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Gadgets, Gizmos, and Dohickeys => Fixing, Modifying and Refurbishing your Lapidary Equipment => Topic started by: robirdman on April 24, 2019, 06:10:50 PM

Title: rehabilitating 24" Nelson saw
Post by: robirdman on April 24, 2019, 06:10:50 PM
 I just got the motor repaired and only 28 days left on the warranty.  It runs again. Do I have the belts on right?  The one is very floppy.  There is a spring loaded thing, but it barely reaches and popped off when I ran the saw.  Smaller belt is too loose and floppy.  I remember before I used a weight with rocks pulling down where the spring attaches to the nut, and that worked before but it is still too floppy, as in the blurry shot.  Also the gear mechanism seems to be leaking.  Pictures attached. I Just testing running, no oil or attempt to cut anything yet.  I'm hoping I can get some help and actually cut rocks before the warranty on the motor expires.
Title: Re: rehabilitating 24" Nelson saw
Post by: peruano on April 25, 2019, 04:43:17 AM
The "thingey" that jumped off is your belt tensioner. It snugs the belt to insure the correct tension.  Do you have it running on the right belt?  The weight undoubtedly helped maintain that tension too. Make sure you have not used the wrong belts which would cause things to be too loose or tight. Pull that tension pulley down until it snugs the belt and then tighten it enough to make it stay at the appropriate position unless you weight is enough to do so. 
Title: Re: rehabilitating 24" Nelson saw
Post by: Stonemon on April 25, 2019, 07:39:47 AM
In my experience, the belt that pushes the blade does not go through the pulley on the feed drive. So the only place the motor powers is the blade. The feed screw is the driven by the second belt off of the blade arbor shaft. The feed screw belt is tightened by the idler pulley.
Running both belts around the feed screw drive with different pulley sizes will lead to thing smoking and jumping around.
Try powering the blade arbor directly from the motor and the driving the feed screw with the other belt. The three different sized pulleys on the feed drive allow you to change the speed of the feed.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 25, 2019, 07:57:42 AM
Thanks for the info.  I'll see if there is a smaller belt.  I thought those were the 2 that were on before.
So I'm sure I do the right arrangement, could you include a diagram based on my setup?
Which diameter pulley on this is recommended for Agate/jasper?
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on April 25, 2019, 08:59:08 AM
Run one pulley from the motor to the large sheave on the blade axle and around the tensioner pulley.  The other belt goes from the small sheave on the blade shaft to the feed shaft pulley.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 25, 2019, 11:59:17 AM
Running the pulley from the motor to the large sleeve on the blade and around the tension pulley doesn't work. The belt then rubs against that part.
Correct was motor to blade (large sleeve and then the small pulley on the blade shaft to the tension pulley and then to the feed shaft pulley. 
Trying the different combos, I found that then the belts were the right length.  The belt to the tension pulley was not turning it though.  I added oil to the shaft and more weight, and pressing down a few times got it to keep going by itself.  So these suggestions were a great help in finding the right configuration. 
Now my problem is getting the oil remaining in a 55 gallon drum to the saw.  I tried tilting the drum so the small hole in the top would go into a 5 gallon pail but the angle wasn't shallow enough for anything to come out.  I guess I need a long tube filled with oil to be able to siphon it out.  I have some tubing and chain saw oil.  If I pinched the end of a tube and filled with oil, maybe it run out before I put the open end to the drum.  I don't want to suck with my mouth.  Any suggestions? This is all I need to  go.  Big rock in the vise whose cutting was ceased years ago. Feed is working.  Just need to transfer the oil.
Thanks.
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on April 25, 2019, 12:06:46 PM
Walmart sells a shaker siphon hose for around 8 or 9 dollars.  Drop the shaker valve into the oil and pump the hose up and down until the hose fill with oil.  They actually work very well.
Title: Re: rehabilitating 24" Nelson saw
Post by: Stonemon on April 25, 2019, 03:26:14 PM
The idler acts as a safety for the feed screw. If the feed speed is too fast, the drive belt is intended to slip and not create too much pressure at the blade. Good to have a nice solid feed screw pressure but it should not be so tight as to bind the blade.
Grab that bad boy 55 gal and dump that oil in the saw!!  Just Kidding! :toothy10:
Title: Re: rehabilitating 24" Nelson saw
Post by: Stonemon on April 25, 2019, 03:30:18 PM
Thanks for the info.  I'll see if there is a smaller belt.  I thought those were the 2 that were on before.
So I'm sure I do the right arrangement, could you include a diagram based on my setup?
Which diameter pulley on this is recommended for Agate/jasper?

The large pulley on the feed screw at the rear will give you the slowest feed which will move well through the harder materials. You can play with it a bit but my experience is with the slower feed speeds, less wear on the blade and a smoother cut.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 25, 2019, 04:14:19 PM
After 30' on hold at the local Wal-Mart, someone came on and asked what I was holding for.  I told and then after another 7' had a dial tone.  Ordering online, said delivery would be May 5.  I looked at Amazon and ordered 1 with a 10' cord, and delivery tomorrow.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 28, 2019, 11:25:08 AM
So how far should the oil go up into the 24" blade?  Thanks!
Title: Re: rehabilitating 24" Nelson saw
Post by: catmandewe on April 28, 2019, 07:29:40 PM
So how far should the oil go up into the 24" blade?  Thanks!

Approx 1/2" or so
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 29, 2019, 11:00:18 AM
The hose came with no instructions.  The only working video I saw showed putting the valve end in the source and shaking and it all poured neatly into the other container, once the flow started.  Other videos only said what to do and one had the non-valve end in the source.  It didn't work nearly as well for me, and I'm not sure why.  I put the valveend in the small hole of the 55g drum and the other into a 5g bucket.  I could never get a continuous flow and had to shake all the time.  The coils of the 10' tube couldn't be completely straightened and I cut off the ends which were pinched flatter.  So maybe it was the coils, the extra length great difference in heights, not being able to see how it was in the drum, but after an hour of continuous shaking and emptying several inches into the saw multiple times, I still hadn't even reached the blade.  Then I had a such a simple idea, I wish used earlier.  I had thought that whatever method, I would just come close to filling the 5g pail and that would be enough, and I couldn't tilt the 55g drum far enough to get any flow.  So I just got a plastic basin that was only about 5 inches deep and poured into that 4x, and emptied and got past 1/2" and turned the saw to cut. It looks like it may take about an hour.  Timing for future reference and hope nothing goes wrong.  Thanks for all the suggestions!
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on April 29, 2019, 05:37:47 PM
The outflow end of the hose must be below the level of the source.  Once started the fluid will flow until the two containers have equalize levels.  A bucket on the floor with a weight to hold the hose down should work.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 30, 2019, 06:47:17 AM
I successfully cut a couple of slabs off the rock in the saw.  Each was taking maybe 90'.  Then the next piece I checked and it hadonly moved less than and inch.  I checked that the fee pulley was going and the feed screw turning, and continued.  It is no longer feeding.  I looked at the long threaded feed bolt in the saw, after moving the vice and saw no problems.  Maybe the threads on the vise apparatus are stripped.  Hopes dashed.
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on April 30, 2019, 08:30:34 AM
That's a common problem.  Make sure the thread clamp closes all the way.  If the threads are stripped they can be recut with a standard tap.  You may also have to remove a bit of material so they can then close all the way again.  This can usually be done several times before new parts are needed.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on April 30, 2019, 09:59:51 AM
After I pulled back and restarted it finished this time.  Thanks for the suggestion.  The 2 halves would need to be clamped together.  I can't remember if they meet at the top and bottom over the feed and I have it running again. I'll check later, as if they didn't, that would be more difficult.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on May 02, 2019, 01:33:28 PM
After cutting more slabs and putting in a new rock, after one cut, I went to the garage to check on the 2nd.  It was raining and the rain made the garage door so heavy that it wouldn't stay up at all.  I needed to stick a 2x4 piece to keep it open, but I couldn't reach while holding it open.  I let go to pick it up and the door crashed down and now won't open.  I climbed in a small window with some difficulty, and tried prying the door with some boards and levers, to be about 10" open, but despite the disengagement of the tabs that normally would lock it, I couldn't budge it.  So today, I rearranged some equipment in the basement and cleaned off rocks I hadn't looked at in decades.  The biggest surprise was a box with many slabs of agatized dinosaur bone. Though I know I had 150 lbs, I hadn't remembered cutting so much.
Title: Re: rehabilitating 24" Nelson saw
Post by: Stonemon on May 02, 2019, 02:15:12 PM
Nice find! The dino bone is not inexpensive...
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on August 15, 2019, 10:38:54 AM
Neither Home Depot nor Menard's had the large tap size, and I ordered at Grainger. Got it, clamped in vise and after 1st feeling loose, I felt resistance as it went in further, as though it was cutting.  I put the 2 halves back in the apparatus and attached to the vise platform in the saw.  I didn't put the heavy vise back on top.  I just ran the saw to test and came back to see it had traveled about 9".   I put bolted the vise back on, put a big rock in and checked back after I heard the saw still running after what I thought was enough time to cut and shut off.  The vise hadn't budged, so there was no cut.  What a disappointment.  As I wound the vise to get the rock out of the saw path, I noticed how much inertia there was to push the vise ahead, by the amount of force.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on August 24, 2019, 07:55:39 AM
Slabber cabber:  The tapping didn't work.  I notice that there seems a slight separation from the split nut and the feed bolt.  How would I accurately remove material to reduce this.  It seems that filing or sanding by hand would be inaccurate and change the angle slightly or wear more at the edges than the middle.  so upsetting for this little split nut to bring everything to a standstill.
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on August 24, 2019, 12:04:21 PM
You don't need to be accurate in this.  When you have removed enough material above and below that prevents the split nut from closing all the way, the two halves will center on the threaded rod.  The iron of the clamps will be in free air.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on August 24, 2019, 12:13:51 PM
Maybe I need to remove material at the top where the locking mechanism touches, because that prevents the halves from meeting?
Title: Re: rehabilitating 24" Nelson saw
Post by: catmandewe on August 25, 2019, 05:44:48 PM
Looks to me like the spring on the right has lost its tension.
See if you can find a replacement spring.

Tony
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on August 25, 2019, 08:56:40 PM
Actually it seems like that one has more pressure since the spread is more, causing it to bend.  Isn't that an unlikely thing to be able to find?
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on August 26, 2019, 05:55:42 AM
The right hand spring is an improper replacement.  Measure the wire diameter, coil ID and length.  Go to Mcmaster.com and order a new "die spring".  That may be all you need.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on August 26, 2019, 07:38:37 AM
Sounds useful.  I can measure diameter and length but what is coil ID?
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on August 26, 2019, 10:21:54 AM
Inside diameter.  It specifies the mandrel around which the coil is wound.  Die springs are wound with the last coil on each end flatened and ground so they sit straight and apply proper pressure.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 12, 2019, 11:09:54 AM
Finally got back to this project and took vise apart and springs out.  Photographed adjacent and then found I had a similar photo used in an earlier post.  The one looks less stretched so maybe it lost its tensile strength.  It seems a lighter gauge and I wonder which was original as it was very hard to put back together, last time, such was the pressure.  2 comparison shots. feed one is previous.
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on September 12, 2019, 12:24:29 PM
The spring on the left of the pic is a die spring.  The other looks like someone cut a piece out of a longer spring and then tried to stretch it to proper length.  Even if you have to buy two, they need to be matched or you will just keep fighting it.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 12, 2019, 01:02:50 PM
I try to get 2 closest to the left one, thanks.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 13, 2019, 04:39:59 AM
Looked up McMaster and what a great resource!.  I had a metric ruler and measured, but then saw all their measurements were in decimal fractions of an inch.  I thought maybe I needed a micrometer or something, and maybe I could send to them to get the right type.  Then I see the address in Elmhurst and my phone shows as only 48' away! So I can just bring it there, validate type, gauge, etc!
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 13, 2019, 07:28:59 AM
Unfounded optimism.  Called and just a will call warehouse, can't look at anything.  I need a micrometer for accurate measurement of the gauge wire.
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 18, 2019, 04:54:08 AM
While not a micrometer, I found I had a device for reasonably accurate measurements, sort of like a slide rule, with the sliding parts capable of measuring inside and outside diameters.

It seemed pretty standard.  OD 3/4", ID 9/16" length 1" , wire diameter ~3/32", compression spring, steel I assume, end typ flat and ground.

So I plug into the McMaster chart most of the info, and there are only springs longer than 3" showing.

I use the email to convey this and "I'm sorry, but we don't sell compression springs with the combination of specifications that you need."

So I guess that is why one of the springs looks cut and modified. The whole operation of this saw held up because of this simple need.
Title: Re: rehabilitating 24" Nelson saw
Post by: Slabbercabber on September 18, 2019, 10:57:12 AM
https://us.misumi-ec.com/vona2/detail/250301196974/?CategorySpec=unitType%3a%3a2&Inch=1
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 18, 2019, 11:50:27 AM
Thanks for the link.  Unfortunately, it seems that for 1" L, 3/4" OD, the ID is 3/8" for a 3/16" rod, while my rod is 3/8" and there would be no play.  But McMaster sent another email with a link to some that are closer, also that they can custom make them,, but that costs hundreds of dollars.

Using the fractions on the page, my measurements become OD .75",  ID .5625"  wire thickness .09378

On this page some are close in some aspects, and not so close in others, while others have a different close/not so close relationship.  I'm wondering which is most important.  https://www.mcmaster.com/compression-springs/=2b1ef529b9da4bbaad8102baf170fe33k0pa9m4t
Title: Re: rehabilitating 24" Nelson saw
Post by: catmandewe on September 19, 2019, 09:32:49 AM
I would order an assortment of the ones that I think will work and then test fit them until I find the one that works the best.
You can try to get it on the first shot but if you dont you will spend more than that in shipping costs, might as well have extra springs on hand rather than having to pay the extra shipping costs to try the next two or three springs.

Tony
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on September 25, 2019, 10:49:23 AM
Who would have ever thought that it would be so hard to match a spring when a company has hundreds of varieties. 
I chose the 3 that looked closest in specs, from McMaster.  In the picture, at the left, are the 2 current ones, one of which maybe was original and a later substitution.  Then the 3 new springs.  One hopelessly loose, another lighter gauge than the current, and another so thick that I don't know if I could even compress it enough to get in the mechanism. 
Title: Re: rehabilitating 24" Nelson saw
Post by: hummingbirdstones on September 25, 2019, 06:08:21 PM
I suggest you call Cigar Box Rock in Bend, OR and find out if they have a spring to fit your saw that you can buy from them.

https://cigarboxrock.com/
Title: Re: rehabilitating 24" Nelson saw
Post by: robirdman on March 08, 2020, 02:50:03 PM
The saw has been dormant during the winter, after none of the springs matched.  With the warm weather today, I filed some material off the 2 sides at the top of the split nut, where the separator.  I put this back on the saw's threaded bolt to see how it fit and it was pretty good, so I opened and moved to the platform to bolt on.  It seemed that the holes didn't match up well.  I bolted the far side but then the closer side was off.  It didn't seem like the opener was not in the middle, but I figured I must try turning the split nut assembly around.  I had been able to put the split nut on the threaded bolt before and then assemble the rest of the apparatus, using pliers to squeeze the spring, but now I couldn't get the springs out and had to open and pull with pressure off the threaded bolt.  I turned the apparatus around and now its holes matched much better with the platform, though it seemed that the split nut sides were less symmetrical. so I set it to run with out the vise or rock as a test.  It successfully went about a foot in an hour and then I tested again to make sure it hadn't stopped at that point.  So now I went to pull the platform back.  It made a grating noise as the split nut, though open was rubbing on the threaded bolt.  I added a washer on each side to raise it slightly, and now it didn't rub. It looked more lopsided now. Ran a test and now the platform didn't move at all.
Title: Re: rehabilitating 24" Nelson saw
Post by: lapidaryrough on March 08, 2020, 06:43:37 PM
Copy a Frantom 24'' saw.
For correct pulleys  needed.

https://www.govdeals.com/index.cfm?fa=Main.Item&itemid=723&acctid=4788

Jack
Title: Re: rehabilitating 24" Nelson saw
Post by: Downwindtracker2 on March 28, 2020, 12:10:32 PM
If you find a too long spring that looks like it might work, you can cut them shorter with a Dremel .