Difficulty in drawing...

[Divided he ad]

Well ok, drawbaring I suppose (Yer it's a word!?  )


I just got this new mill you see, and well it's got a stupid drawbar with this odd 3/8 16tpi thread on the end of it!

Well, I'm certainly not going to but all my MT3 tooling again! it's all in M12x1.75 thread.


So I figured I'm make a drawbar.... Shouldn't be too hard? Unless you have nothing suitable to make it from! 

So, I thought up a plan.... This might not work, so in a day or so this post will revert to making a new drawbar after all? But this is what I did instead....

There was an odd drawbar in the bits I got, far too long for this mill, it almost came out the bottom of the spindle. It probably fits something but.... Needs must! (I can always replace it!?)




I cut it's thread off and made a new one to M8x1.25


Then  made a M12x1.75 thread on a bright mild steel bar (better quality than the drawbar too!)


I drilled and tapped it M8x1.25 and made an 8.5mm relief in it.



Then altered the drawbar to fit the thread and relief I had made.



And finally, threadlocked the one onto the other, held the blank in the vice and tightened using it's own hex. cut it off and trimmed/finished off the new thread.





And I've still got the original drawbar that came with it that fits the drill chuck that was in it too


Now I'm just leaving it to set while I tell you guys about it   


Tell you if it works tomorrow!






Ralph.

[sbwhart]

That should work ralph the wort or worst even  that can happen is the two bits come unscrewed.

Stew

[Divided he ad]

That was my theory Stew   


Ralph.

[CrewCab]

Keep it simple, I like it 

CC

[AdeV]

Nice work Ralph - but one question, why didn't you just cut the M12x1.75 thread into the drawbar? 

 

Aaaah, unless the replacement drawbar was already too thin? In which case, nice work * 2 - good piece of lateral thinking there 

[Baldrocker]

Aah! Elegant solution> But what if your mt3 drill chuck has a 3/8 thread, everything else is m12?
Two drawbars is a pita (minor I know, but. ) Duh  how about a double ended drawbar?

[75Plus]

I have, in the past, cross drilled and inserted the smallest friction pin available, 1/16" I think. The logic being if movement can't get started it will never come apart.

Joe

[Divided he ad]

CC,
  Simple all over.... That's me alright 



Ade,

The drawbar is just shy of 11mm.
I had to make the thread slightly under 12mm too, it would only allow 11.9 something mm into the spindle (can't remember the exact figure, made a few plugs in the original bar to find that out)


BR,

The MT3 that came with the machine is old money thread, all my tooling inc. drill chucks on MT3's and collet chucks etc are M12 threaded, so the old stuff will go into storage probably never to be used


Joe,

I'd thought of that originally, I was going to make the threaded part have a sleave to come up the drawbar. But then all the sizes were so close I'd have had to go through the thread...with only about 1mm purchase depth for the pin at the edges. I know it'd be easy enough, I have roll pins 2.5mm dia. I might yet do it, belt and braces 'n' all that. but thought the thread lock should suffice?

I was toying with the idea of silver solder at one point. But changed my mind and went with the chemical option.


Well, test tomorrow evening sometime... Got a little foreigner to do first 






Ralph.

[Divided he ad]

   Works for me   



First bit of chip making this eve'....  Awesome with the power feed!!!

I'll show some pic's of that in the workshop thread 





Ralph.