Too Big?

[DeeDub76]

Has anybody come across a Park Tool reamer that reams slightly too big? I recently purchased a new Park reamer #788, which is supposed to be 43.95mm. But, after reaming a head tube I can literally press in my King headset by hand. In disbelief and frustration I reamed a spare HT and sure enough....too big again.

[Rich Beaudoin]

I have a friend who had same problem with the same tool. He used it on his new custom frame and cups pressed in by hand. For the record he is a professional wrench (15+ years) at a great shop with plenty of experience using frame prep tools.

[devlin]

Saves money on buying a headset press.





I keeeed.

[bencooper]

Have you measured what it's cutting to? CK headsets are often said to be slightly undersized, and I've sometimes found them to be quite easy to press in compared to other headsets.

[Jonathan]

which Headtube stock? I've never had a problem with a beefy paragon tube and park reamer but have had a loose-ish fit on the trutemper tube that's much lighter. It didn't even come all that round. The thinner tubes will have more potential distortion.

[mmoore]

i have the same reamer and it still required pressing of a cane creek 40 headset.

[Will Neide]

I THINK you can call up and King and they'll do a slightly oversized version.

[cicli polito]

Darrel - Mic the reamer first to get a number, then call up park direct. There were some problems with oversize bores reported a few years back when park first put out the reamers for sale. The solution was send it back to Park, and they reground it. I figured those issues would have been solved by now. What supplier did you order the reamer from, and when did you buy it? It's possible it was old stock from that first run.

[DeeDub76]

which Headtube stock? I've never had a problem with a beefy paragon tube and park reamer but have had a loose-ish fit on the trutemper tube that's much lighter. It didn't even come all that round. The thinner tubes will have more potential distortion

I only use Paragon.

Mic the reamer first to get a number, then call up park direct. There were some problems with oversize bores reported a few years back when park first put out the reamers for sale. The solution was send it back to Park, and they reground it. I figured those issues would have been solved by now. What supplier did you order the reamer from, and when did you buy it? It's possible it was old stock from that first run.

I haven't put the calipers on it yet. I had to walk away before stuff started flying. I bought this reamer from QBP about a month ago as a spare. My previous #788 reamer has worked fine other than being a little dull.

[EnginCycles]

I haven't put the calipers on it yet. I had to walk away before stuff started flying. I bought this reamer from QBP about a month ago as a spare. My previous #788 reamer has worked fine other than being a little dull.

So you bought this as a new reamer or (hopefully) a second while the other one gets sharpened. The turn around on a re-sharpen is really fast so unless you need it like everyday why not just get the other one sharpened?

[DeeDub76]

The turn around on a re-sharpen is really fast

It is my plan to have it resharpened, but I bought a spare with the assumption that turnaround time on sharpening was slow.

I have heard Jim Kish does some tool sharpening....is this still true?

[cicli polito]

I haven't put the calipers on it yet. I had to walk away before stuff started flying.

I know what you mean. For what it's worth, an OD mic will give a much more accurate reading for something like this than a caliper. A micrometer will get that .0Xmm digit fairly reliably, whereas a caliper has a tougher time. I have one and rarely use it, but the few times a year I use it I'm glad it's there.

I've heard Jim Kish does, Gary McKenzie in Portland does, and a few others "known in the bike world" do as well. I use a local shop to me. Look up "Tool and Cutter Grinding" in your area, and tell them straight away you have metric and that you don't want an imperial approximation, if at all possible. They'll let you know if they can do it. Good luck!

[Stijl Cycles]

I have had similar problem with a Park reamer. I've also received facers with opposite direction cutting teeth.
In a pinch you can use Loctite retaining compound.

Word to the wise:
If you sharpen a tool, be it an endmill or reamer, it will be undersized.

[mtg]

Word to the wise:
If you sharpen a tool, be it an endmill or reamer, it will be undersized.

That was what I always thought (about reamers), but the local guy that has done some custom grinding for me said that reamers only get sharpened on the leading edge chamfer, which doesn't change the diameter. It seemed odd that the flutes never get sharpened, but the leading edge is pretty much doing all of the work.

[DeeDub76]

In a pinch you can use Loctite retaining compound.

The frame hasn't went to paint yet, so I will flow some brass on the reamed area and ream to the proper size.

[EnginCycles]

Word to the wise:
If you sharpen a tool, be it an endmill or reamer, it will be undersized.

Not true. Only the leading edge gets sharpened. I have a reamer that has been sharpened at least a dozen times. Still dead nuts 27.21mm which is what they ground it to originally from a standard 28.6 reamer. The Park and the like have a heavy chamfer angle and that is what gets sharpened.

[Stijl Cycles]

Not true. Only the leading edge gets sharpened. I have a reamer that has been sharpened at least a dozen times. Still dead nuts 27.21mm which is what they ground it to originally from a standard 28.6 reamer. The Park and the like have a heavy chamfer angle and that is what gets sharpened.

I just went an stared at my reamers (Park and others) and with the geometry of the relief angle, I just don't see how that is mathematically possible.

REAMER.jpg

Let's assume that we have a 44mm dia. reamer with a 5 degree relief angle, if we grind off .5mm from the leading edge, we now have a 43.92mm reamer.

micro.jpg

Not trying to be a smart ass, just sayin'

[Michael Gordon]

Isn't it just the end of the reamer that gets sharpened, and not the flutes along the length of the reamer?

[shirk]

Cutting takes place at the chamfer face not the flute. Flute just moves the chips out.

[abbeyQ]

The frame hasn't went to paint yet, so I will flow some brass on the reamed area and ream to the proper size.

If it's a light press fit, I would install the headset with a bearing retaining compound (loctite 680 or the like) and call it a day. I've done this many times with zero issues. I think it's better than putting the head tube through another heat cycle to flow some brass in there.