|Dave Springate||26/03/2019 07:07:24|
56 forum posts
Hi all, as a novice is it ok to hold a milling cutter in a 3 jaw chuck for basic milling operations or should I get a collet chuck ? If I go for a collet chuck how do you choose a size ie : ER25, ER32, ER40 Or some other size ? I understand that the collet needed is the size of the item to be held but why buy An ER25 over say an ER32 or ER40 Thanks
3651 forum posts
I hold milling cutters up to 25mm diameter in the 80-year-old three-jaw chuck on my ancient Drummond M-Type (The Flagellator) without problem. Haven't had one slip on me yet, including milling 1" thick steel plate etc. A 16mm diameter end mill cutter seems to work best without too much "chunking" that you can get with the bigger cutters. Smaller cutters are a doddle.
So no need to buy ER collets for milling in the lathe. Give it a try with your 3-jaw first.
The 32 in ER32 refers to the nominal outside diameter of the removable tapered collet. The collets are available in a range of inside diameters to suit the size of bar/cutter you wish to hold. An ER32 collet set will hold up to about 20mm bar/cutter, whereas an ER20 collet set will hold up to 13mm bar/cutter. Sets are usually in increments of 1mm.
|Mike Crossfield||26/03/2019 07:58:25|
|190 forum posts|
Aside from having superior grip, a decent collet chuck will have much lower run out than your average 3 jaw SC chuck. With a 3 jaw you will most likely be cutting on a single tooth.
|Howard Lewis||26/03/2019 08:17:54|
|2156 forum posts|
+1 for ER Collets, as Mike Crosfield advises. A good three jaw will probably have a run out of a bit less than 0.005", (A badly worn / abused one could be 0.030". An ER collet will have a run out of about a tenth of a really good 3 jaw )
If you go to the expense of having a collet chuck, and a collet holder, when you graduate being a mill owner, you can use one for work holding, and the other for cutter holding.
ER Collets have a range of 1 mm in all but the smaller sizes, so can be used to hold Metric or Imperial cutters or material.
|Clive Brown 1||26/03/2019 08:39:38|
|251 forum posts|
My experience of using a 4" 3-jaw chuck for end-mills was that it's OK if basically cutting with the end-teeth. However, if heavish cuts are taken using the side teeth, then the helical tooth shape can pull the cutter outward from the chuck. Trying to avoid this by over-tightening can be unkind to the chuck.
ER collets don't seem to suffer this and auto-lock chucks are immune of course.
|not done it yet||26/03/2019 09:09:41|
|3166 forum posts|
Just thinking about days gone by might have given you some insight of past operations. ER collets did not exist in the early days of milling on the lathe. Did those hobbyists not make good models? Did they make inaccurate models?
ER collets are undoubtedly an improvement in tool holding over the standard lathe chuck ... but our grandfathers did not have the benefit of the bits that were not invented back then.
It's all relative. Lots of things have changed over the decades. This is just one example.
Regarding size choice - obviously the larger the better, within reason. But most will likely consider other ER operations and buy the (first) set to also fit their (future?) milling machine - unless their first set was decided upon for other reasons (often size or cost).
1587 forum posts
A word of caution....I bought a cheap collet holder and set oft bay via china for my mill. Great at holding things rigid but a lot of runout...dont be tempted!
|1279 forum posts|
NDIY - you can do just about anything with quite limited equipment and lot's of ingenuity, time and effort. The question is why would you do so, if a better (and quite affordable) alternative is available?
Dave - both my lathes have ER32 collet chucks - the type that mount on backplates - so that you can pass material through them. ER32 used to be the largest type that most dealers sold and is also available in collet block & spin indexer accessories - so it is versatile.
I use mine all the time where it makes sense, not only to hold cutters but also various useful mandrels and other devices where I want to remount them fairly accurately. I also directly hold 'work' with them, so the 20mm max of the ER32 collet is useful - but of course also larger than the material that either of my lathe headstocks can pass.
Before the Chinese made a lot of this stuff affordable to us mere mortals, clever people made all sorts of useful alternatives - including Master/Slave set-ups, MT cutter holders, 3-jaws that could be 'zeroed' (etc) but these days ER collets make many of these things somewhat redundant. Of course, if you already have them, they can still be useful - but much of the motivation to make these items has now gone.
544 forum posts
First time i have had to disagree with you...
|Neil Wyatt||26/03/2019 09:42:06|
16287 forum posts
But they often used a 4-jaw chuck for holding end mills, or used home-made slot drills that were usually only cutting on one edge at a time.
|4536 forum posts|
Holding the cutter in a slightly unsuitable 3-jaw will be the least of your problems! Big machines do better than small ones, but at root lathes aren't designed for milling. The workspace is very limited and the slide likely to move due to the unusual for a lathe forces caused by milling. Clamping the job can be awkward. Lathe milling works, but only within narrow limits - small parts, and gentle cuts. Quite often I would file by hand rather than go to the trouble of setting-up.
Combination machines (ie with a milling head permanently bolted to the headstock or ways) are a better bet, but they are still low capability compared with real milling machines.
Back in the day milling on lathes was common due to lack of affordable mills. Not because lathes are any good at milling! Great work has been done - ingenuity and patience can move mountains. However, at best I found milling on a lathe deeply frustrating. Even worse the machine simply wasn't big enough to hold rather ordinarily sized milling jobs. If you have the space buy a real milling machine. If budget is a temporary problem, save up for one - money spent on vertical slides & collets etc for milling on a lathe is likely to be wasted.
|4536 forum posts|
ER Collet Chucks each cover a range of collet sizes, for example:
ER16 0.5 to 10mm
ER collets are mainly for tool-holding on milling machines but they also do a good job holding work on a lathe. Collets hold lathe work accurately and repeatably but they're Over The Top compared with a 3-jaw for most work. A 4-jaw can achieve collet-like accuracy and hold odd shapes but take more setting up. Which type of chuck is best depends on the job in hand. I rarely use collets in my lathe (rarely chasing high precision), others use nothing else.
|Dave Springate||26/03/2019 10:22:51|
56 forum posts
Wow, how quick was that. Thank you all very much that has shed some light on the subject. Now if I wanted to true up the edge of a piece of 20mm steel would a cutter slightly wider than 20mm be the preffered way to go so that a full width cut is taken in a single pass?
Also would a two or 4 flute cutter be used for this operation.
15776 forum posts
The Minnie in my avitar was done on the lathe and any milling cutters held in the 3-jaw, seemed to work OK for me back then.
I'm sure MT collets were used a lot in the past to hold tooling.
How big is your 20mm steel? can it not me held in the 4-jaw to true it up.
|Russell Eberhardt||26/03/2019 10:41:45|
2465 forum posts
If you're going to hold a milling cutter in a three jaw chuck it's a good idea to interpose some brass shim between the chuck jaws and the end mill. The cutter will be much less likely to slip. I did this for many years, milling in the lathe before I bought a mill.
|Barrie Lever||26/03/2019 10:47:33|
|323 forum posts|
198 forum posts
That sounds like a job for a fly cutter. Personally I use the biggest cutter I can get away with for rigidity.
|4536 forum posts|
I plead guilty to the charge of Gross Exaggeration and ask for 477 other offences to be taken into consideration!
|Dave Springate||26/03/2019 11:12:17|
56 forum posts
Hi Jason, I don't yet have a 4 jaw chuck but it's on the list when funds allow. The piece of steel is 60mm x80mmx 20mm.
Edited By Dave Springate on 26/03/2019 11:21:29
|251 forum posts|
If you cant run to an immediate collet setup then use a 4 jaw and set true.
Unfortunately shelling out on a new half decent collet setup goes against the grain when the cost could be on the way to financing a used milling machine package.
As others have said, once true in a chuck you have the lesser rigidity in a lathe to deal with. Make sure all slideway jib strips have any unwanted play taken up. If you can, lock any slideways up that are not being used. If your compound slide is still fitted, minimise any overhang.
Small cutters also demand much higher speeds than many lathes can achieve, so watch your max chuck rpm and take it easy.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.