Screwed shank end mills

All my end mills are getting blunt so I scoured ebay for some new ones to find that the majority for sale are straight shank. I like the security that the screwed shank gives - they're not going to work themselves out of the chuck and deepen the cut. But are they now obsolete? Does everyone now use ER collets to hold end mills?

cncpoorboy seems to have quite a few...

Yes, ER seems to be the approved method. But please only whisper that in here....

Hi Otley,

Tracy Tools seems to stock screwed shank end mills. I have a few cutters from them and I have had no problems so far. Screwed shank cutters are very hard to find where I live, so yes, I use ER collets both to hold cutters and to hold work.

Thor

Thanks for the replies. I went with Tracy Tools (£50 + VAT + post) for a metric and imperial set.

I get the impression that discussing cutter holding issues here is a bit like asking the storeman for a long weight...

Greetings,

Why not resharpen them?

several excellent methods described over the years, plus when they are really sharp, they cut beautifully.

Regards

Brian

They are still quite available here in NZ, bought a couple of slot drills yesterday, there were three brands of standard length, I bought the cheapest Sonta from South Africa, and a long series one by Trubor UK, in both types the local Patience & Nicholson ones were quite a bit dearer.

Ian S C

Edited By Ian S C on 01/11/2016 11:28:09

Im busy looking for screw shank mills to fit a Clarkson older` type c `chuck that came with my mill.

I have a question, does the screw size of the cutter = the shank size.

For instance i have 1/4",3/8", 1/2" and 5/8" collets which are unmarked. Would a 15/32 " screwed shank cutter fit in the 1/2" collet (i.e screw in?) or do you need a 15/32" collet?

Edited By mark smith 20 on 01/11/2016 12:21:01

I think those are the standard Clarkson collets, sizes that fall between those collets are on one of the standard shanks. Metric cutters are on metric shanks and will require metric collets that usually have a line machined around the driving flange. The metric collets are 6, 10, 12 and 16 for the small collet chuck.

Mike

Hi Michael so a 15/32" shank cutter should fit in the 1/2" clarkson `c type collet?

The collets are the type with two prongs at the back. Ive never came across this type of clarkson before .

I have 3 original collets, the long ones in the photo,which came with the mill in 1/4",1/2" and 5/8" sizes , i assume these take either screwed or plain shank cutters but they have to be the correct exact size??

Edited By mark smith 20 on 01/11/2016 12:47:07

I would expect it to be mounted on a 1/2" shank so yes it would.

Mike

Hi Otley & Guys
To use plain cutters in an Autolock Slice the end of a old cutter and make what we called a dummy centre
Please see photo> Screw into collect fit in holder a tighten up Try it
Nobby

Here is a selection on cutters on shanks different from the cutter size, as you see some are larger than the shank. Clarkson Autolock chucks of all types use the same basic collet sizes but the actual collet design did change with the different models.

Mike

The three long collets are nothing to do with the clarkson system but as you say they will take the screwed shank type of cutter as long as it is a fit for the collet. The screwed shank will be of no benefit but will not be a problem as long as the collet has a good length of plain shank to grip.

Mike

IIRC, the imperial threads, although differing diameters, are all 20 TPI?

.

I believe so ... and that it was done to retain [approximately] the same locking force on all sizes of collet.

MichaelG.

.

Edit: for convenient reference, here's the patent

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=915713A&KC=A&FT=D&ND=3&date=19630116&DB=EPODOC&locale=en_EP

Edited By Michael Gilligan on 01/11/2016 16:22:30