Multiple Drawbar / Arbour Threads

[Mayhem]

One of the issues I face in getting my Kondia FV-1 mill up and running is one of multiple drawbar threads due to several different threads used on the tooling that came with the machine and that which I have acquired since (thread type is not a major factor when a super deal comes your way). My mill uses NTMB30 tooling, which has a small threaded tip at the top into which the drawbar screws into (for those who may not be familiar with this style).

At present, the different thread types are I have on my tooling are:

• M12x1.75
  
• 1/2-12
  
• 1/2-13
  

Initially I had though of simply making 3 different drawbars, one to suit each thread. My mill came with an ER32 collet chuck, so changing endmills will not be an issue. However, If I use my 3/4" drill chuck, then I will need to change the drawbar, as I would for face mills etc. I'm seeking your thoughts and comments, as to how I may best overcome this challenge (and selling off two of the three thread type tools isn't an option).

Some other thoughts I have had include the following:

1. Weld up the 1/2" threads and drill and thread M12x1.75.
   
2. Turn a slug with an external thread to match the 1/2" and then LocTight it into place. Drill and tap M12x1.75.
   
3. Make a male/female adaptor with a M12x1.75 female thread.
   

Your thoughts, comments, suggestions...

[stevec]

I don't think option 2 would work, 12mm is only 26thou under ½".

Option 3 sounds best but you might need three adaptors of the correct length to be able to use one drawbar.

I'd prolly go with 3 drawbars. (well marked!)

[Mayhem]

Thanks Steve - I actually cut out the concerns I had with each option, as it made them a little long and then forgot to add them in later!

Option 1 is probably the easiest but I wonder about heat damage and then holding the tool to drill on centre.

Option 2 has the same drill on centre issue and of course you are correct on there not being a whole lot of 'meat' to play with. I'm not reliant upon the drawbar closing my collets, as with a R8 collet - the drawbar is only there to prevent the tooling falling out, so I was curious as to whether there would be sufficient thread depth and engagement.

Option 3 (as you have said) would require all the tools to have identical adaptors, so that the one length drawbar would work.

I have see the pull studs for sale for use in CNC machines and wonder if they could be used (i.e. a drawbar fashioned to accept them). Of course, I have no idea how they work!

[EdK]

I'd also go with three draw bars. Either way you have to remove the draw bar whether to change the adapter or the draw bar. I'd apply different colors of paint to mark them and hang a color code chart near the mill.

Ed

[Mayhem]

Well that is the thing Ed - I could use a single drawbar by using any of the three other options I mentioned.

Having said that, I have the headroom to change drawbars and I would only need to change that when changing out the actual NTMB30 tool. So, the ER32 collet chuck would stay in place regardless of the endmill I would be using.

[EdK]

(10-06-2013, 09:20 AM)Mayhem Wrote: Well that is the thing Ed - I could use a single drawbar by using any of the three other options I mentioned.

Having said that, I have the headroom to change drawbars and I would only need to change that when changing out the actual NTMB30 tool. So, the ER32 collet chuck would stay in place regardless of the endmill I would be using.

I guess what I was trying to say, and didn't do too well, was except for option 1 the other two options would require about the same amount of work in actual use since both would require removing the draw bar to change to the correct threaded end for the tool.

Ed

[Mayhem]

Ahhh - I haven't been clear in describing my options

Option 2 is another way of achieving option 1, which is to change the 1/2" threads to M12 (option one through welding. Option two through the use of a slug). i.e. both fill the existing internal thread so a new one can be tapped.

Option 3 would provide a M12 thread by using an adaptor (the drwback of which is that the tool hight is increased).

All the options I listed are means to use only one drawbar.

[EdK]

Got it. I should have read it slower instead of a quick scan.

Ed

[stevec]

(10-06-2013, 09:47 AM)Mayhem Wrote: Ahhh - I haven't been clear in describing my options

Option 2 is another way of achieving option 1, which is to change the 1/2" threads to M12 (option one through welding. Option two through the use of a slug). i.e. both fill the existing internal thread so a new one can be tapped.

Option 3 would provide a M12 thread by using an adaptor (the drwback of which is that the tool hight is increased).

All the options I listed are means to use only one drawbar.

I'm sorry, you lost me.

[EdK]

Now I'm leaning towards option 3, but why would the tool height increase?

Ed