[photomankc]

Well,

I'm going to get going on my new thread to convert and modify my Quality Machine Tools PM-25-MV mill. For those that don't recognize it it's a variation on the BF-20 theme marketed by the QMT guys.

http://www.machinetoolonline.com/PM-MV-BenchMills.html

The 25 has about a 1HP motor per the spec but otherwise shares the same travels as the 20. I had some initial difficulty in getting it back together after dragging it to the basement. Got that sorted out and then the motor controller died on me. After some mail parts swapping they paid to ship the head back and repaired it there. It should be on its way back this week.

In the mean time I have put the X2 to work to make my first mod parts. I made some tram tunning blocks like machinechick showed off to allow me to fine tune the X tram using set screws instead of tapping with a hammer back and forth. If I need to tilt the head on an angle I can loosen one and swing it out of the way. Will need to drill and tap a 1/4"-20 hole in the carriage on both sides for them.

Second was a way to mount an X scale using the existing table stop nuts on the front of the table. I measured out the scale and I think the clamps will allow me to get the scale mounted with enough clearance to attach the readout to the saddle and still clear the gib lock handles. I wanted to have it tilted upwards on the mount but that doesn't appear to be possible really given the clearances. If these work then no modifications or holes will be needed to get the X scale mounted. Next will be the Z axis since I want to avoid using the quill for Z movement whenever possible. Last will be the Y but that may not really happen if I CNC first.

CNC conversion is now a priority. It appears I am developing carpal-tunnel from my day job and cranking on handles at night is not helping at all. I may be a one-armed man for a few months here in the future and so I am scrapping my plans of home-built circuitry and I'm going to look at getting some commercial drivers and so-forth. I'm going to see how well my existing 425oz/in Hobby-CNCs can move the tables around. I'm thinking something with more beef is going to be needed on the Z though.

Pictures attached:
First pic is the PM-25 in front of the X2 for a comparison.

Next shot is the X2 face-milling the material for the scale clamps with a Glacern FM-45 2.5" face mill.

Next shot is the two pieces ready to be drilled for the clamp screws.

Last shot is the X tram tuners on the left, one scale clamp on the top left, and the stock for another clamp and base on the right.



My tapping on the first part went poorly. Broke the 6-32 tap in the first hole. I've just got some ACE hardware Irwin taps on hand but I'm going to be going to HSS spiral taps in the future. instead of scrapping the toasted part I used it to make the top clamp by cutting off the section with the tap lodged in it. I've been using the spindle on the X2 to tap by putting it in nuetral and turning the tap using the spindle drawbar.

I'm waiting on a metric drill and endmill to drill the clearance hole and counter bore for the M6 socket cap that attaches the base to the front of the table. Using the existing hardware means metric sizes. The 11mm end mill will be used to cut a counter bore to allow the socket cap screw to fit flush under the scale.

Once all that is done I'll make the final cuts to the base to remove the corners outside the width of the top clamp. I imagine I will also need to fabricate some type of chip guard for the scale.

I'll try to keep this updated with successes and failures as I go.

[Starleper1]

That new draw bar will be a nice touch

[photomankc]

That new draw bar will be a nice touch

I'll be excited to get that in. I think it will be much nicer to use than 'the nub'.

For those wondering what we are talking about:
http://www.cnczone.com/forums/showpo...8&postcount=41

[photomankc]

One X DRO clamp down. One to go. Then I need to design an attachment for the scale face to the saddle. I goofed up and didn't get a center-cutting end mill for the 11mm counterbore for the mill's stop bolt but the 7mm through hole was enough to allow the end mill to plunge in. I also used a 5/16" endmill to recess the clamp bolts a bit.

I clamped the scale on with just the one and let it butt against the gibb clamps just to enjoy the digital goodness of seeing the little display count off while I cranked. That's going to help. Eventually I need to change it to face up instead of forward. It's not real easy to read this way. But it will do for a while I think.

[photomankc]

The clamps are done so now I need to work on the mount for the saddle to attach the scale electronic unit. I had not noticed the small ledge between the side of the X table and the front of the saddle. That's going to add some complication. I'll start drawing up the mount this week. I got raped on taxes this year so my Z scale will have to wait a bit.

I had to mill off a little of the electronics housing on the top. It would protrude above the top of the table even with the scale bottomed out on the gibb screws. I took off about 0.035" and that opened a good gap. I did notice that one of my gibb screws is bent. I guess I snagged it cranking the Y at some point and bent it. Anyone know a source to get a replacement? That forces the scale up a little high and I'd like enough room to put up some sort of chip cover for it over the top of the scale. I'd have enough space I think if the gibb screw wasn't wobbling around.

[photomankc]

Downloaded and started using Google's Sketchup to work out the center mount. That little ledge at the bottom is tough to measure without tearing the Y axis handwheel off but I got a pretty good idea of the space back there from some gauges. I modeled the scale to make it easier to test fit it together.

The bad news is that I can't use the existing holes for the center pointer to mount the scales electronics. There is not enough clearance to flush mount the bolts and the scale face will cover one hole leaving me with only a single bolt to hold it. Seems like that could allow it to pivot and cause inaccurate readings. So it appears I will need to drill and tap two holes to the sides of the center line. I was hoping to avoid that but I don't see how with the scale's dimensions.

[photomankc]

I think I have a workable center mount. Bottom bolts holes will have 0.060" of slotting to allow for the float in the table clamps. Rear attachments for 4-40 screws are also slotted to make the alignment less critical. Will be the most complicated thing I've made thus far LOL. I still pucker a bit slotting with the 'math-practice' wheels on the X2. Wish my mill head would get back in on the PM-25 because working in .100" turns is tons easier.

I'll pick up my stock material for this tomorrow. No scrap on hand with the right dimensions.

[metalworkz]

Hello,
I just stopped by your thread following your link from the tapping questions.
The mill you are working on seems to be a fair sized machine and a good looking one too. I have a small SX3 CNC mill that is pretty good but the travels are lacking in the Y axis. What are your travels on this machine? If i remember correctly I have 12" X, 6"Y(is actually a little less in the Y) and 9" Z. I hope the DRO works out well for you.
Regards,

[photomankc]

Metalworkz,

It's a very similar mill to the G0704 mill in the threads here in benchtops. The travels are 19" X by 7" Y (6" Y if you have the rubber way cover and bellows Z cover installed.). The long table and increased Y was a big upgrade from my X2. The motor is 1KW (rated not sure about actual) which is another big upgrade. 3000RPM top speed. The table is great, not concave like my X2 and it's much less prone to vibration problems.

The motor controller issue was my only problem and that's looking like it's solved and the head should be heading back to me this week.

As an update:
Turns out those 4-40 tapped holes in the scale were actually M3. I was test fitting some screws at the hardware store and they were going in but just not feeling right. Lucky for me the little M3 button head screws they had JUST fit into the slot so no modification needed and now they fit properly and tighten nicely. I cut the thickness of the rear section about .010" thick to try and fit it as close to perfect as possible. After taking off 0.006" it seems to fit really close. Flat against the saddle, and just touching the back of the scale slider without pushing it forward any. Now I just need to pucker up and drill/tap the bolt holes for the center bracket and I'm done with the X axis.

[photomankc]

I'm going to go have a nice cold drink. One modification done. The scale is fully mounted and working. I did flub up a bit drilling the holes. I somehow got off center as I clamped my guide in place and drilled the hole high. Not enough to ruin it but noticeable. That put my other center punch mark off and even making a new guide block bolted with the first tapped hole couldnt seem to keep the bit from being pulled into that punch mark. So the bolts are a little cocked but there's enough slot in the center bracket to deal with it. Makes me not want to do much more hand drilling though or I'm going to need something easier to see where the point is landing at least when I do the column.

I axed the cutout in the middle of the center bracket. Didn't want the old ruler pointer/center stop holes in the saddle to show through.

[machinechick]

I just wanted to write you a quick note on how I hand drill. If I understand how you did it, there is a better, easier way. First off, don't use those silly "guides" that keep the drill straight, those might be ok (not really!) for tapping, so you don't cock the tap and snap it; you sure don't need it for drilling, just relax and have confidence, you can hold the drill at pretty close to a right angle if I can, those guides just block your view, slip, etc. (sorry if I misunderstood you on this point)
Here's how I do it, works everytime for me: 1) Use a plug in drill (non-rechargable), a good quality one with like an 6+ amp motor, so you have enough power!, 2) Just layout where you want the hole, use some dykem or a sharpie marker, scribe, etc. if your concerned about it being accurate 3) center punch where the hole is going to go 4) start the hole with a center drill or a combined center/countersink bit, just like you would when your starting a hole in any metal working (skippping this step will cause you 90% of problems in hand drilling) 5) then finally with small diameter holes like the screw holes for the scale , just drill the hole. For larger diameter holes just work you way up, drilling one bigger hole after another till your at the size you require.
Don't give up on hand drilling, it's easy, accurate enough, and will save you a lot of hassle, just give up on the guides!

[metalworkz]

Hello,
I just wanted to add to machinechick's comment that if you check the hole location after the first step is drilled you can verify if it has wondered off location and if so take steps to work the hole back towards the correct center. If drilling through the material you can usually file the hole in the correct direction to correct it, but that is not so easy with a blind hole and you may have to angle the drill as you drill a small amount and re-check the location.

I think your DRO addition has turned out very well and it looks like a good compliment to your machine! I will be watching to see the continued work with your machine.

Regards,

[photomankc]

Thanks for the complement! I was pretty excited to get it done. It's been fun drawing it out and then making the drawing come to life. Getting a scale on Z will be real nice and that will be my next project. Y is going to be a lot more difficult to fit up and make I readable from the scale. I need to get some thin sheet metal to cover the scale ruler and slider so it doesn't get covered in wd-40 and chips.

Machinechick: I think I agree. I was looking at the situation and thinking that I would have been better off to just free drill it because it was too easy to slip around after finding the center but before getting the guide clamped in place. It did help with getting the taps started though.

[photomankc]

Machinechick's tram aids are now installed. And my head is back from repair and mounted up on the mill again! Looks like the mill is back in business again! Time to tram it up and get my vice moved over.

[Randolph]

Machinechick's tram aids are now installed. And my head is back from repair and mounted up on the mill again! Looks like the mill is back in business again! Time to tram it up and get my vice moved over.

Congratulations on getting your machine back together and the X-DRO looks great.
I talked to Matt yesterday and again today. (He's being patient with me.)
I went ahead and upgraded to the PM-25. It cost me $160 more, but now I don't have to second guess whether I needed the extra 1/4 HP or not.
He said not all of the PM-25s run 3000 rpm. There is an adjustment screw on the control board to set maximum rpm. He said it may go as high as 4K but he wouldn't recommend running it that high for long on the stock bearings.
I'm glad you have this thread for me to kibitz on and leave Hoss in peace for a while. :-)
I am loving seeing your mods since they are the same things I want to do. I have to live vicariously until my own machine arrives.
Show me more!
Oh. Where did you get your DRO?
I am thinking about buying a full 3 axis kit from QMT.

[Starleper1]

This mill uses a very similar DC motor control board that I use on my other mill. I got it at Surplus Center. The only issue is that my motor has no markings (Voltage, RPM, Etc..)

The adjustment screw he is talking about is a trim pot to set the max voltage going to the motor. If I knew the voltage of the motor I wouldn't mind trying it out.

Any of your guys motors have a name plate with this info?

Scott

[photomankc]

My motor is blank as well. Given the heat that develops at 3000, I'd not be comfortable pushing it past that.

Another project is going to have to be fixing whatever the deal is with the Z gib/upper lock. It looks to me like the casting is actually bulging at the dovetail as you lock it down. You can see it move and it throws the tram out by 0.004" but the surface of the casting moves out by over 0.020" when I crank it down. It also just feels mushy compared to all the other locks.

I think it needs a better Z strip anyway. You can really crank it down into there till it starts sticking coming down the way but it will still allow a good bit of up/down slop unless you crank down that top gib lock too. That would have to be solved I think for a CNC conversion.

[machinechick]

That tapered gib is kinda tricky especially when your used to the straight gibs. I think you will find if you get that gib nice and tight down in the taper the majority of the "play" your refering to will go away. That's Chinese cast iron your working with and IMO it is kinda soft, if you try to deal with this issue with the clamps and you really crank on it you most likely could crack the casting.
When I took my machine out of the crate the head was on the column so loose the whole thing shook and swayed when I'd raise and lower the head! (things vibrate on the ship/truck/etc and loosen up in transit if nothing else)
To adjust the gib I found it was helpful to gently lower the head onto a block of wood resting on the table while the head was attached. Not so much that your flexing the heck out of the column, but enough that the pressure caused by the weight of the head is off the gib. Then loosen the bottom gib adjustment screw a good rev, then tighten the top screw, driving the gib into to the taper until it's resting nice and tight in the taper.
If you try this I think you will find the issue goes away. You might have to try this acouple of times before you get it so it works right. Once you get it adjusted I think you will find it stays in adjustment much longer than the straight style of gib.
Also keep in mind there sould be some real way oil on that column. Way oil acts like a hydrostatic bearing between the gib and the dovetail and the oil is an essential part of the whole arrangement. If you got some and the head is off it wouldn't hurt to apply some right on the gib before you slide it into the gap. If you don't have any real way oil, all the usual suspects sell it by the gallon pretty cheap. If your not using it I think you will be pleasantly surprised how it improves the mechanical interaction of the sliding surfaces. It was designed just for this purpose and has a nice clinging action so some of it tends to stay in place even on vertical surfaces and when it's upside down etc. Really worthwhile stuff.
Hope these tips help and it all works out fine.

[photomankc]

I'm using Vactra way-oil actually. Bought a gallon from ENCO. I'll give that procedure a try. It's difficult to describe but that ONE gib lock feels way different than the others and has since the get-go. It never locks like the others do, just sorta smooshes tighter.

I am actually worried it's going to cause a failure like that and wonder if it this is a long-term defect in the casting that maybe it might be better to relocate the hole a bit south of that position. Just thinking out loud. I'll give the the wood rest a try and see what the results are.

[machinechick]

It felt the same exact way to me on my mill. It's caused by all the weight on the head (I think). Once I got that gib set right everything was much better. Remember it's tapered so it isn't uniform. The variance your seeing is the taper, the reason your seeing it is because it's not properly in place. I never had to adjust one before (at the machining jobs I had I would have got really yelled at for touching a gib, that was considered a tech only adjustment) it's a different concept from the ones on the X2. Once you have it adjusted I think you will find you like it alot better. It's less prone to going out of wack and once you get the hang of it, easier to adjust and alot less picky. It's great you have the way oil (: it will really perform with these types of gibs!