This really sucks big time

[bogmonster]

A bit more shed time today - only got half what I wanted done but here is one item some may find interesting:

The vacuum chuck - not the bowl

The bowl is about 18" and has been kicking around for a while to be finished. Ran into difficulty when it shrank a bit and I could no longer fit is on jaws to finish sanding and apply finish. I only used to have a 4" vacuum chuck and a lathe that started fiercely at 350 RPM which meant no way to mount mount on the vacuum chuck and widen the rebate.

The new vacuum chuck is 6" which means way more holding power and coupled with a soft start variable speed lathe I can safely finish this bowl. I am going to make a new 4" chuck as well. The construction is kind of obvious. Soil pipe for the chuck wall. MDF for the base. I used a M33 Tap (new toy) for the spindle mount. The hose is beer line connected up with John Guest fittings (these are the mutts nuts). The bearing is push fit in and it is the weak link as it is a low quality affair - should have bought high quality double sealed.

EDIT: Forgot to mention, I use a loose gasket between the wood and chuck as it is easy to replace and very simple. I use closed cell laminate floor underlay. Had some left over.

The holding force is amazing. Mrs BM was not impressed with 6" though. I think she is holding out for 8.

Other stuff I made was a couple of sanding discs using the same M33 tap and painted up my steady. Also got to try my new DIY tool rests which worker a treat but that is a different thread.

BM

 

[bugbear]

The new vacuum chuck is 6" which means way more holding power [than 4"]

Indeed - more than double (ratio is 36 vs 16)

BugBear

 

[gregmcateer]

BM,
That is good, thanks for sharing.

Could I ask -
Do you use a shop vac, or a meaty, purpose-made vacuum pump? (And if the latter, what and how much? as my shop vac doesn't really have the va va voom for larger bowls/platters.

TIA
Greg

 

[bogmonster]

I use a purpose made vacuum pump. I think it is an Edwards but may be wrong. It is a feeble little mite made about the time dinosaurs were made extinct but it works really well. I bought it off flee bay for 30 or 35 quid, can't remember. The pump pulls 28 inches of mercury which isn't bad at all. The flow rate is a bit low so with the leaky bearing I get about 17 inches of mercury with a bowl attached. This is still a LOT of holding force. Vacuum pumps are usually designed to operate at near full vacuum with minimal air flow whereas a vacuum cleaner expects reasonable airflow so can easily overheat. A vacuum cleaner provides high air flow with low pressure whereas many dedicated vacuum pumps will provide high pressure.

I have tried a vacuum cleaner with some success but it does not compare with a proper vacuum pump. Try ebay for bargains.

BM

 

[gregmcateer]

Cheers for that, Mr Monster.
Greg

 

[bogmonster]

Be careful buying vac pumps on eBay. I spent some time looking before something at the right price and location turned up. EBay learns your searching habits and recommends listings to display as side bars on the website. Unfortunately it is not clever enough to differentiate between industrial vac pumps and 'personal use' vacuum pumps. Took some explaining why ebay kept recommending penis enlargement pumps...

I eventually found you can tell ebay to forget items it thinks you may be interested in.

BM

 

[gregmcateer]

Good advice!

 

[SimonT]

The holding force is amazing. Mrs BM was not impressed with 6" though. I think she is holding out for 8.

BM

I perhaps wouldnt forget that "accidental" ebay search bogmonster, it may stop the wife holding out. :-" :-"

 

[gregmcateer]

Would something along these lines do the job?

http://www.coleparmer.co.uk/Product...rred_id=3482&gclid=COaw8cPRs8ACFazItAodfDUA7g

TIA

Greg

 

[bogmonster]

I would think so. My pump is a Genevac RPC3. Can't find the spec. Motor is only 0.25 HP though. The highest possible vacuum is a bit mute given you will have losses I the system in the bearing and through the item being chucked. The more throughput will allow you to maintain a higher vacuum with a given leak rate. I have had no issue with the pump I use and can normally get about 17" of mercury. You need to accept that some woods are just too porous to work well but short of holes I have got on ok. Even small holes can be covered over with masking tape.

You may want to do some research but 1.5 com and 25 inches of mercury I would think would be sufficient. I am sure my pump is less than 1.5 cfm and it works for me.

Also you need to be realistic about what you can do with a vacuum chucked bowl. I only use the system for finishing the bottoms with light cuts. Touch wood I have yet to loose a bowl and I have done a lot like this.

I used to wax the inside before turning off the base but a very shiny inside is prone to lateral slip that can result in loosing the seal. Now I tend to finish sanding, remove foot and then wax, starting with the outside, with the bowl turning slowly in the vacuum chuck and using a mop in an electric drill. For the inside I may not even run the lathe,saves centre aligning the bow, and just turn by hand as I buff using drill and mop.

BM

 

[gregmcateer]

That's v helpful, thanks.

I haven't got the equipment and definitely not got the knowledge for mercury testing, etc. Are pumps fitted with pressure gauges in general and or bypass valves?

Sorry to be a PITA with all the questions.

Cheers

Greg

 

[bogmonster]

Not a problem. I would definitely recommend using a vacuum gauge in the setup - easy to test if you have a leak. Vacuum gauges come in a variety of units, I choose inches of mercury for some reason I can't recall. I can take some photos tomorrow of the rest of the setup and give you some pointers to what you need to buy. Vacuum gauges are cheap to buy on eBay and the like.

My whole setup was really easy to build due to careful selection easily obtained components. Other than the vacuum gauge and pump the other bits are just regular plumbing fittings and other odds and sods I found kicking about.

BM

 

[gregmcateer]

You're a star - THank you.

No great rush about photos, I've got plenty on my plate at the moment!

Cheers

Greg

 

[Bill Mooney]

Make another sanding disc about 200mm - 300 diameter, cover the face with your closed cell foam, drill a hole in the centre & fix your beer tube as per your chuck. Spin the disc on the lathe & make concentric rings approx 25mm apart with a biro, this helps to roughly centre a bowl so as you can bring up your tail stock to easily centre the bowl. This type of vacuum chuck makes it easy to stop your bowl developing a wobble. I made my setup a few years ago & find the disc holds a big bowl well & make it quite stable because it is held by the rim & not the inside centre as with the cup chuck.
My pump is a Javac vacuum pump which has served me very well. Javac Ltd. have their factory at Middlesborough & can be easily googled. Hope this helps.

 

[gregmcateer]

Cheers, Bill
Greg

 

[gregmcateer]

Bill,
Which size Javac have you got?
TIA
Greg

 

[bogmonster]

Had a bit of nightmare day so no photos. I did make a new 4" chuck and used two bearing this time and got 19 inches of mercury so a big improvement. I actually made 2 4 inch chucks - screwed the first one up with a silly mistake - didn't let the glue gun heat up properly and the fumbled feeding the next stick in meaning pipe was not in properly, pulled it out again and trashed the MDF. Oh well, not a major setback.

Bill, planning to make one of those as well - seen other's versions. At 300mm that will be a serious amount of suction. I have a valve to reduce the vacuum but it is a needle valve and does not let enough air in really so need a different valve. I imagine with the flat disc chuck it is real easy to implode bowls?

I actually have one ready to go, destined for a sanding disc, so will just make up another the same.

I do a lot of crinkly edge (not always natural as I cut many manually) bowls so the tube style chucks work for that where the disc style does not. However, with the tap, making multiple chucks is next to free so I can try as many designs as I like.

Centring with the tube style is not too bad if it fits over the bed as long as you have marked the centre spot, just use the tailstock to align the bowl on the chuck. The tailstock can then be removed for free access to the base. I can see a definite advantage to the disc where bowls won't fit over the bed in terms of centering, but also a big disadvantage, over 16" of diameter will collapse even very robust bowls unless the vacuum is reduced somewhat.....

The difficult bit with the tube style chucks is getting the pipe aligned well. Invariably it is off a bit. Fettling the pipe for uneven depth is easy with a bowl gouge but lateral inconsistencies are not so easily fixed. With a flat disc everything is much easier I am sure, just true up the disc. Added to my to-do list for tomorrow

Spent the day re-configuring my very small turning space - partitioned section of a double garage - after buying a the new lathe. Thought I would tidy up the cables and used one of those cable covers from Ikea. I added an extra emergency stop and NVR switch the other day but had boxed in the bench and needed to re-route the cables. Anyway, it was late and I was tired and I was cutting the cable cover to length thinking this is tough - still had the lathe flex in it - doh. Changing the flex is a real PITA as it means removing the lathe from the bench, accessing the underside if the bed to get to the inverter.......

Think I will repair the flex instead. What a dufus!

Still, worse things happen at sea.

BM

 

[Bill Mooney]

Greg, I have the Javac CC31 vacuum pump. The firm is Javac UK Ltd. Phone no. 01642232870.

 

[Inspector]

BM I don't have much knowledge of vacuum chucking but did set one up for my father's older Nova, a 1624 I think. I bought the fitting for the end of the headstock shaft that has a bearing in it for the hose from the vacuum pump and the vacuum is drawn through the shaft. With your setup it looks like the bearing is in the chuck and the hose attaches to it, leaving the hose stationary inside the revolving headstock shaft. How long will the hose last before chafing through where it exits the shaft? Or am I missing something?
Pete

 

[gregmcateer]

Thanks, Bill. That's helpful.

BM,

Interesting post re the pros and cons of flat / tube vac chucks - Hopefully I'll avoid some, (though I'm sure not all!), of the problems.

I was thinking the same as Pete, above about the pipe/tube. A previous thread discussed this (WoodMonkey, I think - I'll see if I can find it and add the link). Yep, here it is;

https://www.ukworkshop.co.uk/forums/topic79704.html

He (and I), used a bearing in the outboard side and piece of mild steel tube through the headstock, so the tube remains stationary - seems to work pretty well.

I got the bearing from here;
http://www.qualitybearingsonline.com/
for under a fiver.

Cheers

Greg