M16.1 Tap UPDATE

[Fidget]

Not sure if this is the right place but,

I have a friend who wants to make a new backplate for the underwater housing for his camera

This will be made from 20mm thick Polycarbonate which he has already.

He needs to drill and tap a through hole for a vacuum pump attachment which he already has. This has a 16mm x 1mm thread (not so easy to find!) Any suppliers?

Has anyone done this sort of thing before? Got any hints or tips?


I've got the 15mm drill for the pilot.

 

[Rorschach]

Do you mean 16.1mm or a 16mm x 1mm tap?

 

[Fidget]

16mm x 1mm.

Newbie error, sorry

(OP edited)

 

[marcros]

I wonder whether cutting the thread on a lathe might be easier to sort. how big is the backplate?

 

[Myfordman]

M16 x 1 taps sold by loads of suppliers including ebay. What is the problem?

 

[Fidget]

The backplate is ~200x150x20mm, the hole is off centre... and I don't have a lathe

Yes, there are loads on fleabay. I was just hoping that there was some favoured supplier amongst users like Tuff Saws for blades.

Thanks

 

[Eric The Viking]

Given where you are, I'd seek out a scientific instrument makers near Oxford, or someone who does that for a college who can do a "furriner" for you.

You can tap Perspex/polycarbonate, but it's not quite as easy as metal, because it's "sticky" and tends to grab the tap. For this application you need a well-made thread, something that sort of person would be used to doing. This is a bit more demanding than just tapping for, say, a bracket's mounting screws. And big taps are expensive too - not stumping-up offsets the cost of paying someone to do it.

If you DIY it, it would be well worth practicing on a bit of scrap. There may even be a suitable lubricant which would help.

Out of curiosity, what is the reason for the vacuum pump do (don't say "it removes the air" please!)? Is it something to do with condensation, focus or what?

I have a Nikonos II somewhere in a drawer - the 1960s model before they made them bright orange and looking like SLRs. The lens mount is really clever - not only is it pretty watertight, but it also decouples the lens from the pressure of the water, so the outer casing can compress slightly but focusing remains accurate. It's really ingenious.

I was really lucky in my younger days, as the guys in the BBC Bristol mechanical workshop were (unofficially) allowed to do odd jobs. They made a couple of camera/lens mounts for me (one of which I still use). When they weren't doing furriners, they worked on specialised kit for natural history programmes, etc. ;-)

E.

PS: should it be parallel thread or should it taper?

 

[Rorschach]

Any HSS tap will do the trick, I have yet to come across a poor quality HSS tap, low quality carbone steel are pretty common though. Not cheap though, looks at £15 or more.

 

[Daniel2]

I think carbon steel would be fine for a one off, or occasional use.
Tracy Tools have a good reputation. Their CS 16 x 1 taps are £10.00 each.
You would only need a first (taper) tap for that job.

ATB,
Daniel

 

[Fidget]

Thanks Rorschach

ETV, Funnily enough, my friend is an ex BBC Sound man who's gone over to the dark side (cameras).

If time wasn't an issue, I would try an instrument maker although I have no idea how you 'do a furriner' (can't even find a definition). He needs it for next week

As for the reason for the vacuum, well it removes... This video might explain it better than me.

Thanks Daniel, good info

 

[rxh]

+ 1 for Tracy Tools as as tap supplier.

 

[Inspector]

furriner = foreigner At least that's what I think it means.

I would get a starting tap to cut the thread and follow it with a plug tap or whatever you call the one between start and bottom tap it the thickness exceeds the starting tap to cut the full size thread all the way through. Or turn it around and clean up from the other side. I would also chamfer the hole both sides before tapping and lubricate the thread. Cooking oil will work nicely. Drill the hole with the oil too.

Pete

 

[lurker]

A foreigner was engineering slang for a private (non work) job.
was sort of a perk of the job and some employers turned a blind eye so long as you did not overdo it.
This was when loyalty by both parties was considered a valuable commodity. Died out once the bean counters took over and staff just became a number on a spreadsheet.

 

[Inspector]

I got that wrong eh. Among the people I worked with they were called G jobs or Government jobs. Making stuff for yourself on company time with their equipment and supplies.

 

[Fidget]

Yes, furriner=foreigner. I just didn't understand the context. Makes sense now, thanks Lurker

I see that I've just become an 'Established Member' Ha!

 

[SammyQ]

"Homers"

Sam

 

[Eric The Viking]

Yes to the above, but there was more to it: If permission is given it's evidently not stealing, and in some cases (one particular lens mount in my case, ideas got recycled into stuff made officially in the workshop.

Years earlier, when I worked on a light engineering factory floor, apprentices were encouraged to do furriners* for the experience, in part because the production was repetitive and demanded tight tolerances, so they couldn't learn on the job.

Then again, in Hewlett-Packard, R+D engineers had the 10% rule - Friday afternoons were set aside for them to work on anything they wanted to (even using "labstock" parts and materials). That could be any kind of design/prototyping that wasn't for commercial sale (or competitors!). Bill Hewlett and Dave Packard instigated that (and formalized it), and by the time I started with the company (and it had more than 100,000 salaried staff worldwide), it was very much part of the culture. I remember one mechanical engineer who designed and made an extremely high-end vinyl turntable, others made electronic devices of various sorts.


E.

*You have to imagine a Brummie accent. The original Birmingham factory had recently been moved, complete with staff and machines, to a seaside town in the West Country.

 

[TheTiddles]

A cheap tap held in a pillar drill to keep it square will be fine, don’t need an HSS or anything special hand turn it so if it starts to jamb you can feel it

Aidan

 

[lurker]

"Homers"

Sam

I used to work in nuclear and a homer was something entirely different, due to the well known dillegence for the job as displayed by Mr Simpson.

 

[Fidget]

Update!

Had an interesting and fun day on Saturday sorting this out.

Turns out it was only 12mm thick, not 20mm

We used the original housing back as a template, cut it out roughly on my Startrite bandsaw which was much easier than I thought it would be and then used double sided tape to join the template and the new piece together and used a router with a follow bit to trim it down to size. Then marked, drilled and tapped holes in all the right places! It ended up being much easier than we thought having never machined Polycarbonate before. We ended up making 2 new backs for his camera housing, so he now has 3! There are two holes in the face of the back(!), one for the vacuum attachment and on for a BNC connection. When he got it all home he tested the vacuum over 16hours and it didn't lose pressure. So job well done

He would like to find some new clips for the backs rather than swapping them each time. Does anyone know what these clips are called or a source?

Thanks for all your help.

Pic 2 shows a Nikonos lens on the front for ETV