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Centec raising block

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Frank Gorse02/04/2019 18:03:57
26 forum posts

Gentlemen (ladies?), my first post here so please make allowances.

I am the fortunate owner of a Centec 2b milling machine with mk3 vertical head. I would like to add a raising block,not so much to increase capacity as to avoid the daunting job of lifting the head on and off. A member on this site kindly showed pictures of some he used to make but said firmly that he wouldn’t be making any more and Tony Griffiths(lathes.co.uk) hasn’t got any in stock and is unsure whether he will again.In any case I can ill afford the £340 or so required for something that will be used only now and then.

So my next thought was to make one myself,either from a block of ‘continuously cast’ iron or by making a cored pattern and getting it cast(I’m more experienced with wood than with metal).Either way it means a big lump of iron.

So...plan C. The existing overarm is redundant as soon as the raising block exists. It already has one of the dovetails and most of the bulk required and my idea is to cut the top off it like a boiled egg-along the top off the Centec name panel probably- and graft a piece on top in which to mill the top dovetail. I think that with care it could be done without looking too bad.

My questions then are:

Will it work?

Will the overarm casting distort and become useless as soon as it’s cut. It’s 50-60 years old so ‘seasoned’ and I wouldn’t be cutting that much of it away.

The idea is to hold the parts together with Epoxy and screws from underneath,would filling the hollow section with,say,epoxy concrete be a good plan.?

Anyone know a helpful foundry?, I live in North Wales.

And finally,is it a sin to butcher a good bit of old British engineering like this.?

All advice and opinions gratefully received.

not done it yet02/04/2019 18:45:33
3230 forum posts
11 photos

My immediate thought is why that approach had not been taken by all and sundry, who wish to add a riser block?

Andrew Tinsley02/04/2019 19:15:55
910 forum posts

Maybe because folk may wish to keep the horizontal milling facility? Or maybe I am missing something?

Andrew.

Chris Evans 602/04/2019 19:38:40
1447 forum posts

For a one off casting just make a pattern from polystyrene. This can be burnt out of the sand box prior to casting saving the foundry time and you money. Lots of good glues available to fabricate the pattern from poly.

Frank Gorse02/04/2019 20:24:36
26 forum posts

Andrew,yes,the underside of the overarm would remain unmolested for horizontal milling and the vertical head just slid back out of the way.

Chris,thanks for that,I’ll do some research.

Frank

martin perman02/04/2019 20:35:36
avatar
1628 forum posts
67 photos

Frank,

Machine Mart sell a raising block for the CL500M lathe, its approx 5" square cube and costs £77.99p.

Martin P

JonBerk02/04/2019 22:23:35
14 forum posts
1 photos

Hello Frank

If you have the time, trawl through the Photos section of the Yahoo Centec Forum and you will find several examples of home made raising blocks. Find it here https://groups.yahoo.com/neo/groups/centec_milling_machines/info

The Centec Forum seems to have died since Yahoo made changes a year or so ago but the photos and other files are still there. It was/is a good resource for Centec info.

Good luck

Jon

Frank Gorse03/04/2019 06:49:51
26 forum posts

Martin,thank you but the part I need is specific to the machine I have which has not been made for many years.

Jon,thanks,I’ll have to open a yahoo account

Nigel Graham 203/04/2019 09:22:31
356 forum posts

I would urge you NOT to modify any of the original parts. If you want to sell the machine on at any time it will be far more attractive in original condition plus extras, than modified. Also, chopping the existing over-arm as you proposed would mean you could no longer use the machine for horizontal milling - why disable its primary function instead of adding a second?

I owned a Centec 2 for a while, and I did buy a raising block from Tony Griffiths. That pattern does not make any other part "redundant". because the original top-slide fits the block.

To allow horizontal milling while leaving the raising-block and vertical head in place, I made a second, deeper drop-bracket from steel plate, using a small boring-head to cut the bearing hole in-situ by connecting the work-piece to the table with an angle-plate, and with the top slide slackened just enough for free movement. If I remember correctly, I applied gentle hand pressure to the front of the raising-block to ease the strain on the cross-feed, and took very gentle cuts. The bearing itself was a bronze bush - I may have used n "Oilite" one.

If you have one cast, one company used to handling orders from model-engineers is Bridport Foundry, which now makes the Stuart range.

I would suggest fabricating one otherwise, not from a single lump of solid bar though! And make an extended bearing bracket as above, for the horizontal arbor.

Nicholas Farr03/04/2019 09:55:59
avatar
1940 forum posts
922 photos
Posted by Frank Gorse on 02/04/2019 18:03:57:

Gentlemen (ladies?), my first post here so please make allowances.

And finally,is it a sin to butcher a good bit of old British engineering like this.?

All advice and opinions gratefully received.

Hi Frank, if it's your machine, you can do what you like with it (within reason) sins don't come into the equation. However, like Nigel says, it will likely devalue it should you wish to sell it on, and if it goes pear shaped, you may well have a useless machine. I myself wouldn't do it.

Regards Nick.

Paul White 303/04/2019 10:57:07
92 forum posts
17 photos

Hello Frank,

Having the same problem with regard to the weight of the vertical head, I made a lifting block from a piece of 3" sq.

18" long mild steel. Having machined the dove tails I also drilled some lightening holes in the support.

I also fitted a separate motor for the vertical head driven thro a VFD . This set up removes the need to reset the drive belt.

Frank Gorse03/04/2019 10:57:52
26 forum posts

Nigel and Nicholas,thank you both for your comments but I fear we are at cross purposes. The photo on Tony Griffiths’ website shows a raising block the same length as the overarm with the vertical head permanently mounted on it so the horizontal facility is unaffected (though not increased ). My plan was to stick the VH on top of the overarm so as to have both available without any heavy lifting,the increased capacity in vertical mode being a welcome bonus.

However I take your point about modifying original parts. Anyone out there got a spare overarm they’d like to sell?

Frank Gorse03/04/2019 11:17:46
26 forum posts

Thanks for that Paul,mild steel is another option of course. Part of my plan was to reduce the amount of dovetailing to be done,milling is still something of an adventure for me! I do like your independant motor on the vertical head.

Dave Halford03/04/2019 12:13:51
438 forum posts
4 photos

Most Centec raising blocks are made from aluminium.

With a 2B you can make a full length arm, the only pain is the clamp cutouts where you will need 4.

Nigel Graham 203/04/2019 14:22:10
356 forum posts

Thank you amplifying things, Frank.

My own machine was indeed fitted with a lathes.co raising-block, and that was cast-iron though as it is rarely moved and then only to position it, there's no reason it can't be mild-steel or aluminium - but grease the joint well to guard against corrosion.

One way you can simply make dovetails, is to make the dovetailed part by chamfering the sides of a flat bar that is then screwed on to the main block. My Harrison lathe and Drummond shaper uses the same principle, altbeit for rectangular rather than dove-tailed slides. This need only ordinary end-mills.

Beware though that if you use a single, full-length BMS bar it could warp from milling along its length.

Gary Wooding03/04/2019 15:48:56
572 forum posts
137 photos

I've made about 20 Centec raising blocks, only two of which were "short" ones, meaning they had to be removed in order to use the m/c for horizontal milling. The remaining 18 were "long" ones which were slid rearwards for vertical milling and slid forwards (with the VH still attached) to act as the overarm.

All were made from 6082T6 aluminium alloy, and have performed really well. I've had no complaints at all, but was surprised to find that, because Centecs were made in two separate factories, there are slight differences in the sizes of the dovetails.

Cutting the dovetails is easy, but time consuming and tedious, but making the retaining fingers and cutting the pockets was a challenge.

Long raising blocksShort raising block

Gary Wooding03/04/2019 16:06:05
572 forum posts
137 photos
Posted by Dave Halford on 03/04/2019 12:13:51:

Most Centec raising blocks are made from aluminium.

With a 2B you can make a full length arm, the only pain is the clamp cutouts where you will need 4.

Why?

All the raising blocks I've made had only two cutouts.

peak403/04/2019 16:23:44
avatar
809 forum posts
67 photos
Posted by Gary Wooding on 03/04/2019 15:48:56:

I've made about 20 Centec raising blocks, only two of which were "short" ones, meaning they had to be removed in order to use the m/c for horizontal milling. The remaining 18 were "long" ones which were slid rearwards for vertical milling and slid forwards (with the VH still attached) to act as the overarm.

If you'd care to increase your count to 19, please do let me know. wink

Cheers

Bill

Dave Halford03/04/2019 17:57:20
438 forum posts
4 photos
Posted by Gary Wooding on 03/04/2019 16:06:05:
Posted by Dave Halford on 03/04/2019 12:13:51:

Most Centec raising blocks are made from aluminium.

With a 2B you can make a full length arm, the only pain is the clamp cutouts where you will need 4.

Why?

All the raising blocks I've made had only two cutouts.

Good point Gary, I was thinking you would push the head back and clamp it, but you can't. DOH!

PS My Centec2 has narrower dovetails than my late model 2A, but only a few thou.

Edited By Dave Halford on 03/04/2019 18:01:31

martin perman03/04/2019 18:15:24
avatar
1628 forum posts
67 photos
Posted by Dave Halford on 03/04/2019 17:57:20:
Posted by Gary Wooding on 03/04/2019 16:06:05:
Posted by Dave Halford on 03/04/2019 12:13:51:

Most Centec raising blocks are made from aluminium.

With a 2B you can make a full length arm, the only pain is the clamp cutouts where you will need 4.

Why?

All the raising blocks I've made had only two cutouts.

Good point Gary, I was thinking you would push the head back and clamp it, but you can't. DOH!

PS My Centec2 has narrower dovetails than my late model 2A, but only a few thou.

Edited By Dave Halford on 03/04/2019 18:01:31

Gentlemen,

I have a Centec 2A, where does the riser block fit, I have an horizontal arm on my machine and dont have a vertical head.

Martin P

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