Milling collet choices

This is one of these questions I'm sure must wind up the old and bold but after lots of searching I'm still very confused so stand by!!

After a short (30 year) break I'm saying myself back into machining. I've just picked myself up a bridgeport mill with a r8 spindle. So what next? Do I go for a er32 collet chuck or direct R8 collets?. I'm running a chipmaster lathe and I'm thinking it would be good to standardise my collets if possible. Would this be possible?

Do a search here on MEW.

Lots of previous posts about collets.

Colin, ER32 every time.

Robert Butler

I use ER collets. However, my mills are small so cutter sizes are limited. That said, I do occasionally use a shell end mill , abt 45mm diameter, that has a 14mm drive shaft - In Ali I really have to tighten the ER25 collets up on that shaft, I mean really tight, A good DOC sometimes would allow the shaft to slip in the collet. An ER32 collet would probably do better. The bridgeport is a much bigger mill, with more power, and I would think R8 collets would be the way to go. Cost more I suppose. ER collets have limited contact length, but are convenient for quick changes.

Similar thread a couple of days ago about ER vs Finger collets

I have a similar problem MT4 spindle however:My next buy is collets.

The dealer said ER32 is the most popular and will be good for my mill, however a guy I watch on Youtube has opted for ER42 collets on a smaller CNC modified mill, have not had asked him why not ER32....

Possibly he also wants to use the ER40 on his lathe as well in which case the larger capacity makes more sense.

Biggest problems with ER40 on a mill is it becomes like using finger collets the large nut will obscure your vision of small cutters and you run the risk of hitting clamps or not being able to get near work held in a chuck on the vertical rotary table/dividing head. He won't have the problem of needing to see the cutter on the CNC but still hard to clear chips.

Edited By JasonB on 09/01/2022 07:35:13

Depends on your intended cutter use. I use a ER25 R8 which is good for upto 16mm, which covers all my usual end mill sizes, mostly for slotting etc most are below 10mm. Then my boring and facing tools are plain shank held in 3/4” or 20mm taper collet mostly.

Hi Colin,

I use ER collets, ER32 for larger cutters and ER16 for smaller cutters and the small ER-nut doesn't obscure vision. The ER chuck will give you less headroom than using R8 collets, but then you should have plenty of headroom on a Bridgeport so shouldn't be a problem for you. I use the ER 32 collets for work-holding on my small lathe, and my ER collets get used a lot.

Thor

I'm a R8 collet man, but my mill is limited in quill size and table clearance so I like to minimise the amount of overhang.

I use R8 and Clarkson on my Bridgeport. R8 for light and accurate work and Clarkson ( 2 chucks 5/8" and 1" capacity) for heavier work where there is a risk of the cutter pulling down. It helps having a good number of screwed shank cutters and a cutter grinder to keep the mill fed. If you go the ER route consider a bench mounted fixture for tightening the collet nut, Bridgeport brake's are sometimes poor to stop spindle rotation even in back gear/low speed range.

Done to death on here - see for example **LINK**

I'm in the R8 camp - collets fairly cheap, accurate, hold like ****, don't get stuck, no overhang. ER chucks take at least 30 - 40mm of daylight under the quill before you insert the cutter.

The success of the ER system is striking In the world of Model Engineering, where all new ideas are distrusted,. ER is said to be industry's most popular clamping system, and large numbers of Model Engineers have adopted it too. Pretty good for a system invented in 1973, and despite serious competition from earlier clamping systems of high repute such as Clarkson, and the Model Engineering communities strong distrust of innovations: many of us believe all new things are bad and that quality has gone down the toilet since the good old days.

I think ER's success is due to a combination of features rather than a single obvious advantage. Maybe:

• The collets grip over a wider range than most other systems, reducing the overall cost of ownership
• ER collets can be used for work-holding and tool-holding, making ER generally useful on Lathes, Mills, Rotary Tables and Grinding Machines. This is both handy and a cost saving.
• ER chucks are relatively simple to make, therefore inexpensive. Grip is good, and more than adequate when tightened to the recommended high torque.
• Once the need to click collets into place has been spotted, ER is quick and easy to use, and it accepts plain shank and Weldon slot cutters equally well.
• In industry,
  • ER is well-suited to automatic tool-changing. In production, the ER system removes metal faster than most alternatives because it wastes a shade less time doing tool changes.
  • ER is symmetric about the spinning axis, making it easier to both reduce run out and balance chucks and collets for operation at very high RPM. 20,000 to 30,000rpm isn't unusual.

As far as I know, apart from buying defective or too cheap, no-one has regretted going ER. The only disadvantage I've found is the extra head-room taken up by the chuck: occasionally, it's best to plug cutters directly into the spindle with a dedicated one-size taper holder. (Can't remember the last time I did this!)

Dave

I’ve got finger collets I could use but small cutters easily “get lost” under the quill. Using an ER collet chuck allows more space to see what’s going on.

Have you looked at the average ER nut Dave, that ability to click the collet in makes a mess of any symmetry. You have to pay a bit more than most MEs want for balanced nuts.

Thanks everyone and as expected I don't think there is a definitive correct answer. It looks like the general consensus is collets make sense if you have the vertical space. For bigger stuff straight to the R8 collet.

I would humbly suggest using sidelock or clarkson/posilock endmill holders for endmills wherever possible. use collets when there is no locking geometry on the endmill shank, which normally means carbide endmills.

Thanks for this. I'm a complete novice and didn't realise the cutters would require different systems. Is it just the endmills that have the locking geometry. Is there an option to just use the Clarkson system and buy all the same type of cutter?

Every time I think I'm settling on something there seems to be a whole new level of detail. I really like the learning process but I was hoping to minimise the cost of it😀😀

That is the good thing about ER you just need one type of holder and can hold screwed shank, plain shank and Weldon (sidelock) shank. So have a much larger choice of cutters and minimal outlay. Bonus is that they can also be used for work holding which you can't do with say Clarkson type.

It is interesting to look at something like the Dormer catalogue of the 50plus types of milling cutters that they do only two have screwed shanks, just shows that screwed shank are now becoming a dated option.