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JPR
08-25-2006, 11:09 AM
I am working on a mill head. While I have the bridge port spindle out, I would like to get the R8 taper ground to remove some heavy scoring on the upper half of the taper. Can anyone recommend a shop?

JCHannum
08-25-2006, 11:18 AM
Why not your own shop? This post has a couple of techniques by Sir John & Forrest that address cleaning up an R8 taper in the machine.

http://www.homeshopmachinist.net/bbs/showthread.php?t=19754

A major advantage of these methods is that the finished taper will be dead on as it is ground in place.

JPR
08-25-2006, 11:29 AM
Thanks for the link. Since I don't have a tool post grinder (been out bid the last few times), I was planning on sending it out.

pcarpenter
08-25-2006, 11:30 AM
Wells Index actually list spindle regrinding services as a buy-it-now thing on ebay. They do it for Bridgeport as well as their own spindles, and there are various charges depending on which taper you are going to and from.

I would give them a call and tell them you want a cleanup grind and not a complete change in taper and see what they would charge. They get your whole quill assembly as I recall, so it is ground in place using your bearings.

I would be afraid of doing my own without the proper tools as getting the angle off just a bit will mean your collets won't grip well...and you will get more scoring.

Paul

JCHannum
08-25-2006, 11:38 AM
Here's the Wells Index eBay listing for R8 cleanup. I doubt you will get a better price than $100.00. Shiping of course will add depending on your location.

http://cgi.ebay.com/R-8-spindle-taper-grinding-Wells-Index-Bridgeport-Lagun_W0QQitemZ7594441107QQihZ017QQcategoryZ25290Q QssPageNameZWD1VQQrdZ1QQcmdZViewItem

rockrat
08-25-2006, 12:19 PM
If you take your time, double check all your setups, you can do it yourself. I made an adapter for my Van Norman mill and had to grind the id of the part. Here is a link.

http://www.homeshopmachinist.net/bbs/showthread.php?t=12208&highlight=van+norman

Let us all know what you decide and how it turned out.

cheers
rock-

pcarpenter
08-25-2006, 01:17 PM
Maybe I am just being a dingbat, but I am not getting (even after looking at your post, Rockrat) how you grind a taper inside a mill spindle using the mill. Either you have to have a grinding bit of some sort that is the full length and form of the taper, or you have to have some sort of (CNC ?)way of moving both the table and spindle at a prescribed ratio as the spindle lowers onto the bit to make the taper?

If I am just being dense, set me straight....gently:)

Paul

Carld
08-25-2006, 02:05 PM
Set the head off to the required angle. Set up a Dremel type grinder on the table sticking straight up. Put small stone in grinder. Turn on grinder and use cross feed and longitudinal feed to line up in spindle hole at edge of R8 taper. Use knee feed to feed grinder in and out of spindle while spindle is turning at low speed in opposite direction of grinder stone. Take light cuts to clean up. Just remember everytime you take metal out the collet will go in deeper.

You wouldn't have this problem if the lock key is working in the spindle. You did know there is supposed to be a key to keep the collet from spinning in the spindle didn't you? While you have the spindle out replace the key.

JPR
08-25-2006, 03:29 PM
The spindle is out, so it would be easy enough to chuck up in the lathe.

Biggest problem I see at this point is any kind of mounts to for a die drinder, air or electric would have to be made without the use of the mill. Thinking something like this Doc Nickel's grinder mount (http://bbs.homeshopmachinist.net/showthread.php?t=15466)

The previous owner sheared the lock key. Only the upper half of the taper is damaged, lower half looks fine so I have wondered if the broken key actually caused the damaged.

thistle
08-25-2006, 05:11 PM
I would send it out to someone who has the tools like Wells index , (who advertise for such business,) or you might try a rebuilder like Garden State machine in NJ.
they will do it right,if you do it and screw it up what recourse do you have?

rkepler
08-25-2006, 05:18 PM
The folks at Wells Index ground the R8 taper in my Lagun quill several years ago. Nice job, good folks to deal with.

JPR
08-25-2006, 05:43 PM
Just got off the phone with Wells. Will ship it to them on Monday.

japcas
08-25-2006, 05:53 PM
I have a question about the upper half of the spindle bore that is straight. How do you regrind it without making it oversize? It looks as though this would cause runout in the collet. I do know that you are "just cleaning it up" but to do that some metal has to be remove although it is a small amount.

pcarpenter
08-25-2006, 06:55 PM
I would think that the upper part may not be chewed up and may not need touching, but this brings up a question to which I also sought an answer: Is the straight "registration surface " on the back end of an R-8 collet really a registration surface or is the collet pulled up straight by virtue of its taper?

I mentioned having an cutter sharpening fixture with a BS 9 spindle here a while back and labored over whether to make a new spindle to take 5c collets. I finally decided due to dimesions involved that I could make a spindle with an R-8 taper that would allow for the use of the existing bearings and allow me to leave the indexing rings unmodified. I need to figure out if the registration surface at the rear of the collet is really a registration surface or not.

Glad Wells Index is going to be able to take care of your issue for you. I have heard several times that they are a good company to deal with and I even remember reading a posting by a muckety-muck from their company on one of the other forums. I have fondled one of their mills and they seem to be a top-notch product.

Paul

JCHannum
08-25-2006, 09:01 PM
On the subject of the key in the R8 spindle. It has two purposes.

One is to hold the collet in place while tightening the draw bar.

The other is to shear and jam the collet or damage the spindle.

The key is not for driving the collet. The collet is driven by the friction of the taper in the seat. The best advice concerning those keys is to remove them before they cause damage.

wierdscience
08-25-2006, 09:49 PM
On the subject of the key in the R8 spindle. It has two purposes.

One is to hold the collet in place while tightening the draw bar.

The other is to shear and jam the collet or damage the spindle.

The key is not for driving the collet. The collet is driven by the friction of the taper in the seat. The best advice concerning those keys is to remove them before they cause damage.

I second that,throw it away,the only purpose it has is to allow you to unscrew the drawbar if the threads happen to have some goo in them.

If you have a mixed breed set of collets like I do you will find that not all collets have the same width key slot,that makes getting them in and out a PITA.

The "key" is nothing more than a dog point setscrew and it's basically useless in terms of driving torque.

wierdscience
08-25-2006, 09:59 PM
I have a question about the upper half of the spindle bore that is straight. How do you regrind it without making it oversize? It looks as though this would cause runout in the collet. I do know that you are "just cleaning it up" but to do that some metal has to be remove although it is a small amount.

That straight section isn't a register,the spindle is actually .001-.0015"oversized at the point to facilitate easy collet installation and removal.Everything is located and accomplished by the taper.That is where the accuracy of the system comes into play.

It wouldn't matter if that section had damage,so long as there was nothing to interfere with the collet pulling up straight.

Oh,I might also add that the number one cause of R-8 damage is running things like fly cutters and those Holex rigs that are too big.Once you get much over 4" in diameter with a cutter your pushing it with an R-8 spindle.