but you can still see a rythmic series of cuts along the sides. Where you can really see a difference is in facing with a large diameter facing tool. The surface appears to have waves in it. I found a phone number for a place called CM Spindle repair and am going to give them a call after the move to see if they can help me out.

I mean no offense, but if you are relying on the software to tell you the feeds, get someone over there who actually machines stuff by hand, and buy him some beer and see what he thinks. Bad spindle bearings is not my first guess.

I am not offended. I am self taught so any advice is greatly appreciated. When I started using my CAM program I didn't rreally trust it so I always went conservative with the feeds and speeds (plus not knowing the machine I thought it prudent to err on the side of caution). I used some charts I found on the internet, my Machinery's Handbook, and a program called Machinist's Toolbox to find speeds and feeds as well and backcheck against what my CAM program said. I still tend to run conservative and usually turn down the feed override to about 75% when I run. I have had someone come out and tell me I do have some runout - I want to say he said it was 15 thousandths but I can't remember exactly. It may be that I am doing something wrong with the speeds and feeds, but it seems not matter how slow I run a finish pass, I will still get those pesky lines in the part. Once I get the machine moved and set back up, I will see if I can find a local machinist who can come over and I will see if he can help me figure oiut the problem.