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At the risk of posting something most people here already know: Our machinist (this was long ago) at work told me one day that if you drill a pilot hole first followed by a slightly undersize drill bit of the desired size to finish, ?the result be a hole just less than the drill size. He couldn’t explain why that happens. Part of the reason is I think that the drill cuts so little it’s acting like reamer and there is nothing forcing it off Center. I do this frequently.?

Mike is right about the usefulness of the center adapters. Guessing just does not cut it. Even the trick of putting a bolt in the hole and using the hex head and surfaces is not always accurate as most bolts have some tolerance on the edges and straightness. The bolt trick is however a good one in many cases.
There are a lot of challenges for machinists to measure things accurately. Cabinet makers working with hardwoods can have some challenges as well but not quite as bad.
As far as calculating things goes, I have a binder filled with exhaustively calculated measurements for things I expect to do in my shop, in both metric and imperial sizes. A computer and usually a spreadsheet did all the tedious calculations.? I just open the binder and look at a chart for most anything I cannot do quickly in my head or simple calculator. I have spreadsheets set up for more complex things where I just enter a couple or few numbers and it shows the answer. Been adding to this for 40 years so I do less and less math over time.? If I run into anything outside of this, I just look up a calculator on-line.
Am I lazy? Maybe. But it took some time to collect this info. I would rather spend my time now making or fixing something rather than sitting with a sheet of paper grinding out math problems.

Almost everyone has the drilling accuracy problem. It is impossible to drill a 0.500 hole with a 1/2" drill bit in a drill press. All drill press chuck assemblies have a little play, or they would not be able to move up and down very easily, or not at all. Drill chucks are not guaranteed to grip perfectly true. Drill bits generally have some wobble or flex, and have a diameter tolerance range.?? Reamers in collets on a lathe or mill will get you a lot closer but it still may take a lot of effort to even get close to 0.500.

In the case of your face plate adventure, you could put hours of exacting machine practice and science into getting the chuck almost exactly aligned. Or you can accept the realities of the tools and equipment you have and make allowances to calibrate the assembly, the best you theoretically can, after assembly. The little bit of slop in the holes might be needed to slightly move the chuck to get the center of the jaws aligned with the centerline of the lathe spindle and tailstock center. Having no tolerance will mean you may never be able to get it right.

One problem to address is getting the exact center of the backing plate to exactly line up with the exact center of the chuck jaws when they are clamped on something tight. This might be a few thousands or more, off of the center of the hole in the back of the chuck, depending on the quality of the chuck machining.?

Two choices:
You could try mounting the backing plate accurately to the machined back of the chuck, and then carefully check and machine/grind the jaw gripping points to make them grip exactly on the center of a metal rod.
Alternately you can center a pin in a rotary table or mount a rotating pin on a mill table centered under the mill chuck. Flip over the new chuck and grip the pin tightly as you would if you were mounting a rod in the chuck on a lathe. This will remove any slop and give you the exact center of the chuck when holding a round object. Move the table over to the radius of the listed bolt circle and as you spin the new chuck you can determine if the chuck jaws are really centered when under pressure. If it is off, you can see that the bolt holes will be off a little one way vs. the circle when the new chuck is rotated. You could take a dial indicator in the mill chuck and line it up with a machined surface on the new chuck to see how much off center it is and how much adjustment in the position of the bolt circle on the backing plate will be necessary to get as close as possible to the center point of the jaws when the new chuck and mounting plate are assembled an chucked in a lathe. So a slightly offset bolt circle on the mounting plate will correct the position of the jaws center position.? If it is a minor offset, a few thousands of correction might be possible with just clearance in the bolt holes.

Point here is that if you line up the bolt holes perfectly with the chuck center line, mount the chuck in the lathe and chuck a machined rod in the jaws and tighten, there may be a slight offset to the chucked rod as it spins. If it is a lot, it might be hard to adjust out. Good to know this before you get too far machining the face plate. You will also want to mount the face plate in the lathe and machine the back and then the front to make sure the face plate runs true before drilling the holes and before the chuck is mounted. Worst case the back of the chuck might need a slight smoothing if it seems slightly off of true when mounted to the backing plate.? The farther the chuck jaws are from the pressure edge of the spindle the more any run-out is amplified.?

You probably already know this but this thread might be read in the future by a person new to setting up a new chuck with a separate mounting plate. I have done a couple of these and it takes patience to assure the chuck runs true when finished mounting to the lathe.

I bought a pair of these for each my 6" & 12 " Dial calipers 30+ years . Now I have several more caliper's that were my dads I should put a pair on one of them Y leave them on . Pretty handy if ya have more that one caliper .
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Sorry for some reason I couldn't get just the pic to send .?
This set in much more user friendly on the ole budget .
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animal

One thing that threw all our talk of measurements and ascribing into a cocked hat is the fact that this circle *has no center*- the middle of the back plate is the hole where the spindle goes through. So even if I could find true center, I can't reliably indicate from it, as there's no material there.

I suppose I could have made a temporary hub center from a piece delrin or whatnot, let me just chuck that up and... <facepalm>

Good info, thanks! I'll copy that for future reference.

My "math is hard" comment mostly comes from the backlash Mattel received a handful of years ago when they released a talking Barbie, and that was actually one of her preprogrammed phrases! Cue female STEM student shrieking...

No, I actually got it right on. I got the bolt center measurement by threading the bolts in until they bottomed, tightening them square in their bores. I used the corners of their hex heads to scribe lines across their heads to find and strike a center in each head. I used the caliper to measure between centers and verify each to each. That's how I got my equilateral side measurement.

I took this, divided one side in half to create a right triangle, and used the good old Pythagorean theorem to get a center line. The epicenter where each crosses each is 2/3c, so that gave me my bolt circle radius. I subtracted the register hub diameter from the calculated bolt circle diameter and divided by 2 to get the difference movement at the cross slide.

I used a trepanning tool to indicate off the register hub of the back plate, then moved out that cross slide distance and inscribed a mark there. I then punched a mark at an arbitrary point on that circle, used the dividers to mark my other two points from that point, and punched those as well. But problem- the distance between points? A and B and points A and C were the same, the distance between points B and C was different from the other two! Slightly longer.

Oddly enough, what hamstrung me was not taking into consideration the fact that the tip of the tool was 0.03125". This drew the tip of my center punch out away from my actual proposed bolt circle. Had I remembered this, my marks would have been right on. As it was, I went back to my calculations and used the difference in calculated bolt circle vs register hub diameter to measure out from the hub and discover my mistake.

Okay, so now! Got my new marks made and punched, they are ACTUALLY equidistant at my actual bolt distance, time to drill. Went to the drill press, chucked up a center drill, and ... wait. Why does it look like it's wobbling? Put a dial gauge on it and discovered my chuck is THIRTY-SEVEN THOUSANDTHS OUT OF TRUE. Holy crow! Well, what do you want from a 1970s Craftsman press that was made for drilling wood... yeah, that weird one with the 1/8" belt and the 850 RPM "slow" speed. Use what ya got, except the chuck is pinned in place instead of being either threaded or Morse tapered... and the point at which it's out of true is right AT the roll pin, so it was drilled off square from the factory. Balls, there's no fixing that without a lot of surgery.

Fortunately, a neighbor has a Shop Fox benchtop mill he is generous enough to allow me to use. It may not be a Bridgeport, but it should be precise and square *enough* to let me drill my three holes with reasonable precision so I don't have to try to make my own Adjust-tru chuck.

So that's where I'm at. Plate is done, holes are marked, all I lack is drilling them so I can finally mount that chuck. Frustrating! So close.

I have gotten a bit lazy in my old age. Back in the past I would have calculated this by hand on paper. Later I wrote a BASIC program to do the calculations. These days I use one of two methods:?

If I am drilling holes in piece of metal that is not too big. I will just mount it on my rotary table, find the center of the bolt circle, move the table away from the center by the radius of the circle, decide my starting point and use the degree wheel to move the rotary table however many degrees it takes. 90 degrees for four holes, 72 degrees for five holes, 60 degrees for six holes, etc.. This would be the mechanical way of doing things and this works as long as I can fit the metal, wood or plastic on my milling machine.? CNC can also handle this with a servo driven table or by entering the center, how many holes and the first hole coordinates. I don't have a CNC mill so have to use some manual method, which is satisfying my desire to do things the more by skill than automation.?

If I am going to have to layout the bolt holes on something that cannot be done as above, I would just use a web bolt hole calculator, then layout the measurements. Find the center of the circle, draw a circle with a divider, find my starting hole position on the circle and set the calipers for the distance between holes. Then scribe lightly from hole position to hole position, making sure the points on the circle exactly match the scribe distance. Doing this in reverse around the circle is a good check. Once I am sure the points are all correct, I center punch each and drill.

Drilling a bolt circle in a business/production environment, I would probably choose to use CNC or a digital readout setup which can do hole position math.

Something strange happened when I tried to reply to the incoming email with this message.? It bounced because it seemed to have picked up the old yahoo groups address somehow.? Apologies if groups io delivers it twice.? What I was trying to say is this:

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I had a real problem with math in hi school , to the point where i got frustrated I just got up & walked out of the class room . It took me years to appreciate all the numbers & logical thinking .

good luck

animal

Calculating the bolt circle for a chinesium chuck of unknown dimensions...

As a followup to my previous post, the height from compound to cutter tip on this toolpost is a whopping 1.62" if using 1/2" HSS bits or indexing toolholders (0.560" from compound to underside of turret, 0.560" for lower turret land, and 0.500" for the tool itself). Way too high for my 10R, which according to the documentation is supposed to be 1.03125" from compound to center (and by my measure isn't far off). I thought briefly of modifying it, taking the base down to 0.125" stickout and milling another 0.125" off the tool channels to bring the tool tip down to my height, but I can't in good conscience ruin what could be a perfect toolpost for someone else.

I'm going to clean this up and take some pics with measurements and post them here. If I don't get any bites after a week, I'll put it back on ebay.

Nick

I picked up an Enco 3.5" turret toolpost on ebay recently, and am trying to adapt it to use on my 1942 199-Y 10R. It's pretty much identical to this one (), down to the dimensions of the index tabs on the underside of the post and the top of the T-nut it came with (not sure about his "A" dimension though, I haven't measured mine from compound to cutter yet). I used a mill at work to make a T-nut for the 10R's compound, but when I fitted the turret to the compound it sits up half an inch or more above center at the cutting tip!

The ebay seller was a parts reseller, so they had no idea for what the turret was originally spec'd, it just came in a box of parts from a shop. I went with it because I missed out on another auction for an Enco 3.5" turret in which that seller said came off his 1945 10L. That's what I get for assuming one is like another. Given the information at , I think the one I got is actually a 3.5" turret for a SB 13", or something similar.

I'll get some pics tomorrow morning when I get home from work. I'd be interested in a trade for the right one for my purposes if anyone has one DEFINITELY for a Heavy 10; otherwise, if anyone has a need for it for their 13", I'll gladly sell it for what I paid for it ($100+shipping).

Nick

First you have to get the film digitized. I use Cinepost that uses a wet scan machine which is not done by 99% of scanning companies now but it gives a much better scan. They scan each frame individually. I get my scans back as single frame .dpx files which are very large but retain much more of the original details. You can request any format you want. I like the .dpx because it gives me more control. I mostly use DaVinci Resolve to do all the corrections but also a few others for problem.areas. DaVinci is a professional program which has a free but slightly degraded version. The problem is that if you want it to come out as best as possible you have to tweak each setting for each scene change. There are a LOT of things to tweak. Most scanning companies just put in basic corrections for color and let it rip. At the beginning I had 3 different companies scan the same can of film and they were all atrocious but said that was the best they could do. That's why I do it myself. If you have 8mm film get it scanned as soon as possible as the film is rotting bit by bit everyday. I had one can that even Cinepost could not do I had to send it to a firm in Canada which uses highly specialized processes to make the film strong and stable enough to go though a scanner. They do not give you your film back after that toxic mix is used on it.
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Bill From Socal

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What software are ya usin to restore 8 mm film ?

thanks

animal

If he could take the time the videos could most probably be made better if run through software that is designed to improve old video tape. I have restored a lot of 8mm film and am always amazed at the results. There can be scenes that are so dark you can hardly see anything but after restoring you see it as the filmer intended. There is a certain amount of sharpening that can be achived also. Almost anything that is wrong can be improved to a extent. Video tape has even less resolution than film. Film about 720p video about 480p. The problem with most people who restore film or video tape is they just run the whole thing with one setting. To do it correctly it must be done scene by scene which takes a whole lot of time.
As to the complaint the videos are low quality, that was the technology of the time and the most likely the best they could do. 10 years from now the tech of tomorrow will make today's videos look like the video tape of old. Everything gets better but doesn't mean the old should be discarded.?
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Bill From Socal

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Dennis
western NY, USA

It's not dark on a 15" laptop.? Slightly out of focus, did not have sound on.