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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Centec Milling machines
I have a Centec 2A. I'm pretty happy with it considering that I have
barely used it in the couple years that I have had it. I have just rewired it from 220V single phase to 110V to allow me to run it in the house without haveing to pull new wire. Even worked out how the reverse switch was to be wired in, about which I admit to feeling a bit smug (and a bit releived). I know that there are a couple other Centec owners out there. What have you got on yours for a motor (HP?) I have 3/4 HP on mine and am thinking it's possibly overkill on this machine. Any comments? I would like to find a decent very low profile vise to put on it. Whatcha using? I am actually contemplating making a set along the lines of Mitee-Bite's clampling kits for it, referring to it as a Babee-Bite for want of a better term, as I have not seen anyone dealing in really small tooling outside of the sherline/taig stuff that seems, well, awkward to me. Anyone built a riser for their vertical head? Cheers Trevor Jones |
#2
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Centec Milling machines
Trevor Jones wrote:
I have a Centec 2A. I'm pretty happy with it considering that I have barely used it in the couple years that I have had it. I have just rewired it from 220V single phase to 110V to allow me to run it in the house without haveing to pull new wire. Even worked out how the reverse switch was to be wired in, about which I admit to feeling a bit smug (and a bit releived). I know that there are a couple other Centec owners out there. What have you got on yours for a motor (HP?) I have 3/4 HP on mine and am thinking it's possibly overkill on this machine. Any comments? I would like to find a decent very low profile vise to put on it. Whatcha using? I am actually contemplating making a set along the lines of Mitee-Bite's clampling kits for it, referring to it as a Babee-Bite for want of a better term, as I have not seen anyone dealing in really small tooling outside of the sherline/taig stuff that seems, well, awkward to me. Anyone built a riser for their vertical head? Cheers Trevor Jones I and a friend have 2Bs, and another friend has a 2A. They all have 1hp main motors, and the 2Bs have 0.5hp table feed motors. The 2A has a home made cast iron raising block for the vertical head, which adds about 3 inches to the headroom. Since the 2Bs are also hight challenged I'm considering making one myself. All of us are successfully using standard 4" swivel vices, around 3" high. I've fitted VFDs to both motors of my 2B; it was a big job because I had to convert them from star to delta and this involved removing them to split the star points. Well worth doing though, finger tip control has to be tried to be appreciated. I'm in UK, so our 240v supply is OK for the delta wound 415v motors - no good for 110v though. -- Regards, Gary Wooding (To reply by email, change feet to foot in my address) |
#3
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Centec Milling machines
"Trevor Jones" wrote in message ... What have you got on yours for a motor (HP?) I have 3/4 HP on mine and am thinking it's possibly overkill on this machine. Any comments? I've got a 3/4 horse on my 2a, but that was only because I had to get a new motor and this cost only a few dollars more than a 1/2 horse. My biggest objection to a bigger motor (e.g., 1HP0 is that it is a devil of a job putting the motor in and the extra weight would be a bear. I would like to find a decent very low profile vise to put on it. Whatcha using? I use a very nice, low profile vice. 4" jaw, 3." opening, 2.5" high including the swivel base. I have this vice on both my mills (the other is a #4 Burke, Horizontal). It is not sold as a milling machine vice. It is from a small, precision, grinder. Just about perfect for both of these mills. I looked a long time, always hunting for "milling machine" vice in used machinery shops until I saw this on a grinder. Neither the vice nor the mills seems to mind my abusive machinery miscegenation. I am actually contemplating making a set along the lines of Mitee-Bite's clampling kits for it, Several vendors sell small clamp sets with 5/16x18 studs and t-nuts as well as an assortment of step blocks and clamps. The cheapest are those used on bigger mills at about $55 for the set. The smaller gauge sets are typically more expensive, but I have seen them on sale for as little as $65. Anyone built a riser for their vertical head? That's another "one of these days projects." Problem is that whenever I thought I needed that, I found a way around the problem. I guess I'm basically lazy. If someone came out with a casting set (hint, hint) I'd buy it in a shot. Boris BTW --anybody have a power feed for the 2A they want to get rid of? -- ------------------------------------- Boris Beizer Ph.D. 1232 Glenbrook Road Huntingdon Valley, PA 19006 TEL: 215-572-5580 FAX: 215-886-0144 Email bsquare "at" earthlink.net ------------------------------------------ Trevor Jones |
#4
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Centec Milling machines
According to Gary Wooding :
[ ... ] I and a friend have 2Bs, and another friend has a 2A. They all have 1hp main motors, and the 2Bs have 0.5hp table feed motors. The 2A has a home made cast iron raising block for the vertical head, which adds about 3 inches to the headroom. Since the 2Bs are also hieght challenged I'm considering making one myself. All of us are successfully using standard 4" swivel vices, around 3" high. They sound like nice machines. Perhaps similar in capability to my Nichols horizontal mill with the optional right-angle head to make it also a vertical machine. I've fitted VFDs to both motors of my 2B; it was a big job because I had to convert them from star to delta and this involved removing them to split the star points. Well worth doing though, finger tip control has to be tried to be appreciated. I'm in UK, so our 240v supply is OK for the delta wound 415v motors - no good for 110v though. Hmm ... not a real problem, as almost any house in the US which has 120V also has 240V, because it is commonly delivered with two 120V lines either side of a center tapped ground, so the 240V is available between the two sides of the line. (This is normally used for the higher powered things such as water heaters, electric stoves, electric clothes dryers, and central air conditioning -- but this means that it is also available for machine tools.) (With the additional benefit that no single point of the normal power is any higher above ground than 120VAC.) Of course -- industrial motors here are typically dual voltage, but not accomplished by the Delta-Wye changeover but rather by having two of each winding. For lower voltage operation, the second set are connected to a common center point, and paralleled with the primary windings. For higher voltage operation, the second set is split into individual windings, and connected in series with the primary set, which has its own common center point buried deep inside the motor -- not even accessible through the termination box. This results in one voltage being double the other -- e.g. 240V / 480V, rather than the somewhat different ratio which you get from A Wye/Delta switchover -- which I don't remember, because I never have to work with it. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#5
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Centec Milling machines
DoN. Nichols wrote:
They sound like nice machines. Perhaps similar in capability to my Nichols horizontal mill with the optional right-angle head to make it also a vertical machine. I tried Googling the Nichols but couldn't determine which one you have; is there a model number or some other form of identification? The table sizes of the Centec are 16"x4.25" for the 2A and 25"x5" for the 2B, so although very sturdy machines they are not massive like Bridgeports, and can be fitted into small workshops like the sheds that are traditionally used by UK model engineers. Of course -- industrial motors here are typically dual voltage, but not accomplished by the Delta-Wye changeover but rather by having two of each winding. For lower voltage operation, the second set are connected to a common center point, and paralleled with the primary windings. For higher voltage operation, the second set is split into individual windings, and connected in series with the primary set, which has its own common center point buried deep inside the motor -- not even accessible through the termination box. This results in one voltage being double the other -- e.g. 240V / 480V, rather than the somewhat different ratio which you get from A Wye/Delta switchover -- which I don't remember, because I never have to work with it. Don't the dual windings increase the bulk of the motors? Another friend has an old Holbrook lathe with a 3ph 2HP motor. It has 3 sets of windings to give it 3 different speeds. Its massive: at least twice the size of normal single speed motors - that's twice the linear size: eight times the volume! He wants to convert it to run on 240v (via a VFD) but the terminal block shows that its only wound in star format (9 terminals, 3 for each winding), so he needs to remove it from the lathe and dismantle it to expose the star points. Trouble is, its built into the cast iron base and appears to involve lifting the 2 ton lathe and removing the motor from underneath - the motor must weigh around 200 Lbs. Most modern 3ph motors over here have both ends of each winding exposed in the terminal block, thus making it easy to configure into star or delta format. Old motors like those in my Centec have the star point buried inside the windings themselves, that's why I had to remove and dismantle them in order to make the conversion. -- Regards, Gary Wooding (To reply by email, change feet to foot in my address) |
#6
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Centec Milling machines
Boris Beizer wrote:
I use a very nice, low profile vice. 4" jaw, 3." opening, 2.5" high including the swivel base. I have this vice on both my mills (the other is a #4 Burke, Horizontal). It is not sold as a milling machine vice. It is from a small, precision, grinder. Just about perfect for both of these mills. I looked a long time, always hunting for "milling machine" vice in used machinery shops until I saw this on a grinder. Neither the vice nor the mills seems to mind my abusive machinery miscegenation. Got any idea who the vice is made by? I am actually contemplating making a set along the lines of Mitee-Bite's clampling kits for it, Several vendors sell small clamp sets with 5/16x18 studs and t-nuts as well as an assortment of step blocks and clamps. The cheapest are those used on bigger mills at about $55 for the set. The smaller gauge sets are typically more expensive, but I have seen them on sale for as little as $65. I would guess by your comments that you are not familiar with the Mitee-Bite clamps. They are a side clamping unit that locks into the tee slot, and grips the side of the material. They don't eat up any headspace, and allow maximum utilisation of table space. The standard hold down clamp sets are available in sizes small enough to use on the Centec, but you pretty much have to resort to good name brand tooling (and pay accordingly) as they are sold to be used on jig borers and that ilk. Mitte-Bite clamps http://www.miteebite.com/ The Tee Slot kit that is shown in 10mm might work, but I have other cash priorities, so will likely make something simmilar for use when I need. Anyone built a riser for their vertical head? That's another "one of these days projects." Problem is that whenever I thought I needed that, I found a way around the problem. I guess I'm basically lazy. If someone came out with a casting set (hint, hint) I'd buy it in a shot. I figured to just plough one out of barstock off the stack at work. We have a fair pile of larger size steels that are unidentified for one reason or another, and could likely be spared for something like this. Not really useful to us otherwise, but too good to throw away. As castings go, it would be a pretty straightforward casting with a core. Not real tough other than finding someone reasonable to pour it. Cheers Trevor Jones |
#7
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Centec Milling machines
According to Gary Wooding :
DoN. Nichols wrote: They sound like nice machines. Perhaps similar in capability to my Nichols horizontal mill with the optional right-angle head to make it also a vertical machine. I tried Googling the Nichols but couldn't determine which one you have; is there a model number or some other form of identification? You'll more readily find them on eBay, as the company is long gone. Well ... mine is a very old example of the toolroom version. A choice of leadscrew and handwheel or lever for X-axis feed, while leadscrew and handwheel only for Y-axis. You might take a look at: http://www.d-and-d.com/NICHOLS-mill/index.html which will show you some of what I have done to and with it. The weight is about 1100 pounds. [ ... ] Of course -- industrial motors here are typically dual voltage, but not accomplished by the Delta-Wye changeover but rather by having two of each winding. For lower voltage operation, the second set are connected to a common center point, and paralleled with the primary windings. For higher voltage operation, the second set is split into individual windings, and connected in series with the primary set, which has its own common center point buried deep inside the motor -- not even accessible through the termination box. This results in one voltage being double the other -- e.g. 240V / 480V, rather than the somewhat different ratio which you get from A Wye/Delta switchover -- which I don't remember, because I never have to work with it. Don't the dual windings increase the bulk of the motors? Not much -- compared to a single winding of the proper wire gauge for the lower of the two voltages. You simply have two identical windings of a smaller gauge, which take up a bit more room than a single winding of the proper gauge, but when paralleled add up to the proper gauge. And when connected in series (for higher voltage and lower current), they don't need the additional current capacity, so they work out correctly again. All of the wires are used all of the time -- just in different configurations. Another friend has an old Holbrook lathe with a 3ph 2HP motor. It has 3 sets of windings to give it 3 different speeds. Its massive: at least twice the size of normal single speed motors - that's twice the linear size: eight times the volume! He wants to convert it to run on 240v (via a VFD) but the terminal block shows that its only wound in star format (9 terminals, 3 for each winding), so he needs to remove it from the lathe and dismantle it to expose the star points. Trouble is, its built into the cast iron base and appears to involve lifting the 2 ton lathe and removing the motor from underneath - the motor must weigh around 200 Lbs. Hmm ... nine terminals is standard for a two-voltage (but single speed) US-made motor. But there is only one center point for the Wye (star) connection. It looks something like this: Primary Secondary (1) (4) (7) +---wwwwwwww---+ +---wwwwwwww---+ Phase A | | (2) (5) (8) +---wwwwwwww---+ +---wwwwwwww---+ Phase B | | (3) (6) (9) +---wwwwwwww---+ +---wwwwwwww---+ Phase C ^ | +-- Wye center point (not brought out) Note that I may be mis-remembering the actual numbering of the winding terminals, but the principle remains. ---------------------------------------------------------------------- Anyway -- (assuming a 240/480V version) for 240V operation, you would connect terminals (4), (5), and (6) together, and insulate them. Nothing brought out. You would connect terminal (1) to terminal (7) and bring them out to connect to the first phase. You would connect terminal (2) to terminal (8) and bring them out to connect to the second phase. You would connect terminal (3) to terminal (9) and bring them out to connect to the third phase. ---------------------------------------------------------------------- For 480V operation, you connect: Terminal (1) to terminal (4) and insulate Terminal (2) to terminal (5) and insulate Terminal (3) to terminal (6) and insulate. You connect terminal (7) to the first phase. You connect terminal (8) to the second phase You connect terminal (9) to the third phase. ---------------------------------------------------------------------- So -- you get operation at two voltages different by a factor of two and use all of the windings in either configuration. Delta connections are quite uncommon in machines of the size w which I use in my home shop. I've never had to deal with the big machines which were in the shop at work, including a planer which could happily hold and plane down a 1-ton pickup truck, and have room left over to work on a couple of Volkswagen beetles at the same time. :-) Most modern 3ph motors over here have both ends of each winding exposed in the terminal block, thus making it easy to configure into star or delta format. Old motors like those in my Centec have the star point buried inside the windings themselves, that's why I had to remove and dismantle them in order to make the conversion. Because it was made for a single voltage only, while all that I have seen have been designed for dual voltage at the least. What is the ratio of voltages for a Wye-Delta conversion? I should know that but I haven't had to use it, so I forget. Granted -- three-speed motors are a totally different ballgame. :-) Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#8
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Centec Milling machines
DoN. Nichols wrote:
You might take a look at: http://www.d-and-d.com/NICHOLS-mill/index.html which will show you some of what I have done to and with it. The weight is about 1100 pounds. That's a nice machine too; I particularly like the "using its head" feature. I think its a little bigger than a Centec, but not by much; I think a 2B weighs in at around 700Lbs. And thanks for the info about the American electric system; its quite different to the UK one. What is the ratio of voltages for a Wye-Delta conversion? I should know that but I haven't had to use it, so I forget. The ratio is 1 to root-3 or 1:1.732. Thus 240v:415v. -- Regards, Gary Wooding (To reply by email, change feet to foot in my address) |
#10
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Gary ,
I'm trying to work out whether I should get a vertical mill or a combination vertical/horizontal . Basically I will be using this to fabricate adaptor plates and small items for my hot rod hobby . What is the throat radius of a 2b fitted with the vertical head ? Thanks Simon |
#11
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Centec Milling machines
striebs wrote:
Gary , I'm trying to work out whether I should get a vertical mill or a combination vertical/horizontal . Basically I will be using this to fabricate adaptor plates and small items for my hot rod hobby . What is the throat radius of a 2b fitted with the vertical head ? Thanks Simon -- striebs Check out the Centec pages here at http://www.lathes.co.uk/centec/index.html This site is about the best reference material out there when it comes to putting a face to a name, in the small size machine tools. As you can see, the Centecs are not very large machines, I think my 2A has about the same size table as a sherline, or pretty close. In it's favor, it is built of a couple hundred pounds of cast iron, and was expected to be able to work for a living. The 2B is a little larger. Cheers Trevor Jones |
#12
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Centec Milling machines
According to Gary Wooding :
DoN. Nichols wrote: You might take a look at: http://www.d-and-d.com/NICHOLS-mill/index.html which will show you some of what I have done to and with it. The weight is about 1100 pounds. That's a nice machine too; I particularly like the "using its head" feature. I first got the manual for the machine (how could I resist with the coincidence of names), and later found one being offered for a quite reasonable price on eBay. It actually cost more to ship it down from the Boston area than to win it. :-) I think its a little bigger than a Centec, but not by much; I think a 2B weighs in at around 700Lbs. And thanks for the info about the American electric system; its quite different to the UK one. Quite different -- though I believe that delta motors are still used -- but mostly for larger machines. I've picked up some of the information about the UK system from articles here and in a mailing list, and already had a reasonable feel for the US system (though I have learned about strange systems here too -- such as "Wild leg delta", which produces the same voltages as the normal Wye motors use, but has one of the three legs center tapped, so you can run standard 120V loads from either side of the center tap, and yet still have three phase available for the larger loads. (Of course the motors and the supplies don't really care whether it is Delta or Wye configuration as long as the voltages are the same. Wye feeds to shops will have the center point grounded, so they have a non-standard voltage available from each phase to the center. There are industrial fluorescent lamps designed for this voltage, to distribute the lighting load around the three phases. What is the ratio of voltages for a Wye-Delta conversion? I should know that but I haven't had to use it, so I forget. The ratio is 1 to root-3 or 1:1.732. Thus 240v:415v. Thanks! Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#13
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Centec Milling machines
striebs wrote:
Gary , I'm trying to work out whether I should get a vertical mill or a combination vertical/horizontal . Basically I will be using this to fabricate adaptor plates and small items for my hot rod hobby . What is the throat radius of a 2b fitted with the vertical head ? Thanks Simon Hi Simon, The max. distance between horizontal spindle and table is 10.5" and the distance between the vertical centre and column is around 5"; it is variable because the vertical head is clamped to the column in the large dovetail groove originally intended for the overarm and can be slid in and out a little. -- Regards, Gary Wooding (To reply by email, change feet to foot in my address) |
#14
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Hi Gary,
not sure if you will get this post after all this time.. i need help with my inverted centec 2b.. i will explain if you reply haha cheers Ash Quote:
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