Trouble with Horizontal Mill…Very much a beginner

[Nicholas HillParticipant @nicholashill23289]

Hello,

I am very much an amateur who seems out of their depth!

I have recently renovated an old Mill, and when I tried to use it on steel, I can't seem to get anywhere.

I tried with a inch block of brass, and it cut through fine. I tried a 3 inch piece of chemiwood and again it worked fine. But, when I tried EN3….I get an awful noise, and the cutter jams.

I have tried all the speeds, I have tried the cutter going clockwise and anti-clockwise, I have tried a 6inch slitting saw, a more substantial 4 inch cutter…

At one point I was getting sparks out!!

The machine itself seems in good order, I measured the bed to the arbour, and it seems to be parallel.

Its an Ajax AJ8, so I assumed could go up to an 8 inch slitting saw, but if it struggles with a 6 inch saw and a 4 inch cutter. What sizes should I be thinking about?

Any suggestions welcome. The cutters are second hand, but seem sharp, so I don't want to be a bad workman blaming his tools. But my head is getting raw with the scratching going on.

Photos attached are of the set up and a close up of the 'results' of the 4 inch cutter, note the 'stepped' appearance where the cutter jammed.

Nothing works.

PS sorry for the upside down photo…It appears normal in my gallery..but is inverted by the Forum..Even if I load it rotated 180deg…But its a fairly self explanatory.

 

Many thanks,

Nicholas

 

 

 

 

 

 

 

 

 

Edited By JasonB on 12/09/2022 18:43:19

[Nicholas HillParticipant @nicholashill23289]

[Michael CallaghanParticipant @michaelcallaghan68621]

Hi, there are a number of reasons that you can’t get a good cut. First some steel is almost impossible to machine due to its hardness. I purchased some mild steel rod off eBay and no way could I machine that material no matter what lathe tool, speed depth of cut. Nothing would work in my arsenal of tools. Try cutting your material with an hacksaw and see how it cuts. If it cuts ok then you need to look at the machines set up. You say that you have tried all the speeds and feeds. Rotation should be counter clockwise, check that your cutter is correct for this. Start by using shallow cuts, try using cutting fluid. From what I can make out from the lower picture it looks like your cutter is digging in, so rotation is wrong. Feed the work left to right. Hope it helps a bit

[JasonBModerator @jasonb]

What speed did you initially try cutting the steel at and what diameter was the cutter. Of secondary imprtance whet depth of cut, feedrate and number of teeth are on the cutter

A 4" HSS cutter should be running at approx 100rpm, if you have exceeded that by any significant amount then you may well have blunted the cutter

If you ran the cutter backwards (anticlockwise) as opposed to climb cutting then that will also blunt it quickly

Edited By JasonB on 12/09/2022 18:15:04

[not done it yetParticipant @notdoneityet]

It is likely to struggle with steel – especially if using 4” diameter cutters.

I note the lowest speed might be 150rpm (some are 120rpm) unless using carbide cutters.  Both these speeds are quite high for a low powered machine. What power motor is fitted?

If multiple teeth, the feed rate is likely too much for the power, with a reasonable cut per tooth. Or the cut may be so shallow that the cutter will rub and go blunt.

The same applies for slitting saws as they do not like high speeds with hard, tough materials.

On top of all this, if you are hand-feeding, the problems are likely exacerbated unless you have a very steady hand.

Good luck with your mill. If it is a single phase motor, i might suggest either changing the motor pulley to reduce the cutter speed or if three phase wire it to delta and use a VFD. If changing the motor to three phase, then some increase in motor power could be envisaged.

Edited: JB was there long before me!

Edited By not done it yet on 12/09/2022 18:46:27

[JasonBModerator @jasonb]

Having now turned the first photo up the right way it looks from the saw cuts in the bar that you were climb cutting not something that you should be doing with a slitting saw

 

If viewed from the front of the machine it looks like you have the blade set for anticlockwise rotation. if this is so then you should start with the workpiece on the right and move it left into the blade so it contacts the rising teeth

The saw is also far too fine to use for cutting off that large diameter bar as the gullets between the teeth will clog, cause overheating and jamming of the blade as well as make it wander.

Clicking this image should show the climb milling set up a bit larger

Edited By JasonB on 12/09/2022 18:56:19

[DC31kParticipant @dc31k]

Posted by Michael Callaghan on 12/09/2022 18:06:49:

Rotation should be counter clockwise

It is a little problematic to make such a definitive statement without knowing more details of the machine.

What you can say is that the direction of rotation should be such that the cutting forces tend to tighten rather than to loosen the nut on the arbor. Your statement presupposes a right hand thread nut on the arbor, which is not a given.

Once the direction of rotation is known, clearly the cutting tool should be mounted on the arbor so its cutting edges are presented to the work when rotating in that direction.

One thing that has not yet been covered in above replies is climb cutting vs. conventional cutting (ie. direction of feed relative to cutter rotation).

[Andy StopfordParticipant @andystopford50521]

With the cutter arranged as in the photo, the spindle should be rotating ant-clockwise, and the table should be fed from right to left, i.e. against the cutter rotation. This is conventional milling.

If the table is fed from left to right, you are climb milling. This will tend to draw the work into the cutter, with the cutter trying to climb over it, hence the name. To climb mill you need a very rigid machine with minimal backlash in feedscrew and nut. It has advantages, but best avoided until you have more experience.

Have you tried using the side and face cutter in the background? These are far less fragile and demanding than slitting saws. Try taking a light cut with it, say about 0.25mm, at the slowest spindle speed available, and see how you get on. If you get nasty graunching noises check that the table slides are correctly adjusted, and the unused ones are locked. If all goes well, try deeper cuts.

[Howard LewisParticipant @howardlewis46836]

Assuming that bthe cutterv is sharp and rotating in the correct direction, the normal direction of feed is that the work approaches the cutter head on, (IE the cutter is trying to push the work away. If it is trying to roll over the work, that is climb milling nwhich requires all backlash being taken out. On the sort of machines that most of us use, this not possible, so is not advised. Certainly not for a novice! )

The feed rate should be based on the number of teeth on the cutter and be "Feed per tooth" In many cases this is about 0.002" per tooth.

So for a 4" HSS cutter, on mild steel, it should be runnjing at about 95 rpm (100 feet per minute surface speed )

If the cutter has 100 teeth, the feed will be 100 (Teeth ) x 0.002" (Feed per Tooth ) x 95 (RPM ) theoretically the feed should be 19" per minute.

Having ssaid that, the highest that I ever used on an industrial (And therefore heavy and rigid ) machine was 12", with a very gentle manual infeed until the cut was established, using a copious supply of coolant.

You are probably cutting dry, so need to be much more gentle, especially with an older machine which will be worn…

Forcing the feed will lead to a stall, and even if it does not, the surface finish will suffer..

If sparks were being produced, it sounds as if something was very wrong; Direction of rotation, blunt cutter, excessive surface speed, or excessive feed.

Correct each of these and then try again, on steel which is known to be mild, not hardened.

As you try higher feed rates, (Start oiffc gently ) change one factor at a time, or you will never find what caused the problems.

Let us know what you find and how you go on..(Your experience will help others. )

Howard.

[Martin KyteParticipant @martinkyte99762]

With the fine tooth slitting saw you show the gullets will almost imidiately fill and then clog up causing heating and jamming of the saw in the cut (even if you have everything else right, direction of rotation, feed rate, etc.) use a coarse tooth slitting saw, slow rotation, plenty of cutting oil and moderate depth of cut. and don't cllimb mill.

regards Martin

[IanTParticipant @iant]

Posted by Martin Kyte on 13/09/2022 08:51:45:

With the fine tooth slitting saw you show the gullets will almost imidiately fill and then clog up causing heating and jamming of the saw in the cut (even if you have everything else right, direction of rotation, feed rate, etc.) use a coarse tooth slitting saw, slow rotation, plenty of cutting oil and moderate depth of cut. and don't cllimb mill.

regards Martin

All of the above and I don't think i've seen any mention of using a hollow ground tool for deep cuts if you have one.

I've cut flat stock on my mill (12mm steel using a coarse tooth, 1/8" blade), which is very useful for longer cuts (that other machines won't handle) but my horizontal wouldn't really be my first choice for this job. If this is just a test/learning exercise, then doing deep cuts with a narrow slitting saw may not be the best place to start.

Regards,

IanT

[Michael CallaghanParticipant @michaelcallaghan68621]

Posted by DC31k on 12/09/2022 18:59:10:

Posted by Michael Callaghan on 12/09/2022 18:06:49:

Rotation should be counter clockwise

It is a little problematic to make such a definitive statement without knowing more details of the machine.

What you can say is that the direction of rotation should be such that the cutting forces tend to tighten rather than to loosen the nut on the arbor. Your statement presupposes a right hand thread nut on the arbor, which is not a given.

Once the direction of rotation is known, clearly the cutting tool should be mounted on the arbor so its cutting edges are presented to the work when rotating in that direction.

One thing that has not yet been covered in above replies is climb cutting vs. conventional cutting (ie. direction of feed relative to cutter rotation).
one has to start someplace. Most cutters that I have seen and used have been for CCW use. I also took it that the original OP was not a complete ass. Unlike some

[Anonymous]

I prefer to use slitting saws on my horizontal mill. On the vertical mill (with stub arbor) they tend to go walkies on deep cuts. On the vertical mill I limit cuts to shallow slotting, usually one pass. On the horizontal I am happy to take deep cuts, more than 25mm, normally in 5mm steps.

As mentioned above for deep cuts, as opposed to things like screwhead slots, coarse teeth cutters are needed. In this picture all the slitting saws are coarse, except for bottom right:

While I don't think twice about climb milling on the vertical mill I don't do so on the horizontal mill, at least not until I have fixed the backlash adjuster. For slitting saws I tend to run a bit slower than theory, for a 4" cutter around 70rpm. On the horizontal I use 4 thou per tooth as a minimum feed. Below that the cutters seem to chatter. As with all cutting tools they need to cut, not rub. Remember that even with a reasonable depth of cut on a 4" diameter cutter chip thinning applies. So what you get in terms of chip load is smaller than the theory. For steel i always run flood coolant on the horizontal.

I would have the outer support much closer to the cutter to minimise deflection, like this:

My horizontal mill was an impulse buy, but it has turned out to be very useful.

Andrew

[Anonymous]

Posted by Michael Callaghan on 13/09/2022 12:09:04:

Most cutters that I have seen and used have been for CCW use.

I didn't know that horizontal cutters were handed. Surely the required direction of rotation is dependent upon which way round the cutter is mounted on the arbor? My horizontal is happy running in either direction. I normally run cutters clockwise, looking from the front, with the work feeding from left to right.

Andrew

PS: In my previous post I forgot to add that for slitting saws there are those who use drive keys and those that don't.

[SillyOldDufferModerator @sillyoldduffer]

Taking a step back to some of Nicholas's posts suggests to me this one needs to go right back to first principles.

This is the machine, and Nicholas comments the seller dropped and damaged it:

Note the sheered off hand-wheel, but also this:

Plus a question about gears and worms in relation to a need to replace a lead-screw.

So, a second-hand mill in unknown condition, that was significantly damaged before delivery, that's been renovated and is now being tested by a beginner, possibly using cutters and saws that may not be in tip-top condition either!

The picture shows a medium sized single-phase motor, so the machine isn't a powerful monster. However, the report of sparks (at the cutter I hope) suggests the motor and drive to the spindle are OK.

It's hard to debug a machine you have no feel for in normal operation. Therefore I suggest taking it step by step, assuming nothing, and gradually eliminating problems.

First step I suggest is a thorough mechanical check of the knee and table; these should move smoothly in one plane when the hand-wheels are operated, but otherwise be rigidly tight. Any movement in the mill's structure, dovetails, gibs or work-holding will cause chatter and dig-ins. Might be due to wear, but given the history it wouldn't be surprising to find damage or re-assembly errors, for example it's easy to put gibs in wrongly

Second step, make sure the material is cooperative. Many metals don't machine well, for which reason I recommend buying metal specified as free-cutting rather expecting my machines to munch through random scrap without bother. Although EN1a-Pb machines three times better than EN3, EN3 should be OK for testing the mill. But is it definitely EN3? If there's any doubt, change it.

Third step, make sure the speed, depth of cut and feed-rate are all a reasonable match to the cutter diameter and type. Lots of good advice already given. Usually I set RPM, then go for a reasonable depth of cut (depends on motor power and machine rigidity), and adjust feed-rate so the machine sounds as if it's working, but not being pushed. Two common beginner extremes are too-gentle pussy-footing, which causes word-hardening and rapid tool blunting, and grossly excessive expectations, where a bad-tempered gorilla expects a poor little machine to take massive cuts. Off the two the second is worse because it can damage the machine, worse if the heavy handedness extends to repairing the machine is well.

Fourth, make sure the cutter is in good condition, and spinning in the right direction (not in reverse!) Again, if there's any doubt, buy a new one!

Fifth, make sure the operator knows what he's doing. In my workshop more problems are caused by me than all other causes put together. I have to compensate for being clumsy and impatient as well as half-trained. Although confidence is important, it's no substitute for knowledge and experience. I'm self-taught, which took a lot of effort and has left all sorts of odd gaps in my skill-set. I've made some painful and expensive mistakes; the best way I've found to minimise them is to approach learning new tricks with caution. I read-up, search the forum, ask for advice and experiment first; I try hard to eliminate problems before jumping in at the deep end. As they say in the Army "Proper Planning and Preparation Prevents Piss-poor Performance".

Sixth, two or more faults present at the same time make debugging much harder. Don't jump too quickly to conclusions, rushing in and fixing the wrong things never works out well! Especially if they weren't broke in the first place. You can guess how I know!

Dave

[not done it yetParticipant @notdoneityet]

Dave,

The OP states that it works fine with brass, for instance.

I would suggest the mill is simply too fast, under-powered and attempts have been with over-large cutters, apparently climb milling while taking too large a depth of cut and often at high speed.

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