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MT2 collet slipping

Advice sought on preventing tool slip

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mgj19/02/2011 15:17:33
1017 forum posts
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Exactly KWIL - exactly. If you feed fast enough you maintain the load.
 
I used to back of my drills - even posted a pic on these forums of how to do it, but backing off and then resharpening became a PITA, and I thought about  the problem a bit from first principles.
 
So now I don't. The danger bit is when you stick the drill into the centre hole and it can jump - and it should do if i'm right because the load is taken off. So now I just do a dimple, and feed such that I'm feeding faster than the drill cuts and the pressure is maintained. Don't use a pilot either - just a really sharp 4 facet bit that cuts to size. No more grabbing.
 
(Same with parting off - if that reaction is maintained it won't grab.Start applying a forwards force with high rake, or let the pressure off - feeble feed and it'll jam up).
 
All this grabbing and binding is a forward force pulling the tool forwards into the space created by a tad of backlash in front of the feed nut. If you apply pressure it can't grab because the feed nut is being forced back . If in so doing the system is going a bit quick, cut the revs - oh and feed alot of coolant to stop thermal expansion causing a grab - but thats a different phenomenon.
 
All backing off is, is just a smart name for a blunting the drill, which reduces the rate at which it cuts. Same detail - as we all know, feed faster and you reduce the effective rake - same principle, more convenient. Steel, gunmetal, bronze who cares - same bit different speed and feed rate.

Simples.
 
Give it a go and you will see what I mean.


 


 
 
 
,
 
 
 
 

Edited By mgj on 19/02/2011 15:24:54

Nicholas Farr06/03/2011 07:54:22
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3988 forum posts
1799 photos
Posted by Versaboss on 19/02/2011 13:44:32:
Posted by Andrew Johnston on 19/02/2011 11:50:38:
I
 
Can you trust them when they don't even know the correct units for torque? ...

and for those who eventually don't get it: ft/lbs it ain't!

Greetings, Hansrudolf
 
Hi, found the leaflet for my Teng Tools 70-350 Nm torque wrench yesterday, guess you can't trust them either.
 

Regards Nick.

Edited By Nicholas Farr on 06/03/2011 08:14:49

joegib06/03/2011 10:52:40
154 forum posts
18 photos
Does anyone know the "correct" units for torque? (Rhetorical question)
 
I recently got interested in stepper motors in connection with a project I'm undertaking. Going through the manufacturers/retailers spec sheets defining various torque values for their products proved to be a maddening exercise. It seemed as though each one was employing different units for specifying torque!
 
In the end I resorted to an on-line torque converter to carry out comparisons — this one here:
 
 
Somehow it didn't surprise me that the software provided no less than 17 different units for specifying torque!
 
I hasten to say I'm not trying to start a torque war. Torque, torque not war, war.

Joe

Edited By joegib on 06/03/2011 11:24:00

Nicholas Farr06/03/2011 14:52:23
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3988 forum posts
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Hi joe, all them in your link look pretty valid to me. Obiviously when dealing with very small screws ect. Nm or lb/ft, lbf/ft, ft,/lbs or however you wish to term it, is a bit heavy handed, so you would use grams or ounces. Just use whichever is suited to the application, however Nm or KgM are often prefered.
 
Regards Nick.
 
 
Keith Long06/03/2011 15:27:00
883 forum posts
11 photos

Hi

What Hansrudolf is referring to is that the units should by distance ( feet) MULTIPLIED by force (pounds force) not what is shown as ft/lbs. That actually means distance DIVIDED by force, which whatever it is, it certainly isn't torque!

As Nick says the figure that Joe has found are all valid and which you use depends on whether you're working in the mks, cgs or imperial system. The use of cm instead of m or inches instead if feet , ounces rather than pounds and grams rather than kilograms or newtons allows you to specify torque in sensible numbers without having to use powers of ten in the figure which usually leads to confusion - and stripped threads!!!

Keith

Edited By Keith Long on 06/03/2011 15:28:01

Nicholas Farr06/03/2011 16:54:12
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3988 forum posts
1799 photos
Hi Keith, I understood the reference, but I have also seen it written as ft.lb as shown on the leaflet in the photo I've posted, in many maintenace specs that i've come accross.
 
The usual way to write it is lbf.ft. Which is as you say is pounds force X feet. However while the forward slash is often considered as a devision it is a matter of interiptation as I've also seen it written as lb/ft, which also suggests it is pounds devided by feet. It is widely known that it is pounds X feet or feet X pounds. Funny but everyone seems to print Nm correctly, but metric is regarded easyer to understand.
 
Regards Nick.

Edited By Nicholas Farr on 06/03/2011 17:00:11

Gone Away06/03/2011 17:29:21
829 forum posts
1 photos
Posted by Nicholas Farr on 06/03/2011 16:54:12:
Hi Keith, I understood the reference, but I have also seen it written as ft.lb as shown on the leaflet in the photo I've posted, in many maintenace specs that i've come accross.

 
When (long ago) I received my education, using ft.lb for torque or lb.ft for work were considered schoolboy howlers. The convention was always the reverse even though the dimensions are the same.
 
Wouldn't surprise me if there has been some relaxation since those far off days though.
mgj06/03/2011 17:29:31
1017 forum posts
14 photos
Agreed.
Ft lbs (f) is pretty common.
 
By my maths it doesn't matter if you multiply X x Y, or Y x X, the answer is the same!
 
Metric is a lot more consistent -much easier to do the load  calculations in metric. I still munch metal in imperial though.
 
Howlers - well so many different people are writing specs - what matters is getting it wrong, not how its wrtten! One jsust has to be a bit flexibe and adapt a bit?

Edited By mgj on 06/03/2011 17:32:45

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