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View Full Version : Work hold down



gorbo
13-04-2014, 08:26 PM
One problem I have always had is, holding down wood during cutting, successfully.

I have tried clamps, sticky tape even nails,

I would be interested to hear what everyone else uses and the success rate? :disillusionment:

EddyCurrent
13-04-2014, 08:52 PM
I'm planning to use a system like this bloke in the video, not so much what he's on about, just to look at his machine bed.
He has two T slots full length and one each side, four in total. It looks like he made those little clamping blocks from some kind of plastic/nylon but I'm thinking about making them from wood.

Machining parts longer than your machine - YouTube (http://www.youtube.com/watch?v=3jhnKr4fc_c)
Fixing Mistakes - YouTube (http://www.youtube.com/watch?v=8kr1g1VVCP4&list=TLiaEYtYundrlSqo2qeB04g4UwHekKk-Q_)

Also I plan to use a small vacuum table that will be clamped onto the machine bed.
With my pin router, double sided tape proved quite effective as did screwing the stock down onto a sacrificial piece that was clamped to the table.

I've never had clamps move but double sided tape has come unstuck before on small parts, mainly due to small 'glue' area and rough surface, so poor contact. Vacuum table is great if you have a decent pump.

longy
13-04-2014, 08:56 PM
hi gorbo, what particular problem are you having ? if you try to explain a little more someone maybe able to give you better advice. post some pics as well if you can as this can help others to help you.
Mike

longy
13-04-2014, 09:01 PM
I'm planning to use a system like this bloke in the video, not so much what he's on about, just to look at his machine bed.
He has two T slots full length and one each side, four in total. It looks like he made those little clamping blocks from some kind of plastic/nylon but I'm thinking about making them from wood.

Machining parts longer than your machine - YouTube (http://www.youtube.com/watch?v=3jhnKr4fc_c)
Fixing Mistakes - YouTube (http://www.youtube.com/watch?v=8kr1g1VVCP4&list=TLiaEYtYundrlSqo2qeB04g4UwHekKk-Q_)

Also I plan to use a small vacuum table that will be clamped onto the machine bed.
With my pin router, double sided tape proved quite effective as did screwing the stock down onto a sacrificial piece that was clamped to the table.

I've never had clamps move but double sided tape has come unstuck before on small parts, mainly due to small 'glue' area and rough surface, so poor contact. Vacuum table is great if you have a decent pump.

Eddy look at his other vids like his laser shoe it's brilliant, I follow Peter and watch his vids, given me some great ideas. his clamps (white) are cut from and old cutting / chopping board, bet his mrs is looking all over for it LOL
Mike

gorbo
13-04-2014, 09:48 PM
I am just looking for the best way, I tend to cut thick wood (signs) this makes using clamps problematic due to the height and the need to machine around the piece,
I did consider making a vacuum table,
Loved the video some good ideas there
When there is a problem like this I tend to troll through Utube and look at other members ideas

longy
13-04-2014, 10:30 PM
Hi, as long as you've room and don't mind screwing to the back of the signs there is a very simple answer to your problem. see the image for more details, I've used this method on doors with hand routing designs as long as the customer is ok with a few filled holes on the rear. that's one of the reasons I'm building a new machine wide enough to hold down without drilling.
Mike 12052

gorbo
13-04-2014, 11:13 PM
Hi, as long as you've room and don't mind screwing to the back of the signs there is a very simple answer to your problem. see the image for more details, I've used this method on doors with hand routing designs as long as the customer is ok with a few filled holes on the rear. that's one of the reasons I'm building a new machine wide enough to hold down without drilling.
Mike 12052

Thanks for that but holes in the back would be a problem

JAZZCNC
14-04-2014, 04:21 PM
In my experience there is no one best way to work holding.! You just use which ever method gets the job done easiest.?. . . I'd use Chewing gum if it did the job.

Vacuum is ok if you have plenty of it and it suits the job, Often it doesn't if holes or cut thru. I've got some really expensive hold down clamps for alumiium and I've also got some home brew holding devices made to suit jobs at the time and I can tell you the most used by far is the home brew stuff.

I've also got a big box of screws and large rolls of double sided carpet tape and these are often used for holding wood or thin material.! . . . . . Can't beat double sided carpet tape for large thin material. In the past I've used DST while Engraving large and expensive piece of Brass on my machine which vertical mounted and it didn't move fraction of a millimeter.

Often I'll use DST and screws/clamps.? If part doesn't have thru holes or can't be clamped and I don't want tabs then I'll use DST so it doesn't move or get pulled back into cutter when outer profile is finished. I'll use the screws or clamps for holding waste material and keeping secure and flat to table while job runs.

gorbo
19-04-2014, 05:44 PM
Well after much research and advice I have gone for 6mm nut inserts on my new bed and I must say I am very pleased so far,
how long these will last is another story, inserts from Screwfix 2 for 50, MDF board 4 so not a great capital outlay, if it all goes tits up

I will use clamps along with DST for a firm job
1211612117

JAZZCNC
19-04-2014, 06:38 PM
If you screwed them in from bottom it would stop them pulling out.!! That said the MDF would probably bulge anyway.

Ger21
19-04-2014, 07:47 PM
I used T nuts installed from the bottom of the MDF, so they can't pull out. I also have another sheet on the top, that allows me to surface it without hitting the nuts.

Another First Router - Page 15 (http://www.cnczone.com/forums/cnc-wood-router-project-log/1356-another-first-router-post671212.html#post671212)


I also use cam clamps. I got the idea from here. Vectric Forum • View topic - Keystone for arched casing (http://forum.vectric.com/viewtopic.php?p=18096#p18096)

Jonathan
19-04-2014, 08:47 PM
Flip the sheet over?

gorbo
20-04-2014, 12:15 PM
There will little vertical strain on these inserts only horizontal, I use the inserts to hold jigs to the bed which they appear to do very well

EddyCurrent
20-04-2014, 05:22 PM
This is how mine turned out, it uses 40 x 16mm T slot and some home made clamps and knobs with 6mm threaded rod of varying lengths.
Dark patches on the bed are a result of the leveling process on birch plywood ( 2 x 18mm sheets)
The layout looks fancy but I ordered 4 x 1m lengths of T slot with the initial idea of having all 4 spaced out but parallel to the long axis. I didn't like it after trying to clamps some wood down so changed it to what you see now, the best layout I could get without ordering more T slot.

1213912140

gorbo
20-04-2014, 05:23 PM
This is how mine turned out, it uses 40 x 16mm T slot and some home made clamps and knobs with 6mm threaded rod of varying lengths.

1213912140

Looking good

EddyCurrent
20-04-2014, 05:42 PM
gorbo, like you I got a bag of inserts from Screwfix but after looking on YouTube for a while I decided to use the T slot. If I was cutting metal I'd go for a full T slot bed.
I'm also going to make some of the cam clamps that Gerry mentioned to allow the top surfaces to remain flush, sometimes you don't want the piece actually held down, you just want it to stay in the same place.