Any Experience with Rotabroach?

[RonRock]

So I have a project to do with my son. We are going to build him a weight machine. It will be made of 3X3X11gage steel tube. The tube will be line drilled for adjustable accessories.

I plan to use my bridgeport to drill. My plan is to take a steel plate and drill a hole that I can weld a pin into. I'll clamp that to the BP table and use it as a locating pin for the holes that will be 2" on center.

So the question finally.

The holes need to be through holes. I don't think that a drill would be accurate enough and would take too much effort to center drill, then drill. So I figure that a Rotabroach or other Annular cutter might do the trick. Never used or even seen one yet.

I guess there are a couple questions. I plan to use 3/4" bolts for most everything. Will a 3/4" Rotabroach give me enough clearance for a 3/4" bolt?
Most of the Rotabroach's that I have found are 3/4" Weldon shank. That would make the sleeve of the shank larger than 3/4" so that won't work. Anybody know of a 3/4" X 3" deep Anuallar cutter?

I found these "Blair 11132-3 3/4" Rotabroach Cutters"

https://www.amazon.com/dp/B002XMS1AO/?tag=atomicindus08-20

They look like they might work if I can find a shank long enough to go through the 3" tube. Maybe I can make one on the lathe. Not sure what the thread is on the cutter.

Do I need a pilot/center drill with an anuallar cutter?

Any better ideas how I can line bore for 3/4" bolts 2" on center?

 

[Millwrong]

You're going to want a 13/16" cutter for 3/4" bolts. Unfortunately anything with a Weldon shank isn't going to allow you to drill from one side only. Perhaps an HSS or carbide hole saw would work, but I still see you having troubles drilling from one side only, not only due to the depth required, but also the slug getting in the way.




Edit:




I just found that Hougen has some "long reach" cutters available....

https://www.canadamagdrills.ca/product/hougen-4-12226-1316-x-4-reach-rotabroach/

 

[RonRock]

Good find but ouch! A bit out of the price range.

Part of the reason I was thinking of the Blair cutters is that they have a threaded hole for the shank. Not as large as the OD of a shank that will fit a weldon. But I don't know if a shank long enough to get through 3" tube will be stiff enough. Or if it will need a pilot drill.

13/16" seems like it would be a very loose fit. I'll have to check with a hole saw. Maybe something metric will fit better.

 

[lis2323]

Drill a 3/16” pilot hole THROUGH both sides of the 3” square tube then use rotabroach from EACH side. As mentioned though using a 3” long annular cutter would be my first choice.



3/4 Rotabroach hole should be fine for 3/4” CRS

I used pallet racking frames for my rack to eliminate drilling holes.






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[speed bump]

Since it is weight training equipment and not something that requires high precision I would just use a twist drill through or a step bit from both sides. An adjustable reamer would let you make the holes a tight fit on a 3/4 bolt.

 

[RonRock]

Nice job. My first thought was to try and find something that was already drilled. All I could think of was E Strutt. Not large enough.

Got any more photos?

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[BukitCase]

I have quite a few Evolution annular cutters - they make a 3/4"x3" one, it's #cc750X - a bit more reasonable than $135

https://www.discountsteel.com/items...&size_no=1&sku_no=38&itemComments=&qty=1#skus

I can tell you that their 2" length cutters WILL drill thru 2" square tube from one side - but Millwrong is right :=) the slug CAN get in the way.

Most mag drills these days have a "slug ejector", where you raise the quill all the way to the top and the pilot pin pushes the slug out.

About half the time, the slug falls EXACTLY where you wanna drill the second side of the tube but as long as you don't weld caps on the tubing BEFORE it's drilled, you can just stick an air wand in the end of the tube and blow the slug out of the way, then drill the other side.

The comment about clearance is true, if you use a 3/4" cutter it's gonna be close to a "hammer fit" for a 3/4" pin - my usual solution to that is to move up to the next METRIC size, usually gives a clearance of anywhere from .010" to .030" depending on where it falls (1mm= .03937")

Evolution has a pdf catalog, google "evolution steel catalog, should come up. Annulars are on page 14-15-16, inch and metric are in same chart which makes it easy to compare.

Unfortunately, Evolution does NOT offer a 20mm in 3" depth though; maybe somebody else does. A 20mm would give you .0374" clearance instead of .0625" from using 13/16" -

The little rotobroach kits are meant for sheet metal, some will cut 1/4" wall but don't expect that small shank to be stiff enough to ensure on-axis cuts at 3" - you might get lucky, might not.

If possible, use a Weldon adapter on your BP that includes a lube ring - not cheap, but cutters will last a LOT longer with a steady, FIRM feed and continuous lube -

https://www.zoro.com/jancy-annular-...MIxbel38b14AIVhq_sCh2tGg1yEAkYBCABEgJMA_D_BwE

If you don't envision a LOT of this operation, a NON-lube adapter and a spray bottle is about $100 cheaper. Cheaper yet, maybe just a 3/4" collet - I haven't tried that, but maybe...

'Bout all I got, good luck... Steve

 

[bullnerd]

3/4" sounds huge!

What kind weigh are we talking about?

 

[lis2323]

I have quite a few Evolution annular cutters - they make a 3/4"x3" one, it's #cc750X - a bit more reasonable than $135



https://www.discountsteel.com/items...&size_no=1&sku_no=38&itemComments=&qty=1#skus



I can tell you that their 2" length cutters WILL drill thru 2" square tube from one side - but Millwrong is right :=) the slug CAN get in the way.



Most mag drills these days have a "slug ejector", where you raise the quill all the way to the top and the pilot pin pushes the slug out.



About half the time, the slug falls EXACTLY where you wanna drill the second side of the tube but as long as you don't weld caps on the tubing BEFORE it's drilled, you can just stick an air wand in the end of the tube and blow the slug out of the way, then drill the other side.



The comment about clearance is true, if you use a 3/4" cutter it's gonna be close to a "hammer fit" for a 3/4" pin - my usual solution to that is to move up to the next METRIC size, usually gives a clearance of anywhere from .010" to .030" depending on where it falls (1mm= .03937")



Evolution has a pdf catalog, google "evolution steel catalog, should come up. Annulars are on page 14-15-16, inch and metric are in same chart which makes it easy to compare.



Unfortunately, Evolution does NOT offer a 20mm in 3" depth though; maybe somebody else does. A 20mm would give you .0374" clearance instead of .0625" from using 13/16" -



The little rotobroach kits are meant for sheet metal, some will cut 1/4" wall but don't expect that small shank to be stiff enough to ensure on-axis cuts at 3" - you might get lucky, might not.



If possible, use a Weldon adapter on your BP that includes a lube ring - not cheap, but cutters will last a LOT longer with a steady, FIRM feed and continuous lube -



https://www.zoro.com/jancy-annular-...MIxbel38b14AIVhq_sCh2tGg1yEAkYBCABEgJMA_D_BwE



If you don't envision a LOT of this operation, a NON-lube adapter and a spray bottle is about $100 cheaper. Cheaper yet, maybe just a 3/4" collet - I haven't tried that, but maybe...



'Bout all I got, good luck... Steve

Collet will work, Steve!


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[RonRock]

3/4" sounds huge!

What kind weigh are we talking about?

You are right about that. We are copying a setup that he considered buying. It has 1" holes. That is way overkill and removes too much material in my opinion. But if I was to go back to the 1" holes it would be easier to figure out a drilling option. The larger hole would give me clearance for a shank.

1/2" or 5/8" would be plenty strong I'm sure but that also complicates the hole drilling. I figured that 3/4 would look beefy enough and hopefully easy enough to figure out a drilling setup that would work.

Appreciate all of the thoughts guys. Always good for me to hear other peoples thoughts.

 

[lis2323]

Nice job. My first thought was to try and find something that was already drilled. All I could think of was E Strutt. Not large enough.

Got any more photos?

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Just took a few...





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[bullnerd]

Beautiful job Lis!

Is that for you or a customer?

Now I can workout when I visit your shop!

It seems like with a little thought, pallet racking and/or uni-strut can pretty much do anything we need.

 

[RonRock]

Very nice! I wish you would have done a build thread. I'd be working on a clone. Looks pretty straight forward, but I can see a couple details that I would need help or pictures of.

Cheers to you, good job.

Ron

 

[RonRock]

I have quite a few Evolution annular cutters - they make a 3/4"x3" one, it's #cc750X - a bit more reasonable than $135

https://www.discountsteel.com/items...&size_no=1&sku_no=38&itemComments=&qty=1#skus

I can tell you that their 2" length cutters WILL drill thru 2" square tube from one side - but Millwrong is right :=) the slug CAN get in the way.

Most mag drills these days have a "slug ejector", where you raise the quill all the way to the top and the pilot pin pushes the slug out.

About half the time, the slug falls EXACTLY where you wanna drill the second side of the tube but as long as you don't weld caps on the tubing BEFORE it's drilled, you can just stick an air wand in the end of the tube and blow the slug out of the way, then drill the other side.

The comment about clearance is true, if you use a 3/4" cutter it's gonna be close to a "hammer fit" for a 3/4" pin - my usual solution to that is to move up to the next METRIC size, usually gives a clearance of anywhere from .010" to .030" depending on where it falls (1mm= .03937")

Evolution has a pdf catalog, google "evolution steel catalog, should come up. Annulars are on page 14-15-16, inch and metric are in same chart which makes it easy to compare.

Unfortunately, Evolution does NOT offer a 20mm in 3" depth though; maybe somebody else does. A 20mm would give you .0374" clearance instead of .0625" from using 13/16" -

The little rotobroach kits are meant for sheet metal, some will cut 1/4" wall but don't expect that small shank to be stiff enough to ensure on-axis cuts at 3" - you might get lucky, might not.

If possible, use a Weldon adapter on your BP that includes a lube ring - not cheap, but cutters will last a LOT longer with a steady, FIRM feed and continuous lube -

https://www.zoro.com/jancy-annular-...MIxbel38b14AIVhq_sCh2tGg1yEAkYBCABEgJMA_D_BwE

If you don't envision a LOT of this operation, a NON-lube adapter and a spray bottle is about $100 cheaper. Cheaper yet, maybe just a 3/4" collet - I haven't tried that, but maybe...

'Bout all I got, good luck... Steve

Good find. $54.99 is getting reasonable. I'll have to take a look at their website and see if I can find a set that will have a shaft that will drive the 3" cutter as well as whatever is in the set. I think that I'm going to like annular cutters. Don't know why since I've never had one, but they just seem much better than hole saws, at least in steel.

 

[sanddan]

3/4" x 2" depth of cut.
https://www.amazon.com/dp/B003LY4EFY/?tag=atomicindus08-20

 

[lis2323]

Beautiful job Lis!

Is that for you or a customer?

Now I can workout when I visit your shop!

It seems like with a little thought, pallet racking and/or uni-strut can pretty much do anything we need.

Thanks, bullnerd. It was for my personal use. And you’d be welcome anytime!


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[lis2323]

Very nice! I wish you would have done a build thread. I'd be working on a clone. Looks pretty straight forward, but I can see a couple details that I would need help or pictures of.

Cheers to you, good job.

Ron

Thanks, Ron

Let me know if I can help with a closeup photo or explanation.


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[BukitCase]

SandDan, the OP needs to drill THREE inch square tube from one side...

Ron, found a couple more options, bit more but gives you the clearance without reamers/sandpaper/cussing, etc :=)

https://www.amazon.com/dp/B01KKO6T00/?tag=atomicindus08-20

https://www.amazon.com/dp/B009KGX1QU/?tag=atomicindus08-20

First one's a "stack cut", meaning you can drill multiple layers without having to clear the plug for each layer - not sure if that'd be any benefit with 2" or more between "layers" - wouldn't be too bad if you just chucked the cutter in a 3/4 collet and used spray bottle lube.

Another possible advantage of the collet mount (thanks for confirming, lis) - nothing says you hafta seat the weldon shank all the way in a collet, just in case 75mm isn't quite enough depth (considering that a REAL 3" is 76.2mm) - in practice tho, I've found all my cutters in 2" DOC WILL cut thru 2" OD tubing, with a little left over, so probly just my "OATS" (OverAnalyzingThingsSyndrome) ... Steve

 

[strength_and_power]

I’ve built many a power rack, around 175 of them over the past 10 years and a sh!t ton of other gym equipment. For my racks I used a laser cut jig that was formed 90* and clamped onto the tubing. Drill a 3/16” pilot hole, flip the tube, reclamp the jig and pilot drill the other side. Slow the drill down and use a carbide hole cutter to get to your final size. 4 uprights 84” long with 1” and 2” hole spacing, 3/4” finished hole size will take about 2.5 hours. Building gym equipment is somewhere between building a sledgehammer and putting a man on the moon.
Send me a PM and I will be more than happy to share my experience



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[Jason280]

If you are serious about using an annular cutter/Rotabroach, I have a Hougen in 20mm I'll send you to try....

 

[RonRock]

If you are serious about using an annular cutter/Rotabroach, I have a Hougen in 20mm I'll send you to try....

That's an offer that's hard to resist. Is it for sale? I'd hate to put use on someone else's cutter.

 

[lis2323]

I’ve built many a power rack, around 175 of them over the past 10 years and a sh!t ton of other gym equipment. For my racks I used a laser cut jig that was formed 90* and clamped onto the tubing. Drill a 3/16” pilot hole, flip the tube, reclamp the jig and pilot drill the other side. Slow the drill down and use a carbide hole cutter to get to your final size. 4 uprights 84” long with 1” and 2” hole spacing, 3/4” finished hole size will take about 2.5 hours. Building gym equipment is somewhere between building a sledgehammer and putting a man on the moon.
Send me a PM and I will be more than happy to share my experience



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That’s effin ’ awesome s and p! You’d laugh at the amount of time and crude methods I used to make my rack.

Nice work!


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[Jason280]

That's an offer that's hard to resist. Is it for sale? I'd hate to put use on someone else's cutter.

Nope, email me your address and I'll mail it to you....

[email protected]

...you may or may not néed the center locator pin, though.

 

[E.rodz]

if you are using a bridgeport then there is no need for a pilot as long as you lock x and y before drilling the hole. 13/16 should give you a little wiggle room otherwise a 3/4 pin will still go through however it will be a tight fit. you can machine an adapter to go all the way through with a shorter bit. it would also be easy to drill from both sides easy on a mill you just have to use an edgefinder to make sure you are starting and stopping in the same repeatable spots. the ends for the cutters will fit right in a 3/4 collet for you mill. once you try on you wont go back to a drill! all the bigger holes were drilled with rotobroach bits last night.

View media item 91117

 

[Jason280]

once you try on you wont go back to a drill!

This is the absolute truth. I have a Hougen mag drill that is set up for annular cutters, and its ridiculous how much faster it is over a twist drill...especially in the larger sizes.

 

[strength_and_power]

This is the absolute truth. I have a Hougen mag drill that is set up for annular cutters, and its ridiculous how much faster it is over a twist drill...especially in the larger sizes.

I can see how the cut time would be faster but I’d have to wonder about overall time when you include setting up the mag drill.


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[E.rodz]

This is the absolute truth. I have a Hougen mag drill that is set up for annular cutters, and its ridiculous how much faster it is over a twist drill...especially in the larger sizes.

i did 1" holes through 1" thick alum and each hole took about 45 sec and the holes are 10 times cleaner.

I can see how the cut time would be faster but I’d have to wonder about overall time when you include setting up the mag drill.
sounds like someone has never used one either! try one and there will be no return to a drill again! especially on a bridgeport!

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[Jason280]

I can see how the cut time would be faster but I’d have to wonder about overall time when you include setting up the mag drill.

Even with the added set up time, which is minimal in most cases, the annular cutter is still faster. Now, its one thing if you are talking about two 1/2" holes in 1/4" plate, but quite different when you get into 1/2"+ in thicker materials. Plus, the benefit is the hole is much more consistent, cleaner, and has fewer chips to clean up.

 

[strength_and_power]

Here is a picture of a jig I use that has been very handy. 24” long, holes spaced 1” apart. Each row of holes puts me in the center of 2”,2.5” and 3” square or rectangular tubing.
My laser guy laser cuts and forms the piece for $25.


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[lis2323]

Here is a picture of a jig I use that has been very handy. 24” long, holes spaced 1” apart. Each row of holes puts me in the center of 2”,2.5” and 3” square or rectangular tubing.
My laser guy laser cuts and forms the piece for $25.


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**** that would be just too handy! Especially for square and rectangular tube.


What size holes? 3/16”?

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[dr_clyde]

Rotabroaches are super handy for larger holes. I have a Hougen mag drill and its amazing how fast that thing can put a hole in some serious steel.

They work great in a mill too.

I see lots of work on this thread that is begging for a tube laser though. If you guys are making lots of these things, maybe you should look into having them cut for you. It would save hours of labor and you'd have dead nuts holes.

 

[lis2323]

You will find yourself using the rotabroaches a LOT more than you may have envisioned. I bought extra arbors for my set of inch and under. I will do the same for the larger sets someday.


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[strength_and_power]

Rotabroaches are super handy for larger holes. I have a Hougen mag drill and its amazing how fast that thing can put a hole in some serious steel.

They work great in a mill too.

I see lots of work on this thread that is begging for a tube laser though. If you guys are making lots of these things, maybe you should look into having them cut for you. It would save hours of labor and you'd have dead nuts holes.

I agree a tube laser would be ideal but I think it’d be a bit pricey. I’d occasionally get backed up and would ask a friend to stand in front of the drill press. $10 a stick plus beer after was the going rate. It does open the door for different ideas for sure.

Did a quick googling of a local shop with a tube laser. Rough quote was $125 per piece, I supply the material. One can dream


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[BukitCase]

I have the Hougen 917 with swivel base - until I get another SEPARATE shop for metalwork and other NON-woodworking, my mill has to live in what is mainly a wood shop, so it doesn't get used nearly as much as it would if it had a home of its own (probably 2-3 more years)

So til that happens, 98% of all metal related work happens in 3 OTHER, but not ideal, places - my "MDVT", aka MagDrillViseTable, lives right next to the 3'x7'x1" weld table, and lets me do things like drilling 1-1/2" holes in 2" pieces if I want to, (WITHOUT having to "scab on" a place for the magnets), equally spaced "jack stand" type devises, various tractor hitch mods, etc -

The xy table is this one
https://www.grizzly.com/products/Grizzly-5-1-2-x-12-Compound-Slide-Table/H7979#
and its lead screws are 10tpi - so if I want holes spaced 1-1/2" OC, I just drill, crank 15 turns, repeat - this particular job was 13mm holes (clearance for 1/2" pins) spaced 1" apart. 2.530" OD receiver tubing, no 3" cutter so I drilled all one side doing the "drill/crank/drill" method, then ran the table back to the first hole, ran the cutter into the hole, clamped a "reference" block against the square cut end of tubing, flipped the tubing upside down and repeat.

Did the inner 2" x .120" tube at the same time - Came out accurate enough that NONE of the pins/holes hang up. The 3 pcs on the table are bottoms of legs for a "terrain-adjustable) modular steel tubing framed container roof, not shown are the c-channel "feet" with acme adj. "vernier" between the 1" spaced holes; that allows me to maintaine a continuous roof pitch for the OTHER half of the (total) 24' square roof.

The things we do to maintain what passes for sanity ...Steve

Oh, last pic is fly cutter flattening the "auxiliary vise jaw" that's the main table - table surface has 1/2" thick FB welded to the web of 10" channel (see pic6) so the magnets have enough "grab", and I wanted it flat.