Machinists Corner

[C*H*U*D]

Originally Posted by Duuuuuuuude

I've never learned anything by just buying what I needed, other than how convenient it is to do such a thing.

I agree with doing it yourself. I checked out that link and it's pretty interesting...going into my Evernote I'm just saying $40 really isn't that much if you had to get your machine going quickly versus the learning experience.

Originally Posted by Duuuuuuuude

I said "at least three".

Now you're just getting technical

[Duuuuuuuude]

Originally Posted by C*H*U*D

I'm just saying $40 really isn't that much if you had to get your machine going quickly versus the learning experience.

I agree, but its still usable so I'm going to use it. Just have to be careful with the additional backlash.

[Charlie-III]

Originally Posted by Duuuuuuuude

The PITA part is that I'm going to have to tear the table/screw assembly down at least three times. Once to get the measurements of the current nut, again after roughing out the blank, then again to square up the newly formed nut, then, if everything goes according to plan, once more to install the new nut.

Bitch, bitch, bitch....that's all you've ever done since the dog ate the baby is bitch, bitch, bitch......



Sorry you had an issue, but you now have a direction to make your rig better than ever.

For cheap!!

[rlockwood]

thats a neat method, and ive honestly never seen or considered that before. Ive done spring/slotted/tapered anti backlash nuts before, from delrin, and experienced excellent life out of them. Its genuinely amazing how little delrin wears.

[Crawling Calvin]

Have you thought of filing down one of the edges on the nut to maybe increase clamping force a little bit? Personally I like self adjusting anti-backlash nuts since they don't pinch the screw un-evenly and are "self adjusting" for changes in screw pitch and/or diameter. handy things but don't fit all applications.

[Duuuuuuuude]

Originally Posted by Crawling Calvin

Have you thought of filing down one of the edges on the nut to maybe increase clamping force a little bit? Personally I like self adjusting anti-backlash nuts since they don't pinch the screw un-evenly and are "self adjusting" for changes in screw pitch and/or diameter. handy things but don't fit all applications.

Briefly. It's not the lack of adjustment that concerns me, its the condition of the threads. Kinda sucky 'cause its never worked as nice and as smooth as it does now.

Got started on the new nut assembly. The only thing I had to make a hole that big was a cheap ass wobbly Chinese paddle bit of the 7/8" variety. It actually made a very clean, very straight hole. It came out the other end just a couple of thousands off center, and since things are going to get melty, its not even an issue as far as I'm concerned.

Here's the acetal blank and the aluminum "bridge" that will hold it firmly in place.





Once I get the threads in and the blank squared back up, I'll mill a channel on three sides so that the bridge will lock it in. It'll look like this...



When it comes time to align and locate the holes for the bolts, I think I'm going to reassemble everything and position the bridge where it should sit and mark them from underneath. It seems like the best way to do it without running the risk of having it out of whack and binding the screw up when the table is run to its ends.

[CREEPERBOB]

You know Chris, it probally is'nt a lot, but I would take some measurments on the lead screw in differant places along it's length at the root and crown of the thread and see if you have any wear there also.
Those lead screws are available in stock form and can be made to fit most machines. Is it a square thread or an Acme thread?

[Duuuuuuuude]

Originally Posted by CREEPERBOB

You know Chris, it probally is'nt a lot, but I would take some measurments on the lead screw in differant places along it's length at the root and crown of the thread and see if you have any wear there also.
Those lead screws are available in stock form and can be made to fit most machines. Is it a square thread or an Acme thread?

The diameter of the screw is pretty consistant. I was guessing that it would be way worn in the middle, but it was just a tick or two smaller.

Acme thread.

[Duuuuuuuude]

Giggity. I have threads. Pics to come...

[Duuuuuuuude]

Last night I got the threads formed in the blank, then let it be and went to bed. It wasn't terribly hard to do, just a bit of patience and some heat and pressure.



This morning I left it all clamped down and backed the lead screw out. It wasn't particularly easy, in fact is was extremely tight, but it came out cleanly. Other than being dirty, the threads look perfect.



To chase the threads I used the Dremel on the first few threads to make them cut. They don't work terribly efficiently, it takes a lot of working back and forth, but progress is being made.



The block has been in the deep freeze for a couple of hours now, time to pull it out and work the threads some more.

[CREEPERBOB]

Chris, try to undercut the ends of the threads your using to cut the threads, similar to the way a tap is slightly undercut so the actual cutting surface is sharp. You could probally use a cut off wheel in the dremel to do it.

[Duuuuuuuude]

Originally Posted by CREEPERBOB

Chris, try to undercut the ends of the threads your using to cut the threads, similar to the way a tap is slightly undercut so the actual cutting surface is sharp. You could probally use a cut off wheel in the dremel to do it.

I've done that, I also tapered the backside just in case the full thread was lifting the surface of the block. To make it work twice as fast I did the same to the other side so it would scrape going either direction.

I worked the block on the screw again and it feeling better. I can almost spin it freely all the way on. Once it came back up to ambient temperature it was nearly perfect. Its back in the freezer for a couple of hours so I can give it another go. It would suck to go out in the garage this winter and have the block shrink enough to make it a beeotch to turn the screw. Right out of the freezer it is a very tight fit...you've got to force it to start and spin.

[CREEPERBOB]

Yeah delrin is a awsome material. Where I worked there in Arkansas for 15 years, we used mucho delrin for everything, it has a self lubricating property to it similar to teflon.
I would'nt worry too much about it shrinking in your shop to much in the cold of winter.

Originally Posted by Duuuuuuuude

I've done that, I also tapered the backside just in case the full thread was lifting the surface of the block. To make it work twice as fast I did the same to the other side so it would scrape going either direction.

I worked the block on the screw again and it feeling better. I can almost spin it freely all the way on. Once it came back up to ambient temperature it was nearly perfect. Its back in the freezer for a couple of hours so I can give it another go. It would suck to go out in the garage this winter and have the block shrink enough to make it a beeotch to turn the screw. Right out of the freezer it is a very tight fit...you've got to force it to start and spin.

[Duuuuuuuude]

Originally Posted by CREEPERBOB

I would'nt worry too much about it shrinking in your shop to much in the cold of winter.

30 minutes in the freezer is enough to shrink it so that it fits tight again. Whether or not it'll shrink enough in my non-climate controlled garage is a mystery, but I'll do my best to avoid that from happening.

Made another pass on the threads. Its spinning very nice now. I can flick spin it all the way through. I'll freeze/scrape it one more time.

Since the old nut is out, I measured it all up. It looks like I may have cut my block short by roughly .100". Time to find some shims...

[Charlie-III]

Originally Posted by Duuuuuuuude

It wasn't terribly hard to do, just a bit of patience and some heat and pressure.

Some carbon, lots of time & lots of pressure....Bingo, you have a diamond!!



Sounds great Chris.....nice to use a tool to fix a tool.

[Duuuuuuuude]

Its done! I adjusted the height by milling the top notch .04" deeper than I had originally planned, knocked it in tight, then drilled and tapped two holes for some #6 screws to lock it in place. I then cleaned all the heavy grease off of the screw, sprayed it liberally with MooSlick, threaded that puppy on and put it all back together. It fits a bit tighter now that its in the aluminum gusset, but I couldn't get any more scraped out. It is what it is.



In its new home.





So the burning question: how does it work?





Fawking awesome. It has just a little bit of drag, and .0025" of backlash. I clamped some scrap material in the vice and made a few passes...smooth as butter. Now the lower nut feels like shit with its .007" of backlash.

[CREEPERBOB]

Your a master machinist Chris , good job man .

[Duuuuuuuude]

Originally Posted by CREEPERBOB

Your a master machinist Chris , good job man .

One one hand, I say thanks.


On the other, you have just insulted master machinists the world over. Hopefully they will spare you their wrath.

[tarmo120]

You are a great at DIY stuff. But actually to get anything done, you just have to have balls to do it.
That goes for machining too. Don't baby it, feed it.

[crawlerhawk]

nice job Chris, looks like it will hold up just fine