Cutter pullout

Hi,

I am waiting for a Bridgeport Series 1 to arrive and need to get some basic tooling sorted. I want to keep costs down at least to start with, so I would be grateful for a bit of advice on cutters and specifically holding.

On my lathe (Myford S7) I was suffering with cutters pulling out of the collets I was using, even with light cuts when I was milling on the slide. Not sure what the collets are that I have for the lathe as they aren't quite ER but are similar. In the end I bought a posilock type chuck using threaded cutters and this worked great.

Now I need to buy some R8 tooling and would like to know if I will get issues using just R8 collets on the quill. I understand ER chucks hold well and I could get another posilock (although they are expensive) but I understand there is more overhang and less height available compared with working straight our of the quill. Interested to know what your recommendations are. Also, can I use the threaded cutters I already have in plain R8 collets or only straight shank? Thanks in advance.

Matt

Matt, Standard R8 collets dirct in the nose work OK.

This is what I use 90% of the time and I'm not renown for hanging about piddling with a few thou.

They will hold plain shank and theaded shank.

Where the ER's score is the fact a collet has a closing range of 1mm and a lot of modern solid carbide cutter have a shank diameter equal to the working diameter so a 5mm cutter will have a 5mm shank.

Ok in an R8 if you have a 5mm collets which are easily available but something like a Clarkson or Posilock are limited to factory made collets in fixed sizes like 6mm, then 10m then 12mm etc.

Hi John,

Thanks for the info. Good to know they will take the threaded shank mills as I have a few of these. I bought a job lot off ebay and there were some sharp good make ones among them. I was just going to buy 4 collets and probably some new cutters initially.

It sounds like an ER chuck might me useful in the future. Good point about the proprietry collets for the autolocks, I hadn't thought about that.

Hi Matt,

I'm not giving here any recommendation but can say the following with some experience. I have used Posilok and ER collets and can vouch for the holding qualities of the latter. A bonus is that not only can they be also be used for work holding but they are not dedicated sizes as are Posilok collets. It is often forgotten, especially by amateurs that ER collets were originally designed specifically for milling cutter holding and it is the ability to comletely collapse along the whole length of the collet on to the shank that gives them such holding powere whereas normal collets close on a relatively small area due to the cone effect i'e. it is only the end of the collet that actually locks onto the shank when closed..

Regards

Terry

Hi Terry,

It seems that ER collets have a good reputation then. The ones I have look the part (slit both ends) so should close up parallel but I suspect fall short in some way. It looks like I will add this to my wish list!!

regards,

Matt