What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Inexpensive (cheap) punches

No, but

apatti said:
Has anyone used these el-cheapo HF punches?

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91201

I am looking for something to put 3/4" holes in my firewall for the metal grommets used for the throttle and mixture cables.

Thanks,
Click to expand...

Tony,
I haven't used those cheap punches and they might be ok but,...
Even a good Greenlee punch won't do as good a job as you would think on the thin stainless steel. It will leave a pretty good burr.

A unibit with some boelube on it worked pretty good for me.
Still leaves a burr, but not too bad.

I know...a unibit that big is about $40 most places, but they are worth it.
Be sure and get the kind with just one cutting edge!!

Mark
 
HF has some El Cheapo Unibits the last time I was there...turn it slow in an electric drill with plenty of cutting fluid and it should be good for a few holes.
 
Mark Burns said:
Tony,
I haven't used those cheap punches and they might be ok but,...
Even a good Greenlee punch won't do as good a job as you would think on the thin stainless steel. It will leave a pretty good burr.
Mark
Click to expand...
You can try backing-up your punches with some scrap metal for less distortion.
 
Buy a good unibit!

It's one of those tools that you'll wonder how you ever got along without it.
 
I have this...

And they seem to work as well as the Greenlee Punches I have borrowed but they are wierd sizes. The 1" punch makes a hole 1.3" in diameter but the 3/4" punch makes a 1.1" hole. As I read the fine print, I think that the listed punch size refers to the electrical conduit size that can be passed through the resulting hole. But they do work well if the size is what you need.

I also have a set of 3 "standard" size (up to 3/4") HF step drill bits ($10 on sale) and a set of 2 larger ones (up to 1-3/8"- $15 on sale) and they DO NOT work well at all on the thin stainless firewall. No matter how slow/fast I go, how much/little cutting lube I use they really distort the metal, bind up and want to get sideways and just generally chew the material up. And they leave the gnarly-est burr I have ever seen. My Irwin, Uni-Bit brand step drill does a really nice job on the firewall so in this case I'm inclined to suspect the tool not the tool user. Here's a link that shows both of these sets http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91616

On the other hand I have had good results using the smaller HF step drills on aluminum. One size was just right for wiring conduit runs in the wings so I chucked it into a 12" extension and was able to drill all the conduit holes through the ribs in my QB wings. I haven't found anything that the big ones work very well on.
 
All,
Thanks for the replies so far. I used my Irwin unibit to drill the hole for the break reservoir and it did a good job. The problem is the unibit now won't cut through aluminum. The stainless ruined it. Did I do something wrong? Not enough cutting oil? I was hoping to not ruin any more unibits since they are expensive.

I also have the HF unibits which are OK in a pinch (like drilling the inboard wing ribs for conduit). But, they chatter really bad and don't make very nice holes. I don't want to take a chance on messing up the firewall.

RVTACH, thanks for pointing out the hole size problem with the HF punches. You are probably right in that they are sized for conduit. I would have been really ticked if my 3/4" hole came out at 1.1"! :mad:
 
The second step of my Irwin unibit is pretty useless now after cutting three or four holes in the firewall. Unfortunately, when you lose one of the early steps, the rest of the unibit becomes pretty useless. I guess I'll need to buy another one at $30 a pop.
 
I'm no expert but I've ruined my share of bits drilling steel... Lately I've gotten much better at drilling steel and being able to use the bit again.

Here's my free advice, I'm sure it is worth every penny;)

Stainless is difficult to machine so don't feel too bad. I think the primary reasons for this are that it is relatively hard and does not dissipate heat well at all.

You'll need to feed more quickly (push harder) when drilling stainless as opposed to aluminum. This can be more difficult to control with a unibit than with a normal bit. Also, with most of the aluminum drilling (small holes) that we do for our airplanes, it is very difficult to turn the bit too fast (most drill motors just don't turn fast enough). This is not the case with stainless, especially when you start talking about larger diameter holes. So, use a significantly slower drill speed for stainless. Also, use plenty of cutting fluid, or lubricant; even motor oil brushed on with an acid brush works pretty well.

You can find tables for drilling speeds for diameters through various materials online.
 
I have the HF punches. The hole sizes they cut are not what they are listed as a previous poster mentioned. The first couple of times I used them they worked ok but not great on thicknesses of .032 and less. When it came time to punch the firewall they did a poor job. I only used them on holes that were larger than my unibits such as the 2" heater valve opening and some of the 1"+ holes for cables, etc through the firewall. On my slider canopy braces after a frustrating run on one of them the other one was left with the 1" unibit holes. I never tried the Greenlee punches so have no idea how they compare.

One of the nice things about cheap tools from HF is that when they do not work you won't feel bad tossing them so give it a shot. Just don't eat or put them in your mouth because they are probably covered in lead paint or a coating of some off the wall drug :D
 
You must log in or register to reply here.
Back
Top