Warco milling machine draw bar

[Michael CallaghanParticipant @michaelcallaghan68621]

Hi, I have an old warco milling machine with R8 spindle. The drawbar thread is 14mm with 1.25 pitch. I am finding it hard to get a drill Chuck that works with this thread. Collect chucks go right on, but the drill Chuck I purchased from the same company just don’t want to know. Can anyone come up with a answer. I don’t use the mill for drilling much, but at times I need more space then the bench drill can give.

[Robert ButlerParticipant @robertbutler92161]

Morning Michael

You should be able to obtain an R8 arbour with a suitable taper for your drill chuck and the only drawbar you need is to retain the R8 arbour.

Robert Butler

[John HinkleyParticipant @johnhinkley26699]

Can you give a little (lot) more detail?  What model of mill have you got?  There seems to be a lot of conflicting detail in your original query.  For example, R8 drawbar thread is 7/16 inch UNF.  A drill chuck would normally be mounted on an R8 to B16 for example. Collet chucks are usually supplied with an R8 spindle, too.

14mm seems a large diameter for a drawbar.  I understand some R8 arbors have an M12 x 1.75 thread, mainly from far eastern sources.

John

Edit: Robert got therefirst – and more succinctly!

[Martin ConnellyParticipant @martinconnelly55370]

R8 with an M12 x 1.75 thread is not R8, maybe it needs a new designation such as R8M to show this and avoid disappointment when things don’t fit the way you expect.

Regarding the drill chuck, does it go into the spindle? If not there may be some corrosion/debris in the spindle that is interfering with the fit of a new R8 arbor. The other thing is that there is possibly a problem with a pin in the spindle socket that is stopping the new R8 arbor from going in, I have had to get a small file and deburr the slot on some R8 collets to get them to fit and also to remove scale from the bottom of the slot, left over from heat treatment I believe.

If the problem is that the drawbar will not fit then the issues mentioned above may be coming into play. Try and measure the drawbar thread to see if it is a standard 7/16 x 20 UNF or some metric alternative that does not fit a standard R8 item of tooling.

Martin C

[old martParticipant @oldmart]

The common drawbar size for R8 is 7/16 UNF and you could get one fairly easily, or maybe get a length of threaded rod and some nuts for the top. The correct length for a drawbar would be about 2 diameters (7/8″) of thread engaged in the tooling when tight. The mills at the museum both have captive drawbars, so we are limited to 7/16 only, but I have a couple of arbors which have the 12 x 1.75 metric and are disused. Before buying any R8, I check the thread size first.

Your drawbar thread is unusual at 14mm as the 7/16″ is close to 11mm. But as long as you only need to swap drawbars which takes seconds then both sizes are usable.

[JasonBModerator @jasonb]

And don’t measure any threads at the top of the drawbar which will be to do with self-ejecting rather than fitting the R8 Arbor

[Bill PhinnParticipant @billphinn90025]

My Warco mill came with two drawbars: a 7/16×20 and an M12 x1.75.

I didn’t think I’d need the M12 until I bought some R8 direct collets that surprised me by being M12, not 7/16 UNF.

 

I’ve never met a collet chuck like Michael’s that has an M14x1.25 thread.

[Michael CallaghanParticipant @michaelcallaghan68621]

Thanks chaps. I think that the drawbar in the mill must of been for a special. Sorted now

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