Thread: I need your help with a gear knob.

Hi Avery, I have moved your thread to CASTING & STABILISATION as you'll get the best help here, as there is some very knowledgeable casting guys here

Originally Posted by DJ's Timber

Hi Avery, I have moved your thread to CASTING & STABILISATION as you'll get the best help here, as there is some very knowledgeable casting guys here

Thank you for your attention DJ.

It always amazes me on the Woodwork Forums that there are Mods like you that so well monitor what goes on and do your best to fix the stuff ups of punters like me. But then, I guess you have to justify the massive moneys that you get payed for it

Sorry DJ , next time I'll look harder to find the appropriate forum.

I'd turn a the burl to a cylinder that fits inside a PVC tube. Glue the emblem on top at one end, then use some hot melt glue to glue wood into the pVC tube, so the emblem is in the middle of the pVC. Then cast using clear casting resin, enough for the dome, plus a decent tennon. Once set, turn between centres and turn off PVC and form a tennon on the resin end. At the other end, drill a hole the inside dia of a suitable threaded nut. Turn your final sphere shape. Carve out corners of hole to form a hex recess and epoxy in the nut. Use another nut on the threaded shaft that will lock on the sphere with epoxied nut.

Heads up - ensure emblem is totally clean and free of anything that may make it debond. I'd suggest cleaning with spirits, then use a seal coat of water based clear spray sealer, and then leave for 24 hours to ensure no vapours. Before gluing into tube, coat by painting with wet casting resin.

You can buy clear casting resin from your local hardware.

Hope this makes sense.

Cheers

Thinking about it a bit more, you could glue in the nut first, then use a threaded shaft (eg cut off bolt) in the nut as a tennon you hold in a chuck to turn it. You could rough it down to shape first on a disc sander to ensure you don't get any chip out of the resin component.

Originally Posted by dai sensei

I'd turn a the burl to a cylinder that fits inside a PVC tube. Glue the emblem on top at one end, then use some hot melt glue to glue wood into the pVC tube, so the emblem is in the middle of the pVC. Then cast using clear casting resin, enough for the dome, plus a decent tennon. Once set, turn between centres and turn off PVC and form a tennon on the resin end. At the other end, drill a hole the inside dia of a suitable threaded nut. Turn your final sphere shape. Carve out corners of hole to form a hex recess and epoxy in the nut. Use another nut on the threaded shaft that will lock on the sphere with epoxied nut.

Heads up - ensure emblem is totally clean and free of anything that may make it debond. I'd suggest cleaning with spirits, then use a seal coat of water based clear spray sealer, and then leave for 24 hours to ensure no vapours. Before gluing into tube, coat by painting with wet casting resin.

You can buy clear casting resin from your local hardware.

Hope this makes sense.

Cheers

Thank you Neil

I think I am pretty much with you in all of this.
I assume that you mean a 50mm PVC pipe, the stuff that you would find under any sink - that is what I had in mind.
I have bought a tin of Diggers Clear Casting Resin and the catalyst - is that the right stuff? How sensitive is this stuff to mixing? it says 1.5 ml to 100ml - i don't know that I can measure 1.5 ml.

Thank you for your "heads up" - the emblem is in 18kt gold so there will be no damage to it by cleaning with spirits , it should come up quite clean.

Do you think that I need to include the brass ferrule on the bottom end. The original 50 year old knob has a steel ferrule and I guess I don't want my new knob splitting - very embarrasing to get a warranty claim sometime in 2052...

Once I have the tenon on the resin end and have mounted it on the lathe and drilled the appropriate hole for the mounting nut, how do I remount it and turn off the dome? I was planning to leave a tenon on the gear stick end,turn off the top of the knob, and then worry about drilling the hole etc. off the lathe - v blocks, drill press etc.


Thanks for your help, I am really sweating over this, I just want it to be really good.

I originally thought it was just a simple wood turning excersise,but now I am panicking about all the other probs.

Originally Posted by dai sensei

Thinking about it a bit more, you could glue in the nut first, then use a threaded shaft (eg cut off bolt) in the nut as a tennon you hold in a chuck to turn it. You could rough it down to shape first on a disc sander to ensure you don't get any chip out of the resin component.

Yep. I thought of that too.

In fact, I think that may well be the best way to do it. I could set the nut into the bottom end (with a ferrule around it perhaps), mount it on a bolt and finish the whole thing to suit.

butI am still not sure of the resin pouring part of this.

G'day Avery, I'm not the expert that Neil is but I count drops of MEKP (catalyst) about 10drops/30ml or 33-35drops/100ml. Good luck with the project. If Neil gives you conflicting advice to me, listen to him and absolutely ignore me.

cheers
undies.

For the catalyst, use a small plastic medicin measure, only 50c at the chemist or a dropper. Yes Diggers is fine.

I wouldn't use a ferrule, there is more strength in burying the nut in the base of the sphere itself.

Gold can be tricker as it is often coated in an oil like coating. So be be careful to clean it thoroughly.

As for the PVC, would 50mm be big enough, you might need something bigger.

All the best. Don't forget the progress photos.

cheers

Thank you very much undies and Neil for your help on this little project.
Without your help Ii probably would not have started this.
Believe me, Ihave along memory and I will get you both

It took me 4 attempts to get it close to acceptable.

The first got junked when I realised that trying to turn the knob with a tenon on the top end was a complete waste of time.

The second went really well. I carved a hole for the nut in the bottom of the knob, epoxied it in, screwed in a long bolt with a lock nut and secured in my chuck, turned it, set the badge in the top and poured in the resin. All was perfect. Sanded, sanded , sanded, finished with a whole bunch of coats of CA, sanded and polished. Brilliant - absolutely fantastic.

What I didn't know was the resin had leaked down from the top into the cavity around the bolt. Locked solid. I could not remove the bolt. The timber ripped apart long before the resin/bolt join gave way.

I had to totally dismember the whole thing and retrieve the badge out of the resin. It took many hours. The resin does soften with acetone, but it is a slow process.

The third attempt was given up when the piece of burl I was using just had too many cracks and holes and was going to fall apart long before I finished.

The fourth attempt worked OK. I am not at all pleased with the result. The shape is not right, the inserted badge does not look right - perhaps a lighter coloured insert behind it would have worked. The finish is OK but not excellent.

I had hoped for better.

I have decide to throw in a Pristina fountain pen turned from the same piece of burl to make the whole gift a little more impressive.


Some photos(mostly really bad) just to prove that it all happened.

The grain looks amazing . Shame about the other tries, but all good learning experience

Yeah, a great learning experience. In a few years when I am asked to do another gear knob I am sure I will do it better.


I did, however, thanks to your help, learn a little about casting resin, and when I go back and read some of your other posts about pen blanks etc. I am amazed.
I need to experiment with this stuff.

The grain in this little bit of eucalypt burl is quite pretty.

I will try and get a couple of photos in some reasonable light tomorrow.

Thanks again for your interest Neil.

Perserverance is definately the key to success , I sometimes do a similar thing with the ball on the end of my pepper grinders ( clear cast some pepper corns into the top ) The casting can definately add more dimensions to your endeavours
Cheers ~ John

Great job with the gear knob and the pen. Persistence won the day. They look great