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Reply by hobby1

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Posted on Blame the .0001 drift.

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hobby1

282 posts in 933 days


#1 posted 672 days ago

Hi,
Another one of my many hobbies, besides woodworking, is home hobby shop machining, model engineering, with small bench top machines.

In that realm I always read about holding tolerances within the “thous of inch”, that’s the only place where it is applicable, and can be expected, because a lot of mechanical movements require tolerances in the “thous.”

But even then the tolerances can be accepted most of the time withing 10 thousanths plus or minus, except for piston to cylinder bores, where it is required to be closer in tolerances.

With that being said, I have produced many good running model engines, and hydraulic models, using what some call inferior tools. The harbor freight mills and lathes.

Yes these tools are not top accuracy, however, you learn the weekness of the tool, and compensate for it, by either modifying it, or adjust operating procedures.

Such as my micromill machine has a inherent drift problem with the quill feed when I lock it, it stays at the proper height, but it has a lot of vibration, due to its design of being a drill press as well as a mill, so in order to compensate for the poor design, (not operator error), I had to fabricate a clamping block that wedges the quill in to a locked position for milling.

That’s one example of tool error designs,

In the woodworking tool error designs, I got the craftsman table saw, that had poor reviews of the blade wobbling, they are right the blade does wobble, however when I run the stock through it, I compensate for it by pushing evenly, whan I notice some vibration, I let up on the feed rate, and allow the blade to catch up, and continue pushing the stock through allowing the saw to keep up with the feed.
This wobble has no bad affects on the stock, because the stock is made out of wood, and all wood projects do not need tolerances in the “thou” range but only in the 1/16th” to 1/32” range, very seldom to a 1/64th”, and the inherent error of blade wobble is within the 1/16th to 1/32” tolerance range, because this is woodworking, not machining.

Another bad review comes with my benchtop bandsaw, it too is said to have excessive vibration, well there right it is definately a design error with the machine, but instead of blaming the machine for inaccuracies, I decide to modify it, I replaced the friction blade guides, with home made sleeve bearings, and by clamping these tight to the blade a lot of the vibration is eliminated, because the vibration seems to come by the blade being bent during cutting a radius and throwing the blade out of kilter which results in broken blades soon after.

Since this modifiction I never broke another blade, as well as I don’t have to tighten the blade so hard to keep it running straight, because it never gets bent when it is riding tight between roller bearings.

In conclusion, there are a lot of inferior designs with tools, but we just learn how to work around them, by modifying them, or adjust our operating procedures with them.

Especially in woodworking, I have never heard of woodworking being tolerated in the “thous” always in the 1/16ths, and ocassionally to a 1/32”, anything smaller than that, is machining metal not wood.


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