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Post by newington on Jul 19, 2018 7:47:31 GMT
I have a centec milling machine and would like to be more proficient with it. It has a vertical head and I use a Clarkson auto chuck in that. I would rather use collets but the hole for the drawbar is smaller than the diameter needed for the collet thread. Any ideas how to get round this? The Clarkson is ok but I do struggle to get it out of the taper.
In horizontal mode what stops the cutters slipping on the shaft. The shaft that came with the machine has no raised key yet the cutters have square cut out for a key! To my mind as soon as the cutter touches the work it will spin on the shaft. I sure a wise sage will be able to put me right!
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Post by Jo on Jul 19, 2018 7:52:35 GMT
The draw bar pulls the Clarkson collet holder into the quill. When you loosen it a half a turn if you tap it with a rawhide or brass mallet it will loose its grip on the quill taper. Sounds like you need to make yourself the correct sized draw bar.
In horizontal mode the only time I use a key is if I am cutting gears. It is better that the cutter rotates on the arbor than it damages your work.
Jo
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Post by newington on Jul 19, 2018 8:00:26 GMT
Jo,
The drawbar for the Clarkson is fine although but even a gentle tap does not release the clarkson from the taper. How do you hold the cutters on the drawbar? Is just through the pressure of the spacers either side applied by the nuts on the arbour end. I have the instruction leaflet but it is not very informative!
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Post by Jo on Jul 19, 2018 8:15:16 GMT
The cutters are held in by the collets and there is holding sleeve/nut that secures the collet into the holder.
Jo
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Post by newington on Jul 19, 2018 8:33:26 GMT
Jo,
Ah Are you talking about vertical milling here? I was talking about horizontal milling. I understand the methods of holding the shall I say "long" cutters in collets. I have a couple of sets of collets however the bore through the quill is smaller than the thread in the collet. I am going to have to make some sort of adapter to hold them.
It is the "circular" Cutters I am struggling with. I tried it once on a piece of scrap and the cutter just stopped still when it came in to contact with the work even with the lightest of cuts. I must be doing something wrong!
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Post by GWR 101 on Jul 19, 2018 11:18:12 GMT
Not sure about hobby milling machines but in industrial applications all the horizontal milling machines I have used the arbour has a keyway along its length into which a key is fitted. The principle being that this provides a positive drive to the cutter, the last thing you would want is the cutter to stop rotating and the feed to continue. In certain instances we had stepped keys so that if the keyway in the arbour was bigger than the cutter the key was made to fit closely in both. The idea being that the key dimensions and material would act as a shear pin if things go wrong.
Clarkson Autolock vertical milling chucks I have always found to be very well designed and useful, the system I used ensured that the centre in the top of the cutter engaged with the centre in the chuck and provided a repeatable cutter height. Most machines have a double key type drive in the machine spindle face which has corresponding slots in the chuck. I have always found it necessary to use a mallet to release them after unscrewing the draw bar a small amount. Modern industrial machines have air operated chuck insertion and removal attachments which I find fairly frightening in their action.
A word of caution, please ensure all the appropriate guards are in place and never attempt to go near the cutter or workpiece whilst the machine is in motion. Sorry if this sounds a bit dramatic but this type of machine is considered one of the most dangerous in the machine shop.
Hope this is of some help. Regards Paul
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Post by heyfordian18 on Jul 19, 2018 12:58:01 GMT
I have a Centec 2A mill, although I have not used the horizontal arbour for quite some time.
I'll be in the workshop later, so will have a look at the arbour.
Fairly sure that there is a clamping arrangement that grips the cutter between the spacers.
More later.
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Post by 92220 on Jul 19, 2018 16:06:54 GMT
Jo, Ah Are you talking about vertical milling here? I was talking about horizontal milling. I understand the methods of holding the shall I say "long" cutters in collets. I have a couple of sets of collets however the bore through the quill is smaller than the thread in the collet. I am going to have to make some sort of adapter to hold them. It is the "circular" Cutters I am struggling with. I tried it once on a piece of scrap and the cutter just stopped still when it came in to contact with the work even with the lightest of cuts. I must be doing something wrong! Hi.
The threads in the Clarkson collets are not for use with a drawbar. They are for screwing in threaded shank endmills. You put the endmill into the collet and then the collet into the collet chuck. The endmill should then be screwed up until it touches the centre inside the chuck. Then tighten the collet locking ring to make the collet grip the endmill. The Clarkson Autolock chuck is not suitable for use with any endmills except threaded shank endmills. Clarkson collets won't hold parallel shank cutters strongly enough to mill with.
As far as horizontal milling cutters go, as previously said, the spacer rings on the arbour grip the sides of the milling cutter by friction. You just have to really tighten the locknut, and take light cuts. Without a keyed drive to the cutter, you are limited in the size cutter you can use on the mill. Without a keyway you probably won't be able to use cutters wider than 1/8" and 3" diameter, without cutter slip when milling because there is not enough frictional area on the sleeves to grip the cutter and resist the cutting forces of large diameter and width cutters. The only alternative is to mill a keyway slot in the arbour.
Bob.
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uuu
Elder Statesman
your message here...
Posts: 2,860
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Post by uuu on Jul 19, 2018 16:43:01 GMT
I had a Centec mill. I had some "finger" collets with it that fitted up into the vertical-head taper and held cutters with very little overhang - perhaps these are similar to the ones you are describing. Fortunately, mine fitted the same drawbar as the Clarkson chuck, so didn't need an adapter. But they were not very good, as their grip was not tight enough, so cutters would get drawn into the work, leading to a number of disasters. Also, they would only hold cutters with shanks dead on size.
Much better is an ER collet chuck. Alas it takes up more room than the finger collets, but perhaps less than the Clarkson. I've not had any trouble with cutters being drawn out, and all shank sizes are accommodated, as well as drills.
I never used it in horizontal mode, so can't comment on you issue there. I've held slitting saws in an arbour without a key, and they slip if you advance too quickly. So I suspect a milling cutter would only take the tinies of cuts without a rigid drive.
Wilf
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Post by heyfordian18 on Jul 21, 2018 13:03:57 GMT
Jo, have spent some time re-aquainting myself with the horizontal arbour on the Centec.
2MT on the drive end, internal thread to take 3/8" BSW drawbar.
1" dia shaft, no keyway, with 1 x 2", 2 x 1", 1 x 1,2", 3/8", 1/4" and 1/8" long collars/spacers.
Large LH threaded clamp nut on the outer end, with a tail end to run in the bearing under the horizontal arm.
I remove a spacer the equivalent width of the cutter, please the cutter with the colars each side of it and tighten up the clamp nut.
Is your drive shaft different to this.? Can attach photo if required to help.
Peter
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Post by ettingtonliam on Jul 22, 2018 2:12:27 GMT
I never use the key when horizontal milling, and just rely on tightening the end nut to lock everything solid. It does work. Make sure the cutter is on the right way round, if it isn't, it won't cut. Don't ask how I know this!
I've cut many gears, 14, 16, 18DP on my Centec, without keying the cutter, couldn't in fact because the shaft didn't have a keyway. If the Clarkson needs a bigger drawbar than the Centec spindle will pass, make a short sleeve to thread into the Clarkson, which is threaded internally to suit the drawbar. Lokset the sleeve into place. The Clarkson may well need a sharp tap on the end of the drawbar with a lead or copper hammer to get it free.
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Post by newington on Jul 23, 2018 20:35:48 GMT
Peter,
My horizontal shaft is exactly the same as you describe. I even have a spanner shaped to fit the lock nuts. Based on what has been explained here I will have another go and try and tighten the lock nuts tighter.
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