FC3 holder tolerances

I would appreciate any help or comments to solve a problem that I am having with my FC3 holder.

I have a Clarkson FC3cutter holder which fits into the standard Autolock holder making it easier to use these throwaway cutters. This is the same type that has been recently featured in MEW as a home project. It has a 6mm fitting.

I have a Genuine Clarkson FC3 1mm cutter which fits perfectly however when I bought extra cutters for this holders some do not fit, some fit and some could be pushed into the holder but I am not sure that I cold get them out again.

I have done a bit of measuring but am puzzled by the results. Does anyone know what the official tolerances for hole and cutter shank should be or can you point me in the right direction.

My results are in 0.001mm compared to 6mm

FC3 holder hole -14

Genuine Clarkson milling cutter -30

Other makes of FC3 cutters -3 to -30

Hello John, If the genuine Clarkson FC3 cutter fits perfectly in the Clarkson cutter holder , there can't be much wrong with either item, are the extra FC3 cutters that you bought foreign imports or what ?

They could be imported rubbish , not on size with no quality control !

Buy some more genuine Clarkson cutters , and see how they fit.

Richard.

Hi There

Why not turn a bit of bar to an exact fit in the holder then put a clock on that?

Then you will know if the holder is running true.

regards David

Hi There

Why not turn a bit of bar to an exact fit in the holder then put a clock on that?

Then you will know if the holder is running true.

regards David

Can't see what difference a true running holder will make to the fit of a cutter in the holder.

Why hot use an ER collet as it has a bit more leaway.

J

It won't make a difference but it will eliminate the holder and then you will know if the cutters are true or not.

regards David

John is not saying anything is running out of true, He's saying the new cutters he's bought are a poor fit in the Clarkson holder.

Richard.

If they are too tight they might be 1/4" instead of 6 mm. I made my own holder that fits in the 5/8" collet. Ian S C

Hi

I had the same problem, it turns out that Clarkson make the cutter shanks a couple of thou under the stated size. So you can only use Clarkson FC3 cutters in the holder. I made up a new holder to take the Omega style FC3 cutters which i am now using.

Will

As you would expect for anything made on a Hole based tolerance system rather than shaft based.

Steve Larner

Every cutter shank is under nominal size to some degree, or it'd never enter the bore/collet. Clarkson have kept a tight tolerance on the adapter bore to try to keep eccentricity down to a level that's in proportion with these small diameter cutters.

Just run a stone over the shanks of those cutters that are a little tight and you'll be fine.

Martin.

Thank you for all your comments.

It is not the difference between 1/4 and metric as I have some of both cutters and they are very different ie. metric in 1/4 holder is very sloppy., whilst 1/4 into a 6mm holder will never go.

The non Clarkson cutters could well be cheap or out of tolerance and this was my puzzle because while they are all less than 6mm when measured they would not go into the holder.

William's comment seems to fit, I was just surprised that they would do something like that.... making the hole under size.

Eccentricity is only a problem if you put a Clarkson cutter in a normally reamed hole because then the sloppy fit lets the grub screw push the cutter to one side.

I appreciate your comments because I was starting to think that I was doing something significantly wrong. I have made my own 1/4 holder. I think I need to do the same for a 6mm one.

If I make it from EN8 and harden it is it likely to distort, of should it hold size?

Edited By John Buckley 4 on 20/11/2012 20:35:07

Edited By John Buckley 4 on 20/11/2012 20:35:32

John.

I can't figure out what the problem is if the Clarkson cutters fit the Clarkson adaptor ok - what size of bore do you intend to make in your new adaptor?

Martin.

Hi Martin,

I was thinking of making the new holder with a Standard reamed 6mm hole which will allow me to use some of the non Clarkson FC3 cutters. The problem being lots of people are selling FC3 cutters but they are not to the Clarkson spec.

If I put a true Clarkson cutter in this holder I could have nearly 2 thou clearance which seems a lot on a 6mm cutter

Being a bit tight I do not always buy the expensive cutters,

Regards

John

John.

All my current FC3 cutters (various makes) are at least 0.015mm under 6mm and the few I've just tried seem to go into my adaptor ok, but have varying amounts of clearance depending on the actual diameter of each shank.

In the past, when I have had tight fitting cutters, I've reduced them by putting a stone or fine diamond file to their shanks whilst spinning in the lathe, which only takes a minute to do.

Martin.

Martin,

Thanks I will try this, It will certainly be quicker than making a holder.

Regards

John

Hi John, For your interest ....

I have been using FC3 cutters for many years both at home and at work. I prefer to use them for most machining even flat surfaces over and above end mills and slot drills of which I have an good selection.

I made the tooling for my mill and the cross slide drilling/milling attachment for the lathe from Arne B01 which is similar to gauge plate. I did not harden them and they are still in use after some thirty years or so without showing any sign of wear. The holes - 1/4, 6mm - were reamed with 'used' reamers to ensure a good fit on the cutters which are mainly Dormer or Clarkson or Presto. I have used others - Hydra for instance and some cheap ones but have never had the situation where one would not fit though the odd one has been a bit tight. Doing as suggested by stoning in the lathe sorts that situation it in quick order.

I have measured quite a few this evening - all the Dormer are a consistent 0.025 mm down (on my mic) only the cheaper appear slightly smaller 0.030 mm but do vary slightly.

Despite home made tooling I have never come across a situation where I felt the cutter was cutting eccentricaly enough to be noticeable

Incidentally - whilst at work we always used Clarkson or Dormer and had one rep who constantly tried to get me to change. One day he left me with a 'Presto' TiN coated 6mm cutter to try. I felt this to be a bit gimmicky at the time but this particular cutter turned out to be seemingly indistructable - it just seemed to go on and on with out losing it's edge - we used to mill a lot of EN9 equivalent and a lot of tool steel - but having ordered them in differing sizes it was only the 6mm that seemed to give this longevity.

Hope this is of interest to you

Regards - Ramon

Hi Ramon,

Thanks very much. A lot of useful information there.

Regards,

John

Hi
Now I'm retired I have made some cutter holders ie 6mm 1/4 " 8 mm 5/16" etc .I find them ok for . I mill 3/32" grooves with no problems The Diameters are reamed then put on a mandrel to turn the 3/4" locating diameter. I know its Heath Robingson but it works

Regards Nobby