Small internal threading tool

[DiogenesIIParticipant @diogenesii]

Hi – a quick question.

I need to cut a 10x1mm pitch internal thread so would like a 60* tool that will fit up an 8.5mm (-ish) hole.

I've noted the little sets of pre-ground round-shank HSS for square holders, that come in sizes down to 6 or even 4mm.

Does anyone have these & know what size holes they 'start' from?

[DiogenesIIParticipant @diogenesii]

hss set entry sizes?

[Clive FosterParticipant @clivefoster55965]

DiogenesII

The baby ones I have need a start hole approximately twice the bar diameter. So you are down in the 4 or possibly 5 mm range. A carefully ground from solid special can have a shank of mostly near 6mm diameter. Much stiffer.

Its a long time since I used them. For me mine turned out to be a bit of a white elephant as I've not got on very well with them. Primarily, I think, because they are made with a fixed length round shank each end of the central square section provided to hold them by. Shanks are way too long and too flexi. Should I ever need to use them again the square bit will get turned down pronto and a clamp down holder made so the projection can be set to something more reasonable.

For your job I'd just buy a tap as being far easier.

With 20/20 hindsight getting general purpose tooling for a special job with the intention of using it for other suitable jobs that may arise has, over the years, often proved a fiscal mistake. I have a number of such things which struggled to to the job I got them for and have not, so far, found any other application.

For old farts like me possibly the most significant change in tooling over the years is how much more affordable the proper thing has become in real terms. 40 or 50 years ago buying a tap for one job was impossible extravagance. Now I do it regularly.

Clive

[jimmy bParticipant @jimmyb]

I use solid carbide threading tools, similar to these – **LINK** for small dia internal threading.

Jim

[JasonBModerator @jasonb]

My set of 4mm ones are about 7mm front to back and mine will enter a 8.5mm hole without rubbing. Looks like I may just have ground a little off the underside to get clearance when on ctr height but the top cutting edge/angle is untouched

Edited By JasonB on 25/09/2022 10:22:36

[OldironParticipant @oldiron]

Posted by DiogenesII on 25/09/2022 09:26:44:

Hi – a quick question.

I need to cut a 10x1mm pitch internal thread so would like a 60* tool that will fit up an 8.5mm (-ish) hole.

I've noted the little sets of pre-ground round-shank HSS for square holders, that come in sizes down to 6 or even 4mm.

Does anyone have these & know what size holes they 'start' from?

Hi. Is there a reason not to use a tap for the thread ? Just asking out of interest.

regards

[Neil LickfoldParticipant @neillickfold44316]

Out here, is HSS tools sold under the brand name Ifanger, they make a series that you grind it back, and can keep using the tool for finer pitches as it gets smaller. Not sure on the brand in the UK. Now days there is micro series carbide bars for threading . Typically for M10, the Bar is around 8mm stock and the min bore size is from 6.5mm to 7mm depending on the brand, and will be around 16mm of reach or so. Longer series ones are available. I have not seen carbide ones like the Ifanger ones, sold through

Have a look at this style.

https://tradetools.co.nz/shop/turning/ifanger–external-parting-threading-turning/threading–ifanger-internal/g60-00-a-cobalt-ifanger-internal-thread-cutting-tool-65mm-min-bore

I have made some offset holders to make tools from 6mm and 8mm shank tools. But the tools I make do not have the helical lead on the from , like the Ifanger tools do.

The advantage of starting a thread by screw cutting, even if it is only to say 9.8mm of the 10 mm diameter, leaves less for the tap to cut and you get a more concentric thread , compared to just tapping it. Another idea that works is using a leading or 1st taper tap, and grind a front guide diameter that follows the hole. I do that on things that need the thread concentric, but can not get down a hole to guide it etc. It all depends on the level of concentricity required. An example is the push pull head inserts for model diesel engines. The contra piston thread is made concentric to the insert, and the nut is screw cut on the inner and the outside. The outside is done with a full form insert, and the inner is thread cut and then a tap run through for the finial sizing. The head is screw cut and the outer thread of the nut is the gauge for the head thread.

In my album is a very small threader that I have made for a difficult to make M5X0.5 pitch thread that is inside a cone. Just to show what can be made.

Neil

[DiogenesIIParticipant @diogenesii]

Many thanks – I have all I wished for and more, there; I'm grateful for the extra thoughts & specific suggestions..

I'm making a backstop to go through the mandrel and have a piece of nominal 10x1mm studding which is perfectly even and nicely formed, but down on major dia. (- it's at 9.37) – bit too small for comfort, especially as I suspect the pitch dia. is under ( – the crests don't look truncated) and as a feedscrew, I want it to have a positive 'feel' and not be a rattle fit.

If it had been a simple fixing, or the studding had been half a mil. fatter, I'd have tapped it.

 

Edited By DiogenesII on 25/09/2022 11:59:46

Edited By DiogenesII on 25/09/2022 12:00:29

[TerrydParticipant @terryd72465]

Hi,

M10 x 1 are available on Tracy tools for £5 – cheaper than set of boring bars for a one off, then sell it on here or eBay.

https://www.tracytools.com/taps-and-dies/metric-taps-dies/10-x-1-metric-sp-plug

or a taper and plug set for £3.95 on eBay

https://www.ebay.co.uk/itm/134100258609?hash=item1f38ff8f31:g:iWEAAOSw0StiapuS&amdata=enc%3AAQAHAAAA4MxpxOH67cqtP9YVZgNFhYPWb0ywTrvErlmSJbx%2Bct6j6FSUuVtbTWMESKNZUZYCF7QTYFEvgBPAhOel8H8rpQyM%2F11LrXFRg%2BI4r6nS%2BZ8heol2XM9NgRm8MGWqqVjkeim60uw%2B6hrGTE%2FZEDPrVmJm9jTjSEfESli7C%2Fkxo2DC6crYEDyRWmX8US041MrQ1vqxeQN%2BtPH7lQculXqoYaB%2BuT8%2F1tA3Ms%2B11K50R5Xc0c2QXGpX68Xq16D1yJAPSCSDpo61S3cUTzn6R6OAjcNksT0trFo%2BIP8UWlltvwFR%7Ctkp%3ABFBMgq-0xe5g

Regards

TerryD

[Paul LousickParticipant @paullousick59116]

An option is to use a tap to make the threaded hole and if the studding is a loose fit make another using a split type die that you can adjust for diameter. Easier than trying to bore/turn an undersize hole.

A tap can also be used as a boring bar/cutter to make a larger diameter hole than the tap size . (Use an M8x1 tap or grind off the opposite side of the tap to bore a slightly smaller internal threaded hole)

https://youtu.be/f-YWsgAHR6A  (video starts at 6:22)

Edited By Paul Lousick on 25/09/2022 13:09:21

[JasonBModerator @jasonb]

You could probably also do it with a M6 x 1 tap held in the tpplpost, no need to grind off any teeth., I've done similar a few times with ME threads where I don't have the right dia/pitch combination

[not done it yetParticipant @notdoneityet]

Posted by Paul Lousick on 25/09/2022 13:05:13:

An option is to use a tap to make the threaded hole and if the studding is a loose fit make another using a split type die that you can adjust for diameter. Easier than trying to bore/turn an undersize hole.

A tap can also be used as a boring bar/cutter to make a larger diameter hole than the tap size . (Use an M8x1 tap or grind off the opposite side of the tap to bore a slightly smaller internal threaded hole)

https://youtu.be/f-YWsgAHR6A (video starts at 6:22)

Edited By Paul Lousick on 25/09/2022 13:09:21

As per Paul, but I think I may cut a matching thread on a piece of known, better quality of bar, if needed as a feedscrew.

[Sam Longley 1Participant @samlongley1]

I might be right off track here BUT:_

Do they not make sets of a certain type of tap that work by increasing the size of tap? So the first one might be less than 10mm The next a bit nearer & the third one might be the recognised size.

If you want to have a tight fit you would only use the first couple of taps & omit the final one

Does that make sense?

Edited By Sam Longley 1 on 25/09/2022 13:28:14

[Andrew TinsleyParticipant @andrewtinsley63637]

Hi Sam,

You are correct. Arc used to sell them, not sure if they still do.

Andrew.

[martin haysomParticipant @martinhaysom48469]

Posted by DiogenesII on 25/09/2022 11:58:32:

Many thanks – I have all I wished for and more, there; I'm grateful for the extra thoughts & specific suggestions..

I'm making a backstop to go through the mandrel and have a piece of nominal 10x1mm studding which is perfectly even and nicely formed, but down on major dia. (- it's at 9.37) – bit too small for comfort, especially as I suspect the pitch dia. is under ( – the crests don't look truncated) and as a feedscrew, I want it to have a positive 'feel' and not be a rattle fit.

If it had been a simple fixing, or the studding had been half a mil. fatter, I'd have tapped it.

Edited By DiogenesII on 25/09/2022 11:59:46

Edited By DiogenesII on 25/09/2022 12:00:29

at the risk of upsetting anyone. is it 10mm, looks more like 3/8" to me

[Clive FosterParticipant @clivefoster55965]

Sam

You are thinking of serial tap sets. Usually two or three in a set. Specifically intended for harder and more obdurate materials because the first, and second if its a set of three, don't cut full depth reducing the cutting force and chance of breaking. Typically the first tap in a set of three cuts 1/3 rd of thread depth, second tap cuts to 2/3 rds depth and the third one finishes it to size. In two tap sets the first tap goes to half thread depth.

Generally I buy serial form sets these days when I want hand taps. Its arguable that spiral point machine taps could be a better bet for general purposes. Serial taps can have issues with gummy materials and don't do well with plastics where threads almost invariably come out undersize.

In M10 x 1 the serial set is commonly two taps so just using the first may well be too small for DiogenesII. I've used the first two of a set of three to get a tight thread with every success. Maybe M8 x 1.

M10 x 1 serial sets are about £27 on E-Bay from DavetheTools (who I buy from) and Rotagrip. Good quality Volkel brand.

DiogenesII

Jasons boring bar / threading set is infinitely better than the one I bought 40 odd years ago. Mine actually take teeny-tiny round bits which, in retrospect, is probably not a terribly sound design.

If you get Jasons set you will almost certainly have to grind the bottom for clearance. Best to spend some quality CAD time drawing the tool shape inside a circle to figure out the amount and angles needed to get clearance. The amount of material needing to be removed can be surprising. There is a sketch in my album showing how to go about this but the samples don't go small enough for you. When working by eye prior to doing the drawings I consistently failed to remove enough material at the bottom of the heel and, usually, a bit too much from under the front.

If you grind your own the neck of the shank can be sort of offset oval in shape taken out of a significantly larger diameter shank rather than simply round which usefully increases stiffness in these small sizes. Naturally the maximum longitudinal depth that can be cut is pre-determined by how long a neck you grind. The style Jason has with a longer, constant diameter shank is much more versatile but less stiff. Obviously you set up with the absolute minimum stick out.

Clive

[DiogenesIIParticipant @diogenesii]

A great response; Thanks all for taking the trouble.

Paul & Jason, it had already crossed my mind to introduce a 1mm-pitch tap to my angle-grinder, of course as pointed out this isn't necessary, so 'trialling' a tap in the toolpost is what is going to happen first.

The threads on the bought-in bar are perfectly formed, even, and clean – only undersize – if I can cut the female side to suit, it'll be a bit of work and extra orders saved.

(Martin, like you I suspect it's been turned on 3/8 stock, saving pennies off their material costs or using up some leftovers).

Thanks for the serial tap suggestions, and also for the 'new-screw' idea – I'll try to avoid ordering extra stuff in if I can, likewise, if I can expedite the job without having to set up to make a new screw I will try and do that first.

Clive, thanks once again – your drawing is useful and somewhere I have GHT's thoughts on small boring tools – a combination of both will see me right, I think.

I'll let you know what happens..

[DiogenesIIParticipant @diogenesii]

JasonB

Found a 7×1 tap (unused since 198?) in a box, clamped it in a toolholder, eyeballed a likely-looking approach for the cutting-edge to the (brass) work, ran it in by hand to test – think it went in 5 passes in the end..

Thanks all for your help & suggestions

[Author]

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