PDA

View Full Version : Using unsupported MT accessories.



Oldgreybeard
3rd September 2015, 10:36 AM
I have just read a very interesting and informative article on SMC forum by Mobyturns.

Would you consider posting it on this forum, Geoff ?

Also a point that you did not mention when discussing ways to prevent the risk of the MT accessories coming loose is the potential to drill and tap the MT to accept a draw bar. Is this possible?

Thanks

Bob

Picko
3rd September 2015, 12:31 PM
"SMC forum"

Single Mother by Choice forum:?

Oldgreybeard
3rd September 2015, 12:49 PM
"SMC forum"

Single Mother by Choice forum:?

Sawmill Creek Forum

Luke Maddux
3rd September 2015, 04:31 PM
I've had two lathes, both with MT2.

With the first one, having a MT accessory unsupported was simply not an option. It WOULD come out, it was only a matter of time. That lathe was a complete POS and was priced accordingly.

My new lathe is pretty high end. I can put a MT2 accessory in and use it unsupported with absolutely no concern, and these are the same MT2 accessories I was using on the first lathe. I do it very, very regularly.

So, at least in my experience, it is all about the quality of the grind on the female end. It is also important to keep it clean, and to very deliberately seat any MT accessory which you're putting into it.

Just my AU$0.02.

Cheers,
Luke

Mobyturns
3rd September 2015, 08:49 PM
I have just read a very interesting and informative article on SMC forum by Mobyturns.

Would you consider posting it on this forum, Geoff ?

Also a point that you did not mention when discussing ways to prevent the risk of the MT accessories coming loose is the potential to drill and tap the MT to accept a draw bar. Is this possible?

Thanks

Bob

I have posted my thoughts in a new post on here.

Most MT2 shanks would be hardened to some degree. I'm not a metal machinist so I guess if you wanted to drill & tap them you may have to heat treat them etc. I will leave that one to others to answer.

Pat
3rd September 2015, 09:35 PM
I've had MT shanks wander out at 3000rpm, certainly wakes one up.

My bottle stopper & pendant jig MT's are now all tapped for a drawbar.

My Drill chuck MT gets seated, spun up and then checked.

I use a Taper mate to clean the MT's especially when I have been playing with bowls and sanding. Blessed dust gets into everything.

chuck1
4th September 2015, 07:51 AM
I use a shotgun pull through for Morse taper cleaning
and it's heart stopping when your Jacobs Chuck comes loose.not so much the tailstock, definitely the headstock!

hughie
5th September 2015, 07:59 AM
Gentlemen Morse tapers are designed to lock and if they dont lock then there is something wrong with them.

Either the female or the male is damaged, or has crud on it or worst of all the angles are wrong. On cheap lathes and or low cost male parts you can except this sort of problem. Any two angles of less than 15' will lock if identical and this is the principle behind them.

https://en.wikipedia.org/wiki/Machine_taper

http://littlemachineshop.com/reference/tapers.php

Morse tapers have been used in Engineering for atleast a 100 years with no dramas and they a standard feature of every day life in a machine shop. The only tapers that commonly have draw bars are normally found on Mills. The tapers here are designed differently to the ones that normally hold drill chucks etc and do need a draw bar to hold them as the angles are different.

The machining of MT is done with the use of a Sine bar and is used also for checking tapers

http://www.frets.com/HomeShopTech/Tooling/LatheSineFixture/sinefixture.htm

What it sounds like to me is some of the MT have some 'galling or gaulding' which is where the metal picks up and damages the surface of the taper. On cheap tapers it would most likely be the result of the quality of the hardening/grinding and or both poor quality steel.

I would be reluctant to add a draw bar to a standard MT due to the additional damage that could occur, that will in time render both the female and the male useless. There are tapered Reamers available to clean out the female MT. But they do require a certain amount of expertise to use otherwise you can actually make it worse.

If they are not locking I would be cleaning both and look for damage and gently removing it. I say gently, as you can add to the problem by the way you do this. I have seen people linish the male part :U yup it was clean but it rattled around like a you know what in a sock.

On your wood lathe or bench drill this would probably be the most accurate and delicate part of it and giving it a hard time will eventually back fire. It is one of the dangers with old gear as some have copped a hiding by backyard sledge hammer welding DIY enthusiasts. :C :U.

Mobyturns
5th September 2015, 09:06 AM
Hughie, are MT 2 accessories used in lathes in "unsupported applications" without draw bars in metal machine shops with the carriage/cutter travelling/cutting away from the head stock?

I agree with all that you say because that is how tapers (Jarno, JT, MT etc) are supposed to work. :2tsup:

I am raising awareness of the potential risks of using MT accessories in "unsupported applications" in wood turning.

It is true that the friction should hold the MT in place however when using a MT accessory like a Jacobs Chuck, a bottle stopper chuck, or a MT 2 spindle for collet chucks it is very easy to over come the friction that holds the MT in place. Often there is not enough force used to generate a firm fit of the male MT into the spindle socket, there is no tail stock support to generate the force. Only answer is to start tapping (pounding) the accessory into the head stock.

This is not a new hazard as wood turners have been using socket chucks for eons. There is a reason the old timers used to pound the work piece into the socket. :D In fact Jean Francois Escoulen does that when demonstrating his eccentric socket chucks.

When you use a skew or a spindle/detail gouge to make cuts on the RHS of a cove or Vee it creates a force which acts away from the head stock. Same goes for using a Jacobs Chuck in the tail stock when drilling or boring, most wood turners use one hand to maintain the friction on the MT 2 or to "keep the MT2 in the tail stock."

Morse tapers and threaded chucks/inserts are antiquated in production manufacturing because of their inefficiency in a production environment and the inherent dangers of using them in particular applications i.e. a MT 2 accessory in unsupported mode or a threaded insert with the lathe running in "reverse." Wood turners and manufacturers continue to use them because they are economical to manufacture, robust, simple to use & maintain but they do have some potential hazards if used inappropriately.

hughie
5th September 2015, 04:39 PM
Hughie, are MT 2 accessories used in lathes in "unsupported applications" without draw bars in metal machine shops with the carriage/cutter travelling/cutting away from the head stock?


Generally only draw bars are used on Milling Machines there are at times on specialist application draw bars. But on lathes, Radial drills, smaller bench drills etc there is no draw bar nor is there a need for one, as long as the MT is in good condition.
On wood lathes there seems to be a need although I suspect its not so great as the need for greater quality control during manufacture. I say this because on lathe and Radial drills vibration, intermittent cuts as for more common and at a greater intensity than most if not all we see in the wood working arena. Rarely do we see Morse tapers failing and when they do they are generally deemed to be stuffed and replaced. Failure happens but generally due to wear and tear over a period of years.