tap not catching, what does it mean?

[juntjoo]

trying to tap a hole, which I've never done and so far its not catching. I'm just turning it and struggling to keep it straight. I really don't want to mess up this hole after all this time I've been working(on this here break caliper), so I was hoping someone would have a tip. I looked it up and didn't find much on the tap not catching. I'm wondering if I need to press on it. don't want to take any risks.

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[Bud92gsx]

You are manually doing that right?

Go opposite way untill it catches, then go clockwise.

 

[juntjoo]

k, I'll try that...

 

[juntjoo]

how much pressure should I use? I'm average build/strength. if I sound paranoid mind you I don't know how many bolts, parts, and extractors even I've broken using the wrong method so yeah.. same results going opposite btw

 

[Bud92gsx]

Pressure is a double edged sword..Too much pressure and a cocked tap, means you have a cocked thread..

You got to ease it in there..I would make jokes but, For once I'm not joking...Yet.

 

[97gst5887]

You can use a good amount of pressure to push down on it. Just don't use too much force to turn it.

 

[pauleyman]

That tap doesn't look tapered. Is it? If it's a bottom tap and you're trying to rethread/restore a hole that likely won't work well. What is it you're working on?

 

[juntjoo]

Pressure is a double edged sword..Too much pressure and a cocked tap, means you have a cocked thread..

You got to ease it in there..I would make jokes but, For once I'm not joking...Yet.

oh I get it. funny AND insightful

 

[Demon33]

Once you get the tap started, turn it clockwise a little then counter clockwise to clear/break the bur that you create with the tap. As stated already, you can push the tap down into the hole with moderate force, but don't turn it too hard. And most of all, keep the tap straight as you turn. Go slowly and don't forget to lube the tap to make the process a little easier.

Is the hole possibly too small for the tap size you're using? Just a thought.

 

[Lou98GSX]

are you putting some oil on the tap

 

[juntjoo]

what if I use a driver really slowly. reason being is I don't trust this manual method. the position is awkward you know? I can aim much straighter with an electric driver.

 

[NHerron]

Make sure to drill it out first before tapping. The tap or tap packaging will say what the recommended drill bit is

Never use an electric driver to tap threads. Make one half turn clockwise then one half turn counter clockwise to clear out the shavings. Use tapping oil or WD-40 works fine too

 

[juntjoo]

1/2 inch drill bit, m10 tap to match a heli-coil, engine oil to lube, ...this chart says for ex. "nominal size" 10, "pitch" 1.25 and "tap drill" 8.8. what do they refer to? all I know is that my heli-coil fits the bolt and is an m10 as is the tap I'm working with. and the hole I've drilled with this 1/2 inch bit seems big enough -I'd be afraid to drill more.

I'm inserting a heli-coil in a hole for one of the caliper's guide pin holes that I broke a screw extractor in inside an already broken bolt. I just wanted to rebuild this dragging caliper. wtf?

 

[juntjoo]

"tap drill 8.8" and "nominal size 10" ???

 

[bryanwheat]

If you drilled it to 1/2 inch the m10 tap should slide right thru the hole. A 10mm tap is around .39 of an inch, the 1/2 bit is .5 .If the helicoil is a m10 inside than you should be drilling to 13/32.

 

[juntjoo]

If you drilled it to 1/2 inch the m10 tap should slide right thru the hole. A 10mm tap is around .39 of an inch, the 1/2 bit is .5 .If the helicoil is a m10 inside than you should be drilling to 13/32.

is there a chart or something available? well, it can't slide through so as long as it doesn't I should still be good to continue tapping no? I mean, if anything it should be easier for me to tap this hole no?

 

[juntjoo]

correction, my hole is smaller. about 3/8.

 

[blasterracer817]

It looks as though you have a closed hole tap for and open hole which is no big deal other than they're a pain in the arse to start the best thing I can recomend is chamfering the top of your hole just a little bit for the tap and use cutting oil, if you dont have any cutting oil use engine oil or some sort of thickish oil, also if you have a 10mmx 1.25 tap you would need to drill with and 8.8mm drill which is equivelent to an 13/32nd drill bit if you did drill to a half inch your tap would slide right through and not even think about catching. As far as pressure goes medium to light down pressure works for me depending on the material being cut. Another tip is when you do get the tap to catch check from two angles to see that it is square with the hole so you have a straight thread, any thing with a square corner can help with that.
Edit
http://www.physics.ncsu.edu/pearl/Tap_Drill_Chart.html
you need to use and 13/32nd drill which is just bigger than a 3/8ths, and if you go to big that means you will have less thread engagment between your thread and heli coil.
your best bet would be to get and 13/32nd reamer and spin it slow through that hole as it is going to be very unsafe to use a drill if your using a hand drill. if your using a drill press go slow using LIGHT pressure. Good luck

 

[bryanwheat]

A quick google search will tell you all you need to know on drill sizing.

 

[Demon33]

is there a chart or something available? well, it can't slide through so as long as it doesn't I should still be good to continue tapping no? I mean, if anything it should be easier for me to tap this hole no?

HeliCoil chart

If you drill the hole too big, even though the tap doesn't slide through it, your threads will be too shallow and weak. The 3/8 drill bit you used should be ok, but getting it started would be a little harder. The chart says 13/32 drill bit as already stated.

 

[blasterracer817]

Also I forgot to add when tapping dont go straigh through the hole, go about 2 turns in and a half turn back to break off the chips or else you risk breaking your tap of which will give you more problems than you want, this applies to all taps big or small its just an extra precaution. Sorry if i'm getting too technical, being a machinist makes me a nerd with this stuff.

 

[Demon33]

you need to use and 11/32nd drill which is just bigger than a 3/8ths, and if you go to big that means you will have less thread engagment between your thread and heli coil.
your best bet would be to get and 11/32nd reamer and spin it slow through that hole as it is going to be very unsafe to use a drill if your using a hand drill. if your using a drill press go slow using LIGHT pressure. Good luck

11/32 is actually smaller than 3/8 (12/32). And HeliCoil says 13/32 is the correct drill bit size which is a little bigger than 3/8.

 

[blasterracer817]

woops, wrong number. Sorry about that. thanks for correcting me.
Fixed it

 

[juntjoo]

I drilled 11.75/32 hole to be exact. maybe some Loctite or something?

 

[bryanwheat]

I drilled 11.75/32 hole to be exact. maybe some Loctite or something?

It needs to be 13/32 so that is why your tap isn't wanting to catch. Having the hole the correct size will greatly help.