Thread: Two thou bigger at one end !

Originally Posted by Hornetb

I'll be in the market for a 50mm face mill myself soon. From reports, on these smaller machines, the 45 degree face mills are the best option unless you need to mill up to a shoulder.

Just thinking back to your issue, I know you have it worked out now, but another observation/caution to watch out for. I was using my mill last night and when trying to take a cut 4mm wide with a brand new 4mm 4 flute endmill on steel my quill was pushing back up into the head even though it was locked off. At least on mine it has a round knob that locks the quill so its quite difficult to put much pressure on it but I would have hoped that wouldn't be necessary. Anyway, as I was taking a cut I noticed a change in the depth of cut and realised that as I cut across the piece the quill DRO revealed that the quill was being pushed back up into the head.

I'll have to have a closer look at this setup and see if I can improve the lock mechanism, either by increasing the contact that the screw makes with the quill barrel or maybe as a second option switch the round knob out to a lever type knob that allows me to put a bit more torque on it.

These mills are certainly a compromise, but I'm starting to learn my way around them.

Hi,
Thank you for your notes. I'm in complete agreement about the pushing back. I took the block of BMS that I used as a test piece with me this morning to a place that lets me have bits of material. The workshop manager that looked at my test piece was quite uncomplimentary about it ! I won't repeat what he said but he suggested that the head or the spindle was been pushed back slightly. He also made the comment that "Did I have the spindle column locked" which I did.

Having said all that, I am well aware that these small mills are nowhere as rigid as much larger machines and should be treated accordingly. But I like many others am learning about and understanding the capabilities and behaviour of the machine that I have.

Originally Posted by BaronJ

Hi,
Having said all that, I am well aware that these small mills are nowhere as rigid as much larger machines and should be treated accordingly. But I like many others am learning about and understanding the capabilities and behaviour of the machine that I have.

Yeah, me too.

Rigidity is something I knew would be limited, but the quill retracting wasn't something expected to look for either. I doubt my lock will be sufficient to hold it so may end up building a different external quill lock. I've seen a few plans. Thank goodness I have a lathe also so building something probably wont be too big an issue but it would be nice to just start using it instead of fixing it.

I'm still trying to sort out the column warp which at the moment is the major deal breaker.

Hi Hornetb,
Sorry I forgot about measuring the column. I can't actually get at it to make any meaningful measurements. The motor is in the way at the top and the ways cover stops you at the bottom. I've been thinking about this pushing back of the spindle. My machine has a lever type locking handle and pushes a rectangular block into a machined slot in the spindle body. This also prevents rotation of the spindle body. The rack is also machined directly into the body of the spindle with the gear machined directly onto the shaft that has the handle boss on one end. It occurs to me that any lift could be in the spindle bearings themselves. There are a pair of opposed tapered bearings with an adjusting collar at the top. On my machine the spindle can be removed with ease in a few minutes.

If you place a block between the table and the spindle face and apply pressure with the down feed handle you should be able to detect any spindle bearing play and a dial gauge from the table to the column at the same time, would register any column deflection.

Don't know if this helps or not.

Hi Guys,

After the issues with the piddly little fly cutter I used to skim the top of my vice, I decided to make another one. This one is made from a 15 mm thick by 75 mm diameter disk of stainless steel, faced both sides drilled and bored 13.25 mm. The shaft is a 65 mm length of 16 mm silver steel with a spigot turned down to 13.30 mm and pressed into the disk. An 8mm hole with a 1/4" whit grub screw holds a short piece of 6 x 6 mm tool steel ground with a radiused cutting edge. I used a 7.5 degree clearance angle on both the top and front edges. This one doesn't take prisoners. At 800 rpm and 0.5 mm depth of cut on BMS there is no chatter and the finish is surprisingly good.

I also checked and had to re-tram the mill before I tried this new cutter. It had moved about 3 thou. Pictures attached.

Hi Baron,

Looking good.

No chance that disk could come free from the shaft is there? That would get exciting quick.

But I was more going to post on the geometry of the HSS tooling. Its hard to tell from the photos but it looks to me my like your geometry might still be off. With the fly cutter ground properly you should get a really, really nice finish. Just looking at your pictures (which may be deceiving), but it looks like the grind isn't quite right. Just remember a fly cutter is a single point lathe tool, just its the tool that it moving rather than the workpiece, so the tool is basically ground like a lathe tool - same geometry. But it looks like you "might" have ground it to cut on the wrong plane. A fly cutter cuts as it moves sideways so you want your cutting edge to be ground and positioned to cut as the tool moves left or right. From your pics it looks like you don't have any back relief on the cutting edge (the outer most side of the tool bit) and could improve your radius also (but that depends on your depth of cut as to whether that comes into play here).

Having the tool meet the workpiece at 90 degrees means you need to thing a little bit more about how you grind the tool. Have a look at this thread, you have to wade through and think a bit to follow it but its a start.

http://bbs.homeshopmachinist.net/thr...l-Bit-Geometry

Of course I could be misinterpreting the pics too. You couldn't show some more pictures of how your tool is ground?

Originally Posted by Hornetb

Hi Baron,

Looking good.

No chance that disk could come free from the shaft is there? That would get exciting quick.

I would hope not ! As you say it would get very lively.
Its a good press fit. The drilled hole has a slight taper on it so the shaft was pressed in from the big side. I could always press it back out and use some locktight on it.
But I would suspect that trying to do that would cause it to gall and ruin the shaft.

But I was more going to post on the geometry of the HSS tooling. Its hard to tell from the photos but it looks to me my like your geometry might still be off. With the fly cutter ground properly you should get a really, really nice finish. Just looking at your pictures (which may be deceiving), but it looks like the grind isn't quite right. Just remember a fly cutter is a single point lathe tool, just its the tool that it moving rather than the workpiece, so the tool is basically ground like a lathe tool - same geometry. But it looks like you "might" have ground it to cut on the wrong plane. A fly cutter cuts as it moves sideways so you want your cutting edge to be ground and positioned to cut as the tool moves left or right. From your pics it looks like you don't have any back relief on the cutting edge (the outer most side of the tool bit) and could improve your radius also (but that depends on your depth of cut as to whether that comes into play here).

I must admit that I initially hammered the tool a bit to see if it would stand up to a big cut. Then I tried a cut on a piece of material that was smaller than the cutting diameter and found that the broken cut stalled the motor when the toolbit hit the workpiece edge. So the maximum cut depth became 0.15 mm. I really do need to play with the cutter geometry and try to understand what I need to do. Other than that this tool is very rigid.

Having the tool meet the workpiece at 90 degrees means you need to think a little bit more about how you grind the tool. Have a look at this thread, you have to wade through and think a bit to follow it but its a start.

http://bbs.homeshopmachinist.net/thr...l-Bit-Geometry

Of course I could be misinterpreting the pics too. You couldn't show some more pictures of how your tool is ground?

Yes I will go and have a read at that link. As far as pictures go not a problem. Its not too easy to see in the ones above.
I ground the original tool for use on the lathe, to cut a groove in a pully for a circular cross section expandable belt. The type used on washing machine pumps.

Watch this space...

Hi Hornetb, Guys,

Here are a few, poor, photos of the tool bits I've ground and tested in my "New Fly cutter". I've tried to show the top, side and face but they seem very hard to photograph. Even using flash, which doesn't seem to have any effect when you are only an inch from the object that you are trying to photograph. Anyway on one of the pictures I drawn red lines to outline the tool bit and its shape. One of the tool bits I used to cut a 5 mm wide circular trench in a piece of rolled plate. That experiment seemed to work just fine.

So pictures as requested with apologies for the poor quality.

The problems with the photos is your camera is not focusing close enough. It probably can't. Every camera / lens will have a minimum focal distance, so a lot closer than others.