Need Help!- Excessive runout on bridgeport

[shiver-91vr4]

Boss 5 Converted Bridgeport Series I

Basically I've been getting a really crappy finish on aluminum (first time machining it after the conversion) and decided to look further into it.

I took a .0005 resolution mic and ran it on the outside of a .75 and .5" end mill holder with a long end mill in there that had a good spot with no flutes on it. I was getting .005 of runout 1" from the bottom of the end mill holder.

I then measured the inside bore of the end mill holder (several) and obtained the same .005 runout on all of the holders I checked.

I then measured the inside of the QC30 taper inside the spindle in several places and was able to see <= .0005 runout. I wish it was a bit less, but that's what I'm seeing.

I can't figure out where I'm getting the large 5 thousandths of runout at if I have very little on the spindle itself. I was thinking it could be some high spots on the taper itself and took some cleaner and cleaned that and the end mill holder up (nothing abrasive) and still nothing.

The inside of the taper does look pretty banged up, so I'm thinking it may just be some high spots that must be ground out or something. I've read about taking a marker and marking some vertical lines on a holder and spinning it in the spindle to see where it rubs....but other than that, what can I do?

I don't think I'd have .0005 of runout on the taper itself and get 10x as much as that just 2-3" down the line at the tool holder itself. And since multiple tool holders ended up at the same .005 of runout I would think the problem is in the taper.

Anyone have any suggestions?

[TOTALLYRC]

There are shops out there that will regrind the taper right on the machine.
Don't know pricing or availability but I would check with a specialist first and see if it is affordable.

Mike

[shiver-91vr4]

I've seen those, but I'd like to shy away from spending a few thousand bucks if I can do something myself to get it mostly back into spec. It's not a machine that's used to make a lot of money etc and I'd hate to have spent all the money converting it over and buying it to have a large paperweight.

Does anyone have any other ideas at what I can look at to see where the runout could be coming from?

[TOTALLYRC]

Originally Posted by shiver-91vr4 I've seen those, but I'd like to shy away from spending a few thousand bucks if I can do something myself to get it mostly back into spec. It's not a machine that's used to make a lot of money etc and I'd hate to have spent all the money converting it over and buying it to have a large paperweight. Does anyone have any other ideas at what I can look at to see where the runout could be coming from?

Didn't realize that is was several thousand dollars.
You could probably rig something up yourself but it would take extreme care to get it right.
Good luck and I will watch to see how it works out.

Mike

[polaraligned]

Originally Posted by shiver-91vr4 I then measured the inside of the QC30 taper inside the spindle in several places and was able to see <= .0005 runout. I wish it was a bit less, but that's what I'm seeing.

I put new spindle bearings in my machine and this is the same runout that I measured. Seeing as though the spindle grinders spec .0002", I decided to not send it to them. In my testing I discovered some da180 collet toolholders that were running out by several thousands. It looked like someone spun the collet in the holder. I found a newer da180 toolholder and it held the tool to about .001" runout maybe an inch or so down the tool shaft. Regular toolholders are not very precise (holding the tool) and I would think that several thou runout would be the normal for them.

[mactec54]

shiver-91vr4

If you don't mind a bit of work you can lap it with some lapping paste, most of the time you can get them with in .0001 which is good enough for this type of machine, You can also make yourself a grinder mounted on a linear slide, if you are a good at machining this is easy to regrind the taper,

If you lap the taper make 2 aluminum tapered laps/bars long enough for you to hang onto, to make the taper set up a tool holder in your lathe & indercate the taper so you now have the taper set you can cut your laps, use diamond laping past, to check your progress use some bearing blue on a good tool holder to check the taper

[shiver-91vr4]

I have no clue how much the regrinds usually cost, but just figured they were expensive and probably most of them don't have the stuff to work on 30 year old technology, or even want to.

mactec54,

I don't have a lathe here...and I would rather try to do something on the machine itself. Is your grinder idea something that you were thinking needs to be done on a lathe or can do on the machine?

Do you have any sample drawings of what you're talking about? I don't quite understand from just what you typed.

I was thinking I could get some type of grinder/file/etc at the exact angle of the spindle (not 100% sure how) and spin the spindle up and raise the piece up into there to grind a very minute amount out to make it perfect again...or is that just wishful thinking?

[shiver-91vr4]

Also, I wouldn't think that a tool holder would have 5 thou of runout in it. I have several and they all have about 5 thou.

I've heard collets have a lot more accuracy in the runout dept, but they don't hold up very well to large endmills and heavy loads, so people go back to the end mill holders.

And from what I've seen in ads etc for holders, they all say very low (maybe .0002 or less) T.I.R.

So maybe mine are just old, but you can still see all of the finish on the holders, they're not worn etc and look like new.

[mactec54]

shiver-91vr4
Also, I wouldn't think that a tool holder would have 5 thou of runout in it. I have several and they all have about 5 thou.

Good tool holder have from .0001 to .0005 run out not .005

If you don't have a lathe then you could use some of the tool holders you have to do the lapping

You are on the right track with the grinder idea, but it would need to be set up very well to grind the spindle, or you will make it worse than what it is

[shiver-91vr4]

Do you think the issue is with some bump/problem inside the spindle that is causing the large runout at the toolholder?

I wouldn't think .0005 of runout inside the taper would cause .005 runout 2 inches or so down. I would think it would have something to do with it not seating properly etc.

[mactec54]

shiver-91vr4

Lap it as I said before & this will take the bumps off

[barbque]

I ended up taking a chance on a Ebay seller Wells-Index. I had a spindle with .003 run out. After getting it back the run out was measured at .0002. I was pleased with the results, and it only ran $250 after you factor in the shipping.

http://stores.ebay.com/Wells-Index-Milling-Machines

Kris