specifications

[socalrider]

when the term "LOOSE" is stated next to a specification , like say for instance TAPPETS:
FIT IN GUIDE---.001-.002 LOOSE
GUIDE FIT---.002 TIGHT -.002 LOOSE
what is the purpose of the "loose and tight".it seems obvious to me that .001" is tighter than .002." i got this right out of the factory service manual for duo-glide/ electra- glide in section 3A pg. 3A1.the guide fit spec is confusing. can someone please explain the reason or purpose? are you supposed to use the middle ,loose or tight values? could the guide fit spec be a typo?
many thanks for the knowledge!
arnulfo

[Perry]

Socal,

I'm not a machinist but as I understand the terms, "loose" refers to a clearance fit where there would be clearance between the two parts. "Tight" would be an interferance fit, for example if the inside diameter of a bore is actually smaller than the outside diameter of the piece that will go inside it. For the sake of explanation say the ID of the bore is 5.000" and the OD of the piece going inside it is 5.002". That would be a .002" interferance or "tight" fit. A .002" interferance fit is tighter than a .001" interferance fit.

Hope this helps,

Perry

[Guest]

I thought it meant that one condition was better for than the other. For example if a clearance is .004 to .007 "loose" its better to be closer to .007 than .004.

Cotten will tell us for certain.

[joe]

Oops I got guested, the last post was Joe.

[FlatHeadSix]

GUIDE FIT---.002 TIGHT -.002 LOOSE
arnulfo

this means that the acceptable tolerance is .004", sort of somewhere between a light press fit to a drop-in.

mike

[hogboy52]

.
It's not usual to use the term "loose" in a motor spec. list but what it means is that's the wear limit beyond which it needs to be repaired or replaced. When rebuilding, one would aim for the smaller number when fitting the parts.
As for the guide, which is a press fit in the head, it means to choose a guide that is .002 larger than the bore in the head.

[FlatHeadSix]

absolutely correct hogboy. If you had a good selection of parts, your first choice would be to go with the lowest tolerance, in this case the "tight" fit. But, if all you had on hand was .002" smaller than the bore that would be OK too according to the spec, the "loose" fit would be acceptable.

Same thing applies to plug fitting roller bearings, but not everybody has a complete set in each of the oversizes. Sometimes you just have to accept the "loose" fit and keep an eye on things.

mike

[socalrider]

thanks for the info. fellas.your responses cleared the confusion.
arnulfo