Re: Advice on small mill table conversion

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <eexgs@...>
wrote:

>
>
> I'm finding myself struggling to make headway on a number of my
> projects at the moment and to help me out I'm knocking up a small
> machine for milling/routing aluminium parts when required. It is
> based on the Proxxon KT150 compound table, this has a table size of
> 8"X8" and a travel of 6"X6" which is big enough for most of the parts
> I require. These include adapter plates, mirror mounts etc etc.
>
> Here are the parts I have got together: the Proxxon table, an Aerotech
> ballscrew slide, A bracket for a Kress router and the router itself.
> I also have a aluminium based plate and a structural aluminium column.
> Things are going quite well, I only started on Monday and now have a
> pretty good idea of how it will go together.
>
> http://www.indoor.flyer.co.uk/kt150mill.jpg
>
> I do however need some advice on the motor mounting and leadscrews.
> The screws are 10mm ACME with a lead of 2mm. They run in brass/bronze
> nuts which are quite loose fitting. The shaft passes through a collar
> before exiting the extrusion to go into the handwheel which is
> attached by rolled pin.
>
> As it stands I am happy with the bed but the screws have far too much
> backlash and the use of washers as bearings is not great either. I
> need to get rid of the backlash and stiffen up the bearing
> arrangement. I'm not sure if the best bet is to replace the screws or
> make new nuts or ebay some ballscrews.
>
> Some pics of the leadscrew arrangement here:
>
> http://www.indoor.flyer.co.uk/leadscrew.jpg
> http://www.indoor.flyer.co.uk/leadscrew2.jpg
>
> Any advice appreciated.
>
> Cheers,
>
> Graham

You need to put thrust washers on the handles to make sure the screw
does not move axially. that is the easy part with your design.

The nuts can be made pretty easily, I think. you did not show the
drawing, but it might be possible to add a second nut, and bolt it to
the first with some tiny screws on the perimiter.

The more you tighten these, the less backlash and the more friction.

Dave

>