When using a vacuum bag to form a holster how many HP do you use?

[AzShooter]

I've been trying to use a 2 hp dry vac to form my holsters and I don't seem to be getting enough suction.  What power do you feel is sufficient?

[chuck123wapati]

41 minutes ago, AzShooter said:

I've been trying to use a 2 hp dry vac to form my holsters and I don't seem to be getting enough suction.  What power do you feel is sufficient?

I think you would need a vacuum pump. Its not the same as a vacuum for cleaning i have this one it works well.

https://www.harborfreight.com/25-cfm-vacuum-pump-61245.html

[Hags]

Ditto the HF vac pump. I use the same one.

[Dwight]

Me too . . . Harbor Freight sold me my vacuum pump . . . and it will collapse . . . and I mean COLLAPSE the leather on the mold . . . big time.

I think I tried the giant vac I have once . . . and it just did not do the job . . . so off to Harbor Freight I went.

I got this guy:  https://www.harborfreight.com/25-cfm-vacuum-pump-61245.html

May God bless,

Dwight

[DrmCa]

I use the same pump for my cars' AC. It pulls 30 psi vacuum.

[Northmount]

1 hour ago, DrmCa said:

It pulls 30 psi vacuum.

That would be 30" Hg (mercury) vacuum.  Atmospheric pressure is nominal 14.7 psia.  So you can't pull a vacuum exceeding that number.

Not that this makes any difference to what you are doing.  Just clarifying actual numbers. 

[sbrownn]

5 hours ago, AzShooter said:

I've been trying to use a 2 hp dry vac to form my holsters and I don't seem to be getting enough suction.  What power do you feel is sufficient?

It's not a matter of horsepower but rather the type of pump the motor is driving.  Vacuum cleaners are designed to move a relatively large volume of air at a low level of suction using a centrifugal fan.  What you need is a vacuum pump, a pump designed, not to move air, but to pull a vacuum.   

[chuck123wapati]

36 minutes ago, Northmount said:

That would be 30" Hg (mercury) vacuum.  Atmospheric pressure is nominal 14.7 psia.  So you can't pull a vacuum exceeding that number.

Not that this makes any difference to what you are doing.  Just clarifying actual numbers. 

 14.7 at sea level 

[AzShooter]

Thanks for all the info.  Seems I need a new pump.

 

[alpha2]

On 1/1/2022 at 4:09 AM, chuck123wapati said:

I think you would need a vacuum pump. Its not the same as a vacuum for cleaning i have this one it works well.

https://www.harborfreight.com/25-cfm-vacuum-pump-61245.html

I have that pump also, how do you handle the oil mist from the exhaust side of the pump?

On 1/1/2022 at 7:20 AM, Dwight said:

Me too . . . Harbor Freight sold me my vacuum pump . . . and it will collapse . . . and I mean COLLAPSE the leather on the mold . . . big time.

I think I tried the giant vac I have once . . . and it just did not do the job . . . so off to Harbor Freight I went.

I got this guy:  https://www.harborfreight.com/25-cfm-vacuum-pump-61245.html

May God bless,

Dwight

I'll ask you what I asked Chuck123Wapiti, how do you handle the oil mist from the exhaust side of the pump?

Jeff

[chuck123wapati]

8 minutes ago, alpha2 said:

I have that pump also, how do you handle the oil mist from the exhaust side of the pump?

I'll ask you what I asked Chuck123Wapiti, how do you handle the oil mist from the exhaust side of the pump?

Jeff

its mineral oil I don't do anything with it. But I don't stand over it huffing it either lol. My machine is out in the garage so well ventilated and about 6 foot of tubing away from my work.

[Northmount]

23 hours ago, chuck123wapati said:

14.7 at sea level 

or 14.6954 if you want a couple more decimal places.

[chuck123wapati]

1 hour ago, Northmount said:

or 14.6954 if you want a couple more decimal places.

no big deal unless your at 6900 ft like me lol. 11.3 here approx. 

 

[fredk]

My place is 29ft above Irish Sea Level, or about 10 ft above Mean Sea Level of the British Isles. I was told many years ago that mean air pressure here is about 15.1 lb

[Northmount]

Here you go for all the atmospheric pressure measurements you'll ever want!

https://en.wikipedia.org/wiki/Atmospheric_pressure

Quoted from Wikipedia:  The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar (105 kPa; 31 inHg), with record highs close to 1085 mbar (108.5 kPa; 32.0 inHg). The lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar (87 kPa; 26 inHg).

https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html for altitude versus atmospheric pressure calculations and table.

For conversions 1 psi = 6.8954 kPa.  So the record high in Siberia of 108.5 kPa = 15.74 psia while the lowest 87 kPa = 12.62 psia

Calgary AB atmospheric pressure runs around 88 kPa (12.77 psia).  This is uncorrected to sea level, so not the same as you will see used by the weather office, but the same as used to calibrate airplane altimeters.  Weather office currently shows 101 kPa here.

I could tell you a story about an engineering firm doing tests for designing an electrostatic precipitator, but we are already way off topic.

[DrmCa]

I feel under so much pressure now!

[Northmount]

1 hour ago, DrmCa said:

I feel under so much pressure now!

LOL Better move to higher ground, that should reduce your headache!

[alpha2]

2 hours ago, fredk said:

My place is 29ft above Irish Sea Level, or about 10 ft above Mean Sea Level of the British Isles. I was told many years ago that mean air pressure here is about 15.1 lb

Irish Sea Level? If Irish Sea Level is 19 feet lower than the rest of the sea, It seems that there would a pretty good infow from north/south or both ends to level it out. 

It would seem that it should be fairly close to the mean sea level. 

Jeff

[alpha2]

5 hours ago, chuck123wapati said:

its mineral oil I don't do anything with it. But I don't stand over it huffing it either lol. My machine is out in the garage so well ventilated and about 6 foot of tubing away from my work.

That would work. Mine is in a second floor shop, sending it out through the window would be interesting. I wish I knew what the thread was in the body housing. Any idea?

[Dwight]

6 hours ago, alpha2 said:

I have that pump also, how do you handle the oil mist from the exhaust side of the pump?

I'll ask you what I asked Chuck123Wapiti, how do you handle the oil mist from the exhaust side of the pump?

Jeff

As Chuck said . . .  nothing to worry about . . . I have about a 6 or 8 ft nylon tubing on mine  . . .  it sits on a shelf . . . never saw any oil residue of any sort on it or around it.

May God bless,

Dwight

[fredk]

2 hours ago, alpha2 said:

Irish Sea Level? If Irish Sea Level is 19 feet lower than the rest of the sea, It seems that there would a pretty good infow from north/south or both ends to level it out. 

It would seem that it should be fairly close to the mean sea level. 

Jeff

My place is between 35 and 50ft below Atlantic Mean Sea Level. (ie the other side of the island of Ireland) There are large whirlpools at the North end where the Irish Sea becomes the North Channel and meets the Atlantic. The whirlpools are those of legend, big enough to take a small ship to doom. At the South end of the Irish sea where its wider the tides are stronger as the sea tries to level it self. We have several small airfields and a small airport nearby and pilots are astonished that they have to set their altimeter for minus 35 or 50 feet

Sorry for off-topic. Just answering

 

[PeterinID]

I have a chamber vac, it's gauge reads MPa and I've found .08 MPa forms well while still letting me mold & model the leather. I think that is about 11mmHg. When I tried a little more (.1 MPa) there was no room to shape the leather further. The bag was sealed too tight and small wrinkles in the bag made impressions in the leather.

[Double Daddy]

I use the same HF pump that Dwight uses...as well as a similar bag and hose setup...sucks it all right down, good and tight. I believe I originally saw the design/materials list from a post that Particle (Adams Leatherworks) put up here on LW.net or on his own website/blog a number of years ago. Oil residue from the pump has never been an issue, as Dwight said...hose is really long since I like having the pump out of the way. I have had dye transfer from a leather piece to the bag itself but that was my fault (rushing a black dip-dyed project without allowing proper drying time).

Edited January 19, 2022 by Double Daddy

[DaveP]

1 hour ago, Double Daddy said:

I use the same HF pump that Dwight uses...as well as a similar bag and hose setup...sucks it all right down, good and tight. I believe I originally saw the design/materials list from a post that Particle (Adams Leatherworks) put up here on LW.net or on his own website/blog a number of years ago. Oil residue from the pump has never been an issue, as Dwight said...hose is really long since I like having the pump out of the way. I have had dye transfer from a leather piece to the bag itself but that was my fault (rushing a black dip-dyed project without allowing proper drying time).

I haven't tried any of this yet! You bring up a question for me. Assumption that when forming in a bag the leather has to be wet. If after dye dries and wet the leather enough for wet forming won't it do the same thing? I don't know hence the question.

 Thanks again

[Double Daddy]

2 hours ago, DaveP said:

I haven't tried any of this yet! You bring up a question for me. Assumption that when forming in a bag the leather has to be wet. If after dye dries and wet the leather enough for wet forming won't it do the same thing? I don't know hence the question.

 Thanks again

IMS, my problem with that particular holster was that (a) I didn't let the leather dry long enough after dip dyeing...and (b) I got it WAY TOO WET and didn't let it dry off for a bit before going into the vacuum bag (it was somewhat soggy). These two factors resulted in dye transfer to the inside of my bag...which proved "difficult" to remove, to say the least.

Unlike others, I don't do a lot of dip dyeing...don't like handling that much dye at one time (especially the black, which has a NASTY tendency to "migrate" onto things it ought'n to). I prefer the effects I get from the use of large pieces of shearing (being sure to double-glove up while handling said shearing piece). I mark my pieces on the leather to be cut, dye it, then cut it out after it dries. Oiled and finished at later steps. This allows me to do contrasting stitching if the order requires it.  Just my own personal method...