Minigraf M4 Clamping Pressure Query

[Rod_B]

Hi Everyone,

Sorry to post help queries for my first submission, but I've recently acquired a second-hand Minigraf 4 in very good condition and have a couple of questions relating to it.

Firstly, when I was using it for the first time the oil/glycerine-filled pressure gauge exploded on me, blowing off its plastic cover and scattering its oil all over the workshop! I've since discovered that this was because there was a slight internal air-leak within the gauge, but was just wondering if this was a common problem and whether they still use the oil-filled type gauges for resistance to vibration/etc. - I was planning on fitting a more readily available non-oil type.

Secondly, does anyone know whether the air pressure to the V-nailer part can be adjusted separately from the clamping pressure? At present I'm using 15 mm long V-nails into oak framing and sometimes the nails are not quite fully inserted. However, it's difficult to tell whether this is because the V-nailer pressure isn't high enough, or the clamping pressure isn't great enough to hold the frame securely enough - on occasion it seems to be lifting slightly. Having had a quick look on the underside at the myriad airlines, I don't think there's a separate regulator for this, but maybe I've missed it. I'm currently using the recommended pressure of around 60 psi.

Hope all this makes sense.

Kindest regards,

Rod.

[yorkframing]

Hi Rod,

Firstly you need an air/oil regulator system as the oil is needed to lubricate the machine. You can get these fairly cheap online and there is no reason why you cant go for a different make as the metal works ones are very good but also expensive.

Secondly, the clamp and nail pressure go hand in hand, the more pressure going up with the nail then the more pressure going down with the clamp.

Oak can be really hard to join, I use 1 x 10mm wedge maximum and lots of glue to hold.

Have you got the right wedges, they do softwood and hardwood ones, the softwood ones wont work very well so need the hardwood ones (brown I think?)
You can also get "red" wedges by minigraf that are designed for very hard wood, these are even better.

Make sure you have the right wedges (red or brown) then try on around 5 bar pressure and see how it goes

Cheers
Steve

[Mark Thornton]

The Minigraf 4 wedge hammer pressure is none adjustable as it always works at the incoming airline pressure from your compressor, the clamping pressure can be adjusted via the pressure regulator mounted alongside the gauge, the gauge only tells you the clamping pressure - not the machine pressure.
When it comes to underpinning the harder the wood the greater the clamp pressure required, in the case of the Minigraf 4 use a solid pad attached to the vertical clamp rod not the felt covered one that usually ships with the machine.

Mark

[Rod_B]

Hi Rod,

Firstly you need an air/oil regulator system as the oil is needed to lubricate the machine. You can get these fairly cheap online and there is no reason why you cant go for a different make as the metal works ones are very good but also expensive.

Secondly, the clamp and nail pressure go hand in hand, the more pressure going up with the nail then the more pressure going down with the clamp.

Oak can be really hard to join, I use 1 x 10mm wedge maximum and lots of glue to hold.

Have you got the right wedges, they do softwood and hardwood ones, the softwood ones wont work very well so need the hardwood ones (brown I think?)
You can also get "red" wedges by minigraf that are designed for very hard wood, these are even better.

Make sure you have the right wedges (red or brown) then try on around 5 bar pressure and see how it goes

Cheers
Steve

Hi Steve,

Many thanks for your kind help and advice. I think I've confused you with my explanation! I do have an oil/air lubrication system fitted, but it was the glycerine-filled pressure gauge that exploded. The fluid in these gauges is completely separate from the lubrication system and is there to prevent long-term damage to the gauge mechanism through vibration. The dial area of the gauge shouldn't be pressurised, but in my case it was due to an internal air leak.

I am using the correct Alfamacchine hardwood wedges and have now increased the pressure to around 5 bar which seems to be working much better.

Kindest regards,

Rod.

[Rod_B]

The Minigraf 4 wedge hammer pressure is none adjustable as it always works at the incoming airline pressure from your compressor, the clamping pressure can be adjusted via the pressure regulator mounted alongside the gauge, the gauge only tells you the clamping pressure - not the machine pressure.
When it comes to underpinning the harder the wood the greater the clamp pressure required, in the case of the Minigraf 4 use a solid pad attached to the vertical clamp rod not the felt covered one that usually ships with the machine.

Mark

Hi Mark,

Many thanks for the explanation of what pressure is applied to which area - I had wrongly assumed that increasing pressure on the top gauge would increase both hammer pressure and clamping pressure. I've now increased the clamping pressure and removed most of the felt padding from the hold-down block and am managing to insert the 15 mm wedges OK without the frame moving - great!

Kindest regards,

Rod.