Cutting Internal threads

Hi All,

Have recently seen an internal thread cutter, which looked like a snail shell as the cutter. To sharpen it is easy as the degree angle is already set so just a matter of facing off.

Can anybody please tell me what they are called and who sells them.

Regards Ponce

Hi Peter

Most I have seen have been home made, a 55 or 60 degree raised shape on the end, a 90 degree segment cut or ground out to provide the cutting edge for threading.

Emgee

I have seen a picture of one on www.practicalmachininst.com but that is all. It is possible to make something similar with a tap if you have one with the correct thread form but wrong diameter. This is a good reason to keep snapped taps. You can grind them back to one or slightly more than one pitch to get full form cutters for internal threads. I have a ground up 1" 8tpi tap that I use for cutting the threads to suit the lathe spindle I have which is 1.75" x 8tpi. I know the helix angle will be slightly wrong but if you raise the tool above centerline slightly it compensates. It is also possible to use it for thread milling if you have access to a CNC mill. If thread milling all other teeth on the tap need removing to just leave the one and a bit for full profile.

P Horn do end mounted inserts for threading with a similar idea to what you are after but they only do metric threads from 1mm pitch upwards as far as I am aware.

Martin

Its a circular chaser,I found some in a box at a second hand tool dealers years ago,they are very good for internal screwcutting in small bores,and lathe backplates.

Ifanger (Swiss). It's a helix of the correct threading profile. There was (is?) an American company with an equivalent design, but I cannot remember the trade name.

Edited By JasonB on 16/12/2015 18:11:43

One of my favourite tools ever bought Martin the PH Horn internal grooving/interpolating milling cutter with interchangeable heads. Not cheap £30-£45 for two tips in a box but do they cut well in a lathe.

Not the one but gives the idea OP was after **LINK**

Usually home made.Glen Bunt's article on clock gear cutters in MEW 235/6 (I think) explains how to make and use them, the principle is the same using them for thread cutting.

Neil

Really a 1950s thing when we made a squillion widgets a year per machine to feed the empire

Have no clue if there's anywhere left that does these things nowadays

I would think it was the Ifanger tools that the OP had seen - or one similar if, as MyrtleLake suggests, someone else makes them. Ifanger make nice cutters, but they're expensive. You can rock up at the factory and buy them, generally cheaper than from your local distributor. But they won't ship them to you if there is a distributor in your country. Well, that was true ten or more years ago, I haven't been to Switzerland for quite a while.

Roger

Edited By Roger Head on 17/12/2015 04:50:54

Ady1

I have one of those pre-insert days external threading tools marked up as Eskilstuna - Sweden. I will upload a photo and post it. The circular die is about Ø42mm so it would be hard to use for any small internal threads if a suitable holder was made. It has a screw at the front for small adjustments to the stick out and the head can be swiveled on the body to allow for different helix angles. As I say it was pre-inserts. I think they have been replaced with throw away inserts now. Reduces the need for someone to sharpen it and then for the tool to be re-set.

Jon

I have a thread milling tool I made with Horn inserts in it. Could be used for internal threads if there is a big enough bore.

You can see it in action here.

**LINK**

Martin

Hi all, during my apprenticeship I did shedloads of large bosses with BSP threads in them for hydraulic tanks, we used Alfred Herbert circular cutters with a 1 inch round shank in a holder specifically for them in the 4 way tool post, have not seen one in years although I do have a holder. Can't even find a picture, but I would suggest that anyone thinking of going down that road, HSS, easy to offhand sharpen, easy to set, could do worse than to use orphan circular dies from BSA / NAMCO dieheads still made in modern times, world probably waist deep in them especially odds & sods. Attach to boring bar along front of toolpost with single screw etc etc. Take side trip to gear cutting section, fill Fairy Liquid bottle with viciously politically incorrect sulphurised cutting oil apply as necessary, wash hands occasionally, get beautiful shiny finish on thread, job done.

Bob.

The OP was asking about internal threads, I have some cutters, look a bit like a boring head tool, they have a disc formed on the end with a segment cut out. The discs have a V profile and spiral form to suit the helix angle of the thread.

Dave

Hi All,

Thanks for all the responses. All are around the mark but not quite there. I may have an opportunity to take a picture of the device and will post it on this thread in the next week or so.

To the novice there a great many tools that have been used over the years mainly before the inserts came on the scene and it is wonderful to be able to talk to or communicate with fitters, toolmakers and the like to discover about these devices.

Thanks all,

Regards Ponce

Even inserts aren't new, first there were tool steel, in the 19th century, then HSS inserts, all that before carbide inserts. In the first year of "The Model Engineer and Amateur Electrician" in 1898 there is a version of the "Diamond Tool Holder".

It's sometimes useful to make a tool holder to take a piece of tool steel/old file to make a special form tool.

Ian S C

I have some by MESA Tools in the US

Same holder holds the insert side, front for external threading and across the rear face for internal threading.

Works well for me.

Edited By John Stevenson on 18/12/2015 10:46:05

Are these the sort of thing the OP had seen.

Bought a load years ago (£5) at a motorcycle auto jumble. Various Whitworth form threads.

Simtek DX - German system, available with threading inserts, available from Cutwel.

This is the one I have seen. More pictures on ym album.

Regards Ponce.

Nice idea. Looks like it could be turned out out of silver steel and hardened. The cutout could maybe be done on the offhand grinder.