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K&M Force Measurment

DeltaBravo

Gold $$ Contributor
Can someone explain how the K&M Force Measurement add-on works? I just got mine today and it does not register anything. It feels/looks like it's bound up, with the belleville washers already compressed. And the rod between the lower and upper units doesn't seem to move either, assuming it should so that it can move the dial indicator rod, and it doesn't appear to be in contact with the washers.

What am I missing or doing wrong? I just can't get my head around it.

Thanks.

Dennis
 
DeltaBravo said:
Can someone explain how the K&M Force Measurement add-on works? I just got mine today and it does not register anything. It feels/looks like it's bound up, with the belleville washers already compressed. And the rod between the lower and upper units doesn't seem to move either, assuming it should so that it can move the dial indicator rod, and it doesn't appear to be in contact with the washers.

What am I missing or doing wrong? I just can't get my head around it.
My Belleville assembly (square and round part) is 1.75" tall (unloaded). If your's is a lot less than that, then yes, you got a defective Belleville unit.
 
The Belleville Washer section should measure 0.75" approx unloaded.

When you attach the bottom section it should have a slight clearance to the bottom of the press head unloaded. On the back of the main rod there is a slot milled with a slope from the bottom of the main shaft with a small section that is not milled. I wonder if you have installed the square section of the force gauge too high and tightened it up on the slope forcing the screw down the slope and compressing the belleville washers.

Undo the bottom section, remove the fastening screw and look through the threaded hole. Make sure it is lined up to clamp again the round bottom section of the main shaft and not into the cutout slope then tighten the attachment screw making sure it does not move further up the shaft and the bottom force section is clear of the press head.

I can take some photo's to explain if you wish.
 
Thanks dixie and mega. I'm still not clear on this. My washer section is about 9/16" for just the washers. I don't have a "slope" on my shaft, but there is a machined out part for the spring/etc., but the washer setup doesn't come anywhere near it. Is there a way to disassemble the lower unit and maybe fix this? It looks like there should be some internal movement within the lower unit, but I'm not sure what that should be. Right now it looks/feels like the washers are compressed; the only movement on them is to rotate around the mounting.

Mega, pics would be great, thx.

Dennis
 
Some Pics:

The Belleville Washer section with tape measure.
33jkzsp.jpg


The Slot in the Ram that Mega was talking about (sorry for tge out of focus).
25rf24k.jpg


The Whole enchilada with a 6br Wilson Seater.
6igwef.jpg


Hope this helps.....
 
dixie,

Thanks for the pics. Mine looks almost the same, same measurements, etc., except I have about 1/2" on the bottom for the set-screw to attach to. I still don't see how anything moves, tho. Does the small rod in yours move up/down? How do the washers compress? It just seems as tho something should MOVE!

With the bottom unit attached to the arbor, and the top unit also attached, I don't understand how any indication can happen!? :o

Thanks again for the help!

Dennis
 
You may need to adjust your linkage. The dial isn't supposed to move just by operating the handle. The compression of the stack transfers movement through the linkage to the dial indicator. I know I had to play around with the linkage to get a reading.
 
Thanks "dixie" for the photo's and that is pretty much what is I have. Been awhile since I looked at the Slot so forgot how big it was.

Dennis, when you have the bottom unit attached to your Arbor Press and it's at normal height position the bottom unit shoud be clear of the press housing. Put something under it like a Wilson Die just clear of the Force Measurement Unit and bring the Arbor Press arm down. You should see the washers compress and the shaft moves upwards slightly, more pressure the further it travels until it compresses all the washers.

If you still say all your washers are already compressed and cannot move, how about a photo. Especially with the unit not attached to anything. 9/16" is a long way from where it should be at around 3/4" as is mine and "dixie". Photo's tell a thousand words.... ;)

Sounds like something is very wrong or broken perhaps.

Dennis, an after thought.

Was the unit purchased new. I have not tried to dissmantle the bottom section but I'm wondering if someone has done so. I would imagine that the washers are held in place by the ram on the bottom which must perhaps screw into something in the unit. Perhaps someone have very much over done the pre-tension on the washers. I'm now thinking that unless someone knows how the bottom section is assembled then it may be a lot easier to email or even ring K&M who no doubt will solve your drama in a flash. If the unit is faulty I would imagine it would be fixed without hesitation.

Not quite the Topic but I am still not convinced using the Force Measurement Unit is of much value in general, let me explain.

For a long time I have simply relied on my own feeling on the seating pressure felt by my hand and I will say that came with a lot of practise / use seating the same bullets in the same cases which I work on a neck tension of about 0.001" so anything out of the ordinary be it heavier or lighter was felt and then duely marked so as to not use for competition score shots. I had an accident and broke my hand therefore loosing most feeling so a friend (K&M Australian Dealer) sent me the Force Measurement Unit for free so I could test and get a visual aid rather than feel with my hand which was in Plaster. It worked, when I remember to go slow and keep a close eye on my 0.0005" Dial Gauge.

Now my hand is almost back to normal after 11 months I still forget to keep an eye on the dial gauge but when I do it is very visual what the difference in pressure is but the hand gives me the best indication of when things aren't consistant so I mark those rounds for fouling, warmers and/or sighters.

I think my system works good enough to give me 5 shot groups at 550 yards (500 metres here) of around 1.20", best being 1.182" and I know I can do better. My aim is to beat the 1.00" mark and get closer to our Range record of 0.965" one day. I am not a very experienced benchrest shooter, in fact only starting out at 65yo for a bit of fun.

I'd come and have a look but you are a long way from me in Australia.
 
THANKS to everyone who helped out on this! ;D

I finally got it working - it was binding up inside the lower unit, either due to too much loctite or something else causing an interference in the closely machined parts. Took it all apart, cleaned it up, used a little 0000 steel wool to smooth everything out, put on a little Imperial die wax, and VOILA it works!!

Thanks again for the help!! 8)

Dennis
 
Dennis, I sure wish you had taken pictures of everything when you had it apart. I'm real curious as to what all is inside of the Belleville lower unit. Since mine is working properly, I don't want to take a chance of taking it apart just out of curiosity. Anyway, glad you got it working.

Please keep us advised on the consistency of your bullet seating tension. Just to give you an idea of what I'm finding and what I do about it or don't do about it. When loading rounds that are made up of components that are all consistent within their lot, or as consistent as I have the ability to weigh and measure, I still have rounds where the seating tension of the bullet falls way out of the average that I'm getting.

I no longer worry myself with trying to figure out why. I don't even take the round back apart and try to salvage the components. I mark it and use it for anything except a load workup or scoring round. After firing that round I will add that piece of brass to other brass that has been fired the same amount of times.

When I load that group of brass again I will take note of that marked piece of brass when seating the bullet just to see if the same anomaly happens again. More often than not it will go through the process and fall right into the seating tension average. Again, I've stopped concerning myself with why and just make sure that I have as many rounds loaded that fall within the parameters I set to go and do the job that I want to do whether that be load work up or shooting for score.

In other words I'm not smart enough to come up with why so I just work around the anomaly. At least I have most of the tools that tell me that I have an anomaly with a component or round. And there are always uses for an anomaly round, its not a complete waste of components.
 
dixie,

There are two allen head screws in the lower unit. The smaller one is accessed from the bottom of the washer stack. The larger one from the inside of the unit. Just take the big one out and "persuade" the washer stack holder out of the lower unit (I used a nylon "drift"). The smaller allen screw simply holds the indicator rod in place.

Clean it all up and reassemble. The washers are in pairs; just clean them up and put 'em back together.

On my lower unit, there was too much "loctite" or similar mucking up the works. Either that or the bigger screw was causing the washer stack to get out of alignment. Whatever; the unit works now, so I'm a happy camper! ;D

Don't be afraid - I don't think you can mess it up; it's pretty straight-forward. 8)

Dennis
 
Dennis, I think you were asked this but I don't know if you answered... Did you purchase this new from K & M or did you purchase it used from an individual? I'm just wondering if K&M is letting stuff go out the door that is either manufactured or assembled this sloppily without any quality control even looking at it to see if it's working or not before sending it to the customer.
 
dixie,

I bought it from Bruno's. It was originally sent to Dave's Shooting in PA and sent to me. It was new in OEM packaging and looked like it. I just think someone put a tad too much loctite on the big screw and it slopped over and caused an interference fit in the tightly machined "hole" for the washer holder.

Dennis
 
DeltaBravo said:
Can someone explain how the K&M Force Measurement add-on works? I just got mine today and it does not register anything. It feels/looks like it's bound up, with the belleville washers already compressed. And the rod between the lower and upper units doesn't seem to move either, assuming it should so that it can move the dial indicator rod, and it doesn't appear to be in contact with the washers.

What am I missing or doing wrong? I just can't get my head around it.

Thanks.

Dennis

The manufacturer should always be your first source for an inquiry.

Have you Called Roger Miller at K&M [the Designer & Manufacturer]?

I have no doubt that he can explain its proper use and solve any problems you may be having.

There won't be any guessing, speculation, opinions, or conjectures associated with his response. :)
 
I sent them a message on their site - no response; I called and got a recording saying they were out until the 26th, hunting of all things! ::)

It was a simple fix once I got over my initial concern about disassembling it.

Dennis
 

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