HG-1 build quality issues - Page 7

Grinders are one of the keys to exceptional espresso. Discuss them here.
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AssafL

Postby AssafL » Apr 28, 2019, 2:59 am

Now my espresso has a hint of flounder. Thanks Jake...

Somehow the fish analogy does not ring true to me. I don't think the fish in this case is the bean. Actually I think the fish is Gary (sorry Gary - but the fish ain't mine...).

If Gary were to hang the HG1 from the ceiling and hang (as Gary the fish) from its base - maybe. But in this case when force is applied (in a manual grinder) it is usually applied downward. So not really a spring but a prestressed column. (Like the bottom spokes of a bicycle - which actually carry the rider).

Now unlike the column on the bicycle which is "free" in space, the base in this case is not free to move (especially given the dowels) so apart from the bolts loosening there no real reason to tighten down hard.

Compare to the top bolts of the Versalab (don't know the HG1 equivalents) which actually keep the burrs parallel and thus actually receive the "bean as fish " tensioned spring.

I may be wrong...

(And sorry Gary - I hope you like fish...)
Scraping away (slowly) at the tyranny of biases and dogma.

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drgary
Team HB

Postby drgary » Apr 28, 2019, 3:05 am

I certainly enjoy fish stories ...

:roll:

For the sake of experiment and because it's now 2 engineers against 1, I'll tighten down further as I don't see how this can damage anything.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

OldNuc

Postby OldNuc » Apr 28, 2019, 9:35 am

The reason you found the first screw much more difficult to remove than the 2nd one is the column and base are not perfectly flat and the first screw is run in and torqued and then the 2nd is run in and first has to pull the column and base into complete contact as it is torqued so which ever bolt is selected for removal first is under a higher tension than the 2nd one will be. This is almost always the case when you have a metal to metal joint with multiple fasteners. This is why if there are more than 2 fasteners in the assembly you start by removing or loosening every other one to relieve this stress. The base and column mating surfaces are not precision machined for perfect contact as it would not be cost effective and the selected bolting is more than adequate. Commercial grade finished plate cut to shape and machined as required will not be perfectly flat but it will be adequate.

This thread has turned into a very good discussion of the various issues that arise when a modification or design change of an existing product is undertaken.
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drgary
Team HB

Postby drgary » Apr 28, 2019, 11:22 am

OldNuc wrote:The reason you found the first screw much more difficult to remove than the 2nd one is the column and base are not perfectly flat and the first screw is run in and torqued and then the 2nd is run in and first has to pull the column and base into complete contact as it is torqued so which ever bolt is selected for removal first is under a higher tension than the 2nd one will be.


Rich,

It was odd that once I broke the initial tension it turned out okay. Then it became harder midway. Would I have done better to loosen the other bolt when the first started to become difficult, maybe turning the first one back in until it turned easily?

Also, is it possible that my hammering the hex key helped break some of the aluminum threading that had started to oxidize and had too tight a grip on the bolt?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

OldNuc

Postby OldNuc » Apr 28, 2019, 1:06 pm

drgary wrote:Rich,

It was odd that once I broke the initial tension it turned out okay. Then it became harder midway. Would I have done better to loosen the other bolt when the first started to become difficult, maybe turning the first one back in until it turned easily?
When it got harder midway the best approach is to turn it back in about a half turn then try again. You may end up rocking it back and forth repeatedly but it has to come out and if the threads come out with it that is just the way it goes. As there 2 bolts I would have loosened the other one as ther was less tension on it. Keep in mind the direct sharp light blows on the head tends to cause the aluminum oxide to fracture as it is brittle. Once fractured it has lost most of its grip. The function of a rotational impact is not to turn the wrench but to shock the oxides. This is why you apply a continuous light rotating torque and then mechanical vibrate the tool. You are simulating an impact wrench.

Also, is it possible that my hammering the hex key helped break some of the aluminum threading that had started to oxidize and had too tight a grip on the bolt?
That was the purpose of the mechanical agitation, fracture the oxide.


Aluminum has some unique characteristics that make disassembly a small nightmare. Using a good electric or air driven impact wrench with adjustable/controllable impact force increases the potential for easy disassembly greatly.

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drgary
Team HB

Postby drgary » Apr 28, 2019, 1:56 pm

Rich, I tried my puny electric impact drill, and it didn't budge the grip of either bolt. What's the minimum necessary impact drill that is likely to work? Mine does not have an adjustment.

BTW I used my torque wrench to tighten the bolts to 30 ft/lbs. This took a fair amount of effort and positioning the HG1 so I could apply body weight.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

OldNuc

Postby OldNuc » Apr 28, 2019, 2:36 pm

Torqung bolts does take a bit of practice to hold onto everything at the same time.

This is capable of either removing or banging on them long enough they usually come out. DeWalt DC823. This is an older model that is rated at 120ft-lb max and runs on nicads, NiMh, or Lithium all at 18V. They sell on Amazon for 88 and change bare tool. You have to buy a charger eBay is the best bet there and the battery of choice. For casual use the NiMh is the lowest cost vs performance and service life. There are a ton of the DeWalt 18v series tools out there for real low prices and for low cost homeowner use they are a real bargain. The DC820B is the lithium ion battery version.
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peterlada

Postby peterlada » May 11, 2019, 10:55 am

I've had the HG-1 for half a year now, zero issues, no rusting anyplace.