Cyberthrasher Report post Posted October 16, 2012 (edited) Just as an additional option, I use one of bearman's dremel burnishers in my variable speed dremel mounted horizontally to the dremel drill press (it will rotate either vertical, horizontal, or diagonal). This allows me to see the burnishing edge and just slide my straps right through with both hands on the leather. If I'm doing something larger I can just change the mounting angle on it. Edited October 16, 2012 by Cyberthrasher Quote Share this post Link to post Share on other sites
CustomDoug Report post Posted October 25, 2012 Original Poster here.. I wanted to get you guy's opinions on this possible motor set up to do my burnishing (remember I'm wanting a horizontally mounted burnisher). Harbor Freight has a 6" bench mounted buffer for $40, it has a 1/2" threaded arbor. Plus Harbor Freight also has an electrical plug thing that's called a "Router Speed Control" which essentially turns any "AC/DC Brush type motor" into a variable speed unit. You plug this into the wall then the buffer into this and it has a speed control knob on the front. Here are the two items: http://www.harborfreight.com/6-inch-buffer-94393.html and http://www.harborfreight.com/router-speed-control-43060.html . This would make the 3450rpm buffer run at a slower speed, if they'll work together... the 6" electric buffer would be a "brush type motor" wouldn't it? . HF also has a universal Jacob bit drill chuck BUT I have no idea what the thread pattern is on it and whether it would thread onto the Buffer's arbor.. so I don't want to get it without knowing. Thoughts, comments on this set up ? Thanks. Quote Share this post Link to post Share on other sites
Northmount Report post Posted October 25, 2012 The links aren't working for me, but a 3450 RPM motor is not a series wound brush type motor. It is a standard 2 pole induction motor. Depending on the methods used in the speed control, it may give you some control of the speed on an induction motor, at the risk of overheating the motor. If it isn't working hard, and shouldn't be for burnishing, you could be okay. The threaded jacobs chucks are fine thread. You need to determine if it is 3/8 or 1/2". Tom Quote Share this post Link to post Share on other sites
CustomDoug Report post Posted October 25, 2012 The links aren't working for me, but a 3450 RPM motor is not a series wound brush type motor. It is a standard 2 pole induction motor. Depending on the methods used in the speed control, it may give you some control of the speed on an induction motor, at the risk of overheating the motor. If it isn't working hard, and shouldn't be for burnishing, you could be okay. The threaded jacobs chucks are fine thread. You need to determine if it is 3/8 or 1/2". Tom I just noticed that the Jacobs chuck has a 1/2"-20 thread count... I have no idea what the buffer's thread count is though. They did look awfully course though. I suppose a thread adapter could be sourced if nothing else. Here's the chuck: http://www.harborfreight.com/1-2-half-inch-jacobs-keyed-chuck-45731.html Quote Share this post Link to post Share on other sites
CustomDoug Report post Posted October 25, 2012 (edited) OK upon further research - I found the link to the buffer's manual and the end nuts that hold on your buffing pad, etc is 1/2"-12 . So I'd have to see if an adapter is available somewhere I guess. The motor parts break down shows a "Rotor , spindle, and housing", uses a capacitor, circuit breaker - I see no mention of windings or brushes. Edited October 25, 2012 by CustomDoug Quote Share this post Link to post Share on other sites
Northmount Report post Posted October 25, 2012 OK upon further research - I found the link to the buffer's manual and the end nuts that hold on your buffing pad, etc is 1/2"-12 . So I'd have to see if an adapter is available somewhere I guess. The motor parts break down shows a "Rotor , spindle, and housing", uses a capacitor, circuit breaker - I see no mention of windings or brushes. Or look for another grinder/buffer. I see a number of them with fine thread. If they are double shafted, one end may have left hand threads. All 1750 and 3450 RPM motors are induction motors. They are for practical purposes nearly constant speed. Series wound have windings on the rotor, connected in series with stator windings, hence the need for brushes to connect with the armature (rotor) windings through a commutator. These are the typical motors used for power tools like drils, routers, benchtop planers and many high speed kitchen appliances. They run high speed with no load. As they are loaded, they slow down and draw more current. They are not constant speed motors. There's your electric motor lesson for today! Tom Quote Share this post Link to post Share on other sites
CustomDoug Report post Posted October 30, 2012 (edited) OK I'm back on this (sorry).. and I think I'm getting closer. I bought a low RPM (1725) 8" bench grinder off craigslist local for cheap (it's made by woodcraft). Unfortunately it's got a 5/8" shaft with 11tpi threads on the end or "5/8-11". This thread count is fairly rare, and I can find no drill chucks to match it (lord knows I've tried). So today I went to a local industrial bolt supplier and picked up a long hexagonal nut (3" or so) that has female 5/8-11 threads on one end and female 1/2-13 on the other (to be the first piece after my Grinder's shaft). I also got a short length of threaded stock that's male 1/2-13 on one end (to fit into the end of the hex adapter) and 1/2-20 (for the chuck to mount onto) on the other. Harbor Freight has a threaded drill chuck with that thread count for $10 that I want to use if possible. The problem is that when I mount the two adapter pieces onto my Grinder's shaft there is a quite obvious unbalanced thing going on (the adapters are not completely straight together). I thought of heating the assembly up until glowing red and then whacking the top of the threaded end (with a nut mounted to protect the threads) to correct the alignment. OR.. I found the following website's adapter that looks kind of right and is described the way I think it should but I'm not sure - does it seem like the right item to ya'll? I don't know why there's two hex pieces there and that's kind of throwing me. Also not sure if that small threaded side is long enough to mount the chuck. http://www.toolfetch...s/541404609.htm What do you think? Edited October 30, 2012 by CustomDoug Quote Share this post Link to post Share on other sites
Northmount Report post Posted October 30, 2012 OK I'm back on this (sorry).. and I think I'm getting closer. I bought a low RPM (1725) 8" bench grinder off craigslist local for cheap (it's made by woodcraft). Unfortunately it's got a 5/8" shaft with 11tpi threads on the end or "5/8-11". This thread count is fairly rare, and I can find no drill chucks to match it (lord knows I've tried). So today I went to a local industrial bolt supplier and picked up a long hexagonal nut (3" or so) that has female 5/8-11 threads on one end and female 1/2-13 on the other (to be the first piece after my Grinder's shaft). I also got a short length of threaded stock that's male 1/2-13 on one end (to fit into the end of the hex adapter) and 1/2-20 (for the chuck to mount onto) on the other. Harbor Freight has a threaded drill chuck with that thread count for $10 that I want to use if possible. The problem is that when I mount the two adapter pieces onto my Grinder's shaft there is a quite obvious unbalanced thing going on (the adapters are not completely straight together). I thought of heating the assembly up until glowing red and then whacking the top of the threaded end (with a nut mounted to protect the threads) to correct the alignment. OR.. I found the following website's adapter that looks kind of right and is described the way I think it should but I'm not sure - does it seem like the right item to ya'll? I don't know why there's two hex pieces there and that's kind of throwing me. Also not sure if that small threaded side is long enough to mount the chuck. http://www.toolfetch...s/541404609.htm What do you think? You only need the left hex fitting displayed in the photo at toolfetch, plus a short 1/2 x 20tpi threaded stud. This still gives you a longer extension than you would like, but probably the shortest conversion you will come up with. The bench grinder probably isn't balanced all that well. You may be able to keep the grindstone on, use the adapter to lock it on tight, to help with the balance problem. You can play with attempting to balance it by adding a couple pieces of about 18 AWG sheet metal, cut in a strip about 2" wide and about 5" long. Round both ends. Drill a 5/8" hole in one end of each. Mount directly against the stone, or if there is not enough space, drop the stone and make a circular disk 8" in diameter, what ever thickness will fit with the two layers of 18 AWG. When the two strips are opposite to each other, they balance each other out. As you swing one around, it will produce a centrifugal force vector point halfway between the two free ends. Keep a guard of some sort around these so you don't get chopped up. Think of a meat slicer. You will have to do many attempts, but you should be able to experiment positions of the adjustabel weights (the two strips) until you find a position that reduces the unbalance. (There are blancing kits you can buy for grinders. They work the same.) If the bearings are really nice and free, you can do a static balance by adjusting positions until the rotor doesn't turn heavy side down by itself. If you were a lot closer to me, I could balance it for you. That's just another of my past jobs, balancing rotating equipment. Good luck. Tom Quote Share this post Link to post Share on other sites
CustomDoug Report post Posted October 30, 2012 ... You can play with attempting to balance it by adding a couple pieces of about 18 AWG sheet metal, cut in a strip about 2" wide and about 5" long. Round both ends. Drill a 5/8" hole in one end of each. Mount directly against the stone, or if there is not enough space, drop the stone and make a circular disk 8" in diameter, what ever thickness will fit with the two layers of 18 AWG. When the two strips are opposite to each other, they balance each other out. As you swing one around, it will produce a centrifugal force vector point halfway between the two free ends. Keep a guard of some sort around these so you don't get chopped up. Think of a meat slicer. .... Tom Wow Tom that balancing technique is a brilliant idea. I would never have come up with that. Thanks! I'm thinking that since this setup from TOOLFETCH is made for this sort of thing, a lot of the imbalance will have been engineered out of it. Actually, when just watching the shaft of my grinder rotate it looks very straight (of course added length will accentuate the slightest bit). But the two parts I got from the industrial bolt supplier were not intended for the use of rotating mass as a team. If you look at it the male threaded piece seems very straight on it's own.. but the long hex piece was obviously drilled and tapped at a slight angle. So causing the unevenness when put together. Here's one more thought - would it be feasible to shorten the grinder shaft's threads (cut part of them off with a cut-off wheel) and also shorten the 5/8-11 end of the hex piece from toolfetch ? Quote Share this post Link to post Share on other sites
Northmount Report post Posted October 30, 2012 Wow Tom that balancing technique is a brilliant idea. I would never have come up with that. Thanks! I'm thinking that since this setup from TOOLFETCH is made for this sort of thing, a lot of the imbalance will have been engineered out of it. Actually, when just watching the shaft of my grinder rotate it looks very straight (of course added length will accentuate the slightest bit). But the two parts I got from the industrial bolt supplier were not intended for the use of rotating mass as a team. If you look at it the male threaded piece seems very straight on it's own.. but the long hex piece was obviously drilled and tapped at a slight angle. So causing the unevenness when put together. Here's one more thought - would it be feasible to shorten the grinder shaft's threads (cut part of them off with a cut-off wheel) and also shorten the 5/8-11 end of the hex piece from toolfetch ? It is always better to start out with a straight rotor rather than a bent rotor. So straightening should be done as far as possible first. (It is possible to balance a bent shaft, and is usually done as a temporary repair in order to get back into production on large expensive equipment where it takes 2 years to get a new rotor.) The adapter nut should have been made on a lathe so should be straight ... but depends who and where. You might consider returning it and having it replaced to see if you can get a better one. Yes you can cut things shorter to reduce the overhang, but the offset will still be there. Shorter will reduce the unbalanced centrifugal force. Just make sure you have enough length to make a solid connection. For 5/8", I would say no shorter than 5/8" long. For 1/2", same rule of thumb. Something sticking out unsupported 10" or more that is out of balance spinning at 1750 RPM is dangerous and scares the heck out of me. I did some diagnostics on a steam turbine pump shaft one day, running 5000 RPM. The vibration on one bearing (supporting a bent shaft) was over 100 inches/second. 0.5 ips is shutdown level. I got out of there in a hurry! Tom Quote Share this post Link to post Share on other sites
CustomDoug Report post Posted October 30, 2012 I'm sure my grinder's shaft is not bent - I can not detect any unevenness when just running it without anything mounted. Those two extra adapter pieces are though. I just held the adapter combo to a straight edge and it's obvious. So I went ahead and ordered the toolfetch adapter. I'll report on how it works out. It's coming from the NY area so, with this current storm situation I'm afraid it'll be a while before it arrives. I just hope our forum members from that area have kept themselves safe! Quote Share this post Link to post Share on other sites
Northmount Report post Posted October 30, 2012 I'm sure my grinder's shaft is not bent - I can not detect any unevenness when just running it without anything mounted. Those two extra adapter pieces are though. I just held the adapter combo to a straight edge and it's obvious. So I went ahead and ordered the toolfetch adapter. I'll report on how it works out. It's coming from the NY area so, with this current storm situation I'm afraid it'll be a while before it arrives. I just hope our forum members from that area have kept themselves safe! When I'm talking about a bent shaft, I'm talking about the complete assembly. It functions as one rotating element. Tom Quote Share this post Link to post Share on other sites
