Thread: More gear head mill problems - SM-MD45

First thing I would check is run-out on the spindle, particularly at the depth of extension you are working at.

What type of spindle is it, MT4 or R8?

You are using the drawbar I am assuming?

Next thing would be to check how well the work is being held down.

Is it showing chatter on the workpiece or does it just sound terrible?
What rpm are you running? what dia is the cutter?
Its a single toothed cutter? if so then runout doesnt matter.
Sure you arent climb milling?

I dont recall what the drawbar is like on these machines. Is there a smooth section you can rub your fingers against?*
I'm guessing its just backlash in the gears or the spindle, running your fingers on the drawbar provides some drag so they dont clatter about. Though I dont have a real fix. While it can sound shocking I'm not sure how much damage it does?

I assume you are feeding with the X, if so moving the Y
so the cutter loadsup slower or unloads slower might help.

Stuart

*just to be clear I'm talking about at the top of the machine.

p.s. was it you that made his own fly cutter? is this the one that has issues?

Originally Posted by Big Shed

First thing I would check is run-out on the spindle, particularly at the depth of extension you are working at.

What type of spindle is it, MT4 or R8?

You are using the drawbar I am assuming?

Next thing would be to check how well the work is being held down.

I have not checked the run-out at depth. I checked it full up and it was 0.01mm. I will extend the quill and check. I am running an R8 spindle. The arbor of the fly cutter is 3/4 and it is mounted in a 3/4 R8 collet.

I am using the standard R8 7/16 drawbar into the 3/4 R8 collet.

The work is in the vise on parallels. 25mm square steel not extending past the vise jaws. It is tight and rigid.

Originally Posted by Stustoys

Is it showing chatter on the workpiece or does it just sound terrible?

It is showing chatter in the workpiece. It shows some ~1.5 to 2mm wide concave streaks in the direction of travel.

Originally Posted by Stustoys

What rpm are you running? what dia is the cutter?

I have tried different RPMs from ~450 to 1,600. With 1,000 being the main one I have been using as this is what Tormach does on their demo video with the same fly cutter. Cutter diameter is around 8cm total.

Originally Posted by Stustoys

Its a single toothed cutter? if so then runout doesnt matter.

Single carbide insert - Tormach SuperFly.

Originally Posted by Stustoys

Sure you arent climb milling?

I have tried traveling both directions. It does not make much difference.

Originally Posted by Stustoys

I dont recall what the drawbar is like on these machines. Is there a smooth section you can rub your fingers against?*
I'm guessing its just backlash in the gears or the spindle, running your fingers on the drawbar provides some drag so they dont clatter about. Though I dont have a real fix. While it can sound shocking I'm not sure how much damage it does?

The drawbar is one that has a thread on the top and bottom and smooth in the middle section. It oscillates quite a bit when the machine is running. I have 2 drawbars and they both do this. I am not sure if it needs some sort of tapered bushing to stop this.

It sounds like backlash in the gears. It was enough however to stall the cutter once. It sounds like something is going to give way which does not make much sense. Others with this machine have reported that there is no vibration and it cuts through like butter. I am not seeing it at all. Completely the opposite.

Originally Posted by Stustoys

I assume you are feeding with the X, if so moving the Y
so the cutter loadsup slower or unloads slower might help.

I have tried moving the Y and it really makes no difference. I end up with the same noises and a similar result.

The fly cutter is a Tormach SuperFly. Beautiful piece of tooling.

Edit: For the record, I have got better cuts than the one pictured. This one however illustrates the issues best.

IMG_1936.JPG IMG_1935.JPG IMG_1938.JPG

Don't worry about the Climb milling, doesn't play a part in facing.

Do you have any tips with a different nose radius on them.

Wouldn't be overly concerned about bubbles in your oil,after all it is a gearbox with parts spinning in oil at high RPM.

Is it possible to move the cutting tool further back into the fly cutter body to reduce the amount of tool over hang.

Do you have a Face mill indexable tool,if so do you get the same results with it.

Hi

The fly cutter I use in the DM 45 Mill/Drill is the R8 fly cutter from CDCO , it uses a hss ground tool bit , held in by 3 screws . It works fine .

I've never seen a carbide insert flycutter tool like that one pictured ... The insert itself may be giving you issues ? Is it the correct insert e.g., angles etc. Mike

Just a thought looking at those ripples, have you checked you spindle bearing for slop? They may have settled in from new (or never been adjusted right) and need adjusting.
I would pull the quill out and disassemble the spindle, you will more than likely find what looks like white cooking fat as grease. After cleaning everything up with a bit of kero or similar, use some high quality wheel bearing grease and adjust the pre load. At least then you know you have eliminated that area and it's properly greased.

Also when machining keep the quill in as much as possible and locked.

Dave

Originally Posted by morrisman

Hi

The fly cutter I use in the DM 45 Mill/Drill is the R8 fly cutter from CDCO , it uses a hss ground tool bit , held in by 3 screws . It works fine .

I've never seen a carbide insert flycutter tool like that one pictured ... The insert itself may be giving you issues ? Is it the correct insert e.g., angles etc. Mike

Hi Mike,
Have a look at this home made carbide tipped fly cutter, it's a work of art (could be another project for you). Rob joined here a few years back but mostly posts on the Madmodder forum as he is from the UK.
Fly Cutters

Dave

Originally Posted by pipeclay

Don't worry about the Climb milling, doesn't play a part in facing.

Do you have any tips with a different nose radius on them.

Unfortunately I do not have any others of the same shape. I have the cemented carbide (pictured) and the polished type for aluminum. These were supplied with the fly cutter by the manufacturer. The one pictured was at the end of the run after it had taken a beating. Surprisingly the insert still looks in good shape.

Originally Posted by pipeclay

Wouldn't be overly concerned about bubbles in your oil,after all it is a gearbox with parts spinning in oil at high RPM.

Thanks for mentioning this. I will not look too much into it. It is certainly not foaming right up or anything.

Originally Posted by pipeclay

Is it possible to move the cutting tool further back into the fly cutter body to reduce the amount of tool over hang.

I will have to give this a try. The cutter is very rigid however and is not out as far as shown in the Tormach demo video (see below for the link).

Originally Posted by pipeclay

Do you have a Face mill indexable tool,if so do you get the same results with it.

Unfortunately not. I have been trying to convince myself to pull the trigger on one of those small Glacern 45 degree indexable face mills. I keep reading however that the fly cutter will out perform the face mill as the fact it has a single insert does not hog the horsepower of the motor. I am not sure either way.

As a side note, 13mm drilling into aluminum can give off similar noises.

Originally Posted by morrisman

Hi
I've never seen a carbide insert flycutter tool like that one pictured ... The insert itself may be giving you issues ? Is it the correct insert e.g., angles etc. Mike

Yes. This is the one Tormach supplied and you can see the performance it gives in this video: Tormach-Fab Lab Skill Builder: Fly Cutting with a Tormach Superfly Cutter - YouTube (note about 3min in).

Originally Posted by Dave J

Just a thought looking at those ripples, have you checked you spindle bearing for slop? They may have settled in from new (or never been adjusted right) and need adjusting.
I would pull the quill out and disassemble the spindle, you will more than likely find what looks like white cooking fat as grease. After cleaning everything up with a bit of kero or similar, use some high quality wheel bearing grease and adjust the pre load. At least then you know you have eliminated that area and it's properly greased.

Also when machining keep the quill in as much as possible and locked.

Dave this is all good advise regarding the bearing slop/quill. I have not checked the spindle bearing at all. I will have to check the bearing and pull out the spindle. I am not sure how to adjust the pre-load so I will have to research that one.

As a general rule when milling I try to keep the quill up as much as practical. "Quill is for drill" right?

Wow thats chatter.
Forget everything I said......

Originally Posted by pipeclay

Don't worry about the Climb milling, doesn't play a part in facing.

Sure if you make a couple of reasonable assumptions. I was checking the unreasonable. Given the pictures the problem is elsewhere.

Stuart

Originally Posted by variant22

Unfortunately not. I have been trying to convince myself to pull the trigger on one of those small Glacern 45 degree indexable face mills. I keep reading however that the fly cutter will out perform the face mill as the fact it has a single insert does not hog the horsepower of the motor. I am not sure either way.

If that were true industry would use fly cutters. They don't.

The loading/unloading of your fly cutter at speed as the tip enters & leaves the cut is a recipe for vibration and chatter. A 3 or 4 tooth face mill has at least 1 tooth in the cut at any time thereby preventing this variable load.

It takes X HP to remove Y cm3 of metal per minute. The only way a face mill will remove less than a fly cutter is if the rpm, DOC or feed is radically different - or the tip geometry is worse. Depends on what the limiting factor is.

FWIW I would *never* run an 80mm fly cutter at anything like 1000 rpm in my Bridgeport. Maybe 150 rpm as a starting point - this is over 100 sfm. Yeah I mix up imperial & metric units.....

PDW

Have you tried increasing the depth of cut.

In normal operation with use of a face mill depths of cut of upto 3mm should be achievable on your machine.

I would also think that cuts of upto .5/.75mm should be achievable with the fly cutter.

When you have been running the cutter at 400/1000 RPM have you been able to produce something like the 250mm/min feed rate.

You may find if you can increase the feed rate that the vibration problem may reduce if not already at or about the stated feed rate.
,if the feed rate is to slow this could be causing some of your vibration.

Not sure if you already have any temporary swarf gauding on the mill but at those speeds and feeds it would be advisable,For Sale signs or similar are good to use,just cut to size and lay in the tee slots or support some other way.

Wow, that is pretty severe chatter.

By putting your hand on each section of the mill, mill table, quill etc when cutting you should be able to feel where the chatter is being generated.

There will be some serious shudder being generated when scouring like that occurs.

Something is loose (bearings, gears, gear head, work mount) to get that much marking.

You could try putting a long bar in your largest collet and the table vice (separately), and with the machine off, apply leverage and look for movement. Use a dial indicator on it.

Also heavily oil the gibs and when levering on the various components look for oil squelching in and out of the ways - shows movement very easily.

Don't over do it, you only need light/moderate pressure.

Rob.

Originally Posted by PDW

If that were true industry would use fly cutters. They don't.

This fly cutter is specifically engineered for small machines. Tormach have a great article on the development (TTS SuperFly Cutters: A Modern Update to an Old Shop Standard « Milling Around). Tormach reported far better performance on their small mills with the fly cutter than their indexable face mill. The article goes into some detail on why this works better than a face mill on a 1.5hp machine.

Originally Posted by PDW

The loading/unloading of your fly cutter at speed as the tip enters & leaves the cut is a recipe for vibration and chatter. A 3 or 4 tooth face mill has at least 1 tooth in the cut at any time thereby preventing this variable load.

Yes, but apparently they take significantly more horsepower.

Originally Posted by PDW

FWIW I would *never* run an 80mm fly cutter at anything like 1000 rpm in my Bridgeport. Maybe 150 rpm as a starting point - this is over 100 sfm. Yeah I mix up imperial & metric units.....

Believe it or not, at 1,000rpm I get the best finish and least chatter. It was what Tormach were using on their mill which is apparently less rigid and has less power than the RF45.

Originally Posted by pipeclay

Have you tried increasing the depth of cut.

In normal operation with use of a face mill depths of cut of upto 3mm should be achievable on your machine.

I would also think that cuts of upto .5/.75mm should be achievable with the fly cutter.

To be honest I have been a bit gun shy on this. I did not want to wreck anything. I might have to try a bit deeper and see how it goes. I am however convinced that something is up with the gear drive as others with the same mill have had excellent results. Mine so far do not match up to where they should be.

Originally Posted by pipeclay

When you have been running the cutter at 400/1000 RPM have you been able to produce something like the 250mm/min feed rate.

You may find if you can increase the feed rate that the vibration problem may reduce if not already at or about the stated feed rate.
,if the feed rate is to slow this could be causing some of your vibration.

Yes, I have been able to do 250mm/min. I have tried a variety of feed rates. I try to be as consistent as possible with the wheel. I have been paying attention to the sections (feed rate) that produce better results.

Originally Posted by pipeclay

Not sure if you already have any temporary swarf guarding on the mill but at those speeds and feeds it would be advisable,For Sale signs or similar are good to use,just cut to size and lay in the tee slots or support some other way.

The machine does have a perspex guard (which incidentally keeps dropping out - note to manufacturers: something about threading plastic is not a good idea) but it is not useful for stopping the swarf exiting from the sides. It is however on my "todo list" to make a full enclosure. I just finished up the 3 axis DRO install (took a couple of weeks as I had to machine all the mounts and cut down the guards) and the next cab off the rank is a power drawbar. Then the enclosure will come next. It has literally been non-stop work since I purchased this mill. I purchased it to make parts for my car, yet I have spent all my spare time making parts for the mill.

I was only playing with some mild steel to make a few more (I have a standard clamp kit) tee-nuts in both M12 and M8. I am also making a few clamps for use on the table per one of Harold Halls books.

Originally Posted by nearnexus

Wow, that is pretty severe chatter.

By putting your hand on each section of the mill, mill table, quill etc when cutting you should be able to feel where the chatter is being generated.

There will be some serious shudder being generated when scouring like that occurs.

Something is loose (bearings, gears, gear head, work mount) to get that much marking.

You could try putting a long bar in your largest collet and the table vice (separately), and with the machine off, apply leverage and look for movement. Use a dial indicator on it.

Also heavily oil the gibs and when levering on the various components look for oil squelching in and out of the ways - shows movement very easily.

Don't over do it, you only need light/moderate pressure.

Rob.

Thanks Rob. These suggestions are helpful. I will print them off and give it a try. I will report back the results.