Biax replacement Stroke Adjustment Screw

[mooserov]

Bought a 7EL off the 'bay and it worked fine for about 20 minutes or so. it locked up and sheared the teeth off the helical gear, Yay! Did some inspection and found that the adjustment screw for stroke length had lost it's castle nut, allowing the screw to back out and bind.
broken screw end in the attached photo where the castle nut has departed.
Does anyone know of a source for a replacement? Anyone have an extra they wouldn't mind parting with?
I can probably make one at work, but it looks like a tiny acme thread, and metric. Anyone have the specs on the thread so I can buy a tap?

I have a replacement phenolic gear on the way but can't find anything about the screw. Part 48 in the snip provided sourced from Vintage Machinery manual (german).
Part 203 001 255
Cheers!

 

[Bakafish]

Finding someone with a spare bolt is really a long shot, so you should be preparing yourself to make one. Metric Acme style threads are typically called Trapezoidal "Tr" threads and you should be able to get a die to cut your own. I've seen people modify standard metric threads of the same pitch to fit in Trapezoidal, but I couldn't comment on how effective that might be. From memory, the bolt has a couple of shoulders on each end to keep it aligned in the wobbler housing, you can hopefully pull all those dimensions off of your broken bolt. Lastly, it may be possible to bore the broken bolt and tap it, and use a small loctite fastened M2 or M3 screw to keep it in place. Keep in mind the adjustment tension needs to be pretty high otherwise the adjustment will loosen when using it.

 

[TGTool]

You should probably also check with Ed Dyjak as Rich King often recommends. He has some used replacement parts I expect from basket cases and that's a part that doesn't usually break or wear so should be available.

 

[Richard King]

You should probably also check with Ed Dyjak as Rich King often recommends. He has some used replacement parts I expect from basket cases and that's a part that doesn't usually break or wear so should be available.

He is listed on Google - I have an appointment and no time to look it up now. ES Dyjak in Milford MI. It says he is closed, but he is open. If he doesn't have one I know some guys in Austria with a trove of old BIAX parts

 

[mooserov]

He is listed on Google - I have an appointment and no time to look it up now. ES Dyjak in Milford MI. It says he is closed, but he is open. If he doesn't have one I know some guys in Austria with a trove of old BIAX parts

left a voicemail for him.

 

[mooserov]

Ed is helping me out. Thanks for the help tgtool and Richard!
Already got the fiber gear from ebay.

 

[Peter.]

Glad you got sorted out but for the benefit of future visitors, that adjuster bolt is a more or les standard M8 socket cap with a short plain shank under the socket head, and the end turned down and threaded M6 then cross-drilled for a M6 castle nut. Easily manufctured by any semi-competent person with a lathe and metric die.
When you fit it, make sure you don't fold the split pin over the end of the bolt - go around the nut. It will probably foul the housing otherwise.

 

[mooserov]

Glad you got sorted out but for the benefit of future visitors, that adjuster bolt is a more or les standard M8 socket cap with a short plain shank under the socket head, and the end turned down and threaded M6 then cross-drilled for a M6 castle nut. Easily manufctured by any semi-competent person with a lathe and metric die.
When you fit it, make sure you don't fold the split pin over the end of the bolt - go around the nut. It will probably foul the housing otherwise.

Ed warned me that there may not be a hole for the pin, or castellations in the nut. Biax parts QC is iffy.
what stopped me from making one is I don't have the ability to grind a trapezoidal threading tool to make the thread. pictured is the bolt, minus the threads where the castle nut goes.

 

[Peter.]

I will go back and check one here but I'm fairly certain it's nothing more than a close-fitting vee thread. I never bothered to check it against a standard nut but even in your pic with a scale alongside it is apparently 1.25mm pitch which is standard for M8.

 

[Bakafish]

M and Tr (Trapezoidal Metric) can share the same pitch, just the thread profile is different. As I mentioned earlier in the thread they are similar enough that either running a normal tap through the nut, or filing the tips off a metric bolt is all you would likely need to do to make it work with standard metric hardware. That adjustment isn't something that you have to do often enough that it needs a perfect fit, and I found that it needs to be stiff turning anyway. That said, I still think tapping the end of the broken bolt for an M3 screw is the least destructive and easiest way to fix the original hardware.

 

[Hobby Shop]

Do you know anyone with a shadow graph? It wouldn’t take more than 5min to get all the critical information to remake that screw.

 

[Richard King]

Ed is helping me out. Thanks for the help tgtool and Richard!
Already got the fiber gear from ebay.

Tell us what is happening. Did Ed have some old parts (screw and nut) he sent you

 

[mooserov]

sorry for ghosting the thread, I'm at work (boat in the middle of the pacific). Ed gave me a price and is ordering the bolt/nut as well as a strap for me. He is going to invoice me before shipping and I told him there is no rush as I'm overseas for 60 days. I was planning on updating once I got back and received the parts.
Cheers