Eccentric bolts
Anyone ever heard of these? I know a person can get Eccentric studs for Cam-Follower Bearings, however they usually are pretty pricey..
I'm thinking to use them in the same type of situation as the cam followers however just use a cheaper, smaller bearing instead.. $30 ish [each] for the Cam-Followers vs. $2.00 for a plain bearing was pretty much the convincing factor. Especially when I plan to use about 50 of them. I guess I could buy some hex shaft, bore the center eccentric, machine the od. concentric w/ the od of the hex and then use that as a rotatable bush .. any idea's suggestions. How did you do it? I'm doing this to save having to buy actual Linear rails. I don't have the $4500++ to buy what I need [and those are guestimate Ebay prices]. I figure w/ some CRS and enough adjustable bearings I should be able to make rails which do the trick as close as I'm going to need it [as far as accuracy is concerned]. Hence the eccentric bolts [or bushings] to adjust the bearings.
JerryFlyGuy
Similar Threads:
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Gerry, Thanks! Thats exactly what I was envisioning,however it would appear that the center is only 0.25" The Bearings I'm looking at are 1/2" i.d., I still may end up having to do it myself.. or get it done for me.
Jerry
Just be careful of the press fit you use to mount the eccentric bushing. The inner ring with go out of round due to the thinner cross section at the thinner, heavy offset zone with a heavy press.
A separate thread recently gave a link to a bearing fit table. CRS disease prevents me from recalling it.
They can get away with a lot of offset in the cam followers if the eccentric hole was bored into a solid inner ring if it is a homogenious pieces. This is why they charge so much, the inner rings are a PITA to make that way and they are not made in huge quantities.
Jerry, the ID of the cadcam eccentrics is .25” but the OD is .375”. I know this is still not the .5” that you want, but I just wanted to clear the air.
Steve
NC, thanks.. I actually don't even plan to press fit these. I'm planing on just a shoulder and then make the mating surface just under 3/8" [ width of the bearing] then a loose [ couple thou] fit and tighten the bolt through the bearing, bush and into the back block. Once the bush is tightened in I don't think it will turn any more than if it wasn't. It's going to fit the same on the bolt regardless, the only other way I can think of to do this is to press these onto the bolt [prob. wouldn't need the shoulder then] and the slide the bolt/bush into the bearing.. either way there is 1 mate that isn't pressed. I'm not really keen to press anything into a bearing as its to easy to overload it and significantly shorten the bearing life.
Spalm.. thanks, I'm thinking I'll just have to get one of the fellows at work to bang me out a bunch of them.. it shouldn't take long as we have a complete cnc lathe at work.. once its programed he can just bang them out.. and I'm going to need like 50 of them so.. it will probably work out comparable in the cost dept.
Jerry
Hey Jerry, have you thought about getting cadcams with the 3/8" od and buying a 1/2"od x 3/8"id bronze sleeve to fit over it? I think it might be worth a try. Who knows?
Or get a standard shoulder bolt with a larger diameter shoulder and turn the shoulder eccentrically - seems cheaper/faster than turning from scratch - except with a CNC lathe it might not be that big of an issue.
Scott
Consistency is a good thing....unless you're consistently an idiot.
nice idea, i was looking for ideas on making one for the bearings I use. By the way, I just noticed I posted a reply to a year old thread. but thx for the idea!
Or, you can just do like I did and stop thinking about doing a DIY rail system and buy one. When it was all said and done, I was over 1/2 the cost of actual THK type linear rails, so I just opt'd for them instead. I've not regreted it either.. mind you the machine isn't running under its own power.. yet.. in a few week's it will be.
Jerry [boy you guy's are diggin up old threads]
JerryFlyGuy
The more I know... the more I realize I don't
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Do you mind me asking where you got your rails from? I found them at mcmaster or mscdirect, but i think they were the dipped in gold series.
Jerry: Do not know if these from ENCO would solve any problems, but I use them for timing belt tensioners..just an idea that might help.
Described as "Stud Cam Folllowers" several sizes , with one listed at 8010 dynamic load Cap. (lbs).
If you have the ENCO Catalog for 2006, page 815, if not , go to use-enco.com and search for p.n. 325-7619.( that gets to the listing for several sizes)
Adobe (old as dirt)
The easiest way to get them made is ask a first year apprentice machinist, one of the slooooowww ones, anyway tell him/her thay must run perfectly true, I think you will get at least .03" eccentricity, maybe more :-)
Bill
MTD, they are available from various places, HIWIN rails are suprisingly cheap, [well compared to other types] and can be purchased from several suppliers. Keep in mind that they are still a fair amount of money. I ended up spending $4500 USD on mine, the excentric cam followers I'd planned to use were in the range of $2500 plus the hassel of getting a rail made [ from Sqr CRS] and the machining as needed to set them up, it was a better idea to just go to the rails.
Suppliers:
Nook now sells them.
Automation4less.com is probably as cheap as they come
The supplier I bought from was just from their distribution list, if you want to go that route just go to Hiwin's website and find your local distributor.
HTH
Jerry
JerryFlyGuy
The more I know... the more I realize I don't
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
ive always bought rails and bearings on ebay with great success. i got 2 nine foot+ thompson 1/2 fully supported round rails with 6 bearings for $300 us, two ten foot thk 55s they are HUGE with 6 bearings for $875 us and several other large sized rails for fractions of the cost of new. for the cost in parts, time, repair and adjusting of homemade systems, I cant see why anyone would choose that route when compared to buy it once and it does its job perfectly forever linear rails. I think what we need to find tho is some rich old guy to finance all us poor young fellas trying to build quality machines.
Any old Texas oil barrons want to step up?
Re: Eccentric bolts
How about cutting a 1/2 shouldered bolt and then drilling it with an offset hole and then use a smaller cap head screw to attach.
Posting Permissions
Reply with Quote
