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Spring meet up in Ontario, April 6/2024. NEW LOCATION See Post #31 Discussion AND THE
NEW LOCATION
"blind hole spotters"? Your image is just a tad too small to make out what they are. A very short transfer punchs?
I used 1/2" plate with the idea in mind that I would use counter sunk hex head cap screws. In hind sight now I should have used 1/4" or 1/8" plate and V-Head (? not the correct name) screws.
The plate will also need to accommodate a 4-bolt 3" chuck some time later.
I like the idea of employing the RT to locate the holes. Prove it's useful for something.
I’m sorry that the image of the tranfer pins did not show clearly. Here is another try:
Socket Head Cap srews or Flat Head Cap screws (FHCS, the countersunk version of a SHCS) should work fine for you. The difference is that a SHCS allows for lateral movement of the fastener in an oversized hole whereas the FHCS does not because of the countersink cone it is drawn into. This meas that hole location with FHCS needs to be more accurate.
Sure the ROTAB will do the trick just fine. Gives you a chance to practice a bit as well. Might want to do a prototype in a piece of plywood (plastic or even stiff cardboard) to see how things go. The reason i say that is: you have spent a lot of time on your adapter plate already and also have discovered some nasty backlash issue with your rotary table that you have not been able to solve yet. I hate to see you scrapping the good work you have done thus far.
Once you have proven the concept and know the hole location is good, both for your 3J and the 4J and, while you’re at it, the adapter to ROTAB fastener placement, you can then with confidence go make some metal chips....
Sure the ROTAB will do the trick just fine. Gives you a chance to practice a bit as well. Might want to do a prototype in a piece of plywood (plastic or even stiff cardboard) to see how things go. The reason i say that is: you have spent a lot of time on your adapter plate already and also have discovered some nasty backlash issue with your rotary table that you have not been able to solve yet. I hate to see you scrapping the good work you have done thus far.
Once you have proven the concept and know the hole location is good, both for your 3J and the 4J and, while you’re at it, the adapter to ROTAB fastener placement, you can then with confidence go make some metal chips....
That's a very good suggestion. I'll do just that with a piece of wood.
I figured out the RT backlash adjustment. The backlash can be reduced but at the cost of making the table hard to rotate.
The bolt pattern on my lathe FP is the same as the 3J chuck. If I could figure out how to center the FP on the adapter plate I could transfer punch the hole locations. Still scratching my head on that idea.
That's a very good suggestion. I'll do just that with a piece of wood.
I figured out the RT backlash adjustment. The backlash can be reduced but at the cost of making the table hard to rotate.
The bolt pattern on my lathe FP is the same as the 3J chuck. If I could figure out how to center the FP on the adapter plate I could transfer punch the hole locations. Still scratching my head on that idea.
Every situation is a bit different, but generally if you can establish a reference that will be common to subsequent machining setups, that will maintain the best accuracy & make your setups more reliable, For example
- mount the rough stock to the mill table
- drill a center hole using 60-deg center drill even if its just temporary. Now you have 0,0 established on the dials
- utilize this reference & drill other holes at their respective X,Y coordinates. Now you have your pattern of holes accurately spaced.
- scribe a circle from center like you did & rough it out
- now you can register the stock on the lathe face plate using a 60-deg center perfectly mated to the center hole like the video
Similarly, you could center on an RT to make a series of radial holes or slots by dropping a 60-deg center down. This isn't considered quite as accurate as dialing in an ID or OD surface using an indicator, but for just clearance bolt holes, probably fine. Remember FIRST dial in the center of the RT before mounting stock, THEN dial in the stock during mount up.
Sometimes I've drilled/reamed a hole & inserted a dowel pin to center off that (protrusion as opposed to hole) or offset distance from the pin. Lots of ways to skin the cat depending on the task.
Well, I nailed the chuck bolt pattern using the RT.
After centering the RT and test piece to the quill, I setup a reference bar attached to the bench so that I could use my digital caliper to move the table 1.3" right.
Here I'm drilling a test pattern into a piece of hardwood flooring.
Took two test patterns to get things right. First attempt I miss measured the table offset and indexed the RT to the wrong setting for the third hole Daaaa. Second test pattern looked good so I proceeded to drill the adapter plate and mill the mounting slots. I'm pretty pleased with the results.
I'm kind of in awe that the disk I made started from this.
Here is the final arrangement. The run out on a piece chucked to the RT is very minor according to my center finder. I suppose I could check the run out with my TDI to.
You guys warned me about this. With the RT, adapter plate, and chuck there is very little room left to do anything. In the setup pictured, I can't remove the drill chuck from the quill. The commercial chuck offerings for RTs are a lot shorter depth wise. The chuck pictured here is for my lathe.
Figuring out the sequence of operations and asking yourself “what if....” a lot just in case something does not go according to plan is the secret to success. Its almost like playing chess: its not the next move that’ll get you, its the tenth one down the line...
You will find the more complex the parts, the more of this you’ll use and the more little “prototypes” you’ll make because you just don’t want to scrap the part you have so much time invested in.
