Accurizing the 502 scales.
- Thread starter 1066
- Start date
Hi 1066
Do you have a video showing the "details" of how you made the actual changes - specifically adjustments/enhancements you may have done to the bearing components (knives, agate bearings, bearing housings etc)? I have two RCBS 5-10's that I suspect have issues with either the "knives" or the bearings or the bearing seating/housings since they sometimes vary when returning to zero.
Do you have a video showing the "details" of how you made the actual changes - specifically adjustments/enhancements you may have done to the bearing components (knives, agate bearings, bearing housings etc)? I have two RCBS 5-10's that I suspect have issues with either the "knives" or the bearings or the bearing seating/housings since they sometimes vary when returning to zero.
Unfortunately I've not made a real "how to" video but in many of my videos I've shown bits and pieces. I would start with a real clean, that mean taking the bearings out and really scrubbing them, you can't damage them in any way as long as you don't use abrasives. Then scrub the housing, when I'm tuning a set of scales I also polish the pillow bumps and bust any sharp corners or edges of the bearing block with fine wet/dry paper, the blocks need to wobble about with as little friction as possible.
You can check my videos here:
https://www.youtube.com/user/thetargetmaster/videos
Scrub the serrations across the beam, another dust trap and check the copper damping blade is firm, it's fixed with a screw on the 10/10 and 5-10's but staked on the 502, 505 scales.
The knife edges need inspecting with a strong eye glass, looking for any dull spots or burrs, it's also important they are flat and come to a point in line with the edge. When using the scale it's inevitable that the points of the knife edge will touch the bearing endplates, if they come to a point exactly in line with the knife edge, theoretically the beam should pivot on the point and minimal friction occur, if the knife edge tip is chipped or been badly "sharpened" the tip scribes an arc on the endplate causing friction. (The floating bearing makes this imperfect but best of a bad job)
So gently dress the knife edge with a fine flat stone if necessary, I always remove the knife edge to do this, they are a simple push fit.
The pan hanger stirrup often causes a problem, it needs to be completely free to hang in the centre of it's slots with the eyes parallel, it rests on it's own tiny knife edges so also need to be clean.
Bearing housings:
Handmade knife edge (top)
Ruined knife edge:
You can check my videos here:
https://www.youtube.com/user/thetargetmaster/videos
Scrub the serrations across the beam, another dust trap and check the copper damping blade is firm, it's fixed with a screw on the 10/10 and 5-10's but staked on the 502, 505 scales.
The knife edges need inspecting with a strong eye glass, looking for any dull spots or burrs, it's also important they are flat and come to a point in line with the edge. When using the scale it's inevitable that the points of the knife edge will touch the bearing endplates, if they come to a point exactly in line with the knife edge, theoretically the beam should pivot on the point and minimal friction occur, if the knife edge tip is chipped or been badly "sharpened" the tip scribes an arc on the endplate causing friction. (The floating bearing makes this imperfect but best of a bad job)
So gently dress the knife edge with a fine flat stone if necessary, I always remove the knife edge to do this, they are a simple push fit.
The pan hanger stirrup often causes a problem, it needs to be completely free to hang in the centre of it's slots with the eyes parallel, it rests on it's own tiny knife edges so also need to be clean.
Bearing housings:
Handmade knife edge (top)
Ruined knife edge:
Thank you - appreciate the info!
Do you make those new blades on order by any chance?
I had a look at the blades on one of my scales and they look concave or "hollowed out" - meaning that most likely only the edges ever make contact with the agates. Doesn't look like someone worked on them, so they may be ok, or the light was playing tricks with my eyes...
Do you make those new blades on order by any chance?
I had a look at the blades on one of my scales and they look concave or "hollowed out" - meaning that most likely only the edges ever make contact with the agates. Doesn't look like someone worked on them, so they may be ok, or the light was playing tricks with my eyes...
Re the push fit for the knife edge ... what tools do you use to press them out and back in? How much force is needed to to this? BTW I have learned much from watching your vids on YouTube. Thankyou for sharing your knowledge.Unfortunately I've not made a real "how to" video but in many of my videos I've shown bits and pieces. I would start with a real clean, that mean taking the bearings out and really scrubbing them, you can't damage them in any way as long as you don't use abrasives. Then scrub the housing, when I'm tuning a set of scales I also polish the pillow bumps and bust any sharp corners or edges of the bearing block with fine wet/dry paper, the blocks need to wobble about with as little friction as possible.
You can check my videos here:
https://www.youtube.com/user/thetargetmaster/videos
Scrub the serrations across the beam, another dust trap and check the copper damping blade is firm, it's fixed with a screw on the 10/10 and 5-10's but staked on the 502, 505 scales.
The knife edges need inspecting with a strong eye glass, looking for any dull spots or burrs, it's also important they are flat and come to a point in line with the edge. When using the scale it's inevitable that the points of the knife edge will touch the bearing endplates, if they come to a point exactly in line with the knife edge, theoretically the beam should pivot on the point and minimal friction occur, if the knife edge tip is chipped or been badly "sharpened" the tip scribes an arc on the endplate causing friction. (The floating bearing makes this imperfect but best of a bad job)
So gently dress the knife edge with a fine flat stone if necessary, I always remove the knife edge to do this, they are a simple push fit.
The pan hanger stirrup often causes a problem, it needs to be completely free to hang in the centre of it's slots with the eyes parallel, it rests on it's own tiny knife edges so also need to be clean.
Bearing housings:
Handmade knife edge (top)
Ruined knife edge:
Well, there's a blast from the past.. I see I started this thread 12 years ago, was that the first time the reloading world was introduced to a webcam on a scale?
No the knife edges on most scales are not too hard to remove, and certainly much easier to work on once they are out. I just use a vice and something to protect the tips. The orange plastic block has a deep hole that the KE slides into.
This is the set-up I use to push them in/out., just need to make sure they are at right angles to the beam when inserted.
Thank you... this gave me the courage to attempt to repair a 502 scale that had some repeatability issues... image on the left is the knife edge mid honing with noticeable damage from a previous honing attempt... image on the right is the knife edge pressed back into the beam. I found out that this knife edge has left/right side... causing a weight variation if reversed... and a poise error on the large poise of ~.3 grains... the scale is now on par with my other 502 an RCBS M500 scale. and better than my 2 Hornady/Pacific scalesWell, there's a blast from the past.. I see I started this thread 12 years ago, was that the first time the reloading world was introduced to a webcam on a scale?
No the knife edges on most scales are not too hard to remove, and certainly much easier to work on once they are out. I just use a vice and something to protect the tips. The orange plastic block has a deep hole that the KE slides into.
This is the set-up I use to push them in/out., just need to make sure they are at right angles to the beam when inserted.
Well done - Looks like you have done a good job there. The important thing is to keep them flat along the edge right to the tip, any curve at the tip will ruin repeatability.
Also important to centre up the beam by correct positioning of the KE as the main poise is only about 30 thou clear of the scale body when at the zero position.
Also important to centre up the beam by correct positioning of the KE as the main poise is only about 30 thou clear of the scale body when at the zero position.
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