CAD for simple 3-D metal & wood projects?

[Michael A. Terrell]

There's a lot of that going around. :(

[pyotr filipivich]

Gunner Asch on Mon, 25 Nov 2013 15:35:22 -0800 typed in rec.crafts.metalworking the following:

Yep. All depends on what you are used to working with.

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

[pyotr filipivich]

Gunner Asch on Mon, 25 Nov 2013 15:33:52 -0800 typed in rec.crafts.metalworking the following:

I have noticed, over the years, that the simplest instructions are usually the most difficult or time consumptive. Make grade 8 ball bearings. Build a wing in 3D space in CATIA. Put a canal across the Isthmus of Panama. Send men to the moon and bring them back in the next decade. Change the timing belt.

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

[pyotr filipivich]

Gunner Asch on Mon, 25 Nov 2013 15:37:40 -0800 typed in rec.crafts.metalworking the following:

Not me - that was the Experts. The parts themselves had a tolerance of .005 iirc. That was the easy part. Anyone can turn a 3 foot diameter shaft to within 5 thou. The tricky part is making sure that the entire piece was within 4/10ths of a thousandth of an inch at what ever diameter you reached - over a twenty to thirty foot length. On manual machines. Originally installed for war work (I didn't ask "Which war") on what used to be tide flats.

OTOH, ever try to locate and measure the ridges in the bore of a shaft, what is sixteen feet deep? Pretty smooth to look at, but reading a dial gauge when it is more than a couple feet into the bore gets to be a real trick. (Put a scope on a magnetic clamp and sight through that.) Then came honing the bore out. The hones took off about a tenth each pass, it takes six minutes to make one pass. Some of the ridges were 10 to 15 thou high. It was boring work, but it paid the bills.

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

[pyotr filipivich]

"Michael A. Terrell" on Mon, 25 Nov 2013

19:25:25 -0500 typed in rec.crafts.metalworking the following:

Especially at those prices!

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

[Richard]

The new neighbors are a lot nicer tho. They don't stack their trash cans in my driveway. I appreciate that...

[DoN. Nichols]

That is a difference in measurement techniques and machine design. Most machine tools have dials which read on 0.001" (or finer for some machines), but in decimal format anyway.

Way back when, machinists worked to 1/128" at best (the Vernier calipers would measure to that, while scales were marked to 1/64" at best. But then, to make a running fit in a bearing, they would use inside calipers and outside calipers to transfer measurements from one to the other. Bore the bearing hole, take the measurement with an inside caliper, transfer that measurement to an outside caliper (by closing one onto the other by feel -- these had and have no markings) and then machine the shaft to fit the bearing by slowly removing metal until the outside calipers just slide over it with the right "feel". (the calipers will spring a bit, so you need to learn what the right feel is.)

These days, you purchase the shaft, measure it with a micrometer to be sure that it is what it is claimed to be, (in decimal fractions of an inch), make a trial bore with the cross-feed dial on the lathe zeroed, measure the bore it produced, subtract that from the desired size, divide by two (since most machine's cross-feeds are calibrated in radius, not diameter) amd for rough work, just set it and bore. If you need more precision, you approach the final cut in finer cuts, so set that your last cut will be the same depth as the others, measure as you approach it to be sure.

And (on a regular lathe, if you want even finer precision, you set up a toolpost grinder, set the compound at an angle which gives you

1/10th the measurement infeed (5.7392 degrees, but you are likely to only set it near to 5.75 degrees given the accuracy of the compound's built-in protractor, and sneak up on the final dimensions. At last with surface grinding, you don't have the degree of spring that you do with normal turning.

And -- if you need even more precision, you bore and grind to just under size, and then use a roller burnishing tool to mash the surface down to a smoother finish at the desired measurement.

Or -- you use lapping to get that final finish and dimension.

The above is how *I* would approach greater and greater precision on my machines.

This is how it could be done on a manual machine -- especially one in a home hobby workshop (such as mine). CNC changes the game somewhat. But -- the whole time you are working with tools and instruments which read and are set in decimal factions of an inch, so there is never a need to convert something like your 144.531250" to

144 & 17/32", and you never *think* in fractional inches. If you did, you would be reaching for a calculator all the time. Maybe you buy your shafting in fractional sizes, such as 0.500" or 0.375" or 0.125". Yes, these are fractional sizes, but you *think* of them in decimal inches.

BTW The conversion with my scientific calculator (HP 15C) is done with no problems -- discard the integer inch part, multiply the decimal faction by the largest likely denominator (64), see that it reads an even number, so multiply by two (converting to 32nds instead of 64ths and get an odd precise integer number, so you are there. Then add back the integer part of the overall dimension once you have your fractional part right.

There are *some* digital calipers which will read in both decimal factions of an inch, and in the nearest fractional inch size -- but you are unlikely to find a machinist using one of these for the fractional readings -- which are, after all, just a "nearest fractional size", not a "true reading", or you would wind up needing it to display at least down to 1/1024th of an inch (to be close to the metalworking basic of 1/1000" -- in some fields called a "mil" -- such as in the pin layout dimensions for integrated circuits in electronics -- useful for designing printed circuit boards. Some few of us got into metalworking from the electronics field (as did I), but we seldom mention "mils" as it confuses those measuring in mm (Millimeters -- a very different unit.

I've seen these "fractional reading" digital calipers, but never been tempted to buy them. I just don't *think* in fractional inches most of the time. Some few places, it is convenient. 16 Ga steel is very close to 1/16", so I can convert that to 0.0625" and be close enough to tell 16 ga from other sizes. (And no, that does not work anywhere else, as the larger the gauge number, the thinner the metal. This is related to how it is formed, progressively rolled thinner and thinner, so it is just a lucky crossover point -- and where the limits of my sheet metal brake and shear happen to be, so it is easy to check whether I should try the sheet metal in those tools or not.

Enjoy, DoN.

P.S. Not sure why I am bothering to post in this cross-posted argument, but at least it is metalworking related, not political. :-)

[DoN. Nichols]

Turning an *aspherical* lens does need a model, and a very precise and mathematically complex one at that, to cause it to focus where it should. And you can't check a Germanium lens by the techniques used for visible-light lenses -- they are opaque to visible light, so you want it cut right the first time. Same applies to silicon lenses. I've seen both used in various experimental Infrared cameras.

He did not say that he was watching someone else do it. He was watching the *machine* do it. No *human* does it with CNC. At best s/he feeds the data to a program which generates the motions necessary to produce the surface to feed to the CNC machine tool.

Enjoy, DoN.

[Gunner Asch]

Im surprised that no one noticed that the tap...is two taps diameters, two different threads..on the same tap body.

__ "A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects." - Heinlein

[Michael A. Terrell]

The only good neighbors I've had around here have either moved away, or died.

[none]

On Mon, 25 Nov 2013 10:03:05 -0600, Leon

I tried to email you and it bounced back as not being found. Have you by chance changed your email address?

Anyway, I'll try again later in the day.

[dadiOH]

1. Build a giant funnel

1. Attach servo motors so it can track the sun

2. Place over Congress

1. Hot air rises...

[Jim Wilkins]

I thought $600 to change a timing belt was robbery until I did the job myself. jsw

[Jim Wilkins]

Very good description!

I've memorized the decimals down to 16ths but the simple approach is to hang a decimal equivalents chart near the machine, as it also gives the nearest fractional or metric collet size to your workpiece diameter and shows english-metric equivalents.

jsw

[Leon]

I did not change my address, replace dot with "."

[Jim Wilkins]

No thanks, I had friends with MGs and Jags and learned my lesson to avoid them. My Honda Civic cornered tighter than my buddy's MG Midget, though he was the better and crazier racer.

A local dealer had a Lotus in his showroom. I sat in it, opened the glovebox door for a flat place to put my coffee, and watched it sag down under the weight of the cup. jsw

[Jim Wilkins]

The machine was built by Joseph Clement, one of the founding geniuses of the Industrial Revolution, who learned his skills from the great masters Joseph Bramah and Henry Maudslay.

"The recognised excellence of Clement's machine tools and his skill in precision engineering led to him being employed by Charles Babbage in

1823 to work on his project to design and build his mechanical calculating device, the difference engine."

jsw

[pyotr filipivich]

"Jim Wilkins" on Tue, 26 Nov 2013 07:37:57

-0500 typed in rec.crafts.metalworking the following:

Don't ask ...

The one time - I took it to a shop, left it after work (and I worked nights). Got up the next day, walked over - and was informed that it had broken just as they tried to get my truck into the shop. I'd say that was pretty much maximizing the useful life of the part.

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

[none]

On Tue, 26 Nov 2013 08:26:27 -0600, Leon

Between the mortises, rabbets and Domino joinery, I don't know if I'd have the patience to build the way you do. I guess once you develop the system and get in the habit of using it, the rest just comes naturally. It looks good and it's solidly built. I sure hope your customers appreciate the quality of the products they get from you. The everyday furniture I see up here is absolute junk compared to what you build. Maybe I need to visit some good quality cabinet builders.

Was the dado extender jig, the one with the picture that had the Kreg joinery? If you can email me If so, I wouldn't mind some additional explanation. I have your proper email address and I've emailed you in the past, but right now I still can't email you directly. If you can email me, I'd appreciate it.

Thanks

[Leon]

Seriously All of those joints are pretty simple with the Domino. You just have to keep your shit together so that you don't screw up. ;~)

If anyone is going to screw up it would be me but so far after making dozens of these face frames, no problems.

The back face frames are simple, I cut the dado's and or groves first. Then I cut the rabbets that receive the back panels and form the joints between the rails and stiles. The trick here is to cut the mating tenon after cutting the rabbet with out moving your fence. The spacing for the width of the rabbit is the same for the tenon. To cut the mating tenon to fit the rabbet I simply mount my miter gauge and use the fence as the stop for the length. All you have to change is the height of the cut and I use a scrap to sneak up on that.

The trick to the Domino tenons is to simply dry fit the face frame after all cuts have been made and mark the domino locations just like you would with biscuits.

I use the tight fit setting on the Domino to cut the mortises on all pieces that get the mortise in the end of the board. I use the middle width setting on all of the pieces that receive the mortise on the edge of the board. This gives me wiggle room.

A hint here, the 5 mm bit affords you the best fit when you only have the 1/2" left over area under the rabbit. Also remember to reference the same face when that you marked. don't turn the piece over so that you can see what you are doing. ;~) The trick here is to remember to make the Domino plunge and additional 12 mm to the normal 15 mm when using the 5 mm x 30 mm domino. so that setting should be 27 mm. this lets the bit cut 15 mm deep although it had to extend 12mm to start with to cleat the edge of the rabbet and or tenon.

Clear as mud so far? ;~)

Anyway you would think that this would be difficult but I have not yet had a miss fit.

Now if you have not guessed yet the front face frames and back face frames dado's/groves have to mirror each other where the bottom, top and side panels fit. During the cutting operation for the back and front face frames it is critical that the back face frame pieces that receive the tenon to fit the rabbet be "1 inch" longer than the same front face frame parts. Remember that the tenon is 1/2" longer on each end for the back face frame.

Any way after every thing is glued up you will notice that that the groove/dado in the bottom/top rails butt up against the outer stiles. This dado needs to extend to the dado in the stile. Cutting that short distance across the outer stile needs to be done free hand so to speak. Not a problem on the front face frame as it is not easily seen when you look in the cabinet. The back face frame is another matter altogether, you see that cut when you look inside the cabinet. The dado jig in the picture makes completing that dado simple and fast for both front and back face frames.

I sent you an e-mail using the address you used last year so you should be able to return my e-mail for details if you want.