Technical reamer question

goodgrouper

goodgrouper

tryingtobeabettergrouper
Ok, so if I've got a reamer that is .010" retarded on the position of the cutting edges and it's producing chambers that are overly large, is there a way to calculate how much would have to be ground off the reamer to produce the right size chamber? Or should I just throw the damn thing in the trash can?
 
FBecigneul said:
Nearly any reamer can be re-ground. Why throw it out?
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Yeah, the trick here is to figure out how much to grind off. I can't just go by the numbers in a simple subtraction function. I've gotta figure out just how much error the retarded flutes are gonna throw it off before I specifiy a diameter for it to be ground to.
 
Hal said:
Why not send it back to the reamer maker and have him fix it.

Hal
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Because I ain't ever dealing with that company again. Ever. Was treated so badly there that I hope his shop burns to the ground on his B-day. Besides, he'd never admit that he screwed it up in the first place.
 
Any reamer can always be re-ground to a smaller sized case. That will usually save about 1/2 the cost of a new reamer, assuming the steel quality is good enough to warrant a re-grind. Send it to one of the better reamer grinders and let them evaluate it. All it will cost you is the price of shipping.
 
goodgrouper said:
Yeah, the trick here is to figure out how much to grind off. I can't just go by the numbers in a simple subtraction function. I've gotta figure out just how much error the retarded flutes are gonna throw it off before I specifiy a diameter for it to be ground to.
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I don't think you have to figure out any numbers, send it to a different reamer maker and ask for it to be made to his proper spec if it is not correct. Did you recheck your floating reamer holder? Unless a good holder is used properly the chamber stands little chance of being made to size. The reamer should be snug at the chamber mouth when fully inserted.
 
PEI Rob said:
I don't think you have to figure out any numbers, send it to a different reamer maker and ask for it to be made to his proper spec if it is not correct. Did you recheck your floating reamer holder? Unless a good holder is used properly the chamber stands little chance of being made to size. The reamer should be snug at the chamber mouth when fully inserted.
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It's been sent off to someone else. They checked it and said it ran concentric but that the flutes were .010" off center (retarded). Under the optical comparator, it was on the high side of "within tolerance" However, the optical comparator is kinda like a 2-d image of something that is 3-d that bores a hole. In other words, it doesn't necessarily tell you exactly what the finished chamber will be.
And yes, the floating reamer holder was checked. That was the first thing the mnfr blamed the problem on. It appears to be working properly.
 
Just so I understand the question, you are saying the cutting edges of the flutes are not concentric to the body of the reamer, and off by .010?

That's easy enough to check. Set the thing up between dead centers and stick an indicator on it. I'd check the shank area as well. If it truly runs out, tell them exactly what the trouble is and I can't imagine them not at least looking at it, if not fixing it.
 
4Mesh said:
Just so I understand the question, you are saying the cutting edges of the flutes are not concentric to the body of the reamer, and off by .010?
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I was told by another mnfcr that he checked it for concentricity and it was running true. However, he said that he checked the flutes (or cutting edges) and they were .010" off of center. I asked if they were .010" advanced and he said they were actually retarded. He said that because the flutes were basically in the wrong position, the reamer may be making the chambers larger diameter than what they should be. He had a technical machinist term for it, but danged if I can remember it!
 
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goodgrouper said:
I was told by another mnfcr that he checked it for concentricity and it was running true. However, he said that he checked the flutes (or cutting edges) and they were .010" off of center. I asked if they were .010" advanced and he said they were actually retarded. He said that because the flutes were basically in the wrong position, the reamer may be making the chambers larger diameter than what they should be. He had a technical machinist term for it, but danged if I can remember it!
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Some of the old reamer makers insisted that the angle between flutes needed to be staggered to help prevent chatter. If a flute or flutes are at non symmetric angles but they are concentric in relation to the center line, those odd staggers will not cause the chamber to be oversize. If the chamber is cutting larger than the reamer measures, like for example at the neck/shoulder junction then the setup is in error. If you are using a "floating" holder similar to a Clymer, then that is most likely the problem.
 
Goodgrouper,
You will probably not be comfortable with this reamer , even following regrind. Why not have it purposely
ground undersize and use it as a roughing reamer to save wear on a reamer that is more to your approval.
 
If you alter/spend money on this and ever have any problem with the results again you will really be annoyed...

I would treat this like a Savage magazine that doesn't feed... out back on the wood block and a sledge hammer... write it off and cut your losses...
 
Can't remember which reamer maker it is but they charge 80% cost of new for a regrind of another makers reamer. That probably isn't worth the cost, 50% maybe.

Joe
 
goodgrouper said:
I was told by another mnfcr that he checked it for concentricity and it was running true. However, he said that he checked the flutes (or cutting edges) and they were .010" off of center. I asked if they were .010" advanced and he said they were actually retarded. He said that because the flutes were basically in the wrong position, the reamer may be making the chambers larger diameter than what they should be. He had a technical machinist term for it, but danged if I can remember it!
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How bout Asymmetric? Actually, that should be a good thing for the reamer. It makes them much less likely to chatter. It would have nothing to do with what size it cuts.

Well, that would explain why they didn't want to bother with it again, it's the way it should be. If it is cutting the wrong size, I'd say something else is causing it.
 
Goodgrouper,

If it's showing good on the comparator then it's not the reamer causing the problem, unless the person don't know how to use a comparator. I ground thousands of reamers for different applications. However, sometimes, for example any number flute reamer, if you spin the reamer on the comparator, it can be in tolerance but cause a problem with a floating reamer holder. If your spin a reamer on and a flute is cutting the correct diameter and as it goes around, the flutes get a little lower (but in tolerance) and then climb back up, then in a floating holder, it will push to one side and cut to large. Also, if the one of the opposing flutes doesn't have back rake on it, it will cause the same thing. Basically, if a reamber/cutter exibits the first example, then the final passes on the ginder was done while taking to much off. I always set up to grind (manually or CNC) only .001-.0015 off the diameter on a final pass. This is very important on chamber type reamers as a small width grinding wheel is used so you can get minimal radius in corners and a thinner wheel will wear quicker so the more flutes they do, the larger chance of the runout I spoke of.

Hope I made some sense of this.

Hovis
 
HovisKM said:
Goodgrouper,

If it's showing good on the comparator then it's not the reamer causing the problem, unless the person don't know how to use a comparator. I ground thousands of reamers for different applications. However, sometimes, for example any number flute reamer, if you spin the reamer on the comparator, it can be in tolerance but cause a problem with a floating reamer holder. If your spin a reamer on and a flute is cutting the correct diameter and as it goes around, the flutes get a little lower (but in tolerance) and then climb back up, then in a floating holder, it will push to one side and cut to large. Also, if the one of the opposing flutes doesn't have back rake on it, it will cause the same thing. Basically, if a reamber/cutter exibits the first example, then the final passes on the ginder was done while taking to much off. I always set up to grind (manually or CNC) only .001-.0015 off the diameter on a final pass. This is very important on chamber type reamers as a small width grinding wheel is used so you can get minimal radius in corners and a thinner wheel will wear quicker so the more flutes they do, the larger chance of the runout I spoke of.

Hope I made some sense of this.

Hovis
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Yep, sure did Kevin. Thanks a bunch.
So I take it you are in the tool and die business or associated with it somehow?
 
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