Auto-eject Drawbar

It's now been fitted to the Marlow milling machine, and is a joy to use, as is the 'Clutch' I fitted to the BH600G.

I have added another Album, showing how the various parts work together.

If anyone is thinking of making one - DON'T!

Think that is, just do it! You won't regret it.

Geoff - Done for the day.

Can you explain how it works please. I've seen another auto extracting draw bar but that worked on the principle of two different threads working against each other. I haven't made one like that yet though as it requires removal and thread cutting of some parts of my mill, a Warco VMC. This may be easier?

Hi Geof,

That is almost the same as the one I came up with for my little X1 mill, see:

http://mikesworkshop.weebly.com/mill-captive-draw-bar.html

Mike

Thanks Ady1,

For some inexplicable reason I didn't post them. Brain f@rt

The Auto-eject Drawbar, was constructed using a Hemingway kit that comes with everything except for the Collar and Spindle Cap. (Usual disclaimer)

Assembly as follows:

1) The Collar is fastened to the Drawbar by means of 4 grub screws, and they seat in short drilled recesses that hold it in position. On my first attempt the grumpy screws where just tightened against the Drawbar rod and did not prevent the Collar from being pushed down the rod as I unscrewed it trying to eject the tool,

2) The Spindle Cap fits over the end of the Spindle, and again secured by grub screws, but in my case there was no need to drill recesses for them to seat in as all the force is downwards, and is only very light when tightening,

3) Their is a little clearance between the Collar and inside top of the Cap, with everything now held captive.

4) Handle screwed on, and now the Drawbar can be pulled up slightly due to the clearance as in 3).

Operation as follows:

A - Install tool;

1) Push the tool up into the spindle taper, and the screwed end will contact the Drawbar and push it up as far as the Collar will allow,

2) Screw the Drawbar into the threaded end of the tool and the Collar will soon come to rest against the top of the Spindle,

3) Now tighten, BUT ONLY nip the Collar up against the Spindle.

4) Commence machining.

B - Eject tool;

1) Pretty easy and the least fraught, as all that's needed is to unscrew the Drawbar and as it moves upwards the Collar comes into contact with the inside top of the Spindle Cap,

2) The Collar cannot go any further so the pressure as you apply that last bit of slight force to turn the Handle, breaks the taper with a click and the tool is free.

3) Stand back in amazement and scold yourself for using a hammer previously.

Clear as mud with luck

Will do a drawing if requested.

If you have a number of MT tools, then they will all end up at different heights inside your machine's spindle, so use my trick to get them all level so that the one Drawbar will work for them all.

No-one has taken up my challenge, so far, to figure out what I did.

Come on People, if I could, it shouldn't be a problem for the Collective

Geoff - Get the grey matter working

Hello Mike,

Yes indeed, and I should of course have qualified my post by saying that mine is based on others, no doubt yours as well.

I do like the handles you have on your Collar, so may do something similar

My next project will be to finish the Feed Rod Motor, that powers the Saddle and Cross-Slide on my BH600G, that I have based on your excellent Milling Machine power feed.

Geoff - Thanks for jogging my memory about your invaluable website.

Edit of my description on how it's assembled.

Assembly as follows:

2) ALL the forces on the Spindle Cap are in BOTH directions of course, when pulling the tool into the taper as well as when ejecting.

I haven't yet found the need to drill recesses into the Spindle for the grub screws, but it's early days.

Geoff - Took a session on the Throne to realise my mistake

Nice Job Geoff... my machine came provided with a similar auto-eject set up ( Warco 250 V-F ) but without the handle; all I use is a 12 point socket, & a ratchet to nip up / eject the tool, have not had to use a 'Potential to Kinetic energy convertor' for a long time.

George.

Hi Geoff,

I was inspired to make mine after reading Stub Mandrel's recent article.

I look forward to seeing your feed rod motor addition.

Mike