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Horizontal mill cutter

Horizontal mill cutter

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George Jervis18/06/2019 03:34:32
60 forum posts
57 photos

Hi everyone,

I'm looking for some words of wisdom from forum members please, I have a Ajax aj8 horizontal milling machine which I've not had for very long, I have a few issues with it I'm trying to sort out, a friend gave me several cutters to get me going, I think the cutters are blunt/dulled and I would like to have them sharpened would anyone know where I could get them sharpened at a sensible price? or would a kind member here be able to help sharpen them for me for a donation

The other issue I have is when I got the mill is it didn't have a electric motor with it so ive fitted a 1/2 hp 3phase motor and converter I had in my workshop, the motor spindle has a 1" pulley on it going to the 7" spindle/arbor pulley. I've been trying to cut a 20mm slot in BMS 50×50 square bar to make myself some qctp's for my lathe, (the first one took me about a week to do between work and family commitments) what I'm finding is either the cutters won't cut or if I take a cut deeper than 3 to 5 tho it trips the 3 phase converter, I have 2 identical converters and have tried both with the same result (tripping out) the cutters I'm using are HHS 2mm width up to 1/2" I haven't had any problems with slitting saws. Would I need a bigger motor like 1 hp or would this be to big for my mill?

Any help and advice would be appreciated

George

RobCox18/06/2019 08:14:15
26 forum posts
11 photos

Hi George, when I acquired my Elliott horiz/vert milling maching I also got a TC grinder to go with it with the intention of buying used dull horizontal cutters and sharpening them. So far it's worked well. Blunt cutters are cheap and my restored Union grinder sharpens them well.

If your cutters have a 1" bore I might be able to help you out. All my horiz cutters are 1" - smaller bores would require new tooling to fit the grinder.

As for your motor, my mill has a 2hp motor for the horizontal drive, with pulley & belt speed reduction to 100rpm minimum, driven by a vfd. The minimum speed is a tad on the high side, although with the way I have the vfd configured I can use that to slow it down a bit without losing torque. Even with sharp cutters, the mill struggles with cuts deeper than about 40 thou on a 1/2" wide cutter. There's a whole host of things that could be wrong here, starting with the user(!), but I'm guessing blunt tools plus an underpowered spindle may contribute to your problems.

If you PM me maybe I'll be able to help you out. May take a while though, because I don't get too much shop time these days..

Rob

not done it yet18/06/2019 10:48:14
3364 forum posts
11 photos

Hi George,

Several things.

Hertz from the VFD might mean much lower power transmitted than rated motor power.

Too high a speed would quickly blunt a carbon steel cutter, especially if the tool post steel has a higher carbon content.

BMS, while low carbon, may have quite a hard surface.

Too light a cut may well dull the cutters quite quickly if they rub rather than cutting (more so with carbon steel cutters.]

Maybe a ‘swipe’ or two on each tooth with a stone might clean the cutter sufficiently to sharpen it up sufficiently? At least for a short while.

2mm is a slitting saw, to me.

I’ve not attempted to sharpen any of my horizontal cutters yet, but I think I would do it on the horizontal with the rotary table. It should only need the teeth under-cutting very slightly?

The Centec (~1.2HP) has not been used in horizontal mode for months. A 20mm slot in BMS would be cut using a roughing end mill - but probably not a 20mm one, with only half a horse power available.

Bazyle18/06/2019 12:56:11
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4724 forum posts
186 photos

You have to think about it like a lathe working 'about face'. If you had a Myford with only an half horse motor would you try to take a 20mm cut at 5mm feed rate?

Ian S C18/06/2019 14:02:27
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7447 forum posts
230 photos

Even my Rexon vertical milling machine has about 1.5 hp, and that at times feels underpowered, I would say 2 hp would be a starting point for a horizontal mill, maybe 2.5 hp if electronically controlled.

Ian S C

JasonB18/06/2019 14:21:57
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1/2HP is about the same as a SX2P mini-mill, no wonder it's complaining

Andrew Johnston18/06/2019 14:43:58
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4855 forum posts
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Posted by George Jervis on 18/06/2019 03:34:32:

........what I'm finding is either the cutters won't cut or if I take a cut deeper than 3 to 5 tho it trips the 3 phase converter.....

Half a horsepower ought to better than that. Here's a 4"x4" slab mill at work:

slab_milling_1.jpg

Spindle speed is 88rpm, width of cut 40mm, depth of cut 2.5mm and feedrate 160mm/min and the material is hot rolled steel. The slab mill is not blunt, but neither is it sharp; bought secondhand on Ebay some years ago. No doubt somebody will whine that it's an industrial horizontal mill and not applicable to the amateur, aw diddums! smile Sure the mill has a 4hp motor on slow range with belt drive to a countershaft and then a gearbox. But if you do the calculations the mertal removal rate is about 1 cubic inch per minute. A rule of thumb says that requires about 1hp. So half a horsepower ought to be capable of far more than a few thou DOC.

First I'd suspect the drive arrangement; is it definite that there is a half horsepower available at the cutter? Second I'd look at the feedrate. Too slow a feedrate simply means that the cutter rubs rather than cuts, especially with low DOC, which takes more power than cutting. I normally start with a chip load of about 0.1mm per tooth.

I don't know what power motor the mill originally took, but half horsepower seems a little low. I'd be inclined to go up to 1hp.

Andrew

JasonB18/06/2019 14:50:08
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It would also be useful to know the diameter of your cutters. A 4" dia side & face cutter will reduce the mechanical advantage of your belt reduction a lot more than a 2" or so dia slab mill like Andrew shows

Edited By JasonB on 18/06/2019 14:50:49

Andrew Johnston18/06/2019 15:55:55
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4855 forum posts
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Posted by JasonB on 18/06/2019 14:50:08:

...........than a 2" or so dia slab mill like Andrew shows

Errr, as stated the slab mill shown is 4" long and 4" diameter.

Andrew

JasonB18/06/2019 16:24:25
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OK so you have big tools but would you not agree that on the lighter machine that the OP has a smaller diameter cutter such as this would give it more mechanical advantage and that the larger the dia the more likely it is to stall.

George Jervis18/06/2019 16:26:29
60 forum posts
57 photos

Hi everyone

The majority of the cutters I have a 2 1/2 to 3 inch diameter and 1/4 inch ish , apart from one which is 1" thick which I couldn't use I couldn't imagine using a slab cutter on my mill? I've put someone pictures in my album of almost all my cutters I have and tried.

Thank you for the continued help

George

Neil Wyatt18/06/2019 16:46:56
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Posted by George Jervis on 18/06/2019 03:34:32:

Hi everyone,

I'm looking for some words of wisdom from forum members please, I have a Ajax aj8 horizontal milling machine which I've not had for very long, I have a few issues with it I'm trying to sort out, a friend gave me several cutters to get me going, I think the cutters are blunt/dulled and I would like to have them sharpened would anyone know where I could get them sharpened at a sensible price? or would a kind member here be able to help sharpen them for me for a donation

The other issue I have is when I got the mill is it didn't have a electric motor with it so ive fitted a 1/2 hp 3phase motor and converter I had in my workshop, the motor spindle has a 1" pulley on it going to the 7" spindle/arbor pulley. I've been trying to cut a 20mm slot in BMS 50×50 square bar to make myself some qctp's for my lathe, (the first one took me about a week to do between work and family commitments) what I'm finding is either the cutters won't cut or if I take a cut deeper than 3 to 5 tho it trips the 3 phase converter, I have 2 identical converters and have tried both with the same result (tripping out) the cutters I'm using are HHS 2mm width up to 1/2" I haven't had any problems with slitting saws. Would I need a bigger motor like 1 hp or would this be to big for my mill?

Any help and advice would be appreciated

George

What rpm are you using?

Rpm should be about the same as for turning at the same diameter, so probably slower than you expect.

Brian H18/06/2019 16:51:20
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1222 forum posts
92 photos

Hello George, it would help to know your approximate location as there may be someone near you willing to help.

Brian

Howard Lewis18/06/2019 17:10:39
2337 forum posts
2 photos

A half horsepower motor does not sound sufficiently powerful for your machine. the possibility is that the motor is being slowed so much that the current draw trips the circuit breaker.

From my Apprentice Training Notes of 1959 vintage, the Feed per Tooth for a Slitting Saw is 0.003" / tooth, and for a Face Mill is 0.007"/ tooth when machining low carbon steel.

The footnote says " Factors to be taken into account before choice of feed is made are:

a ) power available, b ) rigidity of machine, c ) set up ,d ) convenient cutter life and e ) Accuracy of final dimension."

The note also says: "The above figures are published by a well known milling machine manufacturer, and represent performance under ideal conditions". Which probably includes flood cooling with soluble oil, rather than dry.

So count the number of teeth, and arrange the feed on the basis of the above, but be prepared to work below these rates, if cutting dry. 

A  2 mm wide cutter is a Slitting Saw, rather than a Side and Face Cutter. For your safety, DON'T use a key!

If the cutter is in good condition, you may be surprised by the rate at which you can feed, theoretically.

Once I was slotting soft jaws, taking a 0.180" deep cut with a side and face cutter, using a feed of 6" / minute. The machine was not a big Cincinnatti, but a small, old, Herbert with flat belt drive! The overarm was actually two large diameter ( about 4" ) round steel bars, so an elderly machine that had, no doubt seen a lot use in the main machine shop before being downgraded to the Training School..

As already advised, Cutting Speed would be similar to that used for turning. (With a 3" cutter, circa 100 rpm? )

DON'T make the mistake that I once did on a small universal Mill, of running in reverse! The cutters don't work at all well!

Howard

Edited By Howard Lewis on 18/06/2019 17:14:13

JasonB18/06/2019 17:40:08
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I found this which would seem to suggest they only came with 0.75HP motors and they are quite small benchtop machines so may be lacking in some of Howard's criteria.

Andrew Johnston18/06/2019 20:49:27
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4855 forum posts
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Posted by JasonB on 18/06/2019 16:24:25:

OK so you have big tools but would you not agree that on the lighter machine that the OP has a smaller diameter cutter such as this would give it more mechanical advantage and that the larger the dia the more likely it is to stall.

I wouldn't regard a 4" cutter as big. smile For a given spindle speed then I'd agree that a larger diameter cutter will have less force at the tooth and is therefore more likely to stall. But if the spindle speed is reduced in proportion to the increase in diameter then the cutter is no more likely to stall.

The point I was trying to make is that 1hp can take what looks like a big cut. So a half horsepower should be able to do a whole lot more than the OP intimates. I suspect the drive system. A 1" pulley seems a bit small for what is presumably a V-belt. It's not clear if the motor is being driven by a static, or rotary, converter or by a VFD. And if the latter at what frequency. It would also be useful to know how many poles the motor has. If it's 4 and the motor is running at 50Hz that gives about 210rpm at the spindle, which is a little fast for a 3" cutter in steel.

Andrew

George Jervis18/06/2019 21:29:19
60 forum posts
57 photos

Hi everyone,

Thank you for all your help I've learnt a lot today. I had a very interesting conversation with RobCox earlier this evening, I gave him the information of my 3 phase converter which he has told be is to small for my mill and that's the reason it's tripping all the time, hopefully by changing my motor to my spare 1hp motor and getting a larger 3phase converter will hopefully solve 1 of issues I have. The other having the cutters sharpened he is also able to help with too so a big thank you to Rob for all your help and advise and everyone else's input too. Once I have everything changed I let you know how it's running

George

Dave Halford19/06/2019 00:03:49
462 forum posts
4 photos

I would suggest that the mill speed is set by the belts and not the vfd, you will need to keep the motor speed up.

You can use a slab mill on slowest speed with 1/2hp but only 2" dia x 2 3/4" wide one with about one thou DOC on alloy any more gives a stall/belt slip which isn't very useful.

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