Welcome to our information page for Beaver Motor Coaches. RV acme thread chart pdf exclusive or proprietary to any particular brand or model.
This site originated with information on projects we did on our own coach, a growing proportion is information other owners had and were gracious enough to provide the information for posting here. Disclaimer: You and only you are responsible for any work, maintenance, repair or modification you chose to make to your RV. You are solely responsible for following safe work procedures as well as the results of any work you perform, whether you relied on any information found here or not. The information provided here is just a description of what we did, what worked for us or perhaps what didn’t work for us. Creating an Index to the information on this site got to the stage where navigating the Index was a challenge in itself. The basic Index kept getting longer and more complex resulting in some folks not finding what was in plain sight – including me!
So, I’m redoing the Index in a matrix format. The left column describes the subject matter while the top row describes the type of material available. Well, it appears that there was a gradual shifting of the exhaust manifold as it went through many heating and cooling cycles while being pushed by a constant tension from the exhaust pipe. Even though our first Beaver was an 11-foot cab-over camper, we don’t have much in the way of information, data or history prior to 1993. No information on this site may be duplicated without permission.
I CAN start cutting and just test fit, but all I learn is that it fits or it doesn’t. I need to make a new retaining ring for the sight glass for my Van Norman. I did some measuring today, it’s . 3 recessed into the gearbox, subtract the glass thickness, etc. 4 20 from my charts, subtract the minor diameter from the major diameter, will that be the same number as it would be for this? Can I take that number and add it to 1.
5 and get a major diameter for single pointing the new piece? Again, I could try, and it might work, but I would have to try and hope next time instead of knowing how to do it. Or you could get much closer looking in Machinery’s Handbook. 500-20 numbers – and for more than one class of fit. Yes, we read that yours is larger than 1. I got lost and turned around.
Digital is great, but I need to save my pennies for paper, makes all the difference sometimes. Dunno if you are handy with a calculator or not. You should work this out on paper to be sure you understand before using. For other threads, say 55 Whitworth you have to use the tangent function. Unless you go to acme, which can have different rules for addenda depending where they center. Then deduct it from the OD. In the example described, the amount to deduct would be .
In a sense, you have to “guess” what the logical OD of the plug should have been. 2, inserting in the hole top and bottom, and mic’ing between them or using an expanding parallel and measuring over it. 2″ back on to the parallel height, and you would be within a few . OD thread mics up to 4″, but nothing for ID. Have not tried his product, but it might be a useful option if you do a lot of this.
You can calculate and figure all you want, but in the end, you will be test fitting it, no matter what. I say this as a guy who cuts threads pretty much every day in all kinds of sizes and pitches in hydraulic cylinders. I tried using all the formulas and such, only to have parts kick back or have to put them back in the lathe and set them up again. I fitted a piston PERFECTLY to a rod when I first started there.
Brand new lock nut that came in the next day would not fit. By the time I got the locknut to spin on smoothly, the piston could about be thrown on the threads. My technique for a good starting point on something 1. 5x20tpi would be to just look at the old fish and get the double depth of thread off the chart. That’s your major diam for the new insert. Now, subtract the 20tpi double depth of thread from that and give it another . That should be your minor diam with a little clearance.
Feed in with the compound to half the double depth. Needs to know how much to _add_ to get the correct plug OD. I probably confused the issue by showing why you come up with a given number for a given thread pitch. But once that is grasped, it is easier to add it back on. Or maybe i completely misunderstood his post.
Stephen Thomas, thank you for both posts, the first is what I was asking for, the second did sum up what I was doing. 5″ diameter piece of stock and stick it in the hole, it touches the crests of the female thread. I did, those numbers look about right, thanks! I could have started and just cut away, tried, made another, etc. Doing ‘job shop’ type stuff, knowing a great starting point is a huge benefit and means more profit per job, as less wasted time and materials.