holistic information
holistic information
I'm reminded of the time I had a master machinist cut a hole in a Sinar aluminum lensboard. He put the board in a lathe and cut a perfectly clean hole ALMOST all the way through the metal, then with his little finger he pushed lightly on the disk and poked it out of the board. With my jaw dropped, I asked him how he knew when to stop cutting; he said he could tell by the sound. I asked what if it's a different board material, and he said it would have a different sound!
This bridgeport is a bit odd, the table is 32" x 9" which is the smallest Bridgeport they made. These were made up to the mid-1960's. This specific BP was made in 1959. Previously owned and used by a grinding shop that likely rebuilt it. After that it went to a local machine shop that closed. This BP is in remarkable condition given it's age.
As for cost, the most common BP has a 42" x 12" table. Good condition ones or their high quality made in Taiwan clones or improved ones made in Spain are easily available for $2,000 to $3,000 all the time in the local want-ads. They are 50% or less at a machine shop door closing auction. Owning a machine tool like this is a serious commitment. They take up signifiant space and need a professional machine tool mover (rigger) to get them moved then placed where it will live. Cost of the machine tool is really not bad at all, what IS expensive, tooling to support the machine tool. The Kurt vise runs about $700, decent drill chuck about $300, R8 collets about $20 ea, good cutting tools such as a Niagara 1/2" end mill about $50... and so on.
Then comes measuring tools which is another $ pit.
There was a time when there phase power for machine tools like these where a serious problem for a garage shop. The modern solution is to apply a VFD or Variable Frequency Drive which converts 240VAC to three phase 240VAC variable frequency allowing variable speed with the turn of a knob. These work very well in many ways.
Parts and service for a Bridgeport is easy, plenty of good support nation wide.
Bernice
This is the kind of stuff good machinist do all the time. It is why lens board holes in a lathe is the best way to make a lens board hole for any specific lens. It is not difficult to achieve a 0.001" to 0.003" clearance fit between lens board to lens flange on a high quality lens board like Sinar and the hole can be precise on center or offset as needed.
Bernice
The Bridgeport lathe (I know, it's a vertical mill, not a lathe) is also the only machine tool that I know of to have an entire New Wave song dedicated to it, by "The 2x4s" from Boston: https://johnhovorka1.bandcamp.com/tr...idgeport-lathe
I want to hear the sound of the Bridgeport lathe.
It's metal to metal it really is.
Your basic ordinary men they work at Bend-on Gear.
And the screech of shearing metal is what they wanna hear. ...
While I agree with most said, I would never put a thin, flat piece like a lens board in a vise. A vise clamps 2 sides and will bow the board. I'd use a piece of new MDF under it (these are more than flat enough) and clamp that and the lens board with setup clamps to the table. If you don't trust MDF a piece of flat alu. Same for putting it on the lathe, use the face plate and clamps.
A boring head is also an option. But I'm not a big fan of those.
And for something like a lensboard a smaller machine will do the job as long as you have enough space to clamp the piece. Just measure as you go along. Just go slowly, don't rush.
Expert in non-working solutions.
Don't do flimsy sheet metal lens boards. The cast aluminum Sinar ones with raised Sinar lettering has never been any issue being held in a vise or four jaw chuck if done carefully. Setting up sheet metal to be worked on in a machine tool demands making a jig to fully support the flimsy sheet of metal.
Thick wood lens boards can be held in a vise or four jaw chuck OK, if done with great care.
Better way to put holes or shapes into sheet metal is water jet or laser. Traditional hole making in sheet metal is to punch, which has a completely different set of problems. Shearing action cutting tools do not do well at all with sheet metal.
Boring heads work, skill, knowledge and proper tooling is mandatory to get good results. Nifty boring heads like the T100 series are made by D'Andrea in Italy. These allow very precise movement of the cutting with the machine tool spindle running. The T120 has power feed options.
Regardless, the proper machine tool for this job remains a Lathe.
Bernice
So, let's sum up: use tools properly. If you don't, there might be a problem. I'm glad we have that settled.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
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