square hole broaching

Motoxrrar · Feb 22, 2018

I am a local blacksmith in Arizona. Currently making a few swage blocks and considering broaching square holes or milling, which ever might be cost effective and less time consuming. I was hoping to get ideas on tooling and or methods of broaching these holes from you folks. Here is a list of holes I need to broach.

2.000"
1.500"
1.125"
1.000"
0.875"
0.750"
0.625"

These holes will be through a 2 inch thick plate I believe to be A350 steel.

Any help is greatly appreciated.

Robert Ratliff
Blacksmith

sfriedberg · Feb 22, 2018

Don't overlook drilling (chain drilling around the slug for the larger sizes) followed by die grinding and/or filing to square up the openings/

EPAIII · Feb 22, 2018

You don't say what accuracy you want and that would determine a lot. I suspect for blacksmith work +/- 0.005" may be OK but you may have other ideas.

Getting a set of broaches in all those sizes will cost a small fortune and you are going to need a big press for the larger ones. Think $$$$$$$ +.

If this is a one time job, I would drill. Then mill with a long cutter to do perhaps 75% of the sides. And then file the corners to final size.

A shaper may be another way to do it if you can find a shop that has one.

L Vanice · Feb 22, 2018

Broaches are very expensive. Large broaches require a very large force (very expensive press) to push or pull through the drilled hole.

I suspect wire EDM may be more cost effective than broaching a "few" holes.

If you can get a cheap old key seater with some cheap 90 degree corner cutters, you might get the job done without spending a fortune.

Your least cost will be achieved with drilling and filing, and you probably will not want to make more than one block that way.

What can you sell a swage block for?

Larry

Mcgyver · Feb 22, 2018

can you push a 2" sq broach? I'd have guessed you'd need one of those broaching machines that pulls it. I can't how buying all those broaches would make sense for blacksmith work, i.e. bigger tolerance

I've haven't had something that thick water jet cut so the cost may be high (it'll take awhile), but it would be worth looking into. Too thick for laser and most plasmas and A/O doesn't leave a super neat job.....but waterjet would leave great and accurate to a few thou

RJT · Feb 22, 2018

I second the wire EDM outsourced. No way you can make / buy the broaches needed for the cost of wire EDM. Drill and file if you have the time and energy. If you are in it for making money, outsource to a shop with wire EDM.

D Dubeau · Feb 22, 2018

I've got a 0.360" square HSS toolbit in my box that I ground a 0.375" round shank on. For the odd time I've needed a square inside corner on something it's a simple matter of tossing that into a 3/8" collet in the mill, move the y over to align the "broach" and run the quill up and down, while stepping over in x a couple thou to clean up the corner. An elastic band/bungee cord (or that third hand everybody has) on the spindle brake provides enough force to keep the spindle from turning.

I don't envy you if you decide to do all those square pockets that way as it can be pretty tedious, but it's simple to tool up, and gets the job done.

If you are making a small run of these for resale I agree with the above. WEDM them and build that cost into your price.

Edit to add picture

gzig5 · Feb 22, 2018

I think a water jet or plasma cutter can do 2" thick. Not all machines, but if you find the right shop it would be cheaper than EDM. Grind/file or use a shaper to cleanup?

kazlx · Feb 22, 2018

Could also track down a die filer.

Brianison · Feb 22, 2018

Or, find some old grey haired machinist who still has a decent sized shaper, or slotter. Shapers are great for that kind of stuff, and reasonably quick too. Plus tooling is one size fits....most.

Bobw · Feb 22, 2018

kazlx said:
Could also track down a die filer.

This is on my bucket list.. He sells the castings and the plans, the rest is up to you.

FILING MACHINE (MLA-18)

How sad is it that making a die filer is on my "bucket list"???

Limy Sami · Feb 22, 2018

A die filer for 2'' thick plate? yes I know it can be done, ............but for a swage plate? .......yea gods. :eek:

DDoug · Feb 22, 2018

Limy Sami said:
A die filer for 2'' thick plate? yes I know it can be done, ............but for a swage plate? .......yea gods.

Yup, I don't see the PRACTICAL part in that posting.....

Wire EDM or waterjet, both can cut a prehardened piece of stock.

Comes off the machine, ready to go to work.

michiganbuck · Feb 22, 2018

You can draw the holes at 10x scale (or and scale)..with that you can see the drilled hole.. and determine the small corner hole that will fit each corners you can finish holes. yes that is the old fashioned way..
Other old way to drill and then shaper out the corners.

reedeprintice · Feb 22, 2018

We have some of those . Jess @ High Angle Driveline

bryan_machine · Feb 23, 2018

What machinery is available, what skill of machinist? There are tools meant as "clean out the corner broaches" made by people like Ph Horn (and another name I can't recall) - but they would require a CNC machine with spindle orient and lock, or the ability to line up and lock the spindle on say a manual mill. They take very small cuts. I wouldn't expect them to have 2" reach.

I wonder if the approach shouldn't be to drill out as much as possible cold, then drive a carefully shaped punch through with the material hot.

magneticanomaly · Feb 23, 2018

I think this is why swage-blocks are cast

metalmagpie · Feb 24, 2018

Yup. Swage blocks are cast. Last new one I bought had to have *all* its holes filed to admit the proper sized rods.

metalmagpie

gbent · Feb 24, 2018

You need to define your desired swage block a little better. This is a machinist site, for most of us our default setting is .001. As a blacksmith, your default setting is more likely 1/8. If you truly want the smaller features such as the 5/8 and 3/4 squares to size completely through the block wire edm is probably your best option, but it will be stupid expensive given the usage. Another method would be to counter drill the back of the block so the actual square shape would only be its own width thick (or less). The corners could be cleaned up on a slotter to yield a true square hole.

If you are going to make the block from A350 I expect you will have the outside profile flame cut. Talk to the flame cutter to see what they can offer for size and tolerance. Some cutters are remarkable good. You may need to take the flame cut shape and drill pierce holes for the shapes that will be flame cut.

Your swage block is also in the range of a high-definition plasma. Accuracy will be better than an O/A torch but I'm not sure how small of feature they could cut.

JohnMartin · Feb 24, 2018

Why not a vertical bandsaw?

square hole broaching

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