Utter frustration – Auger Bits
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27 August 2018 at 8:29 pm #550631
I’m working through, or rather trying to work through Paul’s book, ‘Woodworking 1 & 2’. I’m trying to complete the milking stool. To complete it, I purchased a brace and bit from Ebay. Both items were auctioned off separately. I won both items, but only after another bidder came in on both bids and raised my bid to £16.99 each. Thieving so & so.The brace is ok, works well. The auger set had 9 bits, all Ridgeway, Sheffield steel. However, only two work. I’ve followed the videos on sharpening etc. The threads of the snail engage, the spurs cut the wood and the bits also begin to cut but after three or four revolutions the threads in the snail are pulled out of the wood and the bit will not cut. I’ve used red oak, ash and pine the same happens in all three species of wood. Can anyone tell me why this is happening? As I’m a blacksmith by trade and I teach I’m more inclined to repair the bits than chuck them in the bin and buy another set. Any help would be appreciated.
27 August 2018 at 8:41 pm #550632Are the snails fine thread or course thread. Try the bit in pine and see what it does. The edge may be sharpened at the wrong andle and be taking too big of a bite.
A picture or more info could helpYou described the snail and spurs. What about the (horizontal) cutting lip? Sometimes, people file these in a way that the cutting edge is higher than the heel of the bevel. It’s like a plane iron without any clearance angle. The heel of the bevel rubs the wood while the cutting edge is up in the air, not cutting. If this is the problem, you need to spend time on the heel of the bevel to thin out the bevel angle until you have some clearance.
27 August 2018 at 9:04 pm #550634The snails are fine threads, so used in hardwoods. However, it did exactly the same in pine. The angle may be wrong but its similar to the one in the book and the video.
27 August 2018 at 9:07 pm #550635Are you positioning the work so that you can use your body weight to push on the brace as you’re turning it? It’s hard to get those old auger bits to continue in the cut without applying a fair amount of additional pressure. The snail alone usually won’t do it.
27 August 2018 at 9:13 pm #550638I allowed the bit to ‘do it’s thing’ on its own, then applied more pressure until my 17 stone body weight was pressing on it. The bit spins but doesn’t cut. I tried using the brace and bit in both the horizontal and vertical, same result. The two bits that work, no need for any pressure, they both fly the wood.I’ve compared the bits and noted the angles on the bits that are in good order. To me, they all look the same. Therefore, they should all cut the same. RHHHHHUUUUUUBBBBBAAARRRBBBB!!!
27 August 2018 at 9:24 pm #550639Sounds like you need to re-sharpen those bits. The cutting edge isn’t making contact with the wood. That slight angle back from the cutting edge is very slight by the way – hard to see sometimes. If you run the bit in a piece of scrap just to the point where the cutting edge should be making contact, I think you’ll see that the angle is a little bit off.
I want to retract / correct what I wrote earlier. The surface that determines the relief angle on the auger isn’t one you’d normally file. You file the other surface, which faces upwards, and while you might make that thick, the clearance angle won’t be affected. I was confused because the last bit I filed was an expansive bit that *was* messed up in having been filed underneath and having had the clearance angle removed. I don’t think I’ll ever save that bit.
So, I wanted to post this before anything leads you to file the underside of your bit. You shouldn’t need to do that for the kinds of augers that I’ve encountered. There are many kinds or augers, though. I hope Larry responds, because I think he has a lot of experience with them.
27 August 2018 at 11:32 pm #550642Post pictures. Otherwise we are guessing. Though on first glance, bits look the same, they often have subtle differences that affect how they work.
But first off, see what’s different between the bits that work and those that don’t.
The spurs, cutting/lifting edge, and snail snall have to coordinate to lift the wood out of the hole. All three areas could need attention on worn bits.
The spur needs to do its work cutting the circumference of the hole before the cutting/lifting edge that trails it, usually 180° behind. So it has to be closer to the tip than the cutting edge by at least about half a thread pitch of the snail.
You will have to try to achieve this in your sharpening.
How this is done in filing depends on whether your bits are one or two spur bits.
SIngle spur bits are easier to fix, since the spur is usually on a ’false’ helix and the cutter is on the real helix. You can remove a lot of cutter metal.
You might have to make the spur gullet lower so it doesn’t bottom out before the cutter engages. The spur gullet shouldn’t engage the bottom of the hole.
(The ‘cutter’ on a single spur bit that is attached to the spur looks like a cutter, but usually isn’t. It should be 1/2 snail thread behind/lower than the real cutter or more. Ihis is often the issue).sometimes two spur bits will work with only one active spur, so they are still fixable.
Harder to work on, though, since one cutter should be 1/2 turn lower than the other, and each spur should be 1/2 thread taller than the cutter behind it. If you have only one good spur, it needs to be taller than both cutters, one by half a turn, and one by a full turn of the snail.When counting threads on the snail, make sure it isn’t a double helix. Hardwood ones often are.
It could also be that your snail’s thread needs re-cutting, or the base of the snail Needs to be removed a little so the thread can work at the new base level.
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You must be logged in to view attached files.28 August 2018 at 12:38 am #550646Here are a few pictures that might explain how a single spur bit should work. I think those bits are easier to understand.
In the first, the spur is cutting the circumference of the hole. No chips have yet been lifted.
In the second, the cutter is lifting wood. Notice it didn’t remove any wood that wasn’t pre-scored by the spur.
The third picture is at almost a 360° turn. Notice shavings are being lifted by the cutter on the right, but no wood is bein lifted by the spur wing on the left. The bit would bind if it did, because scoring to depth by the spur has not yet occurred there. The binding might strip the snail threads in the wood.
The fourth picture is a two spur bit. The same thing is happening, but twice a turn. Two smaller spiral shavings are being pulled from the hole instead of one large spiral shaving.
Each spur has cut the circumfrence of the hole so the cutter in back of it can lift wood.I picked bits with about the same snail pitch, so they cut about the same depth each turn.
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You must be logged in to view attached files.28 August 2018 at 4:04 am #550656The most common sharpening error I see in old auger bits is that the spurs have been filed on the outside rather than the inside. When this happens, the clearance made by the spurs won’t pass the diameter of the main part of the bit.
28 August 2018 at 12:08 pm #550663Need to see a pic of the threaded bit,if it isn’t long enough it won’t pull itself into the cut much after the initial boring,I’ve had this with many a bit.
If it’s too small I haven’t found a way to remedy this bar chucking em in the bin
28 August 2018 at 9:38 pm #550701The spurs on that are dull. The leading edge is important as is the top of the spur.
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