Adjustable Bit

[Tellurian]

Hi,
I have a couple of adjustable bits but this one seems to have something missing.
Does anyone know what the piece that is missing looks like? If possible I'd like to make a replacement but I need to know what to make.

Just noticed that the underside of the sliding part is toothed so might not be something I can do.

Many thanks.

 

[Trevanion]

The serrated edge and round-ish hole would suggest a screw adjuster of some kind, but I've not seen an expansive bit like that before.

It probably wouldn't be tricky at all to produce a replacement part.

 

[Tellurian]

I was just thinking that I could use a screw or bolt. There's a ridge in the middle that I assume holds the missing part and then rotating it would move the adjustable cutter. So the required notch would be needed.
It looks like the hole?for the bolt is 5/16" but trying such a bolt and the thread won't engage with the seated part. I'm assuming it's imperial so could it be a different type of thread not BSW

 

[AndyT]

I agree with your deduction, but I expect if anyone on here knows for sure it would be @Boringgeoff .
I suggest you wait and see if he replies.

 

[AndyP]

I feel sure I have seen something like that in it’s own wooden box in my father’s old workshop. Would have been my grandfather’s. I’ll get my brother to have a rummage around tomorrow and see if he can find it.

 

[Bod1]

Wait till the car-boot season, shouldn't be difficult to find another complete one.

Bod

 

[Tellurian]

Thanks all. I did find it in a car boot. It came in a wooden box along with a second one which has come in handy a couple of times.
I will probably keep an eye out for another but I like the challenge of getting this one working again, especially if it's a bit rare.
BTW, I think it was made by C. E. Jennings ain't would be interesting to see if it's the same AndyP.
I've had a look through eBay but not found another yet.

 

[AndyT]

Knowing the name makes the quest easier!





From https://archive.org/details/CEJenningsArrowHeadBits/mode/1up

 

[Tellurian]

That's awesome. Many thanks @AndyT
So, now I need to work out the thread.
Ooh, just remembered, I have a thread guage somewhere, I shall have to find it.

 

[AndyT]

Assuming the very reasonably priced original spares aren't available these days , could you count how many teeth per inch there are on the toothed edge?
UNC and Whitworth threads are very similar at these sizes, and if the makers used a standard size, a UK Whitworth bolt could probably be adapted to fit, with just some careful filing.

5/16", which you say is close, has 18 tpi.
1/4" has 20, 3/8" has 16.

There are also fine versions of both of these, and of course, someone with a lathe and an interest in old tools could always make you a special...

 

[Trevanion]

Very cool! I'm not sure if I would want to bore a 3" hole with one though, you'd soon be getting arms like Popeye.

 

[Dr.Al]

I'm pretty sure I've got one of those (but with a smooth shank rather than one that goes in a brace) in the random drill bits drawer in the garage. I think I've used it exactly once!

 

[AndyP]

Sorry to get your hopes up. This is the one I remembered, a Millers Falls no 47 with a much more basic adjustment mechansim

 

[AJB Temple]

Oddly enough I have one of those as well. They are quite a pain to use as they are sloooooow. Hence it has sat in a drawer for a couple of decades, staring up at me.

 

[Tellurian]

No worries @AndyP, thanks for looking anyway.
I've just managed to find two of the patents: McElney's and Jennings. Not much help unfortunately.

 

[Tellurian]

I have used the working one that came in the box twice now. Once to cut a hole for a new lock on my workshop door and now to create the right size hole for a guide scope camera in some protective foam.

 

[Tellurian]

I managed to find the thread guage and an chuffed that I have needed to finally use it.
Definitely a 3/8" bolt with 16tpi.
Off to eBay for a bolt now.

 

[Boringgeoff]

It looks like you've got it all sorted, so the only thing I can add is that I think the patent for this bit is probably William Steers' 1884 https://patentimages.storage.googleapis.com/6b/82/61/f6b91db1e590aa/US296242.pdf
Cheers,
Geoff.

 

[Tellurian]

Thanks Geoff, I couldn't find that patent when I looked, only the two later ones.

Anyway, it turned out that it isn't a 3/8" 16 tpi but 5/16" 16 tpi. I wish I'd discovered that before I ordered from eBay.
I thought that as it's not a standard BSW thread that I might have some problems getting one. So, I have 3D printed one.
I few prototypes and I have it working again.
Seems to be okay so far. I shall have to try a hole and see how it holds up.

 

[AndyT]

Blimey! Ancient and modern working together. Well done!

 

[Tellurian]

Thanks Andy.
Wasn't quite straightforward and took some trial and error to get the sizing right. Then the part wasn't strong enough for the slotted end and broke when I put torque on it with the screwdriver. My solution was to create a very short and deep slot that fitted a small screwdriver. That seems to work so far.

 

[AndyP]

Good to see you found a solution. 3D printers are fast becoming a necessity in any discerning workshop .

 

[Tellurian]

Well it works. 1 3/4" hole. Surprisingly easy but I wouldn't want to have to do too many of them.