Focuser fine focus shaft shim

[RuralBill]

Hi all,

i wanted to ask you ingenious people on here a question

i have fitted a Feathertouch micro touch stepper motor to my newly acquired ZS66, which fits to the fine focus shaft, and after finding out how to eventually remove the coarse focus knob on that side if the scope, it fits a treat, with one small issue, the pinion hear that has to be fitted which comes with the motor, has a bore of 3mm (made for Feathertouch focuser which has 3mm shaft) but my WO has a 2.5 mm shaft, so where or how could I get a shim for the pinion gear to reduce the bore to 2.5mm ??

look forward to any replies

Bill

 

[ChrisLX200]

Better to drill it out to 5 or 6mm and put a reducer in having thicker walls.

ChrisH

[Davey-T]

2.5mm could be a problem, don't think I've seen any reducers smaller than 3mm, you may have to buy a bit of brass tube and split it lengthwise and make your own.

Dave

[RuralBill]

Hmmmm, I did think of that, but if I mess it up I am stumped and I only have the one pinion gear, and can only seem to get new ones from USA..at a high cost...so am a bit reluctant to do that.

i wondered if I could get one made here, but no luck finding a company that will do one.

cheers

Bill

[Davey-T]

5 minutes ago, RuralBill said:

Hmmmm, I did think of that, but if I mess it up I am stumped and I only have the one pinion gear, and can only seem to get new ones from USA..at a high cost...so am a bit reluctant to do that.

i wondered if I could get one made here, but no luck finding a company that will do one.

cheers

Bill

Any local model society near to you ?

Loco builders will have all sorts of thin wall brass tube, someone may be willing to make you one, failing that buy a bit and have a go, you wont have to modify the pinion hopefully.

You could try slicing up a coke can.

Can you post a pic ?

Dave

[Tinker1947]

You could bond it, getting central on the shaft i would cut up a feeler gauge and insert 3 pieces to keep it from moving, this may be a one way trip though it might not want to come off again.....

[RuralBill]

1 hour ago, Davey-T said:

Any local model society near to you ?

Loco builders will have all sorts of thin wall brass tube, someone may be willing to make you one, failing that buy a bit and have a go, you wont have to modify the pinion hopefully.

You could try slicing up a coke can.

Can you post a pic ?

Dave

Here is a pic of the pinion gear in question, I thought I would be able to just buy a new one, but can't find one the right size anywhere, it has an unusual overall diameter of 12.75mm

 

[RuralBill]

1 hour ago, Tinker1947 said:

You could bond it, getting central on the shaft i would cut up a feeler gauge and insert 3 pieces to keep it from moving, this may be a one way trip though it might not want to come off again.....

I though about this idea also, using 2 part epoxy, but it would be pretty permanent, although I re shafted my golf clubs last year, and to get the old shafts out all I had to do was heat them up with a hot air gun, this softened the epoxy so they can be pulled, so maybe not so permanent......?

cheers

Bill

[Davey-T]

I doubt if you could find one with 2.5mm bore, you could try filling the hole with Araldite and drilling it out but the layer left may be too thin and just crumble, probably possible to cut a piece of coke can and roll it up to fit.

Dave

[RuralBill]

This would do the trick, they do a 3mm outer with 2.4mm inner diam, perfect, as I just rechecked the shaft and it shows 2.4 with my caliper.

http://www.ebay.co.uk/itm/Brass-tube-tubes-pipe-for-modelling-in-60-metric-sizes-1-18mm-diam-330mm-long-/162030875927?var=461000547098&hash=item25b9caf517:m:mKZ9GmgXb1IJ1qvHeHSVZgQ

cheers

Bill

[Gina]

Good find

[ChrisLX200]

Feathertouch are Yankie - they don't do Metric ;-) It'll be 3/32" shaft. (and your 'unusual overall diameter of 12.75mm' is actually 1/2" ;-)  )

ChrisH

[Dave In Vermont]

3 hours ago, ChrisLX200 said:

Feathertouch are Yankie - they don't do Metric ;-) It'll be 3/32" shaft. (and your 'unusual overall diameter of 12.75mm' is actually 1/2" ;-)  )

ChrisH

I'd get out the good calipers and measure first to be sure. Americans have a nasty habit of changing the rules in the middle of a game. Especially true when one enters the world of weights & measures.

Dave - the Bicycle-Mechanic

[Peter Drew]

I think concentricity of this component must be important. You would need to be skilled or lucky to drill the bore out to this tolerance, a lathe job would be a better bet.

[RuralBill]

10 hours ago, ChrisLX200 said:

Feathertouch are Yankie - they don't do Metric ;-) It'll be 3/32" shaft. (and your 'unusual overall diameter of 12.75mm' is actually 1/2" ;-)  )

ChrisH

Excellent point, I should have realised that when the shaft came out at 2.43mm.... Another odd size, so if that is actually 3/32" then what would 3mm be ?

thnks for the heads up, all the Astro gear I have that is American is imperial..... 

Cheers

Bill

[RuralBill]

41 minutes ago, Peter Drew said:

I think concentricity of this component must be important. You would need to be skilled or lucky to drill the bore out to this tolerance, a lathe job would be a better bet.

I am not even going to attempt that idea for your exact reason....

cheers

Bill

[RuralBill]

This is now the one I need, with 1/8" outer diam, and 3/32" inner diam..... Around 3.17mm with 2.41 inner bore....

http://www.ebay.co.uk/itm/Brass-Tube-1-16-3-32-1-8-5-32-3-16-7-32-1-4-9-32-5-16-11-32-12-Length-/252351871297?var=551197049605&hash=item3ac157f941:m:mUcJH_hvt0dMu98GLPmJMKg

cheaper too...

cheers

Bill