Spindle collet grub screw

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

Moderators: GlennW, Harold_V

pete
Posts: 2518
Joined: Tue Feb 10, 2009 6:04 am

Re: Spindle collet grub screw

Post by pete »

I'd certainly agree Harold, a normal edge finder doesn't need to be adjusted to run true. These Haimers would only be highly accurate if they are. Adjusting them is done a bit like a 4 jaw independant so it's possible to get them under a couple of 10ths.
earlgo
Posts: 1794
Joined: Sat Jan 29, 2011 11:38 am
Location: NE Ohio

Re: Spindle collet grub screw

Post by earlgo »

A friend of mine has an older Rockwell VMill and the collet orienting pin is so worn that one has to feel it with a finger and then carefully insert the collet. Some of his collets have buggered slots where he or someone was not careful to get it right. He'd take the pin out but it is practically impossible to reach without taking the whole lot apart.
My own R8 collet holder is a NMTB40 to R8 adapter and I have marked the outside of the barrel where the pin/key is located. If necessary it can be taken out with a screwdriver.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
Mr Ron
Posts: 2126
Joined: Tue Dec 22, 2009 12:36 pm
Location: Vancleave, Mississippi

Re: Spindle collet grub screw

Post by Mr Ron »

The grub screw that aligns the R-8 collet in my mill allows some collets to slip in easily while other collets do not. They have to be forced to seat with the drawbar. I'm not sure if it is the grub screw or the keyway on the collet since the collets I have are all different manufacturers. I will have to try measuring the keyways on each collet and look for deviations between a collet that seats and one that doesn't. I know I've pretty much answered my own question, but it doesn't hurt to pick the brains of real machinists.
Mr.Ron from South Mississippi
RSG
Posts: 1541
Joined: Fri Feb 04, 2011 9:59 am
Location: Ontario, Canada

Re: Spindle collet grub screw

Post by RSG »

Pete, I remember that topic about a knee gib but I thought it was from a very old Bridgeport. I don't have the room or equipment to tear mine down so I'll have to just rely on it being sound.

As for the register screw, from what I've read here people are on the fence about it's use, some use it, some don't. My other mill had it and it didn't pose any issues (that I could tell) but I think it was Harold who mentioned inserting collets in the same registration over and over again can cause uneven wear. This IS something I could notice, it was apparent upon close inspection and that was only from 5 years use and the mill was new. Perhaps it could have something to do with the quality of steel used for the spindle or it's hardness IDK but if the general consensus is there are no issues with removing the screw then I think I will do it.
Vision is not seeing things as they are, but as they will be.
spro
Posts: 8016
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Spindle collet grub screw

Post by spro »

This is the everlasting topic. Replacement R 8 collets have different slot depth than whatever was original. Sometimes a screw, modified key, pin( worse thing). If if suits to remove, do it now. Bad key or horrid pin is no good for spindles and collets. It is a like a rotten tooth and will getcha. Okay I said that. Does that help ? I don't think so. Some are perfectly fine. Consider the Van Norman 5V.
spro
Posts: 8016
Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Spindle collet grub screw

Post by spro »

The Brown & Sharpe had a locking taper. The Morse did also but they got away from that. Pounding out a taper against precision bearings was over. Not completely over because they had extreme grip and attached to rear of the spindle was a clever mechanism. Many have been bunged up but it allowed the taper to be pushed out of the spindle. It was not so much a mechanism as facing the issue at that time.
Fast forward to collet angles and why I mentioned VN 5V . They were getting this stuff right and it was Pressure and there was a key across the collet into the taper but it had to work. Nobody mentions 5C and that they have a key.
The R8 is a taper between. It will be locking fine for many then be slipping around for other tightening. It depends upon not only the machine but variables which cannot be known.
Post Reply