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How to make tapered square holes?

drcoelho

Stainless
Joined
Feb 19, 2017
Location
Los Altos
Need to cut some tapered square holes, ranging from 0.5" to 1" square, doesn't have to be super accurate (to be used to hold sheet metal fabrication stakes). Would like to cut these into 0.75" thick A36 steel plates. Wire EDM comes to mind, but I don't have such a machine. How would you do this?
 
WEDM might be the most expensive way of doing that...

drill a hole, use oxy acetylene torch to heat it light red hot around the hole and drive your stake in with few heavy hits - done

slightly less exciting way - drill hole and file the shape

slotting head and universal table on your FP1 might also work, but setting the piece up might be PITA, and using the table in that manner wouldn't be kosher for sure :)
 
Need to cut some tapered square holes, ranging from 0.5" to 1" square, doesn't have to be super accurate (to be used to hold sheet metal fabrication stakes). Would like to cut these into 0.75" thick A36 steel plates. Wire EDM comes to mind, but I don't have such a machine. How would you do this?

Pexto and Dixon made them from cast iron, obviously the easiest way. I think 3/4" is too thin to get proper stability. The castings are much thicker around the holes. There are several Pexto plates on eBay that are probably cheaper than you can have a similar one made to order by EDM.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=pexto+stake+plate&_sacat=0&_sop=15

Larry
 
WEDM might be the most expensive way of doing that...

drill a hole, use oxy acetylene torch to heat it light red hot around the hole and drive your stake in with few heavy hits - done

slightly less exciting way - drill hole and file the shape

slotting head and universal table on your FP1 might also work, but setting the piece up might be PITA, and using the table in that manner wouldn't be kosher for sure :)

Yes, I was considering the slotting head on FP1 as possible solution.
 
Pexto and Dixon made them from cast iron, obviously the easiest way. I think 3/4" is too thin to get proper stability. The castings are much thicker around the holes. There are several Pexto plates on eBay that are probably cheaper than you can have a similar one made to order by EDM.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=pexto+stake+plate&_sacat=0&_sop=15

Larry

Was aware of off the shelf plates, but need a special flavor as add-on to my pre-existing work table.
 
Finegold and Seitz's Silversmithing describes in detail how to mount a tapered shank stake in a stump.
 
Are you going to weld this plate to your existing plate, make it as a loose piece, or make individual parts with tapered holes and weld them into your plate? If individual parts, I'd weld them up and then weld them into the larger plate. In fact, welding them up from individual pieces may be the easiest process. You are putting as cast parts into the holes, so you can use the cast parts as anvils. How much precision is needed?
 
Are you going to weld this plate to your existing plate, make it as a loose piece, or make individual parts with tapered holes and weld them into your plate? If individual parts, I'd weld them up and then weld them into the larger plate. In fact, welding them up from individual pieces may be the easiest process. You are putting as cast parts into the holes, so you can use the cast parts as anvils. How much precision is needed?

My work table is 1" thick A36 steel (blanchard ground flat to 0.001" interestingly) with a matrix of CNC cut 16mm threaded holes and also 22mm straight holes across the entire 36"x60" surface. I only do sheet metal work occassionally, so was thinking of having a modular system whereby I bolt the square hole plate onto the edge of the work table when needed. Accuracy is not a big deal, just need the stakes to be robustly held in place when in use. What I'd like is a plate that is wide enough to allow for a variety of strike holes along the edge of my work table.
 
I fabricated my stake holders out of 1/2" plate and the socket is about three inches deep. I made them to drop into my plate table, they're secured with a single nut from underneath.

The one for the silversmith/tinsmith stakes works great, but the one for the double-seaming stake flexes noticeably, but that thing is three feet long. I'll have to brace it and maybe use a, bigger hold-down stud.
 
I would mount a receiver tube to your bench, that way you can remove when not in use....

Strong Hand BuildPro Fixturing Table Clamps & Accessories

I would fab the socket out of plate and metal finish to suit, or you could make the socket two pieces and bolt/weld them together?

Kevin

My table is standardized on 22mm holes for use with Siegmund welding accessories, but same idea as you've suggested, so yes, I could use the 22mm holes for mounting the plate. But, I'm more inclined to use by threaded 16mm holes and bolt the plate to the table for more robust holding power.
 
I don't know anything about this but why could not the holes be straight and the stakes tapered?
and why not round?

I'm no expert, but I believe you'd have too much motion with stakes wiggling around in the hole while you are pounding on the stake doing sheet metal work.
 
yes, as others have said, four trapezoidal pieces of steel, say 1/2 or 5/8" thick by 2.5-3", TIG weld, full penetration built up corners. I.E., make the trapezoids the same width as the stake's bit, and fully weld the corners in multiple passes. weld to fixture plate of your choice. nice thing is any old hot rolled plate is fine for this application.
 
Round holes and pins using a tapered reamer and the taper attachment on a lathe?

Make a tapered square broach out of hardenable tool steel?

Otherwise a shaper or CNC would be the most accurate.

 
Have the water jet guys cut the sqr holes, then make a drift to match your taper, heat the plate red/org hot and beat the drift in and out, go to the next hole, grind flat when done...or skip all the fun and just buy a used one...Phil
 








 
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