Thread Equivalents for a Draw Bar

[Toolguy]

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.

 

[joco-nz]

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.

 

[Toolguy]

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.

 

[joco-nz]

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?

 

[grapegro]

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

 

[joco-nz]

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.

 

[mcostello]

Excellent idea!

 

[blueywa]

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.

 

[goldstar31]

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.

Really?:hDe:

 

[Wizard69]

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.

 

[Wizard69]

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?

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.

 

[joco-nz]

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.

 

[Graham Sherwood]

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

 

[joco-nz]

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.

 

[Steamchick]

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

 

[Charles Lamont]

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.

 

[Steamchick]

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