Announcement

Collapse
No announcement yet.

Taper Attachment in Latest HSM - spring tension

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • J Tiers
    replied
    Most such systems use eccentric bolts so that there is a range of adjustment on at least 2 and all 4 can be set to be evenly aligned. For instance, my radial arm saw carriage.

    Leave a comment:


  • CCWKen
    replied
    I couldn't get the holes drilled and tapped in proper alignment for four bearings at the time. The one shown with three bearings was the third version. The cutting force is applied to the two rear bearings as they follow the guide. The front bearing has about .005" clearance to the guide but it doesn't even need to be a bearing. I could have just used an adjustable plastic guide/gib there. Eh, you learn as you go. I started with an idea and scraps on hand--No drawings. If I were to do it again, I'd have a better plan.

    EDIT:
    Another change I'd make would be to NOT make the angle sweep so large. The part toward the lathe bed can get in the way. It doesn't need to be so wide for most common tapers. Especially when using a 12" guide bar as I have.
    Last edited by CCWKen; 10-19-2016, 01:21 PM.

    Leave a comment:


  • J Tiers
    replied
    It occurs to me that 3 rollers may be a less desirable design than 4. While 3 are not kinematically redundant, and 4 are, 3 really only work well with the force against the 2. That can be made to be the commonly used direction, of course.

    but if the single roller ever has to do the pushing, it will be unstable. There is always some slop in the system, and if any exists, the single roller might allow the "traveler" piece to twist to the right or the left, depending on direction of forces at a given moment, and thus cause a slight variation in position of the crosslide. Not much perhaps, but with tapers it may still be enough to make a difference.

    I believe the factory-made units I have seen pics of have all had 4 rollers.

    I like the unit in the pics, just wondering if it might be even better with 4 rollers.

    Leave a comment:


  • CCWKen
    replied
    Originally posted by Paul Alciatore View Post
    ...On the other hand, any device that uses a follower that is in a slot or that surrounds a solid guide bar will have to have some clearance between itself and that slot or guide bar. So the cutting forces can push the guide back and forth by the amount of that clearance. This will also decrease the accuracy of the taper.
    Perhaps but in practice it doesn't move back and forth. (At least not while cutting.) It's no different than the play in a cross slide or compound. While cutting, the clearance is taken up by the force of the cut. You still cut by the dial markings and/or measurements. The only variant would be flex in the guide bar and the reason I mentioned that it needs to be pretty hefty stock. It should also be kept as short as possible.

    Leave a comment:


  • Baz
    replied
    Following the logic of Paul's post above a slot or bar guide can always have a spring added when it seems to help. Since CNC has made linear bearings readily available and cheap they seem the obvious choice now.

    Leave a comment:


  • Paul Alciatore
    replied
    I do not have a taper attachment nor have I ever used one. From a purely theoretical view point, I can see advantages and disadvantages to both methods.

    The spring will try to keep the follower against the guide bar with almost zero distance between them. So, in theory, it would produce the more accurate taper. But there are conflicting requirements on that spring. It must be heavy enough to overcome the drag in the cross slide as well as the forces involved in making the cut. But it needs to be light enough to not bend or distort anything in the process. And, the forces involved in cutting may cause the follower to lose contact with the guide bar which will destroy the accuracy of the taper. So multiple passes may be needed to get to the final figure. This can be problematic as a light cut may penetrate less into the work than a heavier cut will.

    On the other hand, any device that uses a follower that is in a slot or that surrounds a solid guide bar will have to have some clearance between itself and that slot or guide bar. So the cutting forces can push the guide back and forth by the amount of that clearance. This will also decrease the accuracy of the taper.

    Personally, I think I would prefer the use of a follower in a groove or that surrounds the guide bar. I don't trust the idea of a spring.

    It may be better to use manual pressure instead of a spring. That way the operator could adjust the pressure as conditions change.

    Leave a comment:


  • Rich Carlstedt
    replied
    A few years ago I posted some pictures of my unit on this board which will do tapers or profiles.
    The concept does not require a spring , but is direction sensitive to follow any profile.

    http://bbs.homeshopmachinist.net/thr...s-Cutting-Tool

    Rich

    See posts # 8,15,and 21
    Last edited by Rich Carlstedt; 10-18-2016, 11:47 AM.

    Leave a comment:


  • CCWKen
    replied
    I can count the number of times I've used mine on one hand but was glad I had it every time. As JT points out, it's a necessity for long tapers. I used mine cutting a few axle tapers, adaptor for my wheel balancer, and a custom gear shift handle. I don't bother to set it up for short tapers--The compound method works but I usually have to run the lathe in reverse and cut on the back side unless the stock is extended away from the chuck. It also means hand feeding and the finish isn't always the best.

    Leave a comment:


  • enl
    replied
    I've use a few designs on different lathes, and currently have a homebuilt based on a factory Atlas commercial style. I use it once in a while, especially for shallow tapers (taper pins, mandrels, taper press fit) and tapered threads. The ones that have worked best just use a solid hardened bar and gibs. Round bar or rectangular doesn't matter much as long as it is rigid enough and the drawbar guides keep it straight.

    The roller units I have used (2 different makes, American was one and the other was a retrofit and I don't know who made it) were ok, but required obsessive cleaning to keep chips and coolant out, or the rollers would skip or jam and slide. The shielding never seemed to do as good as one would like.

    I could see using a spring on the slack side to remove clearance and, maybe, eliminate backlash, but since they can be used wither 'push' or 'pull', one direction is going to have lower rigidity.

    Leave a comment:


  • J Tiers
    replied
    Haven't one for the Logan, and every time I cut a morse taper or the like, I cuss myself for not having made one yet. But I STILL have not made one.

    I can cut an MT2 with the compound, but an MT3 exceeds the travel, so I have to do one a little short. I'm not trying to reset for the small extra part.

    Dunno why I am so stubborn.... Maybe because its a tool to make another tool so I can make the part I want, and I just don't want to go that far off track..

    Leave a comment:


  • v860rich
    replied
    A long time ago I lusted for a T/A for my 9" SB lathe, never found one, never built one.
    About 20 yrs ago I bought a 16" SB with a TA and I have yet to use the thing.
    In fact the only one I have ever used was in a machine tool class 10 yrs ago.
    It seemed like more trouble than it was worth for the few tapers I used it for.
    I've mostly just used the compound for any taper I've needed to cut.

    THANX RICH

    Leave a comment:


  • Toolguy
    replied
    I have made one that used a spring as described. I had to loosen the gib on the cross slide in order to make it work. I didn't like that. It did work more or less, but the cross slide was not as stable as I want. I recently made a thread about mine called "Taper attachment for manual lathe".

    http://bbs.homeshopmachinist.net/thr...r-Manual-Lathe
    Last edited by Toolguy; 10-18-2016, 10:18 PM.

    Leave a comment:


  • CCWKen
    replied
    Here's one of the original pictures.

    Leave a comment:


  • CCWKen
    replied
    Yeah, they are cantilevered but the roller bearings are only 1/4" thick too. Lots of improvements to the design were considered but I wanted it to be easy to install and/or store. Having all the parts fixed or captured by "plates" would not only increase assembly time but also necessitate a major redesign to accommodate the extra thickness added by the plate(s). Changing to grade-8 bolts was an easier fix.

    My point was that there is sufficient force to bend standard 1/4" bolts so I'm thinking a spring is not going to work well.
    Disclaimer: I don't get the mag and haven't seen the design so I don't know how/where the spring is used.

    Leave a comment:


  • J Tiers
    replied
    Originally posted by CCWKen View Post
    I made my own taper attachment. It's in the Shop Made Tools thread somewhere. I used small 1/4" ID bearings on my guide and follower held in place with bolts. After the first trial run I had to change all the bolts to grade-8 because the originals (probably grade-3) were bending. There's considerable force being applied to the guide and follower. If I were to do it again, I'd design-in the use of linear bearings too but the shafting would need to be stout enough to handle the forces. Probably something in the range of 3/4" or better depending on the length of the guide. Or take really, really light cuts.
    Did you attach the bearings cantilevered on the bolts? You should find much improved performance if you set them up so the bolts are in "double shear", supported by plates on each side, instead of cantilevered.

    Leave a comment:

Working...
X