Help ... sizes roller bearings

[DAPPH]

I have a precision ground 1"lenght of drill rod that perfectly fits through two pulley sets , two pulley driving dogs as well as two sintered phosphor bronze bearings that the drill rod shaft is mounted in .
I want to change the two phosphor bronze bearings into a four roller bearing support.... two rollers on each former phosphor bearing support .

My problem is that the 1" drill rod will not be an easy hand push for to get the roller bearings in the right place on the drill rod shaft . If I turn the drill rod down it will be a sloppy fit in the pully's & the driving dogs .
I've had a quick look at bearing suppliers but cant find anything that is a tad bigger than an inch dia that will give me the sliding fit I desire. I E . 1 & 1/64 ID or 26 mm ID .
I do have two bits of 2 Inch dia by four inch long precision round bars that I can make the roller bearing carriers from .

I don't want to use a new set of phosphor bronze bushes as they will still require reaming as a pair ( don't have the reamers or four inch or more long cylinder cutting bars & lubricating at the start of each lathe turning session & the leaning forward to do it is getting harder & harder for me due to progressive spinal problems making life difficult..

Anybody got any suggestions I can explore ?

 

[stevethegrease]

I'm old , so I can only do this in English , but here goes. To get a bearing to fit on a shaft you only need a clearance of one or two thousandths of an inch - not a 64th, which is a little over 15 thou. A tiny amount makes alot of difference. To get motorcycle bearings to fit in the crank case, quite often the cases are heated in a oven and the bearings are put in the freezer to cool them down, all of a sudden the bearings drop right in, then go tight as the heat dissipates. Perhaps you could do something similar in reverse, cool the shaft down and heat the bearings up , also lightly emerying (?) the shaft to reduce it's size by a thousandth of an inch or so might make all the difference, between it not fitting at all and being a transitional ( just right) fit. Generally limits and fits are done on a 'hole' basis so the hole is the exact size (based on the logic that reamers and so on come in exact sizes like 20mm or 5/8" or whatever, not 5/8"+0.003" and therefore to get the correct fit the size of the shaft is varied to get the class of fit required) I did study this in college a long time ago and god it was boring, but basically gentle heat and mild abrasion to reduce shaft size will get you where you want to be.

 

[bricol]

Wot he said ^

You are going about it 180 degree to how I would - pick the bearing first, size everything around those.

I can't work out if you want to slide the shaft sideways in the bearings in use or not? If you do, that strikes me as a recipe for early failure if you don't have enough load to make the shaft drive the bearing - slipping between the two will soon cause wear.

If you still want to go with bearings, I think you need to find a bearing with a larger bore, size the shaft as required and bore the pulleys/drive dogs to suit the new, larger, shaft.

 

[bricol]

If you don't need to slide in the bearings, you can get tapered bore bearings that mount with a tapered sleeve, or even used a taper lock sleeve in a conventional bore, to locate and lock the bearing onto a standard shaft. You might be able to find one with enough movement to tie a bearing down to the shaft successfully.

Of if you have enough room, make your own sleeves to locate on the shaft, fit larger bearings to the sleeve.

Strikes me the easiest, probably cheapest, would be to do what you have discounted - replace the oilites, even if you have to pay someone to size them, and then fit an extension to the lube fitting to bring it to a more accessible position for you.

 

[DAPPH]

I'm old , so I can only do this in English , but here goes. To get a bearing to fit on a shaft you only need a clearance of one or two thousandths of an inch - not a 64th, which is a little over 15 thou. A tiny amount makes alot of difference. To get motorcycle bearings to fit in the crank case, quite often the cases are heated in a oven and the bearings are put in the freezer to cool them down, all of a sudden the bearings drop right in, then go tight as the heat dissipates. Perhaps you could do something similar in reverse, cool the shaft down and heat the bearings up , also lightly emerying (?) the shaft to reduce it's size by a thousandth of an inch or so might make all the difference, between it not fitting at all and being a transitional ( just right) fit. Generally limits and fits are done on a 'hole' basis so the hole is the exact size (based on the logic that reamers and so on come in exact sizes like 20mm or 5/8" or whatever, not 5/8"+0.003" and therefore to get the correct fit the size of the shaft is varied to get the class of fit required) I did study this in college a long time ago and god it was boring, but basically gentle heat and mild abrasion to reduce shaft size will get you where you want to be.

Thanks that would work if I didn't need the precision fit for the driving dogs & Allen keyed end & distance stops .

Heating & shrinking the carriers ( with bearings fitted on the shaft is a no no as one of the carriers is free floating to a degree in between two bakelite pulley wheel sets & two driving dogs . The phosphor bonze bushes have been reamed to a clearance fit bigger than the one inch shaft they slide on .

 

[Brad93]

Plus Two or three thou on a one inch shaft and you'll never move the bearing without 20 ton press, that's complete nonsense above.

I can't tell you about inch bearings as I don't really do much imperial. But the equivalent metric bearing would be a 6205.

Here is the data for the bearing fit on shafts in both metric and imperial.

As you can see for an slight interference fit, you'd be looking at k5 fit on the shaft. Which for a 25mm bearing would be +0.001 to +0.009mm.
That translates to about 4 tenths of an inch over size.

 

[DAPPH]

If you don't need to slide in the bearings, you can get tapered bore bearings that mount with a tapered sleeve, or even used a taper lock sleeve in a conventional bore, to locate and lock the bearing onto a standard shaft. You might be able to find one with enough movement to tie a bearing down to the shaft successfully.

Of if you have enough room, make your own sleeves to locate on the shaft, fit larger bearings to the sleeve.

Strikes me the easiest, probably cheapest, would be to do what you have discounted - replace the oilites, even if you have to pay someone to size them, and then fit an extension to the lube fitting to bring it to a more accessible position for you.

I like your thoughts of extending a lube system and using reamed bearings on the shaft .


Does any one have any idea of likely costs for reaming out a matched pair of bushes 2 " deep to 1" plus 3 thou internal dia ? Trying to get a place to fit such a lube point and associated tubes on the cross shaft carrier arms to feed both bearings might be a tad problematic as there is not much to fit a gravity feed to & it will still be at the back of the lathe . .
The cross shaft in question is to the top left of the picture . The phosphor bronze sintered bearings are between the screws of the yokes , it's a PIA to reset correctly once it's been disturbed unless you have a decent DTI . It's currently lubed at each session via a git oiler pot on each bearing carrier .

I had a dream / nightmare last night, where I chose the next internal dimeter metric bearing size up ie 26 or 27 mm etc ( I haven't looked just yet ) and then 3D printed four half sleeve packers to push in & take up enough slack on the shaft to get that just able to slide the shaft to the right position fit in the anchored bearing carriers.
You may notice on the LH & RH ends of the shaft there are two visible 1" + a few thou precision stop/keeper plate / thick washersheld in place with a high tensile Allen grub screw that is used to keep the shaft in place wrt the bearing carriers & an additional thrust washer ( not visible ) also held in place with an allen grub screwe

The keeper washer on the left of the big pulley with the drive belt on also does the same function . The driving dogs are on the insides of the pulley's either side of the LH bearing.
I might have to ask someone to turn me a pair of " Cotton reels " up to make new bearing carriers as my lathe does not have a fixed carrier or a deep enough chuck to allow me to turn accurately them . ( Perhaps I'll have to dream bit more & see if 3 D printing the carriers is a viable exercise . )

 

[DAPPH]

Plus Two or three thou on a one inch shaft and you'll never move the bearing without 20 ton press, that's complete nonsense above.

I can't tell you about inch bearings as I don't really do much imperial. But the equivalent metric bearing would be a 6205.

Here is the data for the bearing fit on shafts in both metric and imperial.

As you can see for an slight interference fit, you'd be looking at k5 fit on the shaft. Which for a 25mm bearing would be +0.001 to +0.009mm.
That translates to about 4 tenths of an inch over size.

View attachment 323521

View attachment 323519 View attachment 323520

That's an interesting chart ... Very very interesting
So , I look in Simply Bearing selection chart & chose an inch( 25.4 mm ) f7 or g6 buy one of each or send a sample of the drill rod to get them to put the bearing on by hand and still be able to gently slide it along the rod sample ?
Thanks very much , I couldn't find a tolerance / fit chart like that in another engineering place I've often used for bearings . Off to the site ........ to have a peek & play .

 

[DAPPH]

I couldn't find any 1" x f 6 or g 7 internal tolerances on the simply bearings website ... However I did find an engineers bearing suppliers , that had a , " Contact us by email "facility so I've sent them an enquiry email .

 

[bricol]

I couldn't find any 1" x f 6 or g 7 internal tolerances on the simply bearings website ... However I did find an engineers bearing suppliers , that had a , " Contact us by email "facility so I've sent them an enquiry email .

You won't - f6 or g7 is a shaft tolerance.

Bearings are made as standard to specific tolerances - you then size the shaft to fit. Same on the outer diameter - you size the housing to suit. Bearing tolerances should be listed in the bearing manufacturers data.

You change the shaft and housing tolerances according to the load you expect to see, and whether the bearing has a shaft rotating in it, or is rotating around a fixed shaft.

 

[DAPPH]

Many thanks Bricol


That's me boleaxed then .

Back to dreaming of the next bigger metric sized bearings and 3d printed bearing carriers & printed packing sleeves for a tight sliding fit . ? Seems to be the cheaper workable option as there is not a lot of load on the bearings . Just a belt transfer point of torque & rotation between two sets of pulley's I wonder how well PETG will stand up to it and a bit of oil . . Perhaps I can use four or five 2 mm brass pins through each bearing carrier length print to hold things together.

 

[Milkybars]

Maybe some of of these sintered bronze bushes would do the job https://www.wychbearings.co.uk/oil-filled-sintered-bronze-bushes-plain
use the drop downs at the side to narrow things down !

 

[Spark plug]

Usually a bearing with a locking collar on the inner race will be sized to slide on shaft of the same given size.

Like the inserts used in houses self aligning bearings, you can also get the inserts with parallel outer races as well as the spherical ones that fit in cast iron housings.

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