Grinding your own lathe cutters

[Chris TickTockParticipant @christicktock]

Going back to inserts as I have been doing some research. I have found that the inserts that you rotate usually have a negative rake and this makes them unsuitable for a tiny Sherline. However as I am still grappling with the available issues could anyone state that there are decent positive rake carbon inserts suitable for the Sherline.

Regards

Chris

[VicParticipant @vic]

It may be a generalisation too far but I’ve found the polished inserts work very well and suspect they would be good for small lathes like the Sherline, in a suitable size.

Something like this?

**LINK**

Maybe even the next size up.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Christopher judd on 17/08/2019 10:29:47:

OK guys I have come across the CarbideDepot's insert table [ … ]

(1) Looking under the Shape table is a Greek Symbol…anyone care to explain

.

If you mean this table, Chris: **LINK**

http://www.carbidedepot.com/formulas-insert-d.htm#shape

… I see no Greek : Just a misrepresentation of the degree symbol

[ it's a problem with the choice of font ]

MichaelG. [using an iPad]

.

and if that's not what you mean, just ignore me

[Chris TickTockParticipant @christicktock]

Posted by Michael Gilligan on 17/08/2019 13:12:02:

Posted by Christopher judd on 17/08/2019 10:29:47:

OK guys I have come across the CarbideDepot's insert table [ … ]

(1) Looking under the Shape table is a Greek Symbol…anyone care to explain

.

If you mean this table, Chris: **LINK**

http://www.carbidedepot.com/formulas-insert-d.htm#shape

… I see no Greek : Just a misrepresentation of the degree symbol

[ it's a problem with the choice of font ]

MichaelG. [using an iPad]

.

and if that's not what you mean, just ignore me

Thanks Michael that solves that one..well done.

Chris

[Chris TickTockParticipant @christicktock]

Posted by Vic on 17/08/2019 12:25:25:

It may be a generalisation too far but I’ve found the polished inserts work very well and suspect they would be good for small lathes like the Sherline, in a suitable size.

Something like this?

**LINK**

Maybe even the next size up.

Hi Vic, look I am a green horn so I buzz around here and there forming opinions but my thinking based on my findings is that my Sherline works best with HSS but for tiny precise stuff quality brazed carbide will be better as it will be made more exactly than home ground HSS. Having said that the sharpness and rake of the Aluminium inserts has been offered up and seems credible for me at some point to explore. So thanks for your contribution it is noted.

Chris

[JasonBModerator @jasonb]

Do be careful looking at carbide depot and some other US sites as they use ANSI & ISO codes where just about all the information you are being given here is for ISO codes.

Yes There are decent inserts for the Sherline available, sherline even sell them but not worth buying from them as postage will be high.

Not sure what you mean by "rotate" but the CCMT, CCGT, DCGT etc that have been suggested can all be turned around in the holder to use the opposite corner and in the case of CC** inserts with an additional holder the other two 100deg corners can be used too.

[Steve CrowParticipant @stevecrow46066]

Posted by Vic on 17/08/2019 12:25:25:

It may be a generalisation too far but I’ve found the polished inserts work very well and suspect they would be good for small lathes like the Sherline, in a suitable size.

Something like this?

**LINK**

Maybe even the next size up.

I've been using those very same inserts all morning to turn tapers on 3mm silver steel on a Sherline. Run it at full speed – great finish.

[JasonBModerator @jasonb]

Posted by Christopher judd on 17/08/2019 13:40:31:

brazed carbide will be better as it will be made more exactly than home ground HSS.

Chris

When you buy brazed carbide tools they come roughly shaped and will at a minimum need to be touche dup with a diamond stone, in teh long tem they will need freshening up with a bench grinder and that will need either a green grit or diamond wheel, the supplied wheels won't sharpen carbide.

So the brazed ones will be no more exact than HSS and as they are harder to shape and sharpen probably less exact

You then get into the quality of the bit of carbide that is brazed to the holder, plenty of cheap ones about for 50p but the carbide is not the same as ones for £20.

Edited By JasonB on 17/08/2019 13:50:22

[Chris TickTockParticipant @christicktock]

I would be a fool to dismiss anyone's opinion yet on this matter. I suspect the truth is for most instances using the aluminium inserts will do just fine and yes I will be trying these. On the other hand One of the very top craftsman who can machine every part of a clock including the platform escapement only uses hss and quality brazed carbon for very small and fine work. I suspect the degree of accuracy is greater for the really small stuff. On the other hand you guys stating the inserts do a fine job may be right and my other forum friend hasn't had success with them. As always opinions and opinions, everyone welcome.

Regards

Chris

[Chris TickTockParticipant @christicktock]

Posted by JasonB on 17/08/2019 13:43:42:

Do be careful looking at carbide depot and some other US sites as they use ANSI & ISO codes where just about all the information you are being given here is for ISO codes.

Yes There are decent inserts for the Sherline available, sherline even sell them but not worth buying from them as postage will be high.

Not sure what you mean by "rotate" but the CCMT, CCGT, DCGT etc that have been suggested can all be turned around in the holder to use the opposite corner and in the case of CC** inserts with an additional holder the other two 100deg corners can be used too.

Thanks Jason I will watch out for the ISO / Ansi issue.

[Martin Hamilton 1Participant @martinhamilton1]

In my opinion & experience on my Sherline the **gt inserts are superior re finish & tool pressure on the workpiece for small lathes. I still use some HSS tools where i need a more dedicated tool to what i can use in inserts, there are more now starting to use aluminium inserts on very small lathes as they find out just how good the are on most types of metals & plastics etc on smaller machines. Using **mt inserts on these small lathes will not give as nice finish generally but i do also use them as well.

[Chris TickTockParticipant @christicktock]

Posted by Martin Hamilton 1 on 17/08/2019 16:23:29:

In my opinion & experience on my Sherline the **gt inserts are superior re finish & tool pressure on the workpiece for small lathes. I still use some HSS tools where i need a more dedicated tool to what i can use in inserts, there are more now starting to use aluminium inserts on very small lathes as they find out just how good the are on most types of metals & plastics etc on smaller machines. Using **mt inserts on these small lathes will not give as nice finish generally but i do also use them as well.

Thanks Martin, there definetly is a body of opinion supporting their use.

Chris

[Chris TickTockParticipant @christicktock]

To do posters here justice over their views on using aluminium inserts on a small lathe I went back to my horological friend for a second opinion. He stated in his opinion inserts can be used without issue for larger work but on micro work often undertaken in the horological field inserts are not appropriate. Regarding quality brazed carbon cutters as they have been recommended they can be used as they come needing no setting up. The person giving this advice is a world renowned craftsman so you can see why at this stage in my lathe experience I will be sticking with it as all my work will also be horological. Suffice to say though I will at some point try aluminium to gauge the results.

Regards

Chris

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Christopher judd on 18/08/2019 09:33:10:

[ … ] I went back to my horological friend for a second opinion. He stated in his opinion inserts can be used without issue for larger work but on micro work often undertaken in the horological field inserts are not appropriate. Regarding quality brazed carbon cutters as they have been recommended they can be used as they come needing no setting up. The person giving this advice is a world renowned craftsman so you can see why at this stage in my lathe experience I will be sticking with it as all my work will also be horological. [ …. ]

.

Forgive me please, if this an impertinent question

Has your 'world renowned craftsman' friend discussed the use of the graver ?

For work such as turning balance-wheel staffs [which is, I think, your stated ambition], this would normally be the preferred tool.

MichaelG.

.

P.S. have you looked at the Saunier book that I linked on your 'digital calipers' thread ?

[quote]

This is a very good place to start: **LINK**

https://archive.org/details/watchmakershand00tripgoog/page/n4

[/quote]

[SillyOldDufferModerator @sillyoldduffer]

Posted by Christopher judd on 18/08/2019 09:33:10:

…

The person giving this advice is a world renowned craftsman so you can see why at this stage in my lathe experience I will be sticking with it as all my work will also be horological. Suffice to say though I will at some point try aluminium to gauge the results.

Regards

Chris

I think you may be missing the point slightly: what a world renowned craftsman does may not be the best place for a beginner to start! Learner drivers shouldn't begin by asking Lewis Hamilton which oil is best for Formula 1.

Correctly sharpened HSS is very suitable for small lathes and – as lathes go – the Sherline is tiny. So the obvious answer is use HSS, and why not? The main objection is a beginner might find he doesn't have the skills or equipment needed to correctly sharpen HSS. The equipment is easy enough – a grinding wheel – but learning to use it may not be.

As is often the case, the operator is more important than the equipment. If Christopher Judd happens to be a grinding natural, and some people are, then all is well with HSS. But if he's cack-handed like me, then frustration ensues. In that case carbide inserts remove the need for the operator to develop grinding skills. Eliminating causes is useful at the early stages when it's not clear if the lathe, material, cutter-type, set-up, speed, depth of cut or feed-rate are wrong.

In practice I use both carbide and HSS. It's allowed! Mostly carbide because it's convenient – there's no point me wasting time sharpening HSS when carbide will do the job. When carbide fails, mostly by not getting a good finish or something very delicate is in hand, out comes HSS and a short fight with my grinder. It's possible to buy HSS inserts to fit carbide holders, but I'm not that clumsy. A good alternative to HSS for fine hobby use is the carbide inserts used by the grown-ups on non-ferrous metals like Aluminium. Like HSS they're sharp and polished, simple as that.

Part of the fun is developing the skills needed to get the best out of tools and materials. What suits other people doing other types of work on different equipment can be highly misleading. The best way to find out is to grind some HSS tools and cut metal: if the advice works for you, hurrah. If results are poor, try carbide.

You also said 'Regarding quality brazed carbon cutters as they have been recommended they can be used as they come needing no setting up.' That's a booby trap because brazed carbide tools often come unsharpened. The advantage of brazed carbide over inserts is they're cheap and can be ground to shape like HSS and resharpened. A special grinding wheel is needed. I never use them.

Dave

[JasonBModerator @jasonb]

Looks like you have already decided but going back to somebody else's comment that carbide inserts can't take small cuts which seems to be putting you off here is an insert designed for aluminium taking a 0.001" cut of some EN8 steel. Not ideally focused but if you watch it full screen on youtube you can see the nice ribbon of swarf coming off.

[Steve CrowParticipant @stevecrow46066]

Chris, with respect to your mentor, I strongly advise that you take the advice of the forum members.

I did and I don't regret it.

I had a similar problem regarding the Sherline. See my thread "A Kitchen Table Workshop – Grinding Problems" (I don't know how to link it). I took the forums advice and bought a holder and inserts and some HSS Co5 6mm tools.

Centre them properly and you'll be getting excellent results straight away. They are fine with silver steel down to sub-millimeter diameters. I've cut a M1 thread with the HSS and turned a 0.5 diameter with the inserts all in silver steel with a good finish.

Take my word, try these and you can be cutting metal as soon as possible. There is no substitute for getting stuck in and making some swarf.

Steve

[Old SchoolParticipant @oldschool]

I was also helped along my way to "model engineering" by a clockmaker he taught me to grind lathe tools in hss and make form tools from carbon steel for making pillars and fly cutters for wheel cutting. This person was my father who made his living from making clocks from simple skeleton clocks with escapements you only saw in books to orrery clocks all to his own design and made from scratch.

[JasonBModerator @jasonb]

Chris, you also mentioned a need for precision, you don't say what accuracy you are chasing but having now finished the part in the video I posted earlier I thought I had better measure it.

I was aiming for 10mm, on crankshafts I do tend to use my micrometer so dug out the analogue one as I find the feel better than my digital one, as this is imperial I need to get 0.3937", the mic has a 10ths scale that is each line represents 0.0001" or 0.0025mm. I'm happy with the size I managed to hit, you may feel you need more precision.

Even the hand fed cut on the taper came out nicely straight off the tool.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve Crow on 18/08/2019 11:52:19:

[ … ]

I had a similar problem regarding the Sherline. See my thread "A Kitchen Table Workshop – Grinding Problems" (I don't know how to link it). I took the forums advice and bought a holder and inserts and some HSS Co5 6mm tools.

[ … ]

.

Allow me, Steve: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=142594

… It's a thread well-worth a look.

MichaelG.

[Chris TickTockParticipant @christicktock]

Posted by Michael Gilligan on 18/08/2019 09:50:12:

Posted by Christopher judd on 18/08/2019 09:33:10:

[ … ] I went back to my horological friend for a second opinion. He stated in his opinion inserts can be used without issue for larger work but on micro work often undertaken in the horological field inserts are not appropriate. Regarding quality brazed carbon cutters as they have been recommended they can be used as they come needing no setting up. The person giving this advice is a world renowned craftsman so you can see why at this stage in my lathe experience I will be sticking with it as all my work will also be horological. [ …. ]

.

Forgive me please, if this an impertinent question

Has your 'world renowned craftsman' friend discussed the use of the graver ?

For work such as turning balance-wheel staffs [which is, I think, your stated ambition], this would normally be the preferred tool.

MichaelG.

.

P.S. have you looked at the Saunier book that I linked on your 'digital calipers' thread ?

[quote]

This is a very good place to start: **LINK**

https://archive.org/details/watchmakershand00tripgoog/page/n4

[/quote]

Thanks Michael the answer is yes we have discussed gravers and that the advise was years of practice are need to turn a staff on a graver and to not go that way as a beginner.

Chris

[Chris TickTockParticipant @christicktock]

Hi guys thank you for all your posts they have not been in vain because as I said I will use aluminium inserts at some point and assess the difference. At the moment I ask a lot of questions and take a view that in all likelihood may change with experience.

To an extent tools used are like one's politics deeply believed right but at the end of the day we are all but bigots.

Regards

Chris

[SillyOldDufferModerator @sillyoldduffer]

Posted by Christopher judd on 18/08/2019 15:26:57:

…

To an extent tools used are like one's politics deeply believed right but at the end of the day we are all but bigots.

Regards

Chris

I hope not Chris! Evidence based choices are the foundation of engineering, not personal opinion.

As advice often depends on context don't be afraid to test ideas and reject them but never reject advice simply because it doesn't happen to align with what you believe. People are often wrong, especially me!

It takes time and experience to filter good from bad – the important thing with machining is to try it and see. Actually using HSS and Carbide for a few weeks will make the issues much clearer.

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Christopher judd on 18/08/2019 15:18:43:

.

Thanks Michael the answer is yes we have discussed gravers and that the advise was years of practice are need to turn a staff on a graver and to not go that way as a beginner.

Chris

.

I will, genuinely, be very interested to know how you get-on; turning a staff with any tool that is not making a shearing cut.

… I think you mentioned a 20mm long staff for a platform escapement

MichaelG.

[ChrisBParticipant @chrisb35596]

I started off with HSS, could not get proper results with it and rather than turning I spent more time grinding – which was frustrating. So I quickly turned to carbide inserts. Most probable reason for my bad experience with HSS is that the material I use for turning is of ''unknown'' origin, ( read recycled bolts etc) so I could be turning HT steel, stainless etc without any idea of what the speeds and feeds should be.

Using carbide changed all that, I mostly use tnmg inserts which I see as economical (having 6 useable tips). My time at the workshop immediately became more enjoyable and less frustrating. I also got some used cbn inserts (same shape) which give mirror finish at high revs even with shallow cuts (it's more burnishing than cutting I think)

I had read forums (on here as well) telling beginners to only use hss and learn how to grind tools, and to read books etc. To some extent I agree with that, but I think that sometimes it's better to do what you feel comfortable with and learn as you go, rather than getting bored and then loose interest.

My 2cents worth as a beginner.

[Author]

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