Thread: Play in linear bearings
Cutting them is not a problem, I use a 1mm wide cutting disc in my angle grinder, goes through them like butter.
Who's angle grinder ?????????
.John S -
I take it that you know about all the differnt types of thk? If not you want the 4 way equal loading like HSR or SHS, the SSR and SR can only be used horizontally, but if cheap enougth they would be ok for the x axis.
I under stand what you mean about the single rail but once you see a 25mm HSR you will realise just how strong they are,especially given the small cutters you are using. That said, I would probably use a pair of 15mm rails for the x axis and then single 25mm one's for the y and z
If you mount the x rails and blocks upside down then the block ('s) is (are) always directly below the cutter giving max strengh at all times
I have ordered a set of two 510mm rails type HSR25 with four TA carriages. I haven't really settled on what geometry yet, but £90 for this set was too tempting - I can likely re-sell if they are not what I want.
I spent several hours pouring over the datasheets from various manufacturers and found THK particularly helpful - even though the TA carriages don't seem to be on their site (possibly discontinued or special order?) The most worrying thing I have seen so far is that linear guides seem to be extremely intollerant of mounting errors - less of a worry if only a single carriage is used.
I get the point about mounting the blocks and tracks upside down. Presently I am modeling various parts for my various options on Turbocad in the hope of settling on an optimum geometry soon.
Good old ebay.
any system involving two separate bars, rails or what ever needs to be perfectly paralel. Even dovetails with adjustable gibbs only average out the highs and lows when worn. I think the THK's are good at absorbing small amounts of misalignment but you do need to get them fairly level and paralel in the first place.
the 5 bears site has a good 'how to' on setting up rails, using one as a master and dti gauges to set the other.
Are you doing a build log as well?
I guess if I demand high accuracy the bits will have to be set up accurately. The latest info I have seen implies that the rails and carriages should be mounted on the same material - and very preferably steel.
I will start a build log before I even start cutting - sort of thinking out loud in Turbocad.
If you are looking for super high accuracy then you will be facing the same problem as I have for setting up my lathe. and that is that even the bigest and best piece of precision ground steel will twist and defect if not bolted down evenly or to a flat surface. so it would seem it is more important to have a good solid base and if you torque everthing the same then it shoudnt matter if its Ali or steel (just my 2 penneth, I'm sure others will correct me if im wrong)
Have you thought about using a slab of granite worktop as the base and then building it in situ?
I think the significance of not using different materials is that aluminium has a much higher coefficient of expansion than steel - this could be important as my workshop temperature has varied from 4 degrees to 30+ degrees. as far as the order of accuracy that I want, the magical 1 thou will do. I have got an old optical workbench (just a 1000mm by 600mm by 200 mm 'T' slotted extrusion, heavy enough to need two people to lift it) that may as well be the sub base.
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