JPG40504 wrote:Notice the angled profile of the headstock and carriage on both of Dusty's machines. That nub would help those non-parallel surfaces mate consistently.
I thought the two surfaces (headstock and carriage were not intended to meet, hence the permanent rubber bumper between the carriage and the headstock which is quite a bit longer than the nub.
Meanwhile, I was sawing with my 520 this morning and, now that Dusty has pointed this "issue" out (thanks, Dusty
), I noticed that I have the same "issue"
--although I was too busy making sawdust to bother to measure how much off center the blade is.
Over lunch, however, it did occur to me that it could well be that the main table alignment project I recently went through, in which I had the trunnions entirely off the table and re-drilled the rear trunnions for 1/2 inch clearance holes, could account for the table (and hence blade slot) now being a couple of 32nds of an inch closer to the headstock than before when the headstock, bumper and carriage are all in contact since the 1/2 inch clearance holes would allow the table so slide toward the headstock when performing alignment. When aligning my saw I was concerned with squareness of the blade to the table and I was not paying attention to whether the blade was in the dead center of the inserts.
In the end, as long as the blade isn't in contact with the insert, I don't think it makes a difference to anything whether the blade is dead center or not. On the other hand, I do think it would be desirable to have the blade in the same exact position relative to the insert whenever the quill is retracted and the headstock, bumper and carriage are in contact. In other words, repeatability is desirable, especially if one is working with ZCIs or want to use a previously cut kerf in a sacrificial miter fence to align a cross cut.
However, with only a rubber bumper, such precise repeatability is probably wishful thinking without some modifications.
An option would be to permanently afix a dial indicator to the carriage. The indicator would need to have enough "travel" in its tip to extend beyond the rubber bumper and make contact with the headstock yet not bottom out when the headstock-bumper-carriage are brought in contact.
Repeatable distance between the headstock and carriage would be obtained by first bringing the headstock, bumper and carriage into contact and then moving the headstock or carriage slightly away from each other (but with the dial indicator tip maintaining contact with the headstock) until the blade was centered in the slot (or any other desired location in the slot). At that point, the indicator could be set to zero. Later, if the position of the headstock relative to the carriage is changed for any reason, the headstock and carriage could be brought back to the exact same relative location by moving them together or apart until the dial indicator is back to the zero location. This could be done quite precisely if there was a way-tube-sized threaded adjustable stop collar (like the one Shopsmith sells to make precise adjustments to the table height) that could be mounted to a way tube to change the location of the headstock or the carriage by small increments.
Probably way too complicated a system.
