Author Topic: Shaft clearance - horse  (Read 3694 times)

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Shaft clearance - horse
« on: June 10, 2015, 04:45:40 PM »
I was getting ready to online drill and ream the pillow blocks for the crankshaft. The drawings show a .625 reamed hole for a .625 shaft. Is this right?
Best,
Stan

Offline Dave Otto

  • Full Member
  • *****
  • Posts: 3638
  • Boise, Idaho USA
    • Photo Bucket
Re: Shaft clearance - horse
« Reply #1 on: June 10, 2015, 04:57:48 PM »
No, unless maybe you are going to lap it in for a running fit. I would say that you would want at least a thou or less for clearance. Does the crank run in the cast iron for a bearing surface?

Dave

Offline tvoght

  • Full Member
  • ****
  • Posts: 930
  • Indiana
Re: Shaft clearance - horse
« Reply #2 on: June 10, 2015, 05:12:56 PM »
For what it's worth, I reamed it at .625. The shaft as intended in the plans is 5/8 CRS stock supplied in the kit. If that's what you're using, it's certainly worthwhile to measure it and see what you've got.  I just measured my shaft and it appears to be .624. Again, for what it's worth.

--TIm

Offline b.lindsey

  • Global Moderator
  • Full Member
  • *****
  • Posts: 13756
  • Dallas, NC, USA
    • Workbench-Miniatures
Re: Shaft clearance - horse
« Reply #3 on: June 10, 2015, 06:02:17 PM »
As Tim said, measure the shaft first. .625 could be spot on for a good fit.

Bill

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Re: Shaft clearance - horse
« Reply #4 on: June 10, 2015, 06:06:53 PM »
The shaft is CRS (not the supplied material)
I don't have (amazingly) a .626 reamer and I'm not wild about using a long boring bar to make the bearing hole.
The pillow blocks are CI. Looks like my best option is to line drill and ream .625 and just turn down the shaft a thou.
Don't understand why the drawings are like that ?????
Thanks guys. Back to it.
Best,
Stan

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Re: Shaft clearance - horse
« Reply #5 on: June 10, 2015, 06:10:20 PM »
Bill
I'm actually going to bring the shaft down thou. Seems like the easiest option.
I've got over and under reamers from 1/16" to ".
Might add a .624 and .626 reamer to the Enco 20% sale order.
Best,
Stan

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Re: Shaft clearance - horse
« Reply #6 on: June 10, 2015, 06:11:56 PM »
If I get to it, I was mulling over the idea of using ball bearings or Oilite in the pillow blocks.
Best,
Stan

Offline Dave Otto

  • Full Member
  • *****
  • Posts: 3638
  • Boise, Idaho USA
    • Photo Bucket
Re: Shaft clearance - horse
« Reply #7 on: June 10, 2015, 06:43:54 PM »
Hi Stan

For the real estate taken up by a ball bearing there really isn't much to be gained; Oilite would be good, but never has been one of my favorite materials. You are going to lube it anyway aren't you? I would go for a nice set of machined 660 bronze bearings.

If you were building a hot air engine then the ball bearings would be beneficial.

Dave
« Last Edit: June 10, 2015, 08:09:55 PM by Dave Otto »

Offline Tennessee Whiskey

  • Full Member
  • *****
  • Posts: 3776
  • Springfield, Tennessee. USA
Re: Shaft clearance - horse
« Reply #8 on: June 10, 2015, 06:55:49 PM »
Vern, I kind of think a lot of these kits are drawn up not expecting the home  machinist to have the tools we have started spoiling ourselves with.  I bet if you drilled it wit a 5/8" drill and used 5/8" CRS you would have a serviceable fit. It isn't the perfection we strive for, but,  I bet it would run.  Most home level drills cut a hole a few thou over, so, there's your clearance JMO. Hey, how's your tomatoes looking?

Cuzn Cletus

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6766
  • Surrey, UK
Re: Shaft clearance - horse
« Reply #9 on: June 10, 2015, 07:02:25 PM »
Tend to bore them myself, you can then feel the fit as you bore it. Also no risk of the reamer following a drilled hole that may have wandered off line.

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Re: Shaft clearance - horse
« Reply #10 on: June 10, 2015, 07:13:35 PM »
At this point, I'll just go with the CI and see if I like it. Each pillow block has an oil cup.
I did bore the cylinder with the long boring bar in the Criterion head and it's fine. I'll just get over it and make some chips.
Tomatoes? With New Jersey just across the river and a farm stand every 100 yds selling famous Jersey ( or "Joisey") tomatoes, not worth growing them. My herbs, on the other hand: exceptional.
Best,
Stan

Offline gbritnell

  • Full Member
  • ****
  • Posts: 2011
Re: Shaft clearance - horse
« Reply #11 on: June 10, 2015, 08:21:24 PM »
Hi Stan,
On the drawings that I make for my model engines usually the only dimensions that I spell out for clearance are the piston to cylinder bore. For shafts and such I put whatever the nominal dimension is for the hole and shaft, like .625. I guess I figure that the builder knows to allow .001-.0015 for oil and will make the two parts accordingly. Trying to rely on material dimensions, like shafting, is a crap-shoot and like you said having a one over reamer isn't something that every builder has.
gbritnell
Talent unshared is talent wasted.

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Re: Shaft clearance - horse
« Reply #12 on: June 10, 2015, 08:35:53 PM »
George
Now that makes perfect sense.
Even after nearly 4 years of machining, just about everything I do is a "first. So, if the drawing says a 5/8" shaft in a 5/8" hole, I figure that whoever did the drawing knew what they were doing (except the Rider-Ericsson drawings but, that's another story.)
At least I realized that I needed help and got great responses that helped me to understand this.
Your explanation gave me another perspective. That of a designer and draftsman.
Learn something every day.
Best,
Stan

Offline philjoe5

  • Full Member
  • ****
  • Posts: 1011
Re: Shaft clearance - horse
« Reply #13 on: June 10, 2015, 09:59:27 PM »
Stan,
One trick I picked up along the way is this.  Depending upon your supplier(s) your 5/8" stock might range 0.623" - 0.626". 

I also have a set of over/under reamers also up to 1/2".  For fitting shafts to bushings up to that size I pick a reamer to give me 0.001" clearance.

Beyond that, as in your case, try to find some 0.624" stock in your supply, you might get lucky.

Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 5309
  • Barrie, Ontario Canada
Re: Shaft clearance - horse
« Reply #14 on: June 10, 2015, 11:16:46 PM »
Cold rolled round stock generally comes in at .0005 to .001" undersize.  I typically ream holes with an "on size" 3/8" or 1/2" reamer and run "as purchased" 3/8" and 1/2" cold rolled shafting in the reamed holes with no problems.----Brian