Don Young's Black 5

[Jim]

Just to follow on from Pete's valuable comments re machining rods this is a simple method I used for holding the rods while milling the sides and flutes. The jig is based on a short section of square section tube. A centre line was scribed along the top face of the tube so that a series of holding points could be located to hold the variety of rods for a locomotives motion.

Jim

[RGR 60130]

I too like using box section. Instead of tapping holes you can drill right through and put nuts inside for your clamping bolts. Turning it on its side easily changes the orientation. A little check to ensure the box section is straight, square and parallel is advisable before you start and easily corrected with a light skim if it isn't.

Reg

[JonL]

That could easily apply to some of the stuff I do with the vertical slide too, thanks.

[David]

I did mine similar to Pete, Jim, Reg, and no doubt most people.

My jig was 6mm plate with two edges milled square for reference and the hole for one end of the rod drilled at that end so I always had a reliable reference for an edge finder. If I zeroed on those edges I knew the X/Y co-ords of the hole on that side of the rod. The other end had a slot cut to allow for the different rod lengths.

A series of M6 set screws were added along the center line to support the fluted rod when doing the second side of this operation. The bolts holding the rods on were machined so they fit in the holes in the rods and it looks like I used washers to hold the rod boss slightly off the plate so I didn't cut into the plate too much.

[suctionhose]

I generally use two vices. Leave a couple of inches extra length on each end of the stock so the whole rod is suspended in the gap between the vices.
I machine the area to be held in the jaws square and uniform size for all the rods and use an end stop to reposition repeatedly.
Datums are the end and the fixed jaw of vice. Remove and remount as many times as you like without losing the datum.
You can finish all features of the rod, including the bores, oilholes, flutes etc without jigs or changing setups.
Lastly, just cut the excess off each end and round it off on the linisher or rotary table.
Sorry. no pics available.

[runner42]

Feb 19, 2019 11:36:50 GMT @greenglade said:

Hi Brian

Just to add to what's been said, you would find it quicker in the long run if you make a jig to hold the rods, you can see what I did in my own thread as an example. In essence, it was a large piece of steel, perhaps 2 x 3 inch and long enough for the rod in hand, alas I can't remember it's exact size. There are a number of advantages, it will act as a heatsink to help reduce heat build-up which is why the steel bends, it will give a much more rigid setup but of much more use is it gives you a datum to machine multiple rods from. What I mean is once the jig is set in the machine vice (or whichever fixing method you prefer) you can do a number of cutting procedures without needing to remove the jig or reclock the rod's position. So for the job you're doing now, with the jig set, you can machine the top, bottom and both sides without worrying about stopping the cut in the correct place as it will be the same for the top/bottom and the sides will also need to be equal to each other. All you do is undo the bolts that hold each rod through its holes and either turn the rod over or change one side for the other when machining the sides. With the end start positions noted you just do each side the same and then repeat for the next rod, once the profile is done you also use the same jig for machining the flutes. This alone saves an awful lot of time messing around setting up for each operation.

Just trying to pass on my own methods, I'm sure there are plenty of other ways of doing things, at the end of the day, it all comes down to what's best for the machinery that you have to hand....regards

Pete

Hi Pete,

starting from page 50 I found the references to making the coupling rods on pages 106 to 111, but continued to page 136 but couldn't find a similar reference for the connecting rods. Can you help?

Brian

[Deleted]

Hi Brian

Ah, that will be because I haven't got around to the connecting rods yet but they will be done the same way as the coupling rods. Actually I've been doing the finishing touches to those rods over the last few days. All of the motion will be tackled this way when I actually get too it.

Regards

Pete

[runner42]

Thanks for the replies although they are all variations on a similar theme I have chosen the box section method. I got a piece from the metal dealers yesterday for $5. Using the method of using the side cutters of the end mill will enable me to make a cut using one pass since the cutting area at the side is sufficient for a 12mm cut.

Brian

[runner42]

Today was a better day, but it started off badly. I have forsaken the pillar drill which has been my only machine prior to obtaining the mini mill for vertical drilling because the mini mill can provide more accurate positioning drilling. Hence frequent changes to the MT3 attachments has caused some problems with the draw bar. Today I tried to remove the MT3 ER 32 collet chuck but found that the draw bar wasn't screwed into the MT3, so no amount of hitting with a soft hammer would dislodge it. I wont string it out by going into details of how I eventually removed it, but what I found that there is a significant difference in the start of the female thread that the draw bar screws into. The first photo shows the difference in the RH drill chuck supplied with the mini mill has threads closer to the top than the LH ER 32 collet chuck.


MT3 thread differences by Brian Leach, on Flickr

So for the ER 32 collet chuck the draw bar is not long enough. The first thought that buzzed through my head was oh sh*t I have to make a longer draw bar. But no, thinking a little I decided to rebate the draw bar in the position shown so it entered the quill a little further.

draw bar by Brian Leach, on Flickr

So with that little setback out the way I made two locating pieces to affix the connecting rod to the box section and clamping this directly to the bed I have a much more rigid setup. In addition using the end mill side cutters I am able to cover a full 12 mm cut with one pass. So I am on my way, but it is a long process, if I used MEL to provide the blanks I would not have a much metal to remove. I don't think that I can have the patience to use the mill for all the machining I will apply a hacking process to remove a lot of the excess and use the mill for the final parts, but as stated previously I am on my way.

Brian

We're on our way by Brian Leach, on Flickr

We're on our way1 by Brian Leach, on Flickr

[Jim]

I had a similar problem Brian when I discovered the thread for the taper on the boring head had a metric thread not a Whitworth thread as per the draw bar. Dear old Bunnings solved the problem with a length of their long threaded rod and some matching nuts.

The new box jig looks great and you can just tip it sideways when you come to mill the relief in what is currently the upper face of the rod, if that makes sense.

Jim

[David]

I had the same problem as Jim, at least one of my tools had a metric thread. I solved it the same way, with all-thread and a nut. But it seems your thread is the same given you just had to give a bit extra on the length.

Good to see your rods are now under way with a more rigid setup.

[gwr14xx]

Brian, Please be careful when taking roughing cuts - they should be done with the work being fed against the rotation of the cutter - not with it! From the photos, it looks as if the cutter has already had several attempts at grabbing. Also, your clamping arrangement looks a bit 'iffy' - the clamps should be 'packed up' to lay parallel with the table - a serious grab could send your work into orbit around the workshop. A more secure solution would be to mill a short slot in each end of the bottom of the box section so that the clamps bear directly on the fixture without the risk of them creeping away.

Regards,
Eddie.

[runner42]

Feb 22, 2019 7:31:07 GMT Jim said:

I had a similar problem Brian when I discovered the thread for the taper on the boring head had a metric thread not a Whitworth thread as per the draw bar. Dear old Bunnings solved the problem with a length of their long threaded rod and some matching nuts.

The new box jig looks great and you can just tip it sideways when you come to mill the relief in what is currently the upper face of the rod, if that makes sense.

Jim

Hi Jim,

yes a simple but effective setup thank you for the picture. I am able to utilise the position of the clamps at each end to set the box section at an angle to match the taper from the big end to small end. Having positioned the hole centres on the middle of the box section I am able to utilise the edge of the box section as a reference and set the angle by measuring the Y axis distance from the table edge to the box section at the points where the holes are placed in the X axis. In this case it is (a+ 1/32") at the small end and (a + 0) at the big end. I accept that the box section is not uniform to a great degree but sufficient to use as a reference in this case.

Brian


  

[runner42]

Feb 22, 2019 8:19:45 GMT gwr14xx said:

Brian, Please be careful when taking roughing cuts - they should be done with the work being fed against the rotation of the cutter - not with it! From the photos, it looks as if the cutter has already had several attempts at grabbing. Also, your clamping arrangement looks a bit 'iffy' - the clamps should be 'packed up' to lay parallel with the table - a serious grab could send your work into orbit around the workshop. A more secure solution would be to mill a short slot in each end of the bottom of the box section so that the clamps bear directly on the fixture without the risk of them creeping away.

Regards,
Eddie.

Thanks Eddie for pointing that out, I have to be constantly aware of avoiding climb milling. It will be common practice in due course but for now I will have to develop a simple rule something like the hand rule for motors and generators, that's climb milling and that's normal milling. The box section is only 2mm thick and so that the clamps sit squarely on the inside of the box section I have placed washers underneath so the clamp makes full contact with the box section. It appears to be very rigid.

Brian

[runner42]

I am slowly working through profiling the connecting rods in the Y axis. What I would like to know is what depth of cut is advisable when using the side cutters of the end mill. I dial up 20 divisions (0.5 mm) but with this setting it is hard to operate the x axis hand wheel (pity an operator that has a grip issue) and I am not convinced that this amount of metal is being removed, obviously the end mill is flexing away from the job. I imagine that this flexing is apparent in many milling machines. But it begs the question is an end mill the best cutter to use or would a slot drill be better?  Notwithstanding the choice of cutter is a lubricant necessary and if so what is available in spray can? Lastly so that I know that the end mill is cutting effectively what size of metal chips would you expect? What I am seeing is very small chips see above picture for reference.

Brian

   

[uuu]

An end mill sounds appropriate, although one of those wavy-sided roughing cutters would have an easier ride in the early stages. 0.5mm is fine for an industrial machine, but clearly too much for your set-up. Swarf should look like a pile of needles.

I would experiment with a reduced depth of cut - and maybe not do the whole height in one go. And yes, lubrication would help. At the Pumphouse John mostly applies suds by brush, although a laboratory squirt-bottle is used to achieve a flood effect when required. Quite tiring on a long job to be winding the axis with one hand, and squeezing the bottle with the other.

Like Eddie, I also had doubts about your clamping, but you are clearly satisfied that it's not going to move.

At least you're making positive progress - more than my project.

Wilf

[Roger]

Personally, I wouldn't try to cut anything like the full depth on the side of the rod unless I was finishing it. To rough it out, I'd take say 1mm wide cuts at say 0.5mm depth and work down until you reach the bottom.
The key is to finding what your machine is happy cutting. Start conservative and work up would be my advice. So that 0.5mm depth mentioned might start at 0.2mm and then keep increasing it until it chatters or struggles.

It's tempting to try to remove as much metal as possible in one cut, but if that means you have to go really slowly, you're better of taking four times as many at a much faster feed rate. It's all about listening to what your machine is telling you both audibly and through the feel of the handles.

[oldnorton]

Hi Brian

Wilf and Roger are absolutely right and I will only add some comment to reinforce what they have wisely said.

For your size and rigidity of machine there is too much depth of cut on those side flutes (A Bridgeport under power drive is a different matter!). The cutter will have to be very sharp (i.e.nearly new and liable to cut skin if you wipe along it). As Roger says try to cut just one third or less of the depth of the rod but deeper at say 0.5mm. Yes, squirt on some next cutting oil from a hand spray bottle - if it just starts smoking a bit you are cutting well. The job is much harder to undertake with a manual table traverse and you will have to concentrate on getting a steady rate of feed. All the while the tool is rubbing and not cutting it will blunt itself.

You will be much better off with a roughing cutter as Wilf describes. It will take off more material and last longer. It will also produce bitty swarf and not the nasty sharp needles you will get from side flutes.

I wonder if the box section work support will flex more than if the job was bolted to a solid jig on the table. If you get vibration and singing noises the box section might be causing it.

Norm

[runner42]

Well I am surprised that the amount of metal that can be removed at each cut is so small. Comparing it to a modest lathe, the lathe beats it hands down. If I could swing the length required in a lathe I would have gone down that path, even with interrupted cuts. My analysis is that there is enough power output from the mill to undertake more meaty cuts and the rigidity of the setup is good, no vibration so the weak link is the endmill, which is a new Sutton's one but not designed for roughing, so I will purchase a roughing one. Whilst I am awaiting delivery and it is going to be a dreadful week in Adelaide, another heat wave, I shall limit the activity to using the angle grinder to get nearer to the front elevation profile. If I was in the bush, this week is likely to be a total fire ban so I wouldn't be allowed to use the angle grinder, so I must be thankful for small mercies. 

Brian 

[gwr14xx]

Brian,
Once you have become more accustomed to milling, you should be able to rough out each side of the coupling rods in 2 cuts. The limiting factor is not the size of endmill you are using, it's the rigidity of the workpiece. For the roughing out stage, you could rig up a temporary third clamp half way along the rod (to make it more secure). Whilst roughing cutters may give an improved metal removal rate - the advantage only becomes economical on production runs. Stick with the standard endmills and slotdrills - it's amazing the amount of metal that can be removed once you get your speeds and feeds optimised! The main thing is not to try to run before you can walk - find a couple of bits of gash material to practice on - forget about CNC or even power feed (they give no idea of the 'feel' of the cut) - the feedback you get through the handwheels, and the sound the cutter makes, will give you a much better idea of how well the cutter is performing. Armed with this knowledge, you can then set up the power feed (or CNC) accordingly.

Regards,
Eddie.