Ah S H $ $ ! ! ! Bad Setup

[millman5]

Morse tapers, or for that matter any taper used for milling must be held in place with a draw bar/bolt. Or in the case of lots of boring mills a slot in the center of the taper & a pair of wedges to hold the taper in.

Not that it's any consolation but>>>>> I made a similar mistake yrars ago trying to bore a part using a morse taper. Taper came loose & fell out of the quill. basically the same results that happened to you.

[BadDog]

And it's not just the work holding.

I made a similar mistake on my Bpt 2J by pushing a (new of all things!!!) 1/2 3 flute solid carbide to hard in a piece of semi-hard super tough steel (1" Kennametal indexable lathe tool holder) and forgetting to *lock* the knee. It actually PICKED UP THE TABLE AND KNEE before the brand new cutter shattered. Not only did I waste that cutter, but ruined the insert holder, AND had to change my pants...

[CarlD]

I hope you had safety glasses on. Never operate ANY machines without them.

ALWAYS take a common sense approach to what you are about to do. Think of the ways it could fail or hurt you. Yes, it was an accident looking for a time to happen.

Most of all, learn from what you do, both right and wrong.

THINK, what if this happens, what it that happens, should I change what I am doing?

[dgoddard]

This is not the only case in which I have had a work piece slip, but in retrospect it is the one that I should most have anticipated. Letting cutting forces load a taper in tension, DUH ! I had used similar setups with the chuck before but not one in which the chuck was receiving a significant load let alone one that was trying to pull the taper apart.

If I try to characterize the lesson and generalize it to the other cases where I have had a part slip I think I can best represent the problem by saying that I should always analyze the setup to see if any of the cutting loads are in a direction that will have to be resisted by Friction alone, and if they are I will have to see if that can be changed. But with a small diameter rotating cutter it would appear that a vise will almost always have to depend on friction for some portion of the forces.

As someone once told me:
Friction, if it helps you there probably isn't enough, if it hurts you you probably have too much.

And just for the record, I ALWAYS wear safety glasses. Certified industrial grade glasses are the only ones I will buy. (and they are not cheap in CRT trifocals).

[MikeC]

You are correct in that a rotating cutter always ends up putting part of the load in a direction perpendicular to the vise jaw. That's one big advantage of a shaper. I have a current possible paying home shop job that has a large interrupted cut. I will probably use the shaper, as it will lower the tooling cost and reduce the tendency of the part to pull out of the vise. Trade off will be outright speed of production, but that may be a break even, given the lighter cut and multiple passes that will be required of a mill.

[10 Wheeler Rob]

I got one the 3/4" head stock drill style chuck that fits the 1 1/2 - 8 spindle thread for my South Bend Lathe, and found out very quickly that it is only good for drilling and holding stuff for polishing and such. They do like side force either.

Rob

[oldbrock]

Like MikeC said, if you had cut on the other side of the work the cutter would have pushed the morse taper tighter and we wouldn't have this post. Jacobs chuck is a poor workholding device but it could have worked with light cuts. Peter

[seal killer]

All--

This is a great thread, ESPECIALLY for a newbie like me! All my collets are R8 or Weldon except for the single 3/4" MT3 I bought to hold a piece of steel in the MT3 hole in my rotary table. I only use it to roughly align the rotary table to the quill.

However, I am sure I will eventually use that 3/4" MT3 for something else while the RT is in the vertical position. What I have learned here is use a drawbar to secure the MT3 into the table. Since I have never had the RT in the vertical position as of yet, it escapes me how this will look and work. If I cannot figure it out, I will be sure to ask questions, NOW!

Great thread for me, although what I learned may have been off topic.

--Bill

[MikeC]

Use a drawbar and set your cut up so the force pushes into the fixture instead of trying to pull it out. If it manages to pull it the slightest amount, you will get a bigger bite, so it will pull harder, so it takes a bigger bite, etc..... bang. If you are pushing and it slips, the cut is reduced. You may still screw up the part by missing a dimension, but you wont crash.

[joshuaz2]

the other thing that nobody noticed was the first lesson my new to me M-head schooled me in. which is to lock the spindle so that a spiral bit doesn't pull it down. that propably happened first causing excessive bite leading to further disaster.

[Al_Messer]

Forget the flutes and make a half-round single flute counter-sink. Turn the business end of the countersink and then reduce it to one-half of its diameter with a file, harden, draw, and hone.

[MikeC]

In addition to locking the quill, I do not mill with the quill extended. I use the knee to set Z depth and use the quill only for drilling, boring, countersinking and such. Increases rigidity tremendously.