DIY skid plate: is a punch the right tool for the job?

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Hector_Fisher

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Arrma RC's
  1. BigRock 4x4
  2. Granite
  3. Kraton EXB
Outlining designs for a DIY steel skid plate.
Looking to put a formed counter sink into 7/64 inch thick (~2.77mm) metal flat bar. Countersink on the bottom (street) side, recessed against the chassis to match the existing countersinks on the chassis (on right side of image).

My plan is to drill 4mm thru holes and then use some sort of shaped punch to indent the outer rim of the hole to contour to the chassis countersink. I'm not a machinist by trade, so i'm not expecting to get millimetrically perfect results, but would this tool do the job?
https://www.amazon.com/dp/B000936R1O/
I don't have a machine shop, so this would just be myself in my garage with some 2x4's, a 4mm drill bit, a mini sledge and the metal flat bar. Would that work well enough?

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A larger diameter drill bit to match or slightly exceed the head of the screw would also work. Just drill your through hole first then use the other bit to get to a flush depth.
 
A larger diameter drill bit to match or slightly exceed the head of the screw would also work. Just drill your through hole first then use the other bit to get to a flush depth.
If i wanted to match the image on the left, but I'm trying to match the image on the right. The left image would mean the skid is relying solely on the shear strength of the screws to keep in place. If the holes are recessed, then the chassis itself can absorb some of that force. That's my thought anyway.
 
Your best bet is a countersink bit. You “can” use a larger drill but you run the risk of the metal pulling the bit through when material is that thing. A center punch won’t get you very far, you need to remove the material or else you’ll just deform it.

Edit: nvm, I see the recent response.
 
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Your best bet is a countersink bit. You “can” use a larger drill but you run the risk of the metal pulling the bit through when material is that thing. A center punch won’t get you very far, you need to remove the material or else you’ll just deform it.

Edit: nvm, I see the recent response.
I had an earlier thought that I didnt post: drill through 4mm, use a punch to deform the rim downward to match countersink om chassis, then use a countersink bit to achieve the right countersink at the proper depth? Is that a better plan?

I accept that some of the steel would be cold worked (deformed). I don't think I'd have to worry about that any time before the skid plate gets worn down and needs to be replaced anyway.
 
Pardon the dumb question but what aspect of the Arrma steel skid doesn’t work for you?
Not at all, that's a great question. I had considered it. But I was also inspired by products like CRU's awesome skid that covers and strengthens the whole back of the chassis (https://customrcupgrades.com/product/arrma-6s-rear-skid-plate) and figured I could make multiple of a DIY for the same price I could get a CRU one shipped to me--just wouldnt look as pretty. I also liked that CRU's design would better spread out impacts on the rear narrow bit of the chassis rather than creating more stress at that point (notorious for bending). And in the end, I like me a good project. Just want to know if it's somewhat achievable beforehand.
 
Gotcha - thanks for the explanation. Looking at things again, you are probably close enough to be able to just drill a countersink into the material versus indenting to match the chassis - and it would give you more leeway of not having to get the four indents in the exact location. The Arrma steel skid is made that way (which was what prompted my question) but I believe the material is much thinner than ~3mm.
 
Gotcha - thanks for the explanation. Looking at things again, you are probably close enough to be able to just drill a countersink into the material versus indenting to match the chassis - and it would give you more leeway of not having to get the four indents in the exact location. The Arrma steel skid is made that way (which was what prompted my question) but I believe the material is much thinner than ~3mm.
Worst case you're probably right, just go flat bottomed--looking at the CRU option, even theirs isnt indented. The flat bar i'm looking at is $10 for 3 ft, so I may just get ballsy and experiment with both. If I did want to indent the skid plate where it meets the chassis, what tool would best? I was thinking maybe countersink, punch down, then countersink again to reshape where the screw sits. Use the punch I listed? Use a piece of bar stock? I'm expecting some amount of trial and error at getting it to work :LOL:
 
Worst case you're probably right, just go flat bottomed--looking at the CRU option, even theirs isnt indented. The flat bar i'm looking at is $10 for 3 ft, so I may just get ballsy and experiment with both. If I did want to indent the skid plate where it meets the chassis, what tool would best? I was thinking maybe countersink, punch down, then countersink again to reshape where the screw sits. Use the punch I listed? Use a piece of bar stock? I'm expecting some amount of trial and error at getting it to work :LOL:

From a McGuyver point of view, I would try to use a vice to create the indents. Find a piece of backing wood a drill a hole in it. Then put the steel plate on it and then use a small punch with an appropriately shaped tip like this:

s-l1600.jpeg


Stick it all in between the jaws of a vice and slowly clamp down to form the divots.

Someone who's an actual machinist/fabricator is probably laughing/crying at my proposition...
 
From a McGuyver point of view, I would try to use a vice to create the indents. Find a piece of backing wood a drill a hole in it. Then put the steel plate on it and then use a small punch with an appropriately shaped tip like this:

View attachment 230445

Stick it all in between the jaws of a vice and slowly clamp down to form the divots.

Someone who's an actual machinist/fabricator is probably laughing/crying at my proposition...
Oh, it a gonna be a MacGuyver for sure! Just much less... finesse...Then again, I fully admitted I wasnt a machinist and that I'm working with--at best--2x4s, a mini sledge, a drill and bits, and whatever punch tool I purchase... not even a vice or work bench :ROFLMAO: :ROFLMAO: concrete patio for the win!

At least you suggested a vice: a "controlled press". And here I was just gonna do small taps and then big taps with the sledge until I got to the depth I needed. So I'm sure the machinists and blackirons are cringing with my post. Where do I turn in my engineer's badge??
 
I suspect pressing in the contour with a vise (after drilling) would be easier, more controllable, and more repeatable.
Agreed. As far as DIY at home goes, I think the vice would be the better choice. In future iterations, when I have the work bench project done (and/or a place to mount a vice), I will plan to experiment with that.

I'd love to have a machine press, but that's starting to get even more outside the realm of possibilities for me.
 
No 100% on this @Hector_Fisher but surely if you displace the material below yer drilled hole it's more than the factory countersink can accommodate?

@Engineer suggestion of a home brew dimple die would give you a bit more control over it tho.

Cold setting wi a hammer is likely to end up with a funny shaped bit of steel wi four holes in!

Ye'll be grand just countersinking yer steel, honest! 😉 As long as yer centres are spot on. These are hard ally but the ideas the same, never sheared a bolt yet, stick a wee chamfer on aw yer leading edges tho to minimise the chances of it hooking up.
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No 100% on this @Hector_Fisher but surely if you displace the material below yer drilled hole it's more than the factory countersink can accommodate?

@Engineer suggestion of a home brew dimple die would give you a bit more control over it tho.

Cold setting wi a hammer is likely to end up with a funny shaped bit of steel wi four holes in!

Ye'll be grand just countersinking yer steel, honest! 😉 As long as yer centres are spot on. These are hard ally but the ideas the same, never sheared a bolt yet, stick a wee chamfer on aw yer leading edges tho to minimise the chances of it hooking up. View attachment 230463View attachment 230461View attachment 230464
Good thoughts to consider. I'll start with just the counter sink type and then maybe get to more experimenting another time!

Are these your skids you've made, or ones you bought?
 
If i wanted to match the image on the left, but I'm trying to match the image on the right. The left image would mean the skid is relying solely on the shear strength of the screws to keep in place. If the holes are recessed, then the chassis itself can absorb some of that force. That's my thought anyway.

If you want to have repeatable results.. I would suggest you get yourself a cheap drill press -really cheap used on Craigslist or about $90 at Harbor Freight.

60238_W3.jpg




And, get yourself some of these threaded spikes with the tips closely matching your needed countersink angle..

41qJ-R-Dy5L._AC_SX425_.jpg




So, that once you drilled your desired holes in your skid plate..
Switch out the drill bit for the spike and use the drill press to control how much pressure AND depth you press down against your plate that's mounted over your countersink form.

I believe that will give you the best DIY results.
 
Thanks for the suggestions. If i had more projects that used a drill or machine press, i would certainly invest in one. But considering I should probably invest in some wood working equipment for home projects, better drills and tool set for general use, proper yard tools, compressor and various attachments for repairing 1:1's, etc.--I don't see myself needing to use a press very often. It would just take up valuable real estate at this point. I think a vice is probably a decent option/compromise in the near-furture term. It's a bit like a game of chess at this point. Gotta move my pieces in the right way to get the "must-do" projects done so i can get to the fun project I want to do later!
 
Good thoughts to consider. I'll start with just the counter sink type and then maybe get to more experimenting another time!

Are these your skids you've made, or ones you bought?
All home brewed using basic hand tools, just take yer time an if one goes tits up, it's only a wee bit material ye've lost. Learn fae that one then on to the next. Ye've got this @Hector_Fisher, get in aboot it!
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Thanks for the suggestions. If i had more projects that used a drill or machine press, i would certainly invest in one. But considering I should probably invest in some wood working equipment for home projects, better drills and tool set for general use, proper yard tools, compressor and various attachments for repairing 1:1's, etc.--I don't see myself needing to use a press very often. It would just take up valuable real estate at this point. I think a vice is probably a decent option/compromise in the near-furture term. It's a bit like a game of chess at this point. Gotta move my pieces in the right way to get the "must-do" projects done so i can get to the fun project I want to do later!
+1 on 'get a drill press'

I use my drill press way more than I thought I would before I bought it- like more than once a week. It spends most of its time with a 2 1/2" drum sanding head on it. I've used it for making wooden longbows & recurves, light duty milling, and even actual drilling once in awhile.
 
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