# Thread Equivalents for a Draw Bar



## joco-nz (Oct 5, 2016)

Having taken delivery of the last of the new tools (BF20LV) I'm looking at the drawbar with the expectation of getting some tooling.

The manual says its M10, but the JT6 drill chuck arbor that came with the tool has these numbers on it:
MT3-JT6-1/2-12

I have tested the arbor and it screws on to the draw bar just fine.  I also measured the internals of the arbor and the diameter between the top of the threads is a tad over 11mm.  So the draw bar can't be M10 can it.

From some reading around the net it looks like the 1/2-12 will mean 1/2 inch and the 12 refers to a BSW tpi of 12.
This looks to be VERY close to an M12 thread.

My question is can I get away with using an M12 thread. For example an M12 threaded MT3 ER32 collet chuck?  Or am I going to have to either source correctly threaded tools or pull out the existing draw rod (which is fixed in the mill head some how as it "self ejects" the tool as you unscrew) and make a new one with a more standard thread.

Thanks,
James.


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## Wizard69 (Oct 5, 2016)

1/2"-12 is an old standard size in the USA which is more or less out of circulation now.   1/2"-12 is also an old Whitworth thread.    Then you have close metric sizes to contend with.   

At best you would buy a set of thread pitch Gage's if expect to work on older machinery.   In that respect it is always a good idea to state the model and other information for the machine.  Beyond that it isn't uncommon on used machines to find a custom draw bar that has replaced what was original.  Also some metric and Unified screws can be extremely close in size and pitch, M5 and 10-32 come to mind, sometimes you need to measure or use other devices to get the right size.


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## joco-nz (Oct 5, 2016)

The new tool being referred to.   The draw bar is as supplied from the supplier.






Guess I am going to have to pull the draw bar out and test it on an M12 nut to see if it works or binds up.


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## grapegro (Oct 5, 2016)

Hello James, On my BL 17, I found that the drawbar was in fact an odd size. Cannot remember the exact size difference, but your comments recall my problem. I withdrew the original drawbar and made one to suit existing tools which I had, namely 3 MT 12 metric. While the manual states a 2MT arbor, Machinery House seem to have altered this to their own species to entice users to buy their own tools. Mine was made by using a long  12 m High tensile bolt, fitting a collar onto the bolt, and milling a square on the top to enable the releasing action to take place. Good luck, Norm


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## bazmak (Oct 5, 2016)

I thought the draw bars were M12 and 7/16 bsw bothe near enough to be interchangeable on most chinese machines


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## Blogwitch (Oct 5, 2016)

You will find this on MT spindled machines.
Unless you are very careful, or unlucky, tooling for MT3 can come with either thread. 
The easiest way is to either make sure the tooling you buy has the required thread (sometimes you cannot get what you want with the correct thread) or just have two drawbars, which is what I resorted to when I had an MT3 milling machine.
I have just bought some MT3 blank arbors for making tooling for my lathe, and they only come with imperial sized threads, but because I am going to be using screw in tangs, I got those to fit, they were 3/8" Whitworth.

John


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## joco-nz (Oct 5, 2016)

From what I understand from looking about the net the draw bar is a "captured" one.  So its not just a case of pulling it out.   But I think some people have also just used some threaded rod cut to the correct length with appropriate nuts in place.

Anyway ... I think I smell one of my first real turning projects.  :thumbup:


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## goldstar31 (Oct 6, 2016)

I agree with John( Blogwich) about the two necessary drawbars( for me anyway)
So I tapped rod and added square ends welded on. Saves a lot of unnecessary turning!

Cheers

N

Digressing, but feel a further note or two are merited. I have draw bars for both Myfords and also draw bars or whatever they are called so that I can hand tap and screwcut large threads


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## Journeyman (Oct 6, 2016)

Just don't do what I did when I was proud owner of new mill similar to yours but smaller. I carefully read the very  "Chinglish" manual and it said to release the 2MT taper slacken the drawbar and hit it with a hammer! Not knowing any better I did this and promptly broke the square end of the drawbar which had probably been over hardened. The captive drawbar just needs undoing and it will push against the hollow nut and push the tooling out - easy! I too find I need two drawbars one 3/8" whit and the other M10. Strangely the machine (WM 14) is metric but was supplied with an imperial drawbar. Changing drawbars is a matter of a couple of minutes work with two spanners so no great difficulty.
Cheers John


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## joco-nz (Oct 6, 2016)

Cheers guys.  After a little reading and some pics texted to me (thanks Bruce) figured out how easy it is to remove the bar. Definitely going to make a metric one for the ER32 collet chuck Bruce is kindly offering to sell me.

On the material front to make this I don't think I need anything other than mild steel round stock as the starting blank? I can use a file to shape the square section on the top to fit the tool supplied with the mill.

To finish it I properly should either blacken or blue the rod?. Using gun blue chemicals seems the less fussy since its a cold process. The whole heating to red and dunking in motor oil multiple times seems a bit more than I want to get into at this stage. Unless someone has another, easier method?


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## goldstar31 (Oct 6, 2016)

joco-nz said:


> From what I understand from looking about the net the draw bar is a "captured" one. So its not just a case of pulling it out. But I think some people have also just used some threaded rod cut to the correct length with appropriate nuts in place.
> 
> Anyway ... I think I smell one of my first real turning projects. :thumbup:


 
As a first project or two, I'd be looking at Chris Heapy's Model Engineering Support Pages. Possibly I've got to repeating myself but everyone else seems to be resurrecting things. At least, I am giving the various authors due acknowledgement 

Norman


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## joco-nz (Oct 6, 2016)

Norman - this site?  http://easyweb.easynet.co.uk/~chrish/cancelled account/homepge2.htm

The" cancelled account" words in the url were a little off putting and made me wonder if this was an archive of a currently active site.

Cheers,
J.


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## joco-nz (Oct 6, 2016)

I had a play in the CAD software last night and modelled up the draw bar I need to make. Please forgive the slightly odd ball dimension on the M12 thread, that's the CAD doing screwy crap.

From a construction point of view I guess I could either do this from a single blank of say 20mm round stock or approach it as a two part with a 12mm shaft and a smaller piece of 20mm turned to size and a close fit and perhaps braze them in place.  From a turning practice perspective starting with the 20mm stock and using tail support and probably a following steady could be good learning.

Cheers,
J.


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## goldstar31 (Oct 6, 2016)

joco-nz said:


> Norman - this site? http://easyweb.easynet.co.uk/~chrish/cancelled account/homepge2.htm
> 
> The" cancelled account" words in the url were a little off putting and made me wonder if this was an archive of a currently active site.
> 
> ...


This is a 'resurrected site' done, I believe by a Japanese gentleman after Mr Heapy moved to star gazing!

I've a lot of time for the information, made several bits and heeded a lot of advice there.  

Cheers N!


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## Cogsy (Oct 6, 2016)

If you turn down a 20mm bar to 12mm you'll be removing something like 2/3 of the mass of the bar. I'd go for a built up one myself. There'll be countless other jobs to do with your new lathe so I wouldn't go chasing a horribly boring exercise like this one.


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## goldstar31 (Oct 7, 2016)

Cogsy said:


> If you turn down a 20mm bar to 12mm you'll be removing something like 2/3 of the mass of the bar. I'd go for a built up  and one myself. There'll be countless other jobs to do with your new lathe so I wouldn't go chasing a horribly boring exercise like this one.


 
Cogsy is quite right. A bit of cheap studding with a bit of square 'stuck on' or a bit of round and threaded appropriately with a bit of square.

Cheers

N


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## joco-nz (Oct 7, 2016)

Yeah - pretty much my approach 2.


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## Blogwitch (Oct 7, 2016)

J,

One of the main problems with MT tapers is that it is self locking due to the angle of the taper, notice the R8 taper, it is much larger, and so self releasing.

Where people go wrong is that they think the drawbar should be given the white knuckle treatment and then have trouble releasing the taper. Once done up finger tight, it only needs a few more flats to make sure the taper doesn't release while in use, it doesn't need to be over tight.
Get yourself a soft hammer, preferably lead (I make my own for other jobs) and a short sharp wack should have the taper released very easily.
Another point is that if you are not going to use the machine for a while, take the toolholder out as temperature changes or a tiny bit of corrosion can cause the MT taper to stick like it was solid. Remember, even though you think you won't get corrosion, fingerprints are usually acidic and can cause things to rust up.
Some machines have a couple of holes around the top of the machine spindle, these are usually for using a plate and a couple of bolts to press down on the drawbar more gently than belting it with a hammer and are used to release the taper. Others use a 'C' plate that sits in a groove in the nut at the top of the drawbar which does a similar sort of thing, as you screw the drawbar out, it automatically pushes down on the drawbar to release the taper.

John


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## joco-nz (Oct 7, 2016)

Blogwitch said:


> J,
> 
> Others use a 'C' plate that sits in a groove in the nut at the top of the drawbar which does a similar sort of thing, as you screw the drawbar out, it automatically pushes down on the drawbar to release the taper.
> 
> John



John - I'm not sure I have a 'C' plate as such but the the 17mm section near the top of the bar is trapped under a screwed down cover.  So as I unscrew the bar from the taper the bar can not rise up and so pushes the taper out.  No need to "tap" anything so long as you don't try and do the "white knuckle" treatment on tightening things up.

The other tips re skin grease is a good reminder.

Cheers,
James.


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## Blogwitch (Oct 7, 2016)

Sorry J, looks like I had read Journeyman's post just before yours, so got the two mixed up.

But anyway, as long as you got a bit of info out of it, no damage done.

As stated by other people, just a bit of threaded rod will do for another drawbar as not much pressure is required. I actually did what you wanted to do, make up a new drawbar out of some hex bar I had, but that was just me going overboard.

John


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## Toolguy (Oct 7, 2016)

A mild steel drawbar will not last very long. The threads will strip off. It would be better to weld a grade 8 bolt on the bottom or use drill rod and harden the threaded part.

Another approach would be to use allthread and make the top part so it screws on, with a pin through. When the threads wear out, screw the top off and put another piece of allthread under it. Cheap and easy.


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## joco-nz (Oct 7, 2016)

Toolguy said:


> A mild steel drawbar will not last very long. The threads will strip off. It would be better to weld a grade 8 bolt on the bottom or use drill rod and harden the threaded part.
> 
> Another approach would be to use allthread and make the top part so it screws on, with a pin through. When the threads wear out, screw the top off and put another piece of allthread under it. Cheap and easy.



How fast would the threads wear? Given this isnt a production environment but a hobby one and i do have a day job.

The allthread had been something I had started to ponder.  Heck I could get stainless, thats not going to wear to fast. At least I wouldnt have thought so.


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## Toolguy (Oct 7, 2016)

I suppose fast wear is relative. It would wear out fast compared to hard steel.
I get about a year and a half out of my 7/16 - 20 R8 drawbars that get daily use. You might get a couple of years out of an allthread one with hobby use.


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## joco-nz (Oct 7, 2016)

Toolguy said:


> I suppose fast wear is relative. It would wear out fast compared to hard steel.
> I get about a year and a half out of my 7/16 - 20 R8 drawbars that get daily use. You might get a couple of years out of an allthread one with hobby use.



Cool.  I presume the wear is driven by how much you are changing out the MT3?


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## grapegro (Oct 7, 2016)

Hello James, I used a high tensile bolt long enough for the job, plug welded a bush on to match the original and cut the bolt to length and formed the square on the top to be able to use the tool. I still have the original draw bar in the draw, unused, and have saved hundreds of dollars in being able to buy the more common tools that have a 12 mm drawbar thread. Norm


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## joco-nz (Oct 8, 2016)

Thanks gents I appreciate the input.  I think for this time I will turn a bar from 20mm stock.  Yes there are more efficient ways to do this job but I am a complete newbie at lathe work and the fact I need to remove a lot of material is actually a good thing.  There is nothing like practice to improve skills and learn.  This process will do exactly that. I will have a lot of material removal to practice with and I can set myself certain size targets along the way to gain experience in hitting correct dimensions.  This will be valuable when it comes time to get the final dimensions.  I can also have a little play at making threads say at 18mm and 16mm to be ready for the real deal at 12mm.

Cheers,
James.


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## mcostello (Oct 8, 2016)

Excellent idea!


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## blueywa (Apr 12, 2018)

Regarding the BF-20VL drawbar thread.

Sorry I haven't had the time to read every reply to this.
I can tell you that the Australian version which would I suspect be the same as the NZ version has a 1/2 inch Whitworth thread on the draw bar.
Doesn't make sense to me, but I do know that it can make things a little difficult.
Hope this helps..
Cheers.


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## goldstar31 (Apr 12, 2018)

blueywa said:


> Regarding the BF-20VL drawbar thread.
> 
> Sorry I haven't had the time to read every reply to this.
> I can tell you that the Australian version which would I suspect be the same as the NZ version has a 1/2 inch Whitworth thread on the draw bar.
> ...



Really?:hDe:


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## Wizard69 (Apr 12, 2018)

joco-nz said:


> How fast would the threads wear? Given this isnt a production environment but a hobby one and i do have a day job.


In the case of all thread it depends a great deal on the material the all thread is made from.   The softer grades would fail relatively fast even in a home shop.


> The allthread had been something I had started to ponder.  Heck I could get stainless, thats not going to wear to fast. At least I wouldnt have thought so.



Actually even in the case of stainless it depends upon the grade.   But I wouln't use stainless in this application as the risk of galling and seizing is high.   It would be very frustrating to have a stainless drawbar sized in the collet and at the same time find out that the other end will not unscrew either.   Now there are all sorts of qualifications here, stainless doesn't seize readily to other steels but I'm not about to say it never happens.

I hope that I'm not coming off as very negative with respect to Stainless but I work maintenance in a regulated medical device manufacture where in many cases stainless is mandatory.   Removing seized screws is a fairly regular event.   Sometimes you get lucky with a little penetrating oil and sometimes you are at the Bridgeport trying to drill out a small screw and not induce any extra damage.   The killer with stainless is the rather random way in which a screw will seize, a flange might bolt up with 5 screws and 4 of them will come out perfect and the 5th leaves you muttering nasties about the poor screws mother.    Materials like Neverseize only works where it is allowed to be used.

In a nut shell be careful when using stainless, sometimes it is the perfect material.   Other times it is a mistake to even think about it.


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## Wizard69 (Apr 12, 2018)

Sounds like a good idea.  You will also gain experience setting up steady and follow rests, threading and other techniques.

The only thing that comes to mind is this: is 20mm big enough in diameter?



joco-nz said:


> Thanks gents I appreciate the input.  I think for this time I will turn a bar from 20mm stock.  Yes there are more efficient ways to do this job but I am a complete newbie at lathe work and the fact I need to remove a lot of material is actually a good thing.  There is nothing like practice to improve skills and learn.  This process will do exactly that. I will have a lot of material removal to practice with and I can set myself certain size targets along the way to gain experience in hitting correct dimensions.  This will be valuable when it comes time to get the final dimensions.  I can also have a little play at making threads say at 18mm and 16mm to be ready for the real deal at 12mm.
> 
> Cheers,
> James.


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## joco-nz (Apr 12, 2018)

Gents,

Interesting info on SS, something I will keep in mind for the future.

When I finally made the draw bar I took a last minute change in tack and made it from two pieces, mainly cose I was feeling (at that time) a bit a cheap and didn't want to waste so much steel through stock removal.  Anyway see this post for what I actually did and the end result which has been operating very well for the last 12+ months:  http://www.homemodelenginemachinist.com/showpost.php?p=290771&postcount=473

Cheers,
James.


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## Graham Sherwood (Jul 21, 2020)

Complete newby post, please be kind 
Just received my new Warco Wm-14 mill.
First excercise , removed the arbor using the self ejecting system described above no problem.
But how do I remove the drawbar from the machine, to fit the supplied alternate metric drawbar? 
I am guessing it is intended to be drawn upwards and out , but is captive by a plate secured by four screws.
The instructions cover loosening the drawbar to remove the drill arbor, but not how to remove the drawbar itself...
Any help gladly received.

Graham


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## joco-nz (Jul 21, 2020)

Graham - suggest some pics of the top of the drawbar could help with advice. They put the drawbar in so there will be a way to swap it out.  
Cheers.
James.


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## Steamchick (Jul 22, 2020)

Have you tried removing the 4 screws and holding plate?
A photo may help us help you?
K


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## Charles Lamont (Jul 22, 2020)

I do adaptations the other way round. My mill has a 30-INT taper and a 3/8" Whit drawbar. Some tooling comes to fit, and some with an M12 thread, so I just make a reducing sleeve to fit in the tail.


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## Steamchick (Jul 22, 2020)

I make-up draw-bars by cutting a bolt in 2 and welding a long bar in the middle. Got to jig it and weld in stages to get it straight. But I'very made 3 in lengths and threads that I need for my Miller and also to use some tooling in the lathe mainshaft. (Boring bar, etc.).
Easy if you can weld. If not, use some all-thread studding?
K


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