View Full Version : Centering a cutter on horizontal mill...

02-02-2010, 05:29 AM
Hi all,

i'm relatively new to horizontal milling and so far it has outstripped my expectations - freakishly heavy cuts and acurately sized slots in one pass :D

But how do i centre a cutter over say a shaft held in the vise? I have seen no wiggler device for horizontals? Its easy on the bridgeport with an edge-finder and the DRO, but on the horizontal, whats the secret????

Thanks in advance


Ian B
02-02-2010, 05:54 AM
Do you have room to put a square on the table and against the shaft? Measure the gap between the square and the edge of the cutter with calipers, adjust to get the same gap both sides.


02-02-2010, 06:21 AM

Measure and record the width of the cutter and the diameter of the job.

Set the cutter clear of the job - to one side - raise the knee until the dimate rof the cutter is below the job centre height - start the cutter and advance it ("Y") to the job until it just touches the job. Set your "Y" dial to zero. Raise the cutter to clear the job.

Move "Y" toward and over the job by half of the sum of the width of the cutter + the the diameter of the job.

ie Movement of "Y" = (cutter width + job diameter)/2


If the cutter width is say 0.375" and the job diameter is 2.250" the "Y" movement (after "touching" the cutter to the side of the job) is:

Y = (0.375 + 2.250)/2 = 2.625/2 = 1.3125"


Y = (3/8 + 2 1/4)/2 = 2 5/8 x 1/2 = 2 5/16"

Your cutter is now centred over the shaft.

Start the cutter and raise the knee until the cutter just touches the top of the job. Set the knee dial to zero. Using "X", back your cutter clear of the job. Set your depth of cut and start milling - using "X".

I'd suggest a couple of trial runs on scrap until your are comfortable with the process and then "go live" and start on the real job.

Draw it as an end elevation as a sketch on paper and it will pretty well "jump" at you.

Richard Wilson
02-02-2010, 06:55 AM
Put the work in the vice. Gently raise the table till the cutter just touches the work. Stop cutter and lower the table slightly. You should be able to see if the witness mark is central to the cutter or slightly to one side or the other. Adjust and try again. Should only take one or two goes to get it as near as you need. Its in one of Fred Calvin's books on milling - full of useful tips.


Doc Nickel
02-02-2010, 06:56 AM
I've used both techniques, but my normal one is the first- measure the cutter width, measure the stock width, use machinists' square (or 1-2-3 block or whatever's handy) to measure from the cutter (at the tooth peak) to the square, which is butted up against the stock.

If it's a rough part, dial calipers'll do. If accuracy is paramount (which it isn't on my horizontal, owing to worn table ways) I'll use depth mics and regular mics, and take multiple measurements.

My reference books show the "touch off" method, using paper and a turning cutter.


02-02-2010, 07:15 AM
Are gear cutters symmetric? In other words, if you center off the flat faces will the involute also be centered?

I would think this the case but do not have experience to know.

J Tiers
02-02-2010, 08:41 AM
Hi all,

i'm relatively new to horizontal milling and so far it has outstripped my expectations - freakishly heavy cuts and acurately sized slots in one pass

The same things apply here as with end mills....

The width of the cutter is rarely exactly what you need. So you use a thinner one and step over to get the width and edges on dimension, just as with a slot cut using end mills.

If the cutter IS the right width, you have a lot better shot at the one-pass to finish technique, of course, since there is much less wandering tendency with a horizontal.

gear cutters, at least ones not for bevel gears, are intended to be one-pass form cutters, so yes. Bevel cutters are symmetric, but you take a separate cut for each side.

02-02-2010, 09:01 AM
i'm relatively new to horizontal milling and so far it has outstripped my expectations - freakishly heavy cuts and acurately sized slots in one pass :D

it is fun isn't it :D

i think i've used most of the methods here, at least i can't think of any more......maybe a planer gauge>? I might have used a planer gauge to measure between work and cutter as well

Those new to horizontal mills should get a big does of safety caution.

On the vertical i will often do the touch off using a long torn strip of paper (.003") and hold lightly between cutter and work. i say lightly because i want it pulled out my hand. Now, I'm probably violating safety rules, but i'm comfortable with the technique.

I would not think of doing this on the horizontal, limbs stay well away from the action Compared to the vertical, the horizontal has a massive zone of exposed high torque moving parts. Even the pip sticking out of the arbor support is quite dangerous. They are legendary arm removers. A piece of clothing gets caught and you slowly get twisted into the machine. Some machinists who've visited my shop almost seem scared of them....that's going too far, but they deserve a healthy dose of real caution.

I know i've put this up before, but its such great machining porn, like a beautiful woman, how can you get tired of seeing it? :D


02-02-2010, 03:14 PM
Thanks all, all ideas seem workable and have been noted.

Nice pic McGyver, what are the details - DOC, speed, material etc??

I'm finding i need to feed the work in by hand until a couple of teeth are working and then i can whack in the power feed and stand there drooling as another lump of steel gets turned to a massive pile of swarf;) Does that sound normal? This is with straight-cut wheels, i do have some slant-cut but only in a few sizes, i guess they would be easier?


02-02-2010, 04:08 PM
The only thing I do different is use masking tape on the shaft, it easy to see when the cutter hits the tape