Can I adjust the pressure relief valve of my GM myself?

Patrice Lemee

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Oct 11, 2010
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My handpiece is overheating. It is already wrapped in tape but still uncomfortable after a while.

I found this thread:
http://www.engraverscafe.com/archive/index.php/t-15898.html?

So it seems I need to drill holes in the can but also adjust the valve.

The manual says:
E. The pressure outlet of the pump is provided with two special
Muffler/Filters. The first Muffler/Filter contains a filter element
for cleaning the pump exhaust air. The second Muffler/Filter
contains a Pressure Relief Valve set at the factory for 3 P.S.I.
DO NOT ADJUST THIS VALVE. Be sure the aluminum jars are
tight to prevent leakage.

Any idea if I can I do it myself?
 

Patrice Lemee

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Drilled the holes and I am still getting more heat than I think I should. Handpiece measured 104F in some spots.

Any idea how to go from the factory 9 PSI on the pressure relief valve to the 3-3.5 recommended for a 915 handpiece?
 

Patrice Lemee

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Well over a hundred views and no answer. I guess that means it is interesting to many but no one knows how. Or that I should not mess with it.
I did set up a small fan blowing on the GM and that helps a little.
If I ever find out how to change the valve myself, I'll post results here.
Thanks for looking.
 

highveldt

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Well over a hundred views and no answer. I guess that means it is interesting to many but no one knows how. Or that I should not mess with it.
I did set up a small fan blowing on the GM and that helps a little.
If I ever find out how to change the valve myself, I'll post results here.
Thanks for looking.

Patrice;

Unless you are pneumatically challenged do what you want to do with the pneumatic circuits to suit your needs. It sounds as if you are a bit challenged on the subject, however.

Regulators and their circuits are not rocket science. By-in-large they are just a housing with holes drilled through the housing body with a spring, rubber and screws.

I do not use the system you use, but I use the Lindsay Classic and I redesigned and replaced all of the regulators and circuits in my system to make the idle and cuttings air much more responsive and finite overall, plus providing a instant switch over of the pneumatic circuit for doing stippling. I found some high dollar regulators for cents on the dollar on e-bay. One could not expect the Lindsay people to provide their air delivery system the way I built mine as it would add $500.00 to the cost if they sourced the regulators I found as surplus on e-bay..

However, in response to why others are not responding on this issue: it is that they are asking themselves why are you asking us, why don't you ask the technical person(s) who built your system?

As to your heat problem what is the temperature of the air as it exits your air compressor? With not even ever seen one of the regulator systems you speak of, the issue appears to me to find the source of the heat. Run the circuit that you suspect is overheating your hand piece (if that is where you think the heat is coming from) thru a ice water bath (lay the flexible air line in a container full of ice and water). If that does not cool the hand piece then your hand piece is creating the heat.

A worn air compressor that is not producing air quickly to the pressure it formerly did, will produce a great deal of heat in the air.
 
Last edited:

Patrice Lemee

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Canada
First of all, thanks a lot for replying Sam and highveldt. :thumbsup:
The reason I am asking is that from what I got from the search I did, others already have done that and the answer was send the unit back to have it adjusted. Well, this being an old model (bought it used, no idea how many owners) is one of the reasons but mainly, since I am in Canada, doing this would be cost prohibitive.

Since just putting a fan on the compressor itself does help a little I assume that the air is hot and the culprit. Of course that does not mean that the handpiece is not generating some of the heat (pretty sure it does). Of course you are right about me being Pneumatically (among other things ;)) challenged. So I can not tell if reducing the pressure of this valve would influence the temperature of the air coming out of the GM or reduce the heat generated by the handpiece. But either way I am hoping that it would help. Now that I think about it maybe it has already been done in the past so I would need a way to check the valve's pressure too...sigh.... Maybe you have it right and this is way over my head. But still I appreciate your help.
 

mitch

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and maybe we're not responding because we genuinely don't know anything helpful. sorry! :thinking:
 

Patrice Lemee

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Yes Mitch, I figured that was a big part of it. Pneumatics is not something people know a lot about unless they are interested in robotic or some such.
 

tim halloran

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Patrice: Open up the handpiece and clean the piston and the bore it runs in. Take a piece of copier paper and use a piece of it to clean the piston, and don't touch it with your bare hands. Clean the bore in the handpiece the same way, roll up the paper and push it down through the bore. It would be a good idea to wear rubber gloves while cleaning it, as to not contaminate the parts with your finger oil. What kind of oil do you have in your oil bottle? I always used 10W non detergent motor oil in my GM. Also check the bore and piston for signs of scoring or galling as this will affect performance. You may need a new handpiece or some new parts. Also keep the brown fiber filter clean with mineral spirits as it will become saturated with oil and reduce air flow, also keep the canister free of oil. Make sure the handpiece is tuned properly, and it wouldn't hurt to replace the spring in the handpiece. Good luck.
 

Patrice Lemee

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Thanks a bunch Tim, I am very grateful for your help. I'll give that a try and post results.
I think I have transmission oil in there as they recommend, but I don't remember. It sure looks like ATF. I'll check if I still have the bottle to make sure.
As far as a new handpiece or replacing parts, I am saving for a Palmgraver so it might not be an option, not right now anyway.
 

Beathard

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I wish I knew what you were even talking about. What is a GM? What are you asking? What kind of handpiece? Maybe if you are a little less cryptic, someone may be able to help more.
 

Patrice Lemee

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Canada
Sorry, did know I was cryptic.

GM = Gravermeister I got that from members posting here, thought it was the accepted abbreviation.

For the handpiece:

Drilled the holes and I am still getting more heat than I think I should. Handpiece measured 104F in some spots.
Any idea how to go from the factory 9 PSI on the pressure relief valve to the 3-3.5 recommended for a 915 handpiece?

Maybe my poor grasp of English is the reason that I am not explaining myself correctly. Some seem to have understood what I meant. Let me know how can I be clearer, I am not trying to be cryptic as you say.

Thanks
 

Patrice Lemee

Member
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Oct 11, 2010
Messages
61
Location
Canada
Patrice: Open up the handpiece and clean the piston and the bore it runs in. Take a piece of copier paper and use a piece of it to clean the piston, and don't touch it with your bare hands. Clean the bore in the handpiece the same way, roll up the paper and push it down through the bore. It would be a good idea to wear rubber gloves while cleaning it, as to not contaminate the parts with your finger oil. What kind of oil do you have in your oil bottle? I always used 10W non detergent motor oil in my GM. Also check the bore and piston for signs of scoring or galling as this will affect performance. You may need a new handpiece or some new parts. Also keep the brown fiber filter clean with mineral spirits as it will become saturated with oil and reduce air flow, also keep the canister free of oil. Make sure the handpiece is tuned properly, and it wouldn't hurt to replace the spring in the handpiece. Good luck.

Tim, you are a genius! :thumbsup:
I cleaned the handpiece like you said but I had already done something similar so that's not what made the biggest change but the SPRING!!!! :banana: Found in a box of springs I have been saving for over 15 years, one that was the right diameter and slightly stiffer than the old one. I had no idea what would be the result, I thought (wrongly) that it would hit harder. Well to the contrary, it doesn't hit has hard but it made the stroke control curve so much smoother. (no idea how else to describe controlling the stroke with the pedal). The graver doesn't run away from me anymore and the start is so much smoother. I will post more later with some pictures but just wanted to give you a big thanks. :thumbsup:
 

highveldt

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Patrice;

I am pleased that you have been able to learn the source of the problem with your engraving hand piece, and that Tim was able to lead you in the direction that you needed. Your knives are very lovely.
 

Patrice Lemee

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Location
Canada
Thanks for the good words Steve. :thumbsup: Hopefully I can enhance my knives with engraving if I practice enough and get good enough. But in any case I am enjoying the journey. :cool:
I will still take a look at that valve someday. But I have to learn prioritize a bit more or I end up working on the tools/shop more than the knives themselves. :eek:

Here are a few pics. Who doesn't like pics, right? :biggrin:

The GM (Gravermeister) with the added fan blowing on it.


The 915 handpiece. (added tape on the handle after I took the pic)


And a shot of my Jeweler/Engraving workbench.


And finally one with one more question. The hose that goes to the handpiece is two part, probably added when they upgraded to the newer handpiece. This is the connector.


My question is, should I replace it with a single hose? will it make any noticeable difference?

Thanks again for all your help gentlemen.:thumbsup:
 

mitch

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My question is, should I replace it with a single hose? will it make any noticeable difference?

leave it as is. those lines have different internal diameters and are intended to supply the correct amount of air at the correct pressure.
 

tim halloran

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Patrece: I think the tubing is a smaller diameter because the inlet fitting on the handpiece is smaller. Also to remark about the spring, if you were a Hot Rodder in your youth like me you can liken it to valve springs that became weakened, and would cause valve float where at high RPM the valve would bounce on the seat in the head. So engine builders would use two valve springs and each would would be reverse wound so that each spring would spiral in the opposite direction, one inside the other. This along with a stiffer spring would alleviate valve float which would allow higher RPM operation of the motor. So if I haven't completely confused you, I would just like to say that springs can fatigue and need to be replaced occasionally .
 

Patrice Lemee

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Oct 11, 2010
Messages
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Location
Canada
Thanks for the info Tim.
You are right about the smaller diameter inlet of the new handpiece so it had to be done when they upgraded.
And sadly no, I was not a Hot Rodder in my youth. I am too young to have known the good old days of big blocks except through my brother. By the time I could drive it was Ricers and after I had heard the gentle whisper of a 427 with open headers, those buzz box did nothing for me. ;) But I understand what you mean about spring fatigue and that is most likely what happened here.
 

JTC

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Hilton Head South Carolina
That sure is a scary fan you have there. Be careful with those unprotected blades.
To reduce hot compressed air from the compressor I lengthened the tubing to the hand piece to about 20 feet. I discovered this by accident when I moved the compressor into the garage and 20 feet from my bench but I found the compressed air cooled down by the time it got to the hand piece. might help you too.
 

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