Insert tools and tool holders; robustness of method of clamping insert and inserts themselves...

[Tangledfeet]

We have two Warco GH1330 lathes at school so limited to 16mm shank tool holders. As much as I suspect HSS tooling would be more robust, the workshop doesn't have a bench grinder so couldn't sharpen them; so have to use tools with CNMG090304 inserts.



The wee CNMG inserts take a battering and regularly come off the tool holders, fortunately the kids are pretty good about finding them but I have no more spare inserts now.

I've been looking online at the likes of Cutwel for alternative tool holders that use the top or top and hole method:




In people's experiences are these methods more robust that the type P tools we have?

Alas it seems that most top clamp type tools start at 20mm which is no good for the lathes we have, the only one I've found would be this one from Engineering Supplies:

DWLNR 1616 H06 (95Deg) Top Clamp Toolholder - engineeringsupplies.co.uk

distributors of quality & performance carbide inserts, toolholders, boring bars, drills, milling cutters, taps, reamers and other engineering consumables.

www.engineeringsupplies.co.uk

Would these three-sided inserts perhaps also be more robust? I've tried to get away from turning steel unless we absolutely have to as we don't have coolant (discussed previously!) and and I can use aluminium round bar for the vast majority of tasks.

Insert tooling is, amongst many things, I know very little about and have no more than the experiences I've had with the 16mm holders and CNMG inserts above so any help much appreciated!

If I can come up with a case that new tool holders and different inserts would be the way to go I might be able to get approval to buy some; none of the suppliers on the council's purchasing scheme so we'd have to pay VAT thus increasing cost.

Cheers!

 

[Rrobson]

I’m not sure what problem your having with these tool holders because I’ve been using this style of tool for years and I’ve NEVER had a problem with inserts coming out. Be mindful this ranges from taking a whisker off to taking 10mm on the diameter in one cut in various grades of steel.

There is either something wrong with the tool holders, incompatible inserts, incorrect shim etc because they shouldn’t be moving at all. Also, I haven’t clicked the link about using coolant but with carbide tooling on steel you don’t need to… type p is what you currently have and see above for my view on that style of holder.

Steel would be much more suitable over aluminium with this style of insert, get ones that are more designed to cut aluminium if that’s what you do more of.
I really hope you don’t use the inserts that are in the box pictured!!!

 

[Munkul]

Are the inserts jumping out of the holders under vibration, or just when the kids crash it?
If it's just vibration then it's the holders are knackered, but if it's when the kids crash the lathe then it doesn't really matter what you do, may as well stay with the cheapest and most economical solution

 

[James1979]

Can you just buy a bench grinder or will that contravene some rule or other?

 

[Tangledfeet]

I’m not sure what problem your having with these tool holders because I’ve been using this style of tool for years and I’ve NEVER had a problem with inserts coming out. Be mindful this ranges from taking a whisker off to taking 10mm on the diameter in one cut in various grades of steel.

There is either something wrong with the tool holders, incompatible inserts, incorrect shim etc because they shouldn’t be moving at all. Also, I haven’t clicked the link about using coolant but with carbide tooling on steel you don’t need to… type p is what you currently have and see above for my view on that style of holder.

Steel would be much more suitable over aluminium with this style of insert, get ones that are more designed to cut aluminium if that’s what you do more of.
I really hope you don’t use the inserts that are in the box pictured!!!

Good to know that this type of tooling works well - thanks. I know that on at least one occasion a pupil put the lathe in reverse and that pulled the insert right out; they tend not to have much mechanical sympathy and can be quite heavy handed.

I'll look into getting inserts that'll fit the holders and are more suitable for aluminium. No - I just put some old ones back in the box; they'll be getting binned!

Are the inserts jumping out of the holders under vibration, or just when the kids crash it?
If it's just vibration then it's the holders are knackered, but if it's when the kids crash the lathe then it doesn't really matter what you do, may as well stay with the cheapest and most economical solution

As above, reverse in at least one instance. Yup, I think you have a valid point about sticking with what works.

Can you just buy a bench grinder or will that contravene some rule or other?

When I started at the school ten years ago there was one there but was removed a year or so later when there was a big safety review of equipment and some directive saying that all machinery had to stop within ten seconds - and it didn't. At the same time our massive old sweet-as-a-nut bandsaws were removed and replaced with lighter weight modern equivalents, for the same reason. There is a grinder but its in the hut which is where the majority of the woodworking is done; it was bought for sharpening woodturning tools but is never used as I take them home and use my equipment to sharpen them properly once in a while; means the angles stay consistent and my CBN wheels do a better job. Also, I don't have the time (or quite frankly inclination) to go sharpening HSS tools so if the school want me to teach metalworking (something that nobody else seems to be interested in doing... I made a rod for my own back in starting to teach it years ago) they can damn well pay for insert tooling!

 

[Kram]

Sounds like your holders are worn out or filled with swarf, not seating correctly. Inserts should never come out in a cut, in any reusable form!

I use the smaller, much cheaper ccmt0602 and dcmt0702 for most things. They are not double sided but better geometry for small cuts, particually boring, they break chips better. They are significantly cheaper, but not as durable. If your kids are crashing one per session, for example, these would likely perform just as good and be cheaper to replace. The chance of damaging the machine would be lower.

I assume the school is quite frugal with materials, so you wont need to peel off 10mm in each pass, so they should be adequate.


Did you say previously these are secondary school kids, who shouldnt really be using lathes without close supervision (imo). They will likely crash it for fun?!

Can you just buy a bench grinder or will that contravene some rule or other?

Useful for educational purposes but not for any practical ones. If your grinding hss cobalt bits, the best type, then in theory you need a monthly **** test to check your levels and I cant see a school paying for that.

The sort of crash that dislocates a carbide insert would throw chunks of hss around the shop.

 

[Tangledfeet]

Sounds like your holders are worn out or filled with swarf, not seating correctly. Inserts should never come out in a cut, in any reusable form!

I use the smaller, much cheaper ccmt0602 and dcmt0702 for most things. They are not double sided but better geometry for small cuts, particually boring, they break chips better. They are significantly cheaper, but not as durable. If your kids are crashing one per session, for example, these would likely perform just as good and be cheaper to replace. The chance of damaging the machine would be lower.

I assume the school is quite frugal with materials, so you wont need to peel off 10mm in each pass, so they should be adequate. and


Did you say previously these are secondary school kids, who shouldnt really be using lathes without close supervision (imo). They will likely crash it for fun?!

Good point, if we had compressed air I'd give them a good clean but (fortunately for safety) we don't.

Also quite possible that I'm just not tightening them up sufficiently.

They're under pretty close supervision as there's only two lathes; only two or three pupils this session (from a class of twelve) that I have full trust in. If I found a pupil doing anything untoward intentionally I'd take it up with senior leadership; several years ago one lad repeatedly pulled his phone out whilst on a lathe whilst it was on power feed on one occasion and walked away to chat to someone another time. I told the school that I wasn't going to let him pass the course but was basically told to reassess him by the Rector (Headmistress). Yup, they basically make it nigh-on impossible to fail pupils...

 

[Kram]

I dont have compressed air. Take it apart and wipe with tissue or a rag.

Im suprised you allow kids into the workshop if they have been that careless. I once was dared to hit the shop E stop button, I got a proper bollocking and wasnt allowed back in for two weeks, that was yr8/yr9 D&T woodwork.

 

[Tangledfeet]

Im suprised you allow kids into the workshop if they have been that careless.

If it were down to me they wouldn't. But that choice isn't mine to make as I can't refuse to teach a pupil and, quite simply, there wouldn't be anywhere else for them to go!

 

[addjunkie]

If it were down to me they wouldn't. But that choice isn't mine to make as I can't refuse to teach a pupil and, quite simply, there wouldn't be anywhere else for them to go!

Make them buy their own inserts, theyd be much more careful!

 

[Tangledfeet]

Make them buy their own inserts, theyd be much more careful!

Can't make any charges for practical subjects at school; Scottish Gov't made that announcement last year... coincided nicely with the materials shortages and at least doubling in the price of even the most basic wood and metal we use!

 

[Hood]

Putting in reverse will either pull the insert out or break the insert so clamping style will make no difference.
The P Lever style like you have is very good so if you have problems during normal use then tools are knackered or maybe just crap.

As has been mentioned the shim looks like it askew which suggests the wee semi circular spring steel is missing.

 

[Tangledfeet]

As has been mentioned the shim looks like it askew which suggests the wee semi circular spring steel is missing.

Aah, yes come to think of it - I do recall there being one there at one time.

Have some free time today so I'm going to contact a few companies and see if the inserts I'm using can be bettered; I've gleaned as much as they're designed for steel - not non-ferrous metals. Honestly don't know how much of a difference it might make!

 

[Hood]

This is what it looks like, it goes into the shim and into the tool body, holds the shim in place.

 

[Hood]

Aah, yes come to think of it - I do recall there being one there at one time.

Have some free time today so I'm going to contact a few companies and see if the inserts I'm using can be bettered; I've gleaned as much as they're designed for steel - not non-ferrous metals. Honestly don't know how much of a difference it might make!

It will make a big difference for beginners, personally I just use any old insert (quality brand not cheapos) and I do fine but...

 

[Tangledfeet]

This is what it looks like, it goes into the shim and into the tool body, holds the shim in place.



View attachment 322397

Yup, they're definitely not there now - cheers!

 

[RichardM]

Just my two penneth worth.
Don't get a bench grinder, the wheel replacement will probably cause all sorts of H&S issues.
Buy the simplest tool - least number of parts to look after / loose.

 

[Rrobson]

This explains a lot, doesn’t matter the clamping method, carbide is very brittle and running the lathe in the wrong direction will result in at best a chipped insert, worst it’ll throw it out or break it.

For apprentice training you’ll be much better off with hhs, even if you have to sharpen them yourself. Would likely be cheaper too so a bench grinder could be justified.

Good to know that this type of tooling works well - thanks. I know that on at least one occasion a pupil put the lathe in reverse and that pulled the insert right out; they tend not to have much mechanical sympathy and can be quite heavy handed.

 

[Tangledfeet]

@Rrobson Bench grinder not an option therefore neither is HSS. They're not even apprentices; 14-16yo.

Spoke to a few companies today, most informative and helpful was Cutwel. The inserts we've been using are far from ideal for aluminium, especially at the low cutting speeds we're at; new inserts and holders seem to be on the cards - boss seems to be okay with the idea.