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Horizontal milling arbours

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Andrew Tinsley07/12/2019 16:36:46
941 forum posts

I have a Centec 2B milling machine that has 2MT tapers in both the horizontal mode.

I have a large quantity of cutters of all types including gear cutters. The machine is equipped with a 1 inch horizontal milling arbour. The tooling I have includes 5/8", 7/8" 1", 11/8" and 11/4"bore cutters.

Horizontal arbours in 2MT fitting seem to be almost non existent, so how would one make up suitable arbours?

Most commercial arbours and spacers seem to be made by cylindrical grinding to fine limits and then hardened. Not something I have the kit or skills to do. I doubt if I am capable of turning an arbour to fine limits. So how accurate would one need to be to turn an arbour, including the 2MT taper? I could make a good job of the spacers and I suppose that case hardening would be better than nothing?

Any suggestions would be most welcome. The alternative is to sell off the non inch bore cutters and replace them with inch bore alternatives.

Andrew.

Clive Brown 107/12/2019 16:57:50
307 forum posts
7 photos

For occasional home workshop use, I'd consider unhardened, as-turned mild steel arbours quite sufficient. They don't have to be too long.An alternative, for say the 5/8" size could be a 2MT blank bored out with a length of ground silver steel cross pinned in place

2MT tapers are not too difficult to turn if a pattern is available to set the top-slide to match.

Paul Kemp07/12/2019 18:06:49
364 forum posts
18 photos

Andrew,

My Elliot Omnimill is the same, 2MT horizontal and vertical and a 1" arbor. For using cutters with larger bores I have made bushes as I don't tend to use the key. Used a couple of 4DP 1 1/4" bore cutters like this cutting the teeth to full depth and they never slipped. For smaller ones I would agree re a non hardened one will see you OK. No point in worrying about micron accuracy on the diameter or having it ground for normal home use.

Paul.

HOWARDT07/12/2019 18:21:00
484 forum posts
14 photos

EN16T would be suitable. I used to have the arbor tolerances and think they were 0.0005 to 0.001 under, an easy slide fit. Always used a drive key on cutters over 1/8 wide as you rely on the friction between the cutter and collars otherwise.

Dave Halford07/12/2019 19:02:42
521 forum posts
4 photos

Don't bother with cutters much over 3" in outside diameter, they are used on big high power machines.

I have not had wide cutters slip either, just as well given my 2A arbour doesn't have a keyway.

Andrew Tinsley07/12/2019 19:17:37
941 forum posts

Thanks everyone for the advice, looks as if I may well be testing the water and making up a 5/8" arbour.

Andrew.

David George 107/12/2019 19:51:36
avatar
1010 forum posts
320 photos

When you come to finnish turning, finnish it between centers as you are not relying on a chuck to repeat location and you can remove and replace it to check fit ie blue the taper. Also I use a fixed center in both ends with pleanty of grease on the tailstock center. You should be a able to finnish with a runnout of less than 0.001 inch.

David

Phil Whitley07/12/2019 20:31:22
avatar
1000 forum posts
132 photos

Grab any horizintal arbors you can and get adapters from ARC, I have a load of R8 arbors and got an R8 to 30int adapter to use them in my Harrison. You could also fit a collet chuck and put the arbor in a collet.

Good luck with it!

Phil

not done it yet07/12/2019 20:39:55
3774 forum posts
15 photos

I made up a 5/8 arbor with 2MT only about a week or so ago. Very simply achieved.

A blank arbor, drilled and bored in the lathe; over-sized steel bar turned at the end to the size required to fit in the arbor - you choose for shrink fit, press fit, or loctited; turn down the bar to size; sort out the other end to fit the mill. Pin in place for a belt and braces approach! Make spacers and the job is done.

Mine was actually for holding reamed gear blanks while cutting the teeth, so held in the rotary table at one end and supported, by the centre, at the other. Making it suitable for use in the Centec, if ever required, was just a sensible extra.

For cutting several gears at once it needs to be straight and true, but I daresay the error over a single 16mm wide gear is next to nothing at the worst, as the gear has to be located far enough away from the rotary table so any run-out is diminished towards the centre.

Question might be : Are these cutters 5/8” or 16mm? There is a subtle difference. Most modern involute gear cutters are 22mm, not 7/8” - again different enough to matter.

I might even consider using my 2MT >>>3MT sleeve to extend a cutter further over the work if necessary, but only if I ever needed it.

Vic07/12/2019 21:39:08
2384 forum posts
12 photos
Posted by Paul Kemp on 07/12/2019 18:06:49:

Andrew,

My Elliot Omnimill is the same, 2MT horizontal and vertical and a 1" arbor. For using cutters with larger bores I have made bushes as I don't tend to use the key. Used a couple of 4DP 1 1/4" bore cutters like this cutting the teeth to full depth and they never slipped. For smaller ones I would agree re a non hardened one will see you OK. No point in worrying about micron accuracy on the diameter or having it ground for normal home use.

Paul.

My old Omnimill had a 3MT in the vertical head. I no longer have the mill but I still have the Albrecht drill chuck that came with it complete with 3MT arbor.

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