Ideas to remove metal before using cutter

[Martin KyteParticipant @martinkyte99762]

Posted by Chris TickTock on 25/08/2020 10:16:18:

Thanks for all posts, points I have picked up on are;

If using Silver steel anneal it first to be sure it is at its softest.

If you have as I do a rotary table you can run more passes at a slightly different angle.

Do not use abrasives on machine (My comment: but if you do use a cloth to protect ingress)

Because the final cutter is machined HSS is not to my knowledge normally used to make the fly cutter. However I am minded to attempt cutting HSS as Jason says using initially the grinder and then my new bench sander where I have more control. How easy it is to get such a small cutter by hand will be interesting to find out. This HSS cutter in theory should cut a chamfer and be easily modified / sharpened for another pinion.

I would also add I am keeping in mind the use of EN8 to use which is I believe machinable and can be through hardened.

Chris

The suggested steel for clock pinions if you do not wish to use siver Steel is EN24T which is supplied in a tempered condition and is specifically intended for gears.

With regard to your original question. Fly cutting pinions is difficult with pinions in steel due to the need to reduce cutting speed which creates issues with feed rates for single point cutters. Thorntons cutters are recommended to be run at less than 500 RPM Max. which for a 12 point cutter means each edge meets the work 100 times per second.

With a single point cutter this drops to just around 8.3 times per second and to keep the tip loading and surface finish the same the feed rate needs to be 12 time slower which if you are hand feeding is going to be problematical even if you manage to create a fly cutter of the same quality and edge as a Thorntons cutter.

My advice is to bite the bullet and invest in a proper pinion cutter.

regards Martin

[Nigel McBurney 1Participant @nigelmcburney1]

I found that EN8 can be toughened using big calor blowtorch and then queching,snag is that it also shrinks,

[Chris TickTockParticipant @christicktock]

Posted by Nigel McBurney 1 on 25/08/2020 14:05:52:

I found that EN8 can be toughened using big calor blowtorch and then queching,snag is that it also shrinks,

Nigel,

This came as news to me. But after having a quick look it appears you are right that heat treating steel (and other metals) can indeed cause dimensional changes. However I would need to know if the changes are of such a scale to cause ilikely issues.

Thank you for posting this as I need to be aware.

Chris

[John HaineParticipant @johnhaine32865]

At the size and tolerances involved in clockwork it is quite irrelevant I think.

[Thor 🇳🇴Participant @thor]

Posted by Baz on 25/08/2020 12:47:59:

S.O.D. Can you please supply details for a high carbon steel, unalloyed, just plain high carbon steel, what EN number etc as I could do with some and don’t know a stockist.

Edited By Baz on 25/08/2020 13:10:04

Hi Baz,

There are a few explanations on M-Machine's website that you may find useful. They can supply several EN steel grades, Silver Steel and Gauge Plate. Here's another supplier of tool steel.

Thor

[SillyOldDufferModerator @sillyoldduffer]

Posted by Thor on 26/08/2020 07:50:33:

Posted by Baz on 25/08/2020 12:47:59:

S.O.D. Can you please supply details for a high carbon steel, unalloyed, just plain high carbon steel, what EN number etc as I could do with some and don’t know a stockist.

Edited By Baz on 25/08/2020 13:10:04

Hi Baz,

There are a few explanations on M-Machine's website that you may find useful. They can supply several EN steel grades, Silver Steel and Gauge Plate. Here's another supplier of tool steel.

Thor

Building on Thor's answer, in the UK it appears plain carbon and high carbon steels are usually catalogued by purpose. To find a high carbon steel look for Piano Wire, Spring Steel, and Tool Steel, then confirm the absence of elements.

EN43 is a possibility, and the CS range look a safe bet, I see M-Machine sell CS75. The American SAE system makes it easier to find candidates. The range 1070 to 1095 contain increasing amounts of Carbon. None are completely plain carbon steels because they all contain some Manganese, but less than 1%.

This extract from **LINK** may help:

Carbon Steels for Heat Treatment
Euronorm	France	Germany	UK	USA
EN 10132 – 4	NFA 37-502/4	DIN 17222	BS 1449	SAE
C50E	XC50	CK 50	CS50	SAE1050
C67S	XC68	CK67/C67	CS70	SAE 1070
C75S	XC75	CK75/C75	CS70	SAE 1074
C85S	XC90	CK85	CS80	SAE 1084
C100S	XC100	CK101	CS95	SAE 1095

Just for extra confusion, not listed under Plain Steel, High Carbon Steel, Spring Steel or Tool Steel, but 'Carbon Steels for Heat Treatment'. Why is nothing ever easy?

Dave

[Chris TickTockParticipant @christicktock]

Posted by Martin Kyte on 25/08/2020 13:34:31:

Posted by Chris TickTock on 25/08/2020 10:16:18:

Thanks for all posts, points I have picked up on are;

If using Silver steel anneal it first to be sure it is at its softest.

If you have as I do a rotary table you can run more passes at a slightly different angle.

Do not use abrasives on machine (My comment: but if you do use a cloth to protect ingress)

 

Because the final cutter is machined HSS is not to my knowledge normally used to make the fly cutter. However I am minded to attempt cutting HSS as Jason says using initially the grinder and then my new bench sander where I have more control. How easy it is to get such a small cutter by hand will be interesting to find out. This HSS cutter in theory should cut a chamfer and be easily modified / sharpened for another pinion.

I would also add I am keeping in mind the use of EN8 to use which is I believe machinable and can be through hardened.

Chris

The suggested steel for clock pinions if you do not wish to use siver Steel is EN24T which is supplied in a tempered condition and is specifically intended for gears.

With regard to your original question. Fly cutting pinions is difficult with pinions in steel due to the need to reduce cutting speed which creates issues with feed rates for single point cutters. Thorntons cutters are recommended to be run at less than 500 RPM Max. which for a 12 point cutter means each edge meets the work 100 times per second.

With a single point cutter this drops to just around 8.3 times per second and to keep the tip loading and surface finish the same the feed rate needs to be 12 time slower which if you are hand feeding is going to be problematical even if you manage to create a fly cutter of the same quality and edge as a Thorntons cutter.

My advice is to bite the bullet and invest in a proper pinion cutter.

regards Martin

Martin,

My understanding is the rpm recommended is for each individual cutter on the commercial cutter. Whilst it is obviously the case for commercial production a commercial cutter would be more durable and cost effective this does not apply for a man in the shed replicating a single wheel or pinion. A fly cutter is made easily given practice, is cheap as chips to make and is sharpened each time before use so a better result can often be achieved.

Moving on to the choice of metal if not using silver steel. This is a bit more confusing for me so maybe others can chip in. i note Cousins and John Wardle sell pinions made from EN8/EN8DM. Maybe they come from the same supplier, maybe they are trying to replicate age characteristics?

Could anyone compare EN8 to EN24T in terms of using it on a small lathe for making a pinion with a fly cutter?

Chris

Edited By Chris TickTock on 26/08/2020 10:38:23

[BazParticipant @baz89810]

Chris, I think you are overthinking all of this, if the commercial suppliers are using EN8 surely that is good enough for you to use, regarding cutters why don’t you make your own multi tooth cutter, details are in the last couple of model engineers. I really think you should join a horological club or forum and ask people on there what they actually use and how they do the job.

[Martin KyteParticipant @martinkyte99762]

Posted by Chris TickTock on 26/08/2020 10:36:46:

Posted by Martin Kyte on 25/08/2020 13:34:31:

Posted by Chris TickTock on 25/08/2020 10:16:18:

Thanks for all posts, points I have picked up on are;

If using Silver steel anneal it first to be sure it is at its softest.

If you have as I do a rotary table you can run more passes at a slightly different angle.

Do not use abrasives on machine (My comment: but if you do use a cloth to protect ingress)

 

Because the final cutter is machined HSS is not to my knowledge normally used to make the fly cutter. However I am minded to attempt cutting HSS as Jason says using initially the grinder and then my new bench sander where I have more control. How easy it is to get such a small cutter by hand will be interesting to find out. This HSS cutter in theory should cut a chamfer and be easily modified / sharpened for another pinion.

I would also add I am keeping in mind the use of EN8 to use which is I believe machinable and can be through hardened.

Chris

The suggested steel for clock pinions if you do not wish to use siver Steel is EN24T which is supplied in a tempered condition and is specifically intended for gears.

With regard to your original question. Fly cutting pinions is difficult with pinions in steel due to the need to reduce cutting speed which creates issues with feed rates for single point cutters. Thorntons cutters are recommended to be run at less than 500 RPM Max. which for a 12 point cutter means each edge meets the work 100 times per second.

With a single point cutter this drops to just around 8.3 times per second and to keep the tip loading and surface finish the same the feed rate needs to be 12 time slower which if you are hand feeding is going to be problematical even if you manage to create a fly cutter of the same quality and edge as a Thorntons cutter.

My advice is to bite the bullet and invest in a proper pinion cutter.

regards Martin

Martin,

My understanding is the rpm recommended is for each individual cutter on the commercial cutter. Whilst it is obviously the case for commercial production a commercial cutter would be more durable and cost effective this does not apply for a man in the shed replicating a single wheel or pinion. A fly cutter is made easily given practice, is cheap as chips to make and is sharpened each time before use so a better result can often be achieved.

Moving on to the choice of metal if not using silver steel. This is a bit more confusing for me so maybe others can chip in. i note Cousins and John Wardle sell pinions made from EN8/EN8DM. Maybe they come from the same supplier, maybe they are trying to replicate age characteristics?

Could anyone compare EN8 to EN24T in terms of using it on a small lathe for making a pinion with a fly cutter?

Chris

Edited By Chris TickTock on 26/08/2020 10:38:23

Chris

Firstly if you read my post I said that was the maximum recommended RPM for a Thorntons cutter. That's why I added the proviso that this was the best the bloke in the shed could achieve, in practice fly cutters are going to be not as good as this. Clearly the RPM is the same irrespective of how many teeth on the cutter. How ever comparing a 12 point cutter with a single point cutter at the same RPM the single point cutter will take a bite 12 times bigger than the 12 point. In order to keep the tooth loading the same you have to reduce the feed rate by 1/12. which is where the problems start. Even with a commercial cutter the feed rate needs to be quite gentle so with a single point at low RPM it's very hard to feed slow enough.

I was also attempting to point out the problems of cutting solid pinions in steel using fly cutters. I would also like to point out that I am a typical bloke in a shed and I use Thorntons cutters on pinions.

best regards Martin

Edited By Martin Kyte on 26/08/2020 12:29:51

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