finishing ends on a lead screw

The plan is to build a sliding table type router table for making raised panels for doors on a furniture project. I am going to use a
couple of linear bearings on shafts attached to a large aluminum plate for the sliding table, then use an 3/8" x 10 tpi Acme precision lead screw to advance the sliding portion of the table. The plate will have the wooden workpiece attached and feed the wood hanging off the edge into the panel raising bit. The last time I raised panels I sent a couple of workpieces across the room because they weren't fixtured well enough to my plywood jig, so I really need a rigid sliding table for safety and better results.
I definately don't have the skill or thread cutting attachements to make my own lead screw and nut, and the prices on a complete assemby with support flanges and flats milled on the leadscrew are pretty steep. So I am looking at just buying a 3' length of lead screw with an oversized nut. My question is about how to finish the ends of the lead screw. Can I just weld a sleeve, with a tight fit between the OD of the screw and the ID of the sleeve, over the ends of the lead screw - then slide that into a pillow blocks to support the ends of the lead screw? Of would I be better off trying to chuck the 3' lead screw into my HF 3-in-1 and turn the screw shaft down to a smooth round surface that fits into a smaller bearing in my pillow blocks? I have never tried to turn a threaded rod and don't know if the threads would catch on my cutter. I'm quite new to machining metal, and could really use some advice.
thanks James B
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Yes. Hope the chuck is centric. And the lead screw is going through your spindle. It may happen, that the other end will start to vibrate, bend and then slam everything into pieces coming into its way. It is best if you put the free end into a (quite bigger) tube that is well fixed to some heavy <whatever>. I won't tell you the other trick. :-)

Many did before you! :-)

Not at all. Do it like you would do it with a smooth surface.
Nick
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Use a bicycle chain and sprockets. Very little slop in those I have some Thompson linear bearing pillow blocks recirculating ball type for .5" shaft. Model pb8a I'll sell em for 60% of what the bearing places charge.Pls shipping. New in box, 4 pieces. Email me off-group Thx Dan
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Thanks for the offer, but I am going to try to fabricate pillowblocks to hold rollerblade roller bearings. And having fed these raised panel doors by hand previously, I know they can jerk violently in any direction. I have some small shaft mountable sprokets and chain laying around, but am afraid the difference in slop between the Acme screw and a chain would be enough to tear out the wood on my workpiece. I like the chain feed idea though, if I make a sliding table for my table saw that would be a good way to drive it.
- James B
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snipped-for-privacy@yahoo.com wrote:

You'll need to fabricate a support for the far end of the leadscrew. This can be something pretty simple lashed together, with a piece of water pipe to hold the end of the screw. Better make sure the screw can pass through your spindle hole! You won't have to worry about the cutter "catching' on the thread. It will be an interrupted cut, and a bit rough, but it should be able to do it unless the screw is hardened. If you are buying Acme or allthread stock, it won't be hardened. Put the screw all the way through the spindle, so only an inch or so is sticking out of the chuck. That will give solid support to where you are making the cuts.
You may want to rig a Dremel tool or air die grinder to the toolpost to finish the ends. (A toolpost grinder is the tool of choice, but I doubt you have one of these.) You put a small grinding wheel on the tool and grind the OD and flange of the leadscrew to proper dimensions with a fine surface finish. Depending on the screw material, you MAY be able to cut it to a good finish with cutting tools, but it is not guaranteed. Removing the last .001" by grinding will give accurate dimensions and a fine finish for sure. (Protect the lathe from the grinding dust with damp cloths.)
Jon
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snipped-for-privacy@yahoo.com wrote:

Do you really need a lead screw to advance the table? Can't it be advanced by hand (pushing)? The 10 tpi lead screw is going to take a *lot* of turning (180 turns for an 18" edge). Bob
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It's a bit hard to understand why you need precision leadscrew accuracy for a woorworking router table. Why not just some hardware store threaded rod?
John Martin
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Multiple reasons really. Mostly, I tried to build something like this before using plywood, full extension drawer slides, and generally cheap components, and it shreded my workpiece pretty good. I want to do it right this time. An ME could maybe explain better, but the Acme screws have a vertical face will push my table the direction I want it to go, while the hardware store rods have the "V" shaped threads that will transfer some component of the applied turning force in the wrong direction for my application. I think the "V" threads are designed more to hold a night at a high torque than they are to advance the bolt on a rotating shaft. Plus a small threaded rod that my drill could turn would bend when the router bites the wood, and a thicker rod would smoke my drill trying to turn it.
Part of where I need the accuracy is in controlling the feed rate. If the feed rate is to slow the bit will burn the wood deeper than can be sanded away, and if it is too fast I will burn up router number 5. Another place where you need accuracy is stopped dados and sliding dovetails. If you look at something like the Incra jig for routers, it uses a lead screw just for the fence. And mostly I want to might want to use this sliding table as part of a stage some other CNC project.
I won the bid last night for linear bearings on 3' shafts, so parts are on the way. I will try to post a link to a picture when this is finished.
- James B
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