machinists question

[Jos]

Hi fellow machinists,

I'm building a new bearing for my Lenco and need to buy a reamer to get it to the exact size.
Should I go for the H7 fit ? (+0,015)  Reamer DIN 1420 to produce these holes.

http://www.coromant.sandvik.com/sandvik/2531/internet/s003592.nsf/Alldocs/Product*2DMachiningSolutions*2DPDF*2ATH*2DPDFen/$file/3Reaming.pdf

Or should I get an adjustable one and go by "gut-feeling", or as tight as possible to allow for some running in....?

Any thoughts ? Not you, Jeremy, I know you're way to busy and I don't expect you to give away the tricks of the trade  
(much more fun in finding out for myself...I hope...)


Cheers,  Jos

 


*edit wout: fixed link*

[Brumm]

Hi Jos,
I hardly dare (or are qualified) to answer this, but I will try!

I suppose you want to use the original spindle of 9 mm. If this spindle is not undersize, and your H7 reamer does not cut oversize, then I think the bearing fit would be maybe not the optimum, but not bad also (use thick oil then!). On the other hand, you could get also a 8.99 mm reamer and then, if necessary, open the bore a bit by lapping.

What is definitely a no-no is a adjustable reamer, if you mean the type with 5 straight lames moving in tapered slits. With these reamers you cannot get a precision fit (or do I have to say *I* cannot get?).

There are also reamers which can be expanded a couple of /100 by an axial screw, but they are very expensive (>5 times a standard reamer of the same dia.).

These are my ideas, but without any guarantee...
I'm interested what others have to say (if they do)

Greetings, Hansrudolf

[Jos]

Hi Hansrudolf,

thank you for your reply.  I'll go to the toolshop today to find out more about these things.
Your thought about cutting it slightly undersized and then lapping it to a very tight fit is interesting. I've only done the lappingtechnique on a flat surface. My speedskates are lapped as a final treatment. I use lappingpaste 1500 and 2000 on a flat bar of bronze.  But how do I do that inside a 8,99mm hole.  I have to make/buy an expanding lap that fits inside and then rotate it like grinding in valves in a cilinderhead ?  Maybe I'm getting caried away here....
Here's something to read on the subject of lapping.

http://modelenginenews.org/duplex/duplex_laps.html

to be continued

Cheers,  Jos

[reinderspeter]

Looks impressive
Do you plan to use bushings in there?

[Jos]

Hi Peter,

no bushings, its machined from one piece of bearingbronze. Don't know the exact specs, it came from the scrapyard for a very nice price. Supposed to be some kind of nickelbronze.
Hopefully it's the correct type otherwise it will wear out very quickly.......

Cheers,  Jos

[gl78ed]

Hi Jos,
    It's possible to use a wood dowel & abrasive/polish to enlarge the hole accurately by a small amount & get a better finish. Different grades of abrasive can be used from valve grinding compound to car wax & tooth paste.

I have also used a "flap wheel" to remove larger amounts of material from a bore. Take a round steel dowel (or bolt with the head cut off), cut a slot lengthwise in one end, put a piece of emery cloth/sand paper in the slot & use a dremel type die grinder to turn the dowel. Of course you have to remove material evenly over the whole bore & check often that the bore has not gone too big.

I am making my own bearing, but using Oilite type bushings. I'm hoping to get the bearing bore accurate enough that the bushings will press in with minimal clearance with the spindle.
Let us know how you finish your bearing.
Ed

[Jos]

Hansrudolf, thanks for pointing out the possibility of an undersized spindle !

I assumed (and you should never do that, I know; again..) that it was 9 mm; it's hardened and made in Swiss so hey ...but no. Definitely less than 9 :  8,97? on the micromtr. So the H7 reamer was out of the question, it makes the bore bigger.  Took a long hard stare at those iso-charts, and then it dawned upon me (that usually takes a while  ) : the P values are undersized cause they're for press-fittings ..duh.  Of to the shop for a 9 mm P7.



first a very light edge to guide the reamer



In position. A quick prayer to the bearinggods...



almost through, as slow as my good old Clausing can go



that is a very snug fit !! I only have a standardbearing for comparison (and it's knackered!) but this one has no play, if I put my finger on the bottom the spindle pulls a vacuum, can hardly pull it out.


Ed, I will try out your suggestion with the wooddowel for some very light lapping. Thanks for the tip.
Hopefully tomorrow the bottomcap. Plan is to make 2 of them; one for "ball on thrustplate" and one for "ball on ball on thrustplate".

Cheers,   Jos

[Brumm]

Jos, that's a very good result you got, it seems! Maybe the reason for the smaller spindle (if it is not wear) is because the nominal 9 mm sintered bearings close down a bit when they are pressed in.
I am surprised that you could get a P tolerance reamer; you must have a good tool shop near your place! However, I see that this is around -0.02 mm; I buy reamers from the '1/100 mm series' in such cases (means that you can get any dimension in 1/100 steps).

That said, I have to admit that my reaming operations not always give the expected result. I think you had all parameters correct for such a good result. I hope that soon I can also continue with my bearing experiments.

I just wanted to write something about lapping (it was not me writing about the wooden dowel method, but I would have written that also!) The drawing no. 16 in your link to the Duplex article shows something which is easy to do, in hard wood or aluminium. Your 2000 grit lapping paste would be perfect for removing a gnat's whisker i think, but be careful. It is easy to go from a too tight to a too sloppy fit. For the final polish the English use a metal polish called Brasso, unfortunately it is not available here, but maybe you can find something similar. I tried toothpaste a couple of weeks ago, but had not much success.
Don't forget to clean out all traces of the lapping medium (but I think I don't have to tell you that!).

I wish you all the success wit that bearing

Hansrudolf

[gl78ed]

Jos,

If you are able now to put the spindle into the bearing, maybe just run it & change the oil a few times. Just running the spindle in the bearing may "polish" the bore. I think others have had to do this when using custom bearings.

The spindle I have here is under 9 mm also, about 8.97mm. Also the bushings I have are over 9 mm inside. So I hope to press fit to get a close tolerance.
Ed

[Jos]

It's done !!
Will  install it this weekend.  Hopefully with huge audible differences, although it needs running in. 
Any thoughts on what thrustplate ?  I've done 3 varieties: stainless 304  1/2 mm ,  Brass in 1 mm and 1/2 mm.
While at it I've punched a few more for anyone here who wants to experiment with them. 

Cheers,  Jos

 

 

[reinderspeter]

It looks fantastic!
I'd love to try one of your brass thrustplates

Ps. check your email

[Jos]

Hi Peter,

email seen,  must  check with swmbo. Will let you know asap.
3 different thrustplates reserved for you.

Cheers,  Jos

[Brumm]

Jos, please report how these thrustplates look after they have a couple dozen hours (maybe that needs some patience, though...). Neither stainless nor brass are considered as good bearing materials, but maybe - hopefully - that is not important with the almost point contact against the ball.

If your bearing is as good as it looks, you have a winner! Congratulations for a perfect (and fast) job!

Greetings,

[Wout]

I'm officially jealous. Splendid work Jos! 

[jloveys]

While at it I've punched a few more for anyone here who wants to experiment with them. 

Yoda is candidate !

Great job, Jos !