Deburing holes

I often seem to need to drill holes or drill and tap along a round bar or thick tube, what’s the best way of deburing the hole to get the best appearance? Using a standard countersink obviously removes more material on the “high” sides of the hole and sometimes wanders off for some reason leaving it looking even worse. Any suggestions? A countersink with a pilot would perhaps help get a neater result if such a thing existed. I’m using M6 most recently. TIA.

Countersinks with pilots certainly exist ... 'though the ones I have are smaller than M6

That would address one of your two stated problems; but the other is 'interesting'

MichaelG.

Having though about this a bit more I think I’ll try using a centre drill at much lower speed and see how that works. I’ve got into the habit of using spotting drills to start the hole then using a standard drill but a centre drill may be better. Still interested in others thoughts though. The last job was on a quite sticky bronze type of material and didn’t go well.

Centre drills with a 118 degree profile are available and the shallower profile may help. Work with a three square (triangle) scraper by hand is slow but can give a good result.

Spot drill, drill, countersink & tap. having an uneven chamfer was never a problem in my machining days. Better on a mill if you have one to keep location constant.

Tony

Chris, I should have thought of that, I have a small three square scraper.

Use a round file across the hole.

I use a deburring tool.

Helps to have the right tip for the material and to go gently.

If you do use a drill or counter sink, it's often best to just hold the drill in your hand and do it that way, just a turn or two is enough. Ian S C

Back in my machining days we used a 90 degree countersink in a cordless drill to beburr holes for tapping and appearance. Our inspector would not accept any unchamfered holes and woe betide any draughtsman or designer who produced any design without the sharp edge removed! He was not averse to telling the boss that it was not acceptable but he was such a sharp guy that his position was secure. He could spot when there was an error in any project and must have saved the company a fortune over the years.

Alistair.

I had occasion to cut the tip off a step drill and afterwards it occurred to me that, mounted in a suitable handle, it would make an effective countersink/deburring tool:

It works best, of course, when the preceding step is a good fit in the hole being deburred.

On the tricky question of deburring holes in tubes, I suppose a CNC machine could do the job; I just make do with a small half round scraper.

You can get tube/pipe deburring tools designed to be used with a power tool such as an electric drill. I used to use these prior to loading bar into a cnc lathe bar feeder.

They seemed to work quite well so long as you kept your arm steady whilst you did it.

Michael W

Some interesting responses ... most of which would suggest that I started with the wrong assumption: I had assumed [always dangerous] that Vic was drilling for M6 across the the diameter of bar of [say] 100mm or less diameter.

MichaelG.

Michael Gilligan:

I had made the same assumption. Deburring the end of a tube cut square is, of course, easy enough and there are specialised tools (eg for plumbers' copper pipe) for the job.

Axminster have a fancy deburring tool for their PGS system on their website.

Edited By ega on 18/10/2018 16:10:58

The OP refers to holes with high sides and this does imply cross drilling rather than in a faced off end. Noga deburring tools work well for holes like this.

Martin C

Yes, you’re right Martin.

When I was an apprentice at Westlands in the 70's (I did'nt finish the course so I'm not an engineer ) standard practice for deburring holes was a couple of quick twists with a larger drill bit hand held. On the lathe we used a triangular scraper made from a file. The scraper end was used for internal edges and the file part was for the outside.

.

So, having ascertained that my assumption was correct ...

What diameter of bar [or tube] are you drilling, Vic ?

MichaelG.

The three-cornered scraper in my original set of three M&W scrapers tended to be a bit clumsy for small holes.

My real standby, especially for deburring tiny holes, was to modify the tip of a three-cornered needle file; i.e grind off the teeth and bring each flat down to a shallow (pyramid) point. A breeze to sharpen too!

Unlike the results from a standard 60 degree centre drill however, deburring threaded holes this way can leave a less-than-true (none symmetrical) result.

Sam

The book advice for threaded holes is to countersink before threading; I admit I often forget and have to put up with the result.