Eagle 25 Milling Machine
Eagle 25 Mill by Chester UK
At long last I've finally picked up a bigger milling machine! This was bought off Ebay at a very good price and is virtually unused. My brother and I travelled to Stockport to collect it and managed to get it in the Astra Estate by unbolting the column from the base and removing the head. It was still a struggle but worth it!
I've stripped it down completely and cleaned all the sand, grit, and swarf from the castings and holes and then rebuilt it. It's worth doing this to all these cheaper Chinese mills as the cleaning of the parts in the factory before assembly leaves a bit to be desired.
It came with the 4 inch machine vice and a collet set with metric collets. It's a metric machine (not that I'm bothered about that!) with an R8 spindle which I think is better than the MT3 spindle as it's easier to remove the R8 tooling. Unfortunately, the collet chuck and collets are a non-standard spring type (Chinese brand). They are very similar to the normal ER collets but a different size and taper so it's not easy to get other collets to fit. It would be nice to get a set of imperial collets as well as the metric ones as most of my endmills etc. are imperial sizes. The mill came without a drill chuck so I need to pick one of those up sometime, also a proper clamping set would be useful.
I can see changing the spindle speed will be a bit of a pain as this involves moving two belts and undoing a couple of bolts. I've got a spare 1HP, 3phase motor and I think I may eventually fit this along with an inverter to vary the speed. Much easier!
The machine is too big to go in the house workshop so at the moment it is outside the back door in the covered area that runs down the side of the house. Not ideal but it will have to do for now. I am also getting an old Denham Junior lathe from a friend at the club so that is going to have to be found a home as well shortly! I can see that I am going to have to eventually build a proper outside workshop!
The mill has been giving good service in it's new home in the new workshop but there are a few improvements that I want to make to it.
I have yet to fit an inverter drive and a three phase motor to make changing the spindle speed much easier. Having to change two belts has proved to be an absolute pain and it's very awkward to do. Consequently, I tend not to change speed at all if possible. I have picked up a faulty 3HP inverter off Ebay that I'm hoping to repair and fit along with the new three phase motor at some point.
The second improvement has been on the cards for some time and that is to fit a two axis DRO to the table. As mentioned above, the machine is metric but I do most of my work in imperial so I have to convert everything. That's not a problem really but can lead to mistakes being made. The DRO will solve that problem as it can be switched between the two systems. It will also be far more accurate than relying on turning dials which can also lead to mistakes! It eliminates any problems with backlash in the feedscrews as well.
I already have a digital readout for the quill feed. I bought it at one of the model engineering exhibitions at the Fosse a few years back but never got around to fitting it. I decided to bite the bullet a couple of weeks back and buy a two axis DRO kit and use the scale that I already had for the Z axis..
I went for a chinese 'cheapy' direct from China ( advertised on Ebay ) as they are so much cheaper than the ones sold in the UK, most, if not all, of which are no doubt made in China anyway. I didn't go for the cheapest ones but a set made by Sinpo which seem to have quite a good reputation. This came with glass scales with 0.005mm resolution. The actual accuracy will be less than that but far better than I can achieve with the dials. I measured the actual travel of the table in X and Y and added a bit to get the working length of the two scales. I ordered a 150mm travel for the Y axis and a 400mm for the X axis.
The kit took about two weeks to arrive and I had to pay £21 in VAT and other fees when it was delivered. Remember that if you order items with a reasonably high value from China etc. you will be liable to pay import duties and VAT when the item arrives. I think the sellers usually give the items a far lower value than they are actually worth to keep the extra payments as low as possible. You may find that the courier will also add a fee as they have to pay the duties on your behalf before they can collect them from the Customs and they charge you for this.
The DRO kit arrived this morning as two separate parcels and was well packed and everything was in good order. The kit consists of the display unit and mounting arm, the two scales, covers for the scales, and various brackets and nuts and bolts for mounting them. From what I have read, you usually have to modify these brackets or make your own to suit the particular milling machine. These kits are not a simple bolt on job! The kit also included a pressed steel plate for holding collets etc.
I connected up the scales to the display and switched it on and everything seems to work as it should. The only slight problem was that the mains lead had a continental type plug on it which is no use in the UK. I have plenty of suitable leads but I may just chop the plug off the lead that came with it and fit a proper UK 3 pin plug instead.
I haven't studied the manual yet but I gather that they can be hard to follow and understand as they are usually written in 'Chinglish'!
Well, yet another year has gone by! I ventured into the workshop today for the first time this year and did a bit of tidying up and cleaning. The boxes containg the DRO were still on a chair where I had put them in September so I thought maybe it was about time that I did something with it!
I've got one or two jobs to finish before I can spend the time installing the scales but I decided to at least mount the display and get that box out of the way.
The original idea was to mount the display on the right-hand side of the mill but there wasn't really enough room for it to go there. I therefore decided to fit it on the left-hand side by mounting the bracket on the back wall of the workshop. It will be less obtrusive there anyway and can be folded back against the wall when not in use. It was just a case of fastening the bracket to the wall with some wood screws and job done.
The mains lead that came with the DRO kit is much too long and also has the wrong style plug on it so that will be shortened and a proper UK 3 pin plug fitted.
The holder for the mill clamping set was originally on the back wall but I've moved that to the side wall on the right-hand side of the mill. It's easier to get at it there anyway. Those spanners will have to be moved as well!
I've spent some time looking at how to fit the X axis scale to the bed. Most people seem to fit them on the back of the bed but that would mean losing some of the Y axis travel which is a bit limited anyway. So I decided to fit the scale to the front of the bed instead. This also meant that mounting the scale and the reader head would be very simple as the scale could be mounted directly to the front of the bed using the existing Tee slot on the front and the reader could be mounted directly to the front of the Y axis casting. No brackets or any complicated fixings would be needed. This did mean that I would loose the travel stops that used the front Tee slot but I rarely used those anyway. The stops were a rubbish fit in the slots anyway and the slot itself varied in depth and width across the casting! With the DRO fitted I wouldn't really need the stops anyway as I can just use the DRO to stop the table where I want it.
I made a couple of custom Tee nuts to fit each end of the slot and used two of the included M5 bolts to mount the scale to the bed. The Y axis casting was slightly proud of the front of the bed so I had to fit some brass shims between the scale and the bed to make sure that the scale and the reader head were exactly in line. After the scale was mounted and the top set parallel with the top of the table, I used a transfer punch to mark the mounting holes for the reader head. These were then drilled and tapped for two M5 bolts.
The mounting holes in the reader head were tapped M5 as I presume you were meant to mount this onto one of the included brackets. I drilled out these holes to a good clearance fit for the mounting bolts so that the head could be adjusted slightly if necessary. I also reduced the diameter of the heads n the bolts for the same reason as they were recessed into the head.
When I was determining the position of the reader head I left the plastic transport strip in place between the reader and the scale. I then clamped the reader to the scale before marking the position of the mounting holes. That ensured that the reader was parallel to the scale. The transport strip was then removed once the head was bolted on.
Next job is the Y axis scale which will not be so simple unfortunately!
One thing I noticed was that I think there should have been a length of aluminium bar in the kit for mounting the X axis scale to but it was missing. The idea is that you mount the bar to the mill and then bolt the scale to the bar. There is one for the Y axis though. As it happens, I didn't need it for the X axis so no problem.
Also, the cables for the scales are way too long. I could mount the display down the other end of the shop! I suppose the manufacturers have to allow for every possibility when the kits are fitted. I could shorten the cables quite easily if necessary but I'll probably do what everyone else seems to do and just coil up the excess.
The easiest way to mount the Y axis scale seemed to be to hang it off some brackets attached to the lefthand side of the Y axis casting. It couldn't be simply bolted to the side of the casting as the leadscrew assembly was in the way and the scale needed to go below this. The righthand end was not really suitable as the two locks for the Y axis are on this end and I wanted to keep those. In any case, the lefthand side is nearer to the display unit.
So, I cut two lengths of aluminium bar and attached these to either end of the casting with two 5mm bolts. This meant drilling and tapping the casting. This time I used the mounting bar for the scale that came with the kit and this was bolted to the two bars attached to the casting.
The righthand bracket in the photo needs a bit cutting out so that the gib adjustment screw can still be easily reached.
The scale was then bolted onto the horizontal bar.
The handle that mounts on this end of the leadscrew will hit the scale if the table is taken to the extreme of it's travel so if I do need to use the full travel of the table, this handle will have to be taken off. That's no problem as I normally use the handle on the other end anyway.
That's the scale mounted and it just remains to find some way to mount the reader head. That is not going to be simple as the edge of the base casting is at an angle, as the bases of many milling machines seem to be.
Well, fitting the Y axis reader didn't turn out to be too bad after all. After looking at it for a bit I realised that I could mount the reader on a flat plate which in turn would be bolted to the angled face of the base casting. By fitting some grub screws to the plate, these could be adjusted to allow for the angle of the base and form the mounting points for the flat plate.
I found that one of the angle brackets supplied in the kit already had suitable holes tapped for the grub screws so I modified this by cutting off the angled end of the bracket leaving just the flat part.
Two more holes were then drilled and tapped in the plate to take the mounting bolts for the reader. Once again, the original tapped holes in the reader were drilled out clearance size for the 5mm bolts.
The scale was then mounted back onto the Y axis bar, the reader positioned so that it did not hit either end of the scale when the Y axis was traversed, and then the positions of two holes for bolts to fasten the flat plate to the bed were marked out onto the base using a transfer punch. These were then drilled and tapped for the 5mm bolts.
With the reader clamped to the scale with the transit plate still in place, the grub screws were screwed in until they contacted the sides of the base and the two mounting bolts tightened up. The two top grub screws are a bit short so I think I'll replace them with two ordinary bolts for now.
I've still got to check the alignment of the scale and the reader but apart from that it's done. Then I've got to mount the two covers for the scales and put some clips on the cables.
That just leaves the digital readout for the quill feed to be fitted but I'm not sure how to go about this yet. The quill can rotate slightly in the head casting as the only thing that stops it rotating completely is the end of a grub screw running in a vertical keyway in the side of the quill. Obviously, the end of the grub screw is not a very good fit in the keyway. It seems a poor way to stop the quill rotating as the contact area of the screw with the keyway in the quill is very small and I'm sure that it will wear quite rapidly. I've got a cheapo drill press that came from a tool auction and the keyway on the quill for that is very worn and chewed up due to it 'fretting' on the end of the grub screw. I need to find a better way of doing it otherwise this small rotational movement will try and twist the digital readout which won't do it much good.
Today I pretty much finished up the fitting of the DRO. I fitted the cover to the Y axis scale but before I did that I had to remake the vertical brackets that hold the bar that the scale is mounted to. When I first fitted the bar I had a 'Mr Bozo' moment and put it too close to the casting that holds the end of the leadscrew and the gap wasn't big enough for the cover to go under the casting. Rather than try and bodge the existing brackets I made two new ones which was only a 10 minute job. Before refitting the righthand bracket I filed a semicircle in it so that it made access to the gib adjusting screw easier.
The cover for the X axis scale had to be reduced in height so that it cleared the X axis locking screws and the vertical flange on the horizontal part had to be sawn off so it didn't stuck up above the top of the table. It was mounted by two screws into new drilled and tapped holes in the castings on the ends of the scale.
There were only two of the plastic ends that clip onto the covers so I fitted those to the Y axis. I presume the other two had been missed from the kit.
I tidied the cables up by fastening them to the bar that supports the display and fastening them to the wall behind the mill with cable clips. The spare cable just hangs down behind the mill. I might do something a bit better with the Y axis cable as that moves with the table and at the moment it just slides over the back of the swarf tray. There is enough slack in the cables for them not to be strained when the display is moved forward for use. I also shortened the mains lead which was way too long.
Next job is the digital readout for the quill. I bought this a good few years ago and to my surpise the battery was still ok even though it had been fitted for all that time. This unit must be of the better type where the on/off switch switches off the electronics rather than just the display. The cheaper digital calipers suffer from this problem where only the display is switched off leaving the electronics still powered up which is why the batteries never seem to last very long.
It seemed logical to have the display fixed and the scale part moving so I made a simple flat bracket and mounted the display to the front of the mill head with two 4mm scews.
The bottom end of the scale will be attached to the depth stop mounting on the end of the quill so that it moves with the quill. Firstly though, I have to get rid of this problem with the quill rotating back and forth slightly.
As mentioned, the quill is stopped from rotating by a grub screw with a machined end that rides in a vertical keyway in the side of the quill.
I measured the diameter of the end of the screw and compared it with the width of the keyway and no wonder there is so much rotation. The end of the screw is 6.87mm in diameter but the keyway is 8mm wide so there is about 1.1mm of play!
I could just make a new screw by machining the end of another grubscrew but I'm still not happy with this method. There is only a very small area of contact between the end of the screw and the sides of the keyway, in fact you can see where it touches in the above photo. The end of the screw has a small polished area.
Ideally, I would like to fit some sort of square key to give more contact area but that could be easier said than done. I don't really want to have to remove the quill from the head if at all possible. I'll have to think about it some more. Maybe I'm worrying about something that may not be a real problem?
Having thought about the problem with the play in the quill keyway, I've decided that to change the way that the quill is prevented from rotating would involve a major strip down of the quill and head and so I'm going to leave it as it is, at least for the time being. Instead, I machined off the too small diameter end of the grub screw and remachined it to give a good fit in the quill keyway. This has left the screw a bit too short to take the locking nut but I've ordered some longer grub screws and I'll make a new one when they arrive.
I think the problem with the end of the original screw being too small in diameter is that the manufacturer has probably used an off the shelf dog point screw rather than machining one specially for the job.
The quill now had no rotational play in the head and so I could finish fitting the digital readout. This was a simple job involving making a bracket that screwed to the casting on the end of the quill that the depth stop fastens to and then fastening the end of the scale on the readout to this. Job done and a lot easier than I thought it would be.
I was curious to see how the readings on the new DRO would correspond with the travel obtained by using the dials on the leadscrews so I did a quick test of the x and y axis.
One complete turn of the leadscrew dial equals 2.5mm so I set the x axis dial to zero, zeroed the DRO and then turned the leadscrew by 10 complete turns of the dial making sure I took into account any backlash in the dial and leadscrew. In theory, the distance travelled by the bed should be 25mm but the DRO read 24.95mm, 0.05mm less than it should have been. I tried this at different positions of the leadscrew but the results were all very similar with the DRO reading about 0.05mm less than the distance set by the leadscrew dial.
I then did a comparison at every 100mm as indicated by the leadscrew dial and the results showed a fairly consistent error.
It is difficult to set the leadscrew dial exactly on zero every time and a tiny fraction of a turn of the dial makes a few 1/100ths of a millimetre difference on the DRO reading but there is a definite discrepency between the DRO and the leadscrew travel according to the dial.
I then tried the same with the Y axis and the DRO readings matched near enough exactly with the travel according to the leadscrew dial.
So, is there an error in the X axis leadscrew or is the error being caused by the travel of the X axis scale not being exactly parallel with the travel of the bed i.e. is the scale at an angle to the bed travel? If the scale is at an angle then I would expect the error to be linear (unless the scale is bent) e.g. the error at 200mm would be 0.4mm, at 300mm it would be 0.6mm and at 372.5mm (the limit of travel of the bed) it would be 0.745mm. This assumes an error of 0.20mm per 100mm of travel. The error isn't consistent though. I'll have to check the scale again.
Tonight I decided to check the X axis scale for alignment and it was well within the tolerances given in the fitting instructions for the scale. This meant that the scale was not at an angle, or at least not at an angle great enough to affect the readings. The next thing then was to compare the reading on the DRO with an accurate length of travel of the bed. I tried using one of my dial indicators to measure a set distance of travel of the bed but the longest travel indicator I have is only 25mm and I didn't seem to be able to get very good readings using that. I then thought of using gauge blocks. I've got a set of imperial gauge blocks that I bought off Ebay some time ago so I made a stack 10 inches long (the gauge blocks are imperial) and laid these on the bed with another block across the end to make it easy to find the end of the stack using an indicator mounted on the bed. I took care to make sure that the stack was aligned with the direction of travel of the bed. Using the indicator I could then accurately find the start and finish of the stack and thus accurately measure a travel of the bed of 10 inches.
I used the indicator to find the start of the stack of blocks and then set the DRO to zero. I also set the dial on the leadscrew to zero so that I could check that as well. I then traversed the bed until I indicated the end of the stack of blocks. The bed had now travelled exactly 10 inches. The DRO said exactly 10 inches as well so the scale was obviously reading correctly, thank goodness! However, the leadscrew dial only measured 253.325mm (the dials are metric) when it should be reading 254mm (10 inches).So it looks as though the error problem is with the leadscrew which frankly doesn't surprise me. It is only a cheap Chinese mill so you can't expect it to be perfect for the price that you pay for them. It's probable that the error is not equal all the way along the leadscrew which would explain the earlier readings. It could be a bit worn or maybe it wasn't that accurate when it was manufactured. Anway, I'm happy now that I know that the DRO is ok and I can use it with confidence. It should make machining on the mill much easier and hopefully more accurate. Maybe I ought to get one for the lathes!
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