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Old 09-26-2017, 01:57 AM   #11
nautilus29
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To be honest with you wizard, I originally designed it to be much more rigid. I then drew it up to scale and it was giant compared to the lathe itself. 3/4 seemed small to me at first but honestly I think it scales with the work I can do on this lathe. I calculated the weight of this design and it's only a couple of pounds less then the lathe itself. Even though weight doesn't mean it will work, I think it at least shows that compared to the lathe it's not that small.

I would have never considered this idea except for how well the original one actually did work. His was designed with only one bar and the tailstock was held upright with a keyway slot on that bar. Then he added a side adjustment to his tailstock with a dovetail, and had one screw on the top to tighten that down instead of tightening against the dovetail. Considering all of that he put a 7/16 drill in the tailstock and drilled a piece of steel. His tailstock pushed between .003 and .008 thou. I didn't think that too bad considering the buildup, and drilling a 7/16 hole into steel on this lathe is probably pushing it to its limit.

All that being said I really like the bed next to the bed design you mentioned. This could definately add rigidity, and if I raised the tailstock bed up some the tailstock could be mounted better since it wouldn't have to have a riser on it. I could also design a taper attachment that could use that bed as support. I did think about getting the sherline longbed, but I'm trying to keep the lathe as short as possible for both work bench space, and so I can move it around easier. Thanks for your honest opinion. I don't want to put a bunch of time into something that ends up needing a complete overhaul.


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Old 09-27-2017, 12:38 AM   #12
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At work we have all sorts of industrial slides in use for everything from specialized grinder to general automation. My reluctance with round bar slides is the result of man of them being long for the bar size. Such slides can work perfectly well over shorter distance.

The question then becomes is the distance you have with those bars too long for the diameter and the work loads you will have on them. I suppose a good mechanical engineer could answer that question with great precision but that isn't me. The only two issues I have are ringing or vibration in the rods and deflection under load. Lets just say the possibility of problems makes me nervous but we need to temper that with the idea that this is a TAIG and thus you won't be putting 5 horsepower of energy into the work. One other thing to consider the best of the dual rod slides I've worked with have been designed to a very high level of precision and are tight, that is almost zero play in the rod bearings. That is a tough one to achieve without binding at one end or the other of the stroke. The dovetail approach is probably easier to get working to a high degree of prices fit up.

Now that I've slept on this for a night, I'm seeing some other possibilities that might be worth considering. Lets say you go forward with the two rod idea but spread them out just a bit more to put a leadscrew between them. You then get a very nice way to drive the tailstock back and forth. You might also be able to address the tails tock fit on the rods with eccentric bushings. I believe there was a commercial lathe made at one time that had really large steel bars for ways that used bushings to compensate for wear. Another possibility here is to go with a #2 morse taper for greater flexibility in tooling at that end.

So I'm not trying to completely dismiss the ida here I'm just worried and part of that might be due to thinking more along the line of the larger stuff I work on at work.


Quote:
Originally Posted by nautilus29 View Post
To be honest with you wizard, I originally designed it to be much more rigid. I then drew it up to scale and it was giant compared to the lathe itself. 3/4 seemed small to me at first but honestly I think it scales with the work I can do on this lathe. I calculated the weight of this design and it's only a couple of pounds less then the lathe itself. Even though weight doesn't mean it will work, I think it at least shows that compared to the lathe it's not that small.

I would have never considered this idea except for how well the original one actually did work. His was designed with only one bar and the tailstock was held upright with a keyway slot on that bar. Then he added a side adjustment to his tailstock with a dovetail, and had one screw on the top to tighten that down instead of tightening against the dovetail. Considering all of that he put a 7/16 drill in the tailstock and drilled a piece of steel. His tailstock pushed between .003 and .008 thou. I didn't think that too bad considering the buildup, and drilling a 7/16 hole into steel on this lathe is probably pushing it to its limit.

All that being said I really like the bed next to the bed design you mentioned. This could definately add rigidity, and if I raised the tailstock bed up some the tailstock could be mounted better since it wouldn't have to have a riser on it. I could also design a taper attachment that could use that bed as support. I did think about getting the sherline longbed, but I'm trying to keep the lathe as short as possible for both work bench space, and so I can move it around easier. Thanks for your honest opinion. I don't want to put a bunch of time into something that ends up needing a complete overhaul.


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Old 09-27-2017, 08:59 AM   #13
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When I mentioned that I wanted to use an er16 holder for my tailstock I assumed I could buy live or dead centers that would fit it. After doing some web surfing I've realized I was wrong. If there are any options there aren't very many of them. Mt2 taper it is.

My initial idea for locking the tailstock into place was to put a slot in the bottom of the tailstock that partially cut into the bushings that the rails will run on(exposing some of the rail). Then making a block to fit that slot with two radii cut into it it to match the rails. Then I would have a bolt going through the middle of the rails that when tightened would pull the block up against the rails and lock it in place. I figured this would give it some support while using the tailstock.

I really like the leadscrew idea you mentioned. It adds a precise way to take holes to depth, and it takes away some stuff that would need to be machined on the tailstock shaft. I could also make a couple of different tailstock shafts if I I wanted to and swap them out pretty easily. I'm a little worried though that not having the tailstock locked onto the rails will add some give to the unit. What are your thoughts?

I figured I'd mention my plans for machining the rail supports. Before I designed this I cut two rails so I could test how true they ran. One had just under .0002" total runout and the other was at .0001". Much better then I expected to be honest with you. Now for the rail supports... I figured I would set them up and bore them both at the same time. This should help remove any setup variations, and keep the two blocks as true as possible.

I haven't had time to draw up the double bed option yet which is why I didn't mention it here. Once I do I can weight each option better. Thanks for the help, I'm glad I didn't jump right in and build it.

]
Quote:
Originally Posted by Wizard69 View Post
At work we have all sorts of industrial slides in use for everything from specialized grinder to general automation. My reluctance with round bar slides is the result of man of them being long for the bar size. Such slides can work perfectly well over shorter distance.

The question then becomes is the distance you have with those bars too long for the diameter and the work loads you will have on them. I suppose a good mechanical engineer could answer that question with great precision but that isn't me. The only two issues I have are ringing or vibration in the rods and deflection under load. Lets just say the possibility of problems makes me nervous but we need to temper that with the idea that this is a TAIG and thus you won't be putting 5 horsepower of energy into the work. One other thing to consider the best of the dual rod slides I've worked with have been designed to a very high level of precision and are tight, that is almost zero play in the rod bearings. That is a tough one to achieve without binding at one end or the other of the stroke. The dovetail approach is probably easier to get working to a high degree of prices fit up.

Now that I've slept on this for a night, I'm seeing some other possibilities that might be worth considering. Lets say you go forward with the two rod idea but spread them out just a bit more to put a leadscrew between them. You then get a very nice way to drive the tailstock back and forth. You might also be able to address the tails tock fit on the rods with eccentric bushings. I believe there was a commercial lathe made at one time that had really large steel bars for ways that used bushings to compensate for wear. Another possibility here is to go with a #2 morse taper for greater flexibility in tooling at that end.

So I'm not trying to completely dismiss the ida here I'm just worried and part of that might be due to thinking more along the line of the larger stuff I work on at work.
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Old 10-02-2017, 02:38 AM   #14
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Quote:
Originally Posted by nautilus29 View Post
When I mentioned that I wanted to use an er16 holder for my tailstock I assumed I could buy live or dead centers that would fit it. After doing some web surfing I've realized I was wrong. If there are any options there aren't very many of them. Mt2 taper it is.
ER for a tailstock is a little odd however making a live and dead center isn't a big deal in my mind. Where you really loose is being able to buy pre-made MT2 spindle tooling which is widespread and comparatively cheap. For your design you would need a wider tailstock block but that is no big deal and only adds a few inches to your overall length.

In any event it is up to you.
Quote:
My initial idea for locking the tailstock into place was to put a slot in the bottom of the tailstock that partially cut into the bushings that the rails will run on(exposing some of the rail). Then making a block to fit that slot with two radii cut into it it to match the rails. Then I would have a bolt going through the middle of the rails that when tightened would pull the block up against the rails and lock it in place. I figured this would give it some support while using the tailstock.

I really like the leadscrew idea you mentioned. It adds a precise way to take holes to depth, and it takes away some stuff that would need to be machined on the tailstock shaft. I could also make a couple of different tailstock shafts if I I wanted to and swap them out pretty easily. I'm a little worried though that not having the tailstock locked onto the rails will add some give to the unit. What are your thoughts?
Tailstock locks have been around as long modern lathes you will most certainly want a lock solution. You could try cotters as might be used on something like a Quorn grinder.
Quote:

I figured I'd mention my plans for machining the rail supports. Before I designed this I cut two rails so I could test how true they ran. One had just under .0002" total runout and the other was at .0001". Much better then I expected to be honest with you. Now for the rail supports... I figured I would set them up and bore them both at the same time. This should help remove any setup variations, and keep the two blocks as true as possible.

I haven't had time to draw up the double bed option yet which is why I didn't mention it here. Once I do I can weight each option better. Thanks for the help, I'm glad I didn't jump right in and build it.

]
Even if you jumped in this is a design that would be fairly easy to upgrade to other configurations. I still see a longer bed as the overall best solution.
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Old 10-02-2017, 10:31 AM   #15
dennisa49
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Hello Nautilius, I am coming in late here.
May it be worth considering hollow bar rather than solid to support the tail stock.
In general it handles toque and deflection better than solid.
Good luck with your project, regards Dennis


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