Brass_Machine said:
Ok John... That tapper is very cool. care to do some drawings on your design for us?
Eric
There are no drawings, this is my way of working. I searched the Internet for designs, no make that pictures, and there are two common methods, the fixed column and two pantograph arms and the 4 linked pantograph arm type.
I plumped for the 3 arm type as it would be quicker to build.
The lengths of the arms are determined by how far you need to reach. I wanted to get anywhere on the bench including the 2 vises so that gave me the length.
Material in stock was 40mm x 4 mm thick box so that gave me some sizes.
Each of the 2 pantograph arms were drilled close to the end as possible with a 30mm drill on the Bridgy whist they were both tack welded together. this gives equal pivot points.
Eight pieces of 30mm bare were drilled and counterbored to take 8 stock bearings with a 8mm bore, these were cut to 42 mm long so they stand proud and don't foul the arms. These were tack welded inside from the ends of the arms.
The arms were left open as it was just wasting time to cap them [ just my take ]
Four side plate were cut from flat plate and three of these were laid on the ground and the arms laid on them, one was the back fixed plate and the other two represented the max and min movements. Once that had beel worked out the holes were transfered thru and the plates drill as pairs.
The fixed arm was cut to 50 degrees I think it was on the power saw, two 40mm bars were again drilled and counterbored for stock bearings with a 15mm hole. one was welded into place and two long pieces of 15mm bar were pushed thru and the end measured so the offset was the same between both ends and the second slug tack weld, more checking, then more tacks, finally welding the whole lot up.
A bit of sanding with an angle grinder and the bottom pivot made to fit the bottom slug and it was ready to have a block made where one side fitted the side plates and the other end fitted the bought head.
Assemble is just a few bolts but I did put a thin 8mm washer on each of the arm bearings to space it and stop the bearing rubbing on the side plates.
If someone wants the pivot layout for mine I can do a quick and dirty drawing, it certainly won't be in 3D ;D
Ironically it turned out well because I was doing a job that required one 6mm hole to be tapped into this laser cut bar on it's end. The bar could be drilled in the Bridgy but not tapped as the table wouldn't drop low enough to get the tapping head in so I was drilling these and tapping by hand as none of my machines had the reach to do these bars.
These usually can in in batches of 40 at a time so it wasn't too bad.
I had arranged to pick the head up at the Harrogate show and just before the show they upped the order to 180.
When I got back from the show it then stood at 380.
So it took me about just over a day, full time to make this hence the no paint and by the time the bars were delivered it was done and 380 bars were drilled and tapped in 6 hours.
That paid for the head outright, it cost 2 broken drills and no taps.
So far I have broken one tap and that was a 6mm one that just went part way in a hole for some reason, most of the time it's working on 4,5 and 6mm threads in alloy on these CNC conversions.
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