part 3 ....
This is how I made changing the speeds quick and easy. Original design has the intermediate pulley block bolted fast, so needed to loosen the motor adjuster, then the 2 bolts, move the belts, then tighten the motor adjuster and then the 2 bolts. First improvement I made was to mill the intermediate pulley block slot widths to slight slip fit with oil/bronze bushings, then cleaned up the top surfaces so they were same thickness each side and length. I stated in previous post they were headed bushings, but forgot that didn't work so I took the heads off and just used thick washers I filed flat. The intermediate pulley block now just slides back and forth with light hand pressure, never have had need to touch those bolts again. Belt changes less than a minute (with most of that looking at the belt speed chart figuring where I need to put the belts).
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Also raised the motor pulley up to match the top spindle/intermediate block pulley heights. This allows for more usable speed range than the machine came with. Motor pulley used to come loose every so often (single set screw on top of the key) even when thread locker was used, so I added 2 other tapped holes and now have 3 set screws equally spaced around the diameter (matching flats filled to motor shaft). They have not come loose since I did that.
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How much more usable you ask. First is what I started with, and 2nd is where I am today. I gained aprox new 350, 600, 700, 800 & 1000, but lost the max 3440 that I would never use anyway. The red speeds are when you take a single long belt direct from motor to the spindle and bypass the middle pulley. I was going to make a new motor pulley with 4 grooves for even more spreed ranges, but this is working well for me so may never do that.
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and finally my future head riser with slide adjustment. This will be 5" thick, and made from 3 main blocks. Bottom and top will be round to match the mill, but will have dovetails cut into them. A fixed long block with matching dovetails will slide in/out between each upper/lower block. Does not to be super tight precision on the dovetails; I will simply lock the long slider with screws with brass tips pushing against it. As I purchased the steel, this will provide some 14" front/back adjustment. I am not really interested in a nod feature, as my machine is .0015 out on a 8" diameter circle front/back, and better side/side. Plus once shimmed you can easily mark it and you are done (and I now have the surface grinder for things that need to be perfect). This was a simple mock-up I made from wood to double check what I drew on the computer. The final slider block will be longer (only limited by motor mount and rear of spindle casting), but same principal. First photo would be basically as machine is today, 2nd would be head out past table, and 3rd would head back behind table.
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The little steel block above sitting on the prototype was just used to stop the part from tipping over during the photos. It is actually one of a set of 4 (exactly 1, 2, 3 and 4" long) that I made years ago for Bridgeports and fits this machine - I use them to lock the spindle down when milling so quill can't move.
Last is the progress to date on the slide - supplies delivered. I found a deal on ebay one time and bought the 8" dia 4140 blocks thicker than I needed for $80 each delivered. Funny but they came USPS in a priority mail box at about 76 lbs ea for $15 shipping - just barely fit in there (my mailman was glad I was home that day to unload them from the truck). The 8" dia blocks need to be cut about 1.5" (or faced) to length. They did not originally fit into my 4x6 cut off saw, so would have had to face them off. I have since modified that saw so they will fit between the guides (barely) today by adding a new location for the fixed jaw. Will still be limited to 5" height of saw casting restriction, but can cut them from both sides in the saw so won't have to face them off for hours and will have some usable scrap peices.
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Need to make an indexable dovetail cutter (best) and worst case I buy one from Shars. Going to be many hours into this one....
Ted
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