MT4 draw bar

[jack620]

My MT4-ER40 collet chuck turned up today. Now I need to make a 16mm draw bar to suit my hercus 260. The simplest idea I can come up with is a bit of 16mm all-thread, an aluminium bushing to fit the Hercus spindle, a washer and a 16mm nut.

My only concern is that there might be the potential to over-tighten the nut with the spanner and jam the collet chuck in the spindle forever. Just how tight should a MT be drawn into the spindle? Would a hand-wheel be better than a nut+spanner for tightening?

Chris

[scottyd]

I fail to see how overtightening will do anything other than strip the thread in either the collet chuck or the drawbar itself and in either situation, you just back the bar back out and belt it up the freckle until the taper separates, followed by repairing damage as necesary. Given the size of the collet, I would imagine that the job would spin in the collet before the MT4 started to spin, so I would think that a drawbar with a good sized handwheel ought to be enough.

[simonl]

Hi Chris,

My mill has an MT4 spindle. I find I only need to "nip" it up, if I tighten it any further then it's for no good reason and i find I that needlessly have to use excessive for with a hammer to release it. I find that just a gentle nip will give me all the take up I need (for my light duty work) and it then only requires a gentle strike with my hammer to release. A handwheel sounds like a great idea. Maybe something about 100mm in diameter would be sufficient, perhaps more if it was for a person with arthritic hands etc.... I like the idea of a spring loaded spindle lock and a drawbar release bolt, that way you don't have to hit the spindle at all. I have heard that with R8 you don't need to do that anyway :C

Simon

[nearnexus]

I do all my milling on my lathe using a Morse 4 ER32 collet with a similar metric thread draw bar. Thery are p#ss wasy to make and don't have to be anything exotic, just make sure they centre on the drive end - use a stepped washer or a cone.

A nut on the end of the draw bar works fine.

You would have to be a butcher to over tighten it.

You just nip up the bar lightly and when you want to remove it you tap on the end of the bar (nut) to knock out the Morse.

If you want to hit your flash handwheel with a hammer by all means go ahead, but I think you will find a nut is a better proposition :)

Also on a lathe with a drive belt cover, you can close the cover with a nut, but not a handwheel.

Cheers

Rob

[jack620]

Thanks fellas.


..use a stepped washer or a cone.
Yep, I was going to turn a step in a short ali bushing to centre it in the bore.


You would have to be a butcher to over tighten it.
"cough" :)


Also on a lathe with a drive belt cover, you can close the cover with a nut, but not a handwheel.
Good point.

[nearnexus]

When you knock out the Morse taper I would recommend you turn the spindle slowly while you do it.

That way you are not hitting on the rear spindle bearing in the same position.

Obviously you tap lightly, but it's unwise to tap on a roller bearing in one position as you can mark the race.

Cheers

Rob

[Michael G]

A handwheel may have a fly wheel effect - that is, the handle wants to keep going when the spindle is slowing. This may tend to loosen off the drawbar. The taper will still be locked up so next time you start cutting you may get chatter or the spindle will start to slip.
I've made up some draw bars myself and would suggest that rather than a nut on the end of your all thread you work out the length that you need and pin the nut with a roll pin or similar. That way when you loosen the draw bar it's the arbor end that is loosening rather than the nut end. You could also turn a nut with the necessary conical base to save having a separate washer floating around. You only need 2 flats, so a bit of bar with a conical end, tapped M16 and then flats in the mill - easy.
Photo 4 shows the sort of thing http://www.woodworkforums.com/f65/show-us-your-mill-121568/index7.html#post1425224

Michael

[nearnexus]

Hi Michael,

Yes I agree on both counts.

I've milled all day with some really big cutters and never had the draw bar loosen.

My draw bar has the nut bronzed on, so all the thread feed is at the Morse end.

A little dab of arc would suffice if you are not fussed about appearance :)

Those ER collet chucks are the bees knees. Just so damn easy to use and never get stuck or jammed.

Here's a photo of my setup. The flat centering washer is recessed into the end.



Cheers

Rob

[jack620]

thanks for the pics fellas. They're a big help.

[rusty steel]

I have a mill with a MT4 spindle and I use a ring spanner from a Honda motorcycle tool kit to tighten the drawbar . The handle is only 100mm long.
I just give the handle a slight bump with the palm of my hand to tighten the drawbar. I only have to tap the end of the drawbar gently with my copper hammer to release it. My drill chuck socket has the tang end and to release it I drop a piece of 12mm rod (400mm long) down the spindle once or twice and it releases.
I have never had the sockets slip so it appears that very little tension is required to hold the Morse sockets securely.
Russell

[Gerbilsquasher]

I use BT50 tooling in my 1936 Cincinatti 2M with an M25 allthread drawbar. The 'nut' is stepped for centering and has two flat faces on opposite sides so that I can tighten it with a shifter- just a gentle bump with the palm of the hand (against the inertia of the spindle) is enough to tighten or loosen the drawbar, and I release the taper with a gentle tap on the top end of the drawbar with a Huckson hammer.

I was a bit cheap in hindsight, and used only the standard (not high tensile) allthread at the time... nonetheless I cannot see any damage to the threads on the drawbar, even after many inspections.....

[jack620]

I was a bit cheap in hindsight, and used only the standard (not high tensile) allthread at the time...

I've been wondering what type of all-thread to use. I guess the galvanised construction-grade stuff Bunnings sells isn't all that accurately cut? I reckon I'll just turn a 16mm thread on each end of a piece of 16mm BMS. I've got plenty of that. I will use a Bunnings nut though. :)

[pipeclay]

Good luck with the bunnings nut most are like a co-k in a sock.

[jack620]

I just found some 16mm gal all-thread and nuts left over from when I built my house. It's not Bunnings stock, so the fit isn't too bad.

[Gerbilsquasher]

I made the 'nut' from a piece of mild steel merchant bar (once again... bit cheap at the time) and cut the internal thread on the lathe. Now, merchant bar is crap, and I would have got a much better result had I gone to Lockbar and picked up a piece of BMS, for a lot less effort, but whatever you cut the thread from will give you a better fit than buying a 'nut' off the shelf. I then screwed in the allthread, leaving a gap, and filled it with weld with the MIG, ground it off and machined it smooth. Looks 'sorta' professional...

http://www.woodworkforums.com/members/58985-gerbilsquasher/albums/cincinnati-drawbar/239317-cimg0157.jpg

http://www.woodworkforums.com/members/58985-gerbilsquasher/albums/cincinnati-drawbar/239318-cimg0158.jpg

Edit: Just had a look at my own photos.... that is one sexy mill, even if I say so myself :D It has had a quick and lovely spray job (someone painted over the previous paint chips, and blue really isn't her colour...) I might get around to a sandblast and a coat of machinery grey...

[rusty steel]

I have made three drawbars for my mill . One of them is made from two long HT bolts welded together. Another is a piece of bright shaft with the threaded section of a HT bolt welded on to it. On my drawbars I have a captive thrust washer made from Phosphor bronze (about 4.0mm thick) pressed over the centering section . The centering section is slightly smaller in dia. where the thrust washer locates so that the thrust washer is free to rotate. Probably overkill.:D
Russell