Milling drawbar

[Paul VassalloParticipant @paulvassallo49657]

Hi

 

I have recently bought a secondhand bench milling, and when I got it home, and it came to fitting a collet chuck I foundout that it has a MT3 and a drawbar M11 x1,25 pitch. Can somebody help me and tell me where I can buy an M12 x 325MM long Drawbar.

 

Thank for all of you that are willing to help.

 

Paul Vassallo

[Paul VassalloParticipant @paulvassallo49657]

[JasonBModerator @jasonb]

Your best bet is to get some 12mm rod, thread both ends and then silversolder a nut onto the top end. Doing the same with some studding (threaded rod) is another option. In both cases make sure you allow for a heavy waher under the nut.

 

That length is quite close to an X3 mill I’ll measure mine later

 

Jason

 

PS whats the make & model of the mill

Edited By JasonB on 10/07/2011 14:47:01

[JasonBModerator @jasonb]

X3 is too short

[DMBParticipant @dmb]

Agree with JasonB, regarding make your own drawbar but Paul should go one better and copy my previous post describing the trapped nut which forces the MT apart gently instead of a hammer/brute force, wrecking bearings in the process.

 

John

[DMBParticipant @dmb]

Look up “Milling collet arbor jammed in milling machine” of 4 June 2011, in Forums.

 

John

[Paul VassalloParticipant @paulvassallo49657]

Thank you for all the help, the idea that jasonB gave me the best, but one more thing about the material of the rod, will silver steel do?

 

Paul

[John CParticipant @johnc47954]

Hi Paul,

 

In the UK, Screwfix do 12mm threaded rod in 300mm (maybe too short for you) and 1000 mm:

 

http://www.screwfix.com/p/bzp-threaded-rod-m12-x-1000mm-pack-of-5/98942

 

The price is OK, although you will have to find a use for the other 4 lengths!

 

John

[JasonBModerator @jasonb]

Good old mild steel will be fine, you don’t need to be applying loads of torque to the drawbar, just nip it up.

 

The taper takes the drive load the drawbar is mostly there to stop the tooling falling out the end of the spindle.

 

Though at 13″ long a bit of silver steel may be easier to come by (at a price) but most of the ME suppliers or certainly your local steel stockholder will be able to supply longer than the 12″ thats often listed in their catalogues.

 

Jason

Edited By JasonB on 10/07/2011 19:30:45

[David HaynesParticipant @davidhaynes53962]

Paul, if you have an industrial estate within reasonable reach, you may be able to pick up a piece of studding there quickly, easily and cheaply. We have an engineering suppliers that did the trick for my studding and other bits.

 

Dave

[Lawrie Alush-JaggsParticipant @lawriealush-jaggs50843]

Hi Paul

 

The first place I would try is Ebay, then Warco. Failing that I would make on up but I would steer clear of Allthread and get a peice of something with a bit of carbon in it, a bit of 1020 or 1045 rod.

It won’t set you back much. Get a bit of hex while you are at it and when you have silversoldered the nut on, make sure you put a pin through it as well.

 

Lawrie

[Lawrie Alush-JaggsParticipant @lawriealush-jaggs50843]

An addendum

 

I use Bohler Udehom here in Australia. They have an excellent range of steels including the ones I mentioned above and will supply any quantity.

 

http://www.bohler-uddeholm.co.uk/english/b_1835.htm

[John HaineParticipant @johnhaine32865]

Last thing you need (especially with a Morse taper) is a very strong drawbar. Studding is fine, you can even buy stainless if you want something a bit fancier than the builder’s merchant stuff. Biggest danger with MT is overtightening the drawbar and jamming the taper.

[DustyParticipant @dusty]

Hear hear John, I have 4 drawbars for my mill with a variety of threads. I only have one which is a pukka drawbar the rest are studding with a nut on top, this nut just has a roll pin through it. As JasonB says it only needs a nip up, none of this he-man stuff. You can if you want make the nut with an integral washer, tap it not quite through so the studding is a nice tight fit, cross drill for roll pin and thats it job done. One other thing make sure the drawbar does not bottom in the morse taper thread.

Edited By Dusty on 11/07/2011 19:16:00

[Steve WithnellParticipant @stevewithnell34426]

I didn’t bother soldering on the nut, I just locked two nuts together…I t used 12mm studding from the local DIY store and then repeated the trick for the lathe.

 

Steve

[Ian S CParticipant @iansc]

Needed a drawbar, no studding available, took two bolts, one to fit the cutter. Cut the heads off, welded the two cut ends together, put two nuts on the top end, welded the top one to the drawbar. With the assistance of my scrap bin, about 10 miniuts. You could weld two bolts to a bit of rebar. If your welding is anything like mine, it wont look pretty, but thats no matter. Ian S C

[John McNamaraParticipant @johnmcnamara74883]

Hi All

 

Do we overtighten the drawbar? I suspect so.

 

I did the following Google search:

“Torque on a Nut”

  

Found these among many:

http://www.boltscience.com/pages/nutorbolttightening.htm

 

http://www.portlandbolt.com/technicalinformation/bolt-torque-chart.html

 

When I got my new (old) mill I exprerimented with the torque needed to set the tool firmly, Using a short spanner; after taking up the slack a firm push is all that is needed. Getting the taper to unlock is now only a light tap on the top of the drawbar.

 

Looking at the torque tables above it is clear why this is so. How many thousand pounds or kilograms do you really need to set a milling cuter?

 

Cheers

John

Edited By John McNamara on 12/07/2011 07:08:30

[Ian S CParticipant @iansc]

I forgot, under the lose nut on the top puta heavy large diameter washer. Ian S C

[PatParticipant @pat]

Hi John Coleman1

 

Can we have a repeat of your post as your design for a self releasing draw bar sounds good.

 

May be I am looking in the wrong place as the last post in the thread ‘milling collet arbour jammed in milling machine’ is June 2010.

 

Help please – Regards – Pat

 

PS found post as June 2010 and have pasted it here:- 

 

Julian,

“Been there, done that”

My long-term solution as follows.

Trapped nut system works like a dream – try it!

I made new drawbar with nut just touching top of mill spindle, remove, cross-drill + pin.

Large AF hex bar bored out to fit over top of mill spindle and locked on to it with 3AAllen key grubscrews.The rest of it drilled right thro` clearing size for drawbar thread. Make new smaller AF nut, taller than standard, fit  on top end D-bar + wind down to just touch top of large AF nut, cross-drill + pin.

John  

Edited By Pat on 14/07/2011 22:04:09

[DMBParticipant @dmb]

Hi Pat,

I used BMS round bar, NOT Silver Steel for my drawbar. Sil. St. not necessary. Bottom end threaded to suit MT, top end same thread as for the MT. When finished, there is a nut pinned to very top end, along piece of large – AF Hexagon bar, part – bored out to fit over top of mill spindle and locked on to it with 3 grub screws fitted radially and top end is bored out to a clearnce size for drawbar. Another nut is fitted to draw inside the large hex. bar, so its trapped. When the top nut is turned clockwise, it screws thro. the trapped nut and bottom end screws in to MT, drawing male taper into female taper in spindle. Dont over tighten – just nip it up to secure it. When top nut is turned anti – clockwise, drawbar unscrews thro. trapped nut and from MT. The trapped nut wants to stay put and rise up with the unscrewing of the drawbar from theMT but its trapped and cannot move vertically thus preventing drawbar from moving vertically. Something has to give and its theMT shoved down, breaking its grip. Is this now all clear? Hope it helps.

John

[JonParticipant @jon]

Have had MT3 shank holders drop by only ‘nipping’ up.

Not to mention the cutters held in them, even worse.

[DustyParticipant @dusty]

Jon

I would suggest that you look at the fit of your morse taper, it sounds like you may have damage to the socket if more than one type of holder has dropped on you. Morse tapers are self locking and as such they should remain tight even without a drawbar. That is, provided the cutter or drill is not being subjected to undue force causing vibration. The drawbar is a safety feature, it does not need to be overtightened. Nipping up is perhaps an unfortunate expression as it means many things to many people. Nipping up is not just over finger tight, nor is it 30ft lbs on a torque wrench. I normally grab hold of the spindle pulley and with the spanner on the drawbar nut, tighten it until the pulley just starts to slip in my not to firm grip. Never had a morse taper drop or slip on me.

[DMBParticipant @dmb]

Dusty,

Its well known taht a 2MT will part company under a milling load. I have had a 2MT tailsock chuck in mill for drilling holes + thats come loose. Mill or drill chucks just want jamming in by hand and drawbar gently tightened to prevent disasters. I find that Clarkson chuck some times gets stuck fast, possibly when using big (5/8″) endmill or slotdrill, ss needing my type of drawbar to shove the tapers apart. BTW, I dont claim originality for it, I read a description of this somewhere – just passing on my knowledge.

John

[DustyParticipant @dusty]

I still say that the basic problem is ill-fitting tapers and sockets ( I include in this swarf or other inclusions in the socket). I accept that a 2morse taper milling chuck could work loose as it is a small taper. If it has a drawbar fitted and and tightened it should never work loose, provided that the taper and socket are well fitted. A drill chuck or morse taper shank drill should not drop, as the force is going back through the drill and/or chuck pushing the taper and socket together. Most quality drilling machines use a 2 morse socket to mount the chuck, I do not know of any that utilises a drawbar, they do not seem to have a problem with the chuck falling out.

[Clive HartlandParticipant @clivehartland94829]

SPG Tools.com are offereing some draw bars, worth a look.

 

Clive

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