Chester Champion, warco ZX15 drawbar

[martianParticipant @martian]

I need to make possibly two drawbars for my Chester champion mill, I have both 3/8 W and 1/2 W threaded 3MT collet chucks.

The thing that came with the mill has damaged threads and is clearly way too long.

I am thinking of making something like the picture below, can someone tell me suitable dimensions X, Y & Z

[DiogenesParticipant @diogenes]

Does your mill have a slot for a drift in the side of the quill – insert the chuck(s) and reach down with a rod to touch off top and bottom of the chuck’s drawbar hole and mark it at both positions to establish ‘X’.

‘Y’ is whatever diameter suits the thread and is a loose fit down the hole* – 3/8″ or 10mm will do for smaller drawbars, 7/16 or 12mm bar will do for the bigger threads which are equally likely to be found in MT3 spindle tooling.

‘Z’ is depth to bottom of drawbar hole minus say, 20-25%.

*I’m struggling to believe that your ZX15 will pass a 1/2″ bar through the drawbar hole  – are you sure about that measurement?

 

 

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Martian, I’ve just been and looked at my Chester Champion, which is the same as the ZX15, and the drawbar is like the one in your photo. X is 265mm. with Z being 26mm, but this may depend on your your collet chucks, so you may need to measure them as Diogenes has said. The bore down the spindle on mine is 13mm clearance, so both a 12mm and a 1/2″ diameter drawbar will fit. The top section of the drawbar in your sketch, may be too long, and may possibly hit the belt guard when the quill is fully up. If the drawbar in your photo is the right diameter for one or the other, you may be able to shorten it and put an appropriate thread on it.

Regards Nick.

[JasonBModerator @jasonb]

Is it just the photo that makes the ER chucks look like they both have parallel shanks? But that may explain why they go in further and therefore make the drawbar seem too long.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi JasonB, I think it’s just the angle of the shot, causing an optical illusion, like this 3MT arbore below.

Here’s a piece of 25mm bar, which makes it look tapered.

Regards Nick.

[martianParticipant @martian]

Thanks Nick, very useful information.

Jason, it’s just the angle of the photo, they are 3MT. I say the drawbar is too long because it goes all the way through the spindle and the threaded portion sticks out at the bottom. Maybe it is for some other purpose? This is one of the joys of buying second hand tools, you get mystery items and missing parts.

 

Many thanks Martin.

[Howard LewisParticipant @howardlewis46836]

Most 3MT arbors have either a 3/8 BSW thread, or the newer ones, M12

Or it is possible to screw in a piece of M12 and then drill and tap 3/8 BSW, if you want to standardise.

The length of thread engagement will vary slightly from one arbor to another, but as long as you have at least one diameter engagement that should suffice.

Probably the way is to make up a drawbar, with a thread that is a little too long, and by trial and error find which 3MT arbor requires the drawbar to be shortened. If you end up with a thread that is 1 -2 mm shorter than the shortest arbor needs, you should be OK.

Howard

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