Greetings.
A while ago I bought some horn flares with 1 3/8 inch screw threads. They were cheap and I thought they might come in handy.
Today I bought some cheap piezo drivers (3 different kinds to play with) planning to screw them into the flares and take some measurements to see if they were any good. Party speakers maybe.
Well, the threads are so tight that I could only screw the first one in about half way. The effort required to UNscrew it was so great the body of the piezo driver broke off in my hand. One driver down and a horn flare with half a tweeter jammed permanently into it. Boo.
So I tried a different driver, very carefully, in another horn. Same deal. So I carefully unscrewed it, applied some vaseline and tried again. Went in easily, about half way, then stopped. Very carefully unscrewed it again, with much effort.
I have now tried half a dozen driver / flare combinations, all the same.
There are no obvious defects in the threads of the drivers or the flares.
Can an experienced soul tell me if this is par for the course (plastic driver thread into plastic horn thread) and if so, what's the trick to getting them in and out.
If this is unusual, perhaps someone might suggest a fix.
Perhaps I just bought dud flares, which is pretty sad because I have dozens of them.
Any advice gratefully received.
Thanks,
blakk
A while ago I bought some horn flares with 1 3/8 inch screw threads. They were cheap and I thought they might come in handy.
Today I bought some cheap piezo drivers (3 different kinds to play with) planning to screw them into the flares and take some measurements to see if they were any good. Party speakers maybe.
Well, the threads are so tight that I could only screw the first one in about half way. The effort required to UNscrew it was so great the body of the piezo driver broke off in my hand. One driver down and a horn flare with half a tweeter jammed permanently into it. Boo.
So I tried a different driver, very carefully, in another horn. Same deal. So I carefully unscrewed it, applied some vaseline and tried again. Went in easily, about half way, then stopped. Very carefully unscrewed it again, with much effort.
I have now tried half a dozen driver / flare combinations, all the same.
There are no obvious defects in the threads of the drivers or the flares.
Can an experienced soul tell me if this is par for the course (plastic driver thread into plastic horn thread) and if so, what's the trick to getting them in and out.
If this is unusual, perhaps someone might suggest a fix.
Perhaps I just bought dud flares, which is pretty sad because I have dozens of them.
Any advice gratefully received.
Thanks,
blakk
damn throwbacks
seriously though, i reckon thats your problem as thats how it goes with using for example M3 into a 4/40 thread, it'll go in a bit if you force it, but never all the way and you ruin the thread in the process
seriously though, i reckon thats your problem as thats how it goes with using for example M3 into a 4/40 thread, it'll go in a bit if you force it, but never all the way and you ruin the thread in the process
Uh-oh. In my ignorance I was unaware that there was more than one standard. This would explain my dilemma but surely there aren't multiple TPIs in use in this horn / driver application - that would be completely insane.
Please tell me it isn't so.....
They should be.
Problem is, nobody makes a tap and die in that size in case you wanted to clean up the threads.
Problem is, nobody makes a tap and die in that size in case you wanted to clean up the threads.
Hi, Blakk:
Hmmm, maybe the plastic horn flares were cheap for a reason? If the threads are moulded instead of cut (machined) I could see plastic - or "Resin" as it's fashionably called nowadays by marketing types - shrinkage being the cause of your problem. I got myself a Go/No-Go plug gauge for 1-3/8-18 UNEF threads, and it runs easily into any threaded horn that I've tried it on. I've never come across a tapered variant of that thread, and don't know of any standard to that effect either.
If you can get a couple of threads engagement before it binds, why not just make up a spacer you can drop into the threaded hole, thick enough to let the driver's end face butt up against it before the threads bind up? I've seen cork or rubber washers typically used in that location, or maybe you could find a bit of hard plastic tubing of the right ID/OD and just measure and cut the required length.
Hope this helps!
Wilf
Hmmm, maybe the plastic horn flares were cheap for a reason? If the threads are moulded instead of cut (machined) I could see plastic - or "Resin" as it's fashionably called nowadays by marketing types - shrinkage being the cause of your problem. I got myself a Go/No-Go plug gauge for 1-3/8-18 UNEF threads, and it runs easily into any threaded horn that I've tried it on. I've never come across a tapered variant of that thread, and don't know of any standard to that effect either.
If you can get a couple of threads engagement before it binds, why not just make up a spacer you can drop into the threaded hole, thick enough to let the driver's end face butt up against it before the threads bind up? I've seen cork or rubber washers typically used in that location, or maybe you could find a bit of hard plastic tubing of the right ID/OD and just measure and cut the required length.
Hope this helps!
Wilf
Thanks Wilf, that is an ingenious suggestion! Not sure how it might affect performance though.
454Casull, damn, that was my next idea, buy a tap and die and tidy up the threads that way. Sounds like that's out, although I might try some machinery suppliers just on the off chance.
I am thinking of buying some new flares and making an outdoor water scuplture out of these....
Waddya think?
Cherrs
el Blakko
454Casull, damn, that was my next idea, buy a tap and die and tidy up the threads that way. Sounds like that's out, although I might try some machinery suppliers just on the off chance.
I am thinking of buying some new flares and making an outdoor water scuplture out of these....
Waddya think?
Cherrs
el Blakko
I ran into a similar problem. I designed my own adapter in Fusion 360 - using the built in 1 3/8-18 UNEF thread tool. Some compression drivers are screwing in fine, an opposite adapter made from Aluminium goes in with a little effort and an EV DH-3 would strip its thread in it. Another factory plastic adapter screws on fine on all the drivers. A horn, that went with the driver that went fine into the 3D printed adapter does not fit on the DH-3.
Are there any different standards or is that a tolerance issue?
Are there any different standards or is that a tolerance issue?
I found about the thread classes. The original was printed with 3B and now I will try one with 2B, which should be a bit more loose if I understand it correctly.
Look up thread chaser.
Mount the part with external thread between centres, rotate by hand and clean/reduce diameter of the threads.
You may be able to knock up a Heath Robinson contraption to do this.
Mount the part with external thread between centres, rotate by hand and clean/reduce diameter of the threads.
You may be able to knock up a Heath Robinson contraption to do this.
I think this would be quite expensive - not mentioning the shipping costs. I am going to Hull next week. Can one buy things like this in a shop there?
18 tpi is not a common pitch in the UK. Note that SAE threads (as metric) have 60deg angle while Whitworth form is 57deg.
Having just looked up compression drivers, I guess the horn has the female thread and it would be the horn you wished to correct.
A tap that size is horrendously expensive.
Unless you have a friend with a screw-cutting lathe you may be stuck.
The bodgit alternative is to drill out/grind the threads off the least valuable part to create a push fit and glue the horn & driver together.
Having just looked up compression drivers, I guess the horn has the female thread and it would be the horn you wished to correct.
A tap that size is horrendously expensive.
Unless you have a friend with a screw-cutting lathe you may be stuck.
The bodgit alternative is to drill out/grind the threads off the least valuable part to create a push fit and glue the horn & driver together.
I can print any thread on a 3D printer - I am designing a small adapter for myself and I just need to make the model right. I have a horn that fits both types of drivers - but I am definitely not able to measure it - but if I had the correct dimensions, the thread would be relatively easy to model.
So the second print with 2B class is even worse🙂 Could be also some printing issues. It still fits one group of the drivers, but while I could force the aluminium adaptor into the first print, it does not fit the new one. I tried to check splicing the thread with the specified diameters - the inner diameter definitely fits the standard and the outer diameter still leaves enough clearance. I will try to measure the threads with calipers, what the difference could be.