Someone else has a mystery object

Browsing the Jurassic Tools shop … I spotted this:

**LINK**

https://www.jurassictools.com/product/serrated-cutter-90-degrees-x-0-030-inch-pitch-thread-mill/

… any ideas ?

MichaelG.

Am I missing the point ? It's a thread milling tap. Although the tap has a pitch, there is no lead which you would find on a conventional tap. I assume the description of 90 degrees indicates 4 flutes ??

Thread milling

https://www.haascnc.com/haas-tooling/threading/thread_mills.html?utm_source=google&utm_medium=ad&utm_campaign=Europe&utm_term=english&utm_content=English_Tooling_Categories&gclid=CjwKCAiA5Y6eBhAbEiwA_2ZWIYElbZ3D0HhIe8QIL3w8MjRWetCAajIkIbJiVn1q4mG-WNejA98gNBoCSpEQAvD_BwE

If it is a thread mill then quite unusual not to state the thread form and I've not seem them with the square end for a tap wrench and as there is not helix to a thread mill the square would not be of any use if being held in ER tapping collets.

.

I have no idea whether you are missing the point … I just noticed that a very experienced dealer doesn’t know exactly what it is.

… and crucially … it appears that 90° is the thread-form [if that’s the right term for something with no helix]

MichaelG.

Edited By Michael Gilligan on 15/01/2023 12:12:00

I think it is just one of those wood drill and router bits where they set the machine wrong and forgot the drill part and the square on the shank is just because all their blanks are pre-formed like that whatever the use, or to help register it during manufacture.

Given that it seems a bit pricey. A whole pack are that price from Lidl.

Edited By Bazyle on 15/01/2023 14:31:23

It is just a tap, it has the square machined on the top indicating that it can be hand used in a tap wrench. The sizes are a bit obscure and may have been read upside down by somebody employed to enter listings rather than someone with engineering experience.

Phil

Bit of a mystery, the "thread" angle is clearly 90 degrees rather than the common 60 or 55. The square shank is also strange. I would very much like to get hold of something similar with a 90 degree shape and 1/16", 0.0625" pitch, about 3/4" diameter and with about 3" of usable length.

.

I don’t think so, Phil … There is no helix, so it would’t go anywhere

… and the numbers are visible on the photo

MichaelG.

Edited By Michael Gilligan on 15/01/2023 16:31:11

All I can think of is that it was made to special order by a tap making company and they used a tap blank which already had the square on the end. We have some strange taps at the museum, usually foundin boxes of tools and cutters donated to us. I keep them hidden out of harms way in case somebody uses one by mistake.

So what would happen if you stuck this in a hole and instead of using the thread to pull the tap in (which it won't), you apply a known axial feed rate (linked to rotation) to the tap holder?

The hole could be larger than the "tap size".

Edited By Peter Greene 🇨🇦 on 15/01/2023 20:15:09

.

I think it would act as a rather questionable boring-tool

MichaelG.

Peter that would act like a thread mill as per the description rather than a boring bar though you would also need the motion to be helical not just the cutter rotating on it's own axis, the axial feed rate would be 0.030" per rev and could "thread" a hole of any given diameter to that pitch and form subject to clearances.

Then again it may not be intended to produce a thread. If lowered into the hole and moved in a circular motion while spinning it could be used to cut serrations to the inside of a hole or outside of a part purely to form some type of key or grip.

Though as I said earlier doe snot look as though it is intended to be rotated quickly like a thread mill or any milling cutter

Edited By JasonB on 15/01/2023 20:46:04

The site also sell a 9/16 x 22 Acme tap.

https://www.jurassictools.com/product/bates-9-16-22-acme-tap-acme-9-16-tap/ Acme tap

I'm surprised at such a fine acme thread, since they were used to provide accurate motion with lower friction than vee threads, and easier machining than square threads. 22 tpi doesn't seem a handy pitch for precise movement purposes. The image's resolution is low, however the thread looks to me more like a vee shaped thread.

I wonder if Michael's example was a thread milling cutter ground onto a tap blank? A tap maker would be able to produce such a cutter on a relieving lathe with grinding spindle or a similar grinding machine.

Bill

Perhaps for making thread gauge blades. Niko.