Imperial Drawbar for a Metric BF20 Mill

[Johannes GrabschParticipant @johannesgrabsch91508]

I have a metric BF20 Mill with a M10 Drawbar, but also some old tooling with 3/8 threads in their MT2 Tapers. The supplier of the mill seems to be unable to supply me an original drawbar with the required imperial thread (they are metric only…)

Before I start making a replacement drawbar there should be an obvious solution: There are many variants of the BF20 type mill around, and I guess also some imperial mills. Does anybody know weather a drawbar from an imperial Warco WM18 mill would fit into a BF20?

Thanks

Johannes

[Johannes GrabschParticipant @johannesgrabsch91508]

[Chris Evans 6Participant @chrisevans6]

Not sure of your machine but it sounds like a simple turning job to make one.

[Roderick JenkinsParticipant @roderickjenkins93242]

Many people may want to close their eyes to the next bit

You can put a 3/8" Whitworth tap down an M10 thread and get satisfactory engagement with a 3/8 BSW draw bar.

M10 = .393". 1.5mm pitch is 16.9tpi

3/8BSW = .375. 16tpi

A bit agricultural but it works on my mill.  The reverse, an M10 tap down a 3/8 BSW hole ought to work even better.

Sorry,

Rod

Edited By Roderick Jenkins on 04/03/2016 11:03:31

[ASFParticipant @asf]

I made one for my, similar, mill. A little bit more than a simple job though to be fair (well for me!). I found that, because of the length, you need to turn with tailstock support (probably obvious) but needed to use a travelling steady to ensure it was true down the entire length. I case hardened the squared end, as my original metric one had been.

[Ian ParkinParticipant @ianparkin39383]

I recently went down a similar route with a selection of MT3 tooling all with different threads

I made them all the same to M12

Sometimes drilling out to retap and sometimes 1/2" whit just running a m12 tap down

a few needed annealing beforehand

 

if you want a drawbar in 3/8ths i have one for a wm18 machine

Edited By Ian Parkin on 04/03/2016 11:37:48

[HOWARDTParticipant @howardt]

Why not just pin a nut, or special end onto some studding. Simpler and no long turning problems.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Roderick Jenkins on 04/03/2016 10:59:18:

Many people may want to close their eyes to the next bit

You can put a 3/8" Whitworth tap down an M10 thread and get satisfactory engagement with a 3/8 BSW draw bar.

M10 = .393". 1.5mm pitch is 16.9tpi

3/8BSW = .375. 16tpi

A bit agricultural but it works on my mill. The reverse, an M10 tap down a 3/8 BSW hole ought to work even better.

Sorry,

Rod

Edited By Roderick Jenkins on 04/03/2016 11:03:31

 

It does! I would never have admitted to doing such a terrible thing without Rod's brave example. Perhaps we should start a "True Confessions" thread.

Cheers,

Dave

Edited By SillyOldDuffer on 04/03/2016 12:09:24

[Johannes GrabschParticipant @johannesgrabsch91508]

I had already considered cutting M10 threads into the imperial tooling. But unfortunately the very item that I need to use has a taper that appears to be hardened, so tough is it.

The drawbar of the Optimum BF20 is a tricky item. I could just use a long 3/8" threaded rod, but I would loose the safe feature to push out the tool from the spindle. As ASF said, simply copying the original drawbar but with an imperial thread is a bit more complicated than it sounds.

I think I'll buy a spare metric drawbar and I'll braze a length of 3/8 threaded rod replacing the M10 section.

Johannes

[John FieldingParticipant @johnfielding34086]

I have the same machine except it is the Rong Fu RF-25 as they are the makers. I have made plenty of drawbars for various bits of tooling. I use studding rod (all-thread) and sliver solder or cross pin a normal nut on the end and cut it to length. I sometimes need to make a thick washer cum stepped collar to fit the top of the quill where it comes through the top pulley. The original drawbar that was supplied seemed to be made from putty, very poor steel, the common or garden studding sells for almost nothing and makes at least two from a standard length.

[Ian ParkinParticipant @ianparkin39383]

Johannes

heat the end of the taper up with a propane gas blowtorch untill its a red colour let it cool and you will be able to machine it then

I have not noticed any difference in the performance of my tooling….hardened or not on the taper

[Ian S CParticipant @iansc]

I needed a 3/8W draw bar for my mill, took two bolts, cut the heads off, welded them together, the top end has a loose nut, and above that a pair of nuts jambed together, been ok for the last twenty odd years.

Ian S C

[Howard LewisParticipant @howardlewis46836]

+1 for making a 3/8 BSW drawbar. The one that came with my RF25 has the hexagon pinned to the top end.

So no reason why not to cut a 3/8BSW male on the end of a 3/8" or 19mm bar, and pin or weld a bit of hexagon bar on the other end, at the required distance.

(Not REALLY happy at hybridising threads, have come a cropper at times doing things like that)

And it is only a simple turning job to make a 3/8 BSW drawbar, anyway, so time well spent.

Howard

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