Dave Stephens Posted January 23, 2015 Share Posted January 23, 2015 All: Is anyone aware of an accessory for the KMG that would allow for Z axis (up and down) adjustments to the work rest? At the bottom of this post are some shots of how I currently do it, using a MAP arm attachment and a laboratory scissor platform. The problem is that the scissor jack is not rigid enough. While it does pretty well locking in the Z axis, it has about .125" of play in the table itself. While sliding a sword blade back and forth on it to create fullers, it can cause you to fall out of "the groove." Any suggestions on something with more rigidity and precision would be appreciated! Thanks Dave PS: Many thanks to Craig Hashimoto for generously gifting me this scissor jack when I was originally struggling for a solution. -----------------------------------------------"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly; who errs and comes short again and again; because there is not effort without error and shortcomings; but who does actually strive to do the deed; who knows the great enthusiasm, the great devotion, who spends himself in a worthy cause, who at the best knows in the end the triumph of high achievement and who at the worst, if he fails, at least he fails while daring greatly." -- Theodore Roosevelthttp://stephensforge.com Link to comment Share on other sites More sharing options...
Jerrod Miller Posted January 23, 2015 Share Posted January 23, 2015 Dave, can you explain why the MAP arm isn't good enough? I thought the small squared parts (as opposed to the long square or round rod) gave all kinds of z-axis range. I've been planning build like that for my grinder and figured it would give me all the range I needed. Link to comment Share on other sites More sharing options...
Matthew Lomas Posted January 23, 2015 Share Posted January 23, 2015 Hey Dave, I would suggest you go to Travis Wuertz site and peruse the pictures he has of his grinder and work rest. It is not very hard to make if you have a milling maching and is rigid and very adjustable. I don't have any pictures of the one I made but I'm sure I can find the time to snap some if you need it, but I doubt you would have any trouble. Link to comment Share on other sites More sharing options...
James Spurgeon Posted January 23, 2015 Share Posted January 23, 2015 Fixed pin archery sights made in the 90s, the good ones anyway, use a dovetail slide for Z axis adjustment that I would expect would work quite well for a rest as well. Imagine the "tuning fork" that attaches to the tool arm ending in a vertical post, tall enough to encompass the full Z axis, that has been milled into the male side of a dovetail drawer slide. The table is then attached to a 3-4" tall vertical female dovetail slide with a set screw or 2 to lock it at a particular height. Theoretically, the taller the female dovetail is, the more stable the table will be. The 3-4" is just my spitball estimate of a minimum height to ensure stability. With close tolerances on the dovetails, this should be quite solid. I may have to do this for mine, now that you brought it up... James Courage is resistance to fear, mastery of fear - not absence of fear. Except a creature be part coward it is not a compliment to say it is brave. ~Mark Twain SageBrush BladeWorks (New website is in limbo...) Link to comment Share on other sites More sharing options...
owen bush Posted January 23, 2015 Share Posted January 23, 2015 I would look for a vertical slide for a lathe on ebay or such, mount it upside down and build a rest on it... forging soul in to steel owenbush.co.uk Link to comment Share on other sites More sharing options...
Dave Stephens Posted January 23, 2015 Author Share Posted January 23, 2015 Thanks everyone. Owen - My lack of machinist training is showing. I was unaware of the existence of vertical lathe slides. I did a brief search on them and it does, indeed look as if it would be pretty easy to fabricate a shelf that used the slide as the z axis lift. Thanks bud! James -- I just looked up the archery sites. Great, creative idea. I think the lathe slide might be a bit more "skookum" (Alaskan term for robust). Jerrod -- The Mapp arm allows for Z adjustment by loosening two large bolts which them frees the rest swivel and allows you to raise and lower the rest. The problem is that there is not precise control. When lining up a fuller for grinding I need to be able to raise or lower the table slowly and precisely. Before I got the scissor jack I would carefully try to position the mapp rest, put the blade on the rest coated with machinist blue, slide back and forth until the belt scratched a line, undo both bolts and try (by hand) to move the (quite heavy, solid steel) rest up or down a mere fraction of an inch. Sometimes it would take a couple of hours just to set up the rest for a fuller grind. I'm a huge fan of the MAPP arm, but I think my application has over-extended it's intended capabilities. Matthew -- Thanks for reminding me of T. Weurtz. That guy is amazing. My buddy Shane has one of his grinders and it's a badass machine. If I can't get Owen's suggestion to work, I may give Travis a call. Thanks again everyone. If I do fabricate something with a lathe slide, I will post photos. Dave -----------------------------------------------"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly; who errs and comes short again and again; because there is not effort without error and shortcomings; but who does actually strive to do the deed; who knows the great enthusiasm, the great devotion, who spends himself in a worthy cause, who at the best knows in the end the triumph of high achievement and who at the worst, if he fails, at least he fails while daring greatly." -- Theodore Roosevelthttp://stephensforge.com Link to comment Share on other sites More sharing options...
Jerrod Miller Posted January 23, 2015 Share Posted January 23, 2015 I see, thanks for the clarification. Link to comment Share on other sites More sharing options...
Bret Posted January 24, 2015 Share Posted January 24, 2015 How much z axis travel are you looking for? the lathe slide is a good idea, but if your only looking for a few inches, a channel, a block, a screw, and a few springs would give you a compact very rigid set-up. Block tight in channel, return with springs, and move up with screw. basically the same as the slide, but a bit more compact/stable. A set of lock screws in the channel would lock your height, and ensure stabilization at the same time. If you are having trouble visualizing I could draw it up. Link to comment Share on other sites More sharing options...
Craig Hashimoto Posted February 5, 2015 Share Posted February 5, 2015 Aloha Dave, I knew that little scissor jack looked familiar Hope you figured out a solution.... Did the pancake coils work? Have a great day, Craig Link to comment Share on other sites More sharing options...
Bill Kirkley Posted February 6, 2015 Share Posted February 6, 2015 I think the lathe slide is the easiest best way to go. If you want to build something cheaper that has a little wobble you could try a threaded rod. I threaded a 1 inch round bar to use to control the height of a set of rollers I made. I used a slot in the rod and a bolt to control rotation but it has too much play for what you want. A solution to that would be a smooth rod parallel to the threaded rod captured in a hole in the mounting bracket. Link to comment Share on other sites More sharing options...
VaughnT Posted February 21, 2015 Share Posted February 21, 2015 Thought I'd bump this to the top to spread the news. A friend just got a DD workrest off ebay and has nothing but good things to say about the system. A bit pricey if you go with the complete set, but the quality is certainly there. Makes me wonder how hard it would be to come up with a screw system for elevation that would use the existing post as a stabilizing guide rod. Or replace the rod with some heavy acme thread and a nut. As you spin the nut down, it pushes the platform up to the height you want just like the old house jacks. Then lock it all in place with the bolts. When reason fails... Link to comment Share on other sites More sharing options...
Scott A. Roush Posted February 21, 2015 Share Posted February 21, 2015 Yeah... it's frustrating making tiny adjustments like that with the MAPP. If fact... I quit trying to use it for fullers for that reason. I felt that the mistakes I made with the MAPP were more deadly than the small ones I make free-hand. But.. I need to go back to using something. Especially for multiple fullers. So...paying attention to this thread. http://www.bigrockforge.com Link to comment Share on other sites More sharing options...
Brian C Madigan Posted February 23, 2015 Share Posted February 23, 2015 Dave, I've been working on this problem for a few months of weekends (too long!). Last year I built a tilting rest that could be set to a precise, repeatable height. It also was made to adjust for different size contact wheels. However it was based on bunch of square stock with tapped holes and lockdown bolts, which were not as repeatable as I wanted. The next idea was a pantograph like swing arm thing that follows the contour of the wheel exactly, making it unnecessary to adjust the Y-position of the table when adjusting the Z-position. Hanging this off of the tooling arm and making it rigid ended up being too complicated. I was making it out of 1x2 aluminum bar with bronze bushings and 1/2" shoulder bolts for the pivots. I have a problem where I start building something before I've engineered/though out or designed it in enough sketches to prove it out. So I may go back to that pantograph/swingarm design eventually, but it's pretty overcomplicated. So I started over with dovetail slide for the Z-axis and an acme threaded lead screw. I was looking at these designs: http://www.velmex.com/manual_examples3.html That whole site is pure precision mechanical porn. I have a S3 mill and a 11x26 lathe, so I SHOULD IN THEORY be able to make just about anything. So I'm still working on the Z-axis table. I got a little distracted learning how to properly cut Acme threads in smaller sizes. Then I found out the hard way that it's impossible to cut internal threads in bronze with less than 5/8" ID or so. Too much spring in the boring bar. I'm currently looking for Acme taps on Ebay, and attempting to cut my own taps out of W1. I may also try using acetyl or PTFE for the nut. Link to comment Share on other sites More sharing options...
Brian C Madigan Posted February 23, 2015 Share Posted February 23, 2015 I did also make a few iterations of the tool rests that Travis Wuertz makes. Again repeatability was the problem and I knew a precision lead screw would make it a lot easier, kinda like that scissor jack works. A lead screw with the right pitch will make one turn every .1", so you can easily get to up to .001 repeatability on the Z-axis with a micrometer dial. Link to comment Share on other sites More sharing options...
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