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Prima Clamp on Bench Drill

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Paul Matthews 406/01/2017 08:57:18
22 forum posts
13 photos

Hi everyone, I wonder if anyone can help with this query, I've recently bought an English-made Elliot pedestal drill, but fitted around the pedestal above the table was this device (see photo) which has a label "Prima Clamp" unfortunately that's all I can tell you about it, Googling reveals nothing about it, whatever is missing is accepted in a 7/8" bore and a knurled locking screw.

Can anyone help who may have one or know what style of locking device would have been fitted as I would like to try and make it.

Many thanks



Michael Gilligan06/01/2017 09:47:07
11039 forum posts
475 photos


I've not seen that exact device before, but ... Mounting a 'toggle clamp' or even a simple 'screw-down' onto a 7/8" dia bar should make it very useful.



... in case you were wondering.

Edited By Michael Gilligan on 06/01/2017 09:48:28

Muzzer06/01/2017 09:59:43
2723 forum posts
439 photos

I have an identical one that is fitted on my Progress(?) pillar drill. This is the part that slides up and down the main column (it's not fixed). The missing part fits in the smaller hole at the front and is held at the right length by the thumb screw. On the other end of the rod is a cam mechanism with an operating lever and a pressure pad to apply clamp down force to the work piece.

Very handy item. The action of the cam causes the sliding part to lock to the column, so you just swing the pad into position and turn the lever. The work is clamped to the table. Bingo.

A couple of photos of an almost identical clamp here although our British version is all cast and / or  machined. I can take some pics of mine tonight if nobody else has anything to hand.


Ah, I see John Gibbs has posted a picture. That's identical to mine.

Edited By Muzzer on 06/01/2017 10:09:34

Jon Gibbs06/01/2017 10:07:07
731 forum posts

Like this?...

Jon Gibbs06/01/2017 10:21:05
731 forum posts

I guess it's the mechanism that's of most interest...

Muzzer's link eventually leads here with images here...

Edited By Jon Gibbs on 06/01/2017 10:26:02

It looks as if the notches and leaf spring might be replaced by just a single pivot and telescopic bar in the Prima-clamp version which looks a whole load more elegant.

Edited By Jon Gibbs on 06/01/2017 10:49:46

Michael Gilligan06/01/2017 11:38:21
11039 forum posts
475 photos

Well found, Jon yes


Clive Foster06/01/2017 11:43:36
1319 forum posts
29 photos

That would make a nice MEW project albeit modified to use machined clamp rather than bent. Getting that sort of two half circles done accurately is bit difficult if you don't have the proper gear. A creative combination of the most appropriate to Home Shop facilities parts from both designs should work fine.


Muzzer06/01/2017 12:50:59
2723 forum posts
439 photos

If I were planning to copy one of these, I'd use the UK version. Seems easier to make from solid stock and more robust. If you want any dimensions, I'm happy to take some measurements. The cam eccentricity and the positions of the pivots are probably the most critical.


Clive Foster06/01/2017 14:08:49
1319 forum posts
29 photos

Lots of ways to do it. I personally would stay close to the original patent but start with a piece of thick wall tube for the clamp. Slot on opposite sides and weld two lumps on for clamp bolts. Tap blocks right through for clamp bolts then split to make a pair of half round sections. Drill bolt holes in one out to clearance, clamp back together and turn centre hole back to true round just big enough to slide nicely on the drill column. Make the arms from flat steel as per drawing. Bolt up with spaces and weld on. Might need a touch with the file to get sliding clearance back.

If going from solid I'd start with two blocks big enough to contain half clamp and clamping bolts. Drill, tap and clearance the holes for the bolts. Bolt up together and fit central hole. Pretty up outside profile to taste. If copying the Prima version make the arm from thick wall tube, either direct from stock or made to size from bar stock. Fit threaded hole for knurled screw on outer end. Put a short thread on the other to screw into the clamp, pipe thread would seem best. Drill and tap suitable size hole in clamp and loctite in place. Make slotted bar and foot as per original. The bar will be more stable if you can arrange three point contact by cutting a keyway opposite the knurled screw so it clamps against two lines rather than just one immediately opposite the screw. 1/8 - 3/16 or 4 mm wide would seem about right. If making your own tube from solid drilling a small, full length hole on the diameter of the main hole before making the main one works but need to be careful that the small drill doesn't run out.

If you'd prefer flat bar style, like the patent rather than a tube, simply put right angle tabs on the end of the bars and bolt to the clamp having arranged a suitably flat face and appropriate holes. Ought not to be that hard to adapt a commercial toggle clamp from folk such as those linked to by Michael if you don't fancy figuring out the details of your own design of cam operated locking device. There were plans for such camps in one of the earlier issues of MEW which might prove inspirational if anyone has details of which issue they were in. My guess is around Number 40 to 50 mark.


Paul Matthews 407/01/2017 13:49:54
22 forum posts
13 photos

Thanks everybody for the input, much appreciated.


OuBallie13/01/2017 17:20:00
1091 forum posts
614 photos


Something else to add to the ever growing list.

Like it though, so top of list I think.

Geoff - Sorting out one of those ubiquitous bench sandblast cabinets.

Edited By OuBallie on 13/01/2017 17:20:41

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