morticer bits

[lugo35]

Well its got to be a workshop record broke 3 bits today
i was morticing some hard maple.
first one(10mm) was about a week old, didnt feel right when i was using it so was not suprised.
set a new one up. after about 5 cautious mortices bang snapped!!!!
no more 10mm left so waited a while for someone to get some more. fed up waiting i started to use a 6mm(taking it out in 2 cuts, not good i know)
yep bang goes the third after 3 mortices.
starting to think its me setting up wrong but been doing it for 17 yrs should know by now.
the bits we use are the axminster(jap style) cheaper ones in catalogue.
have used them for a while but never had this trouble??

has anyone else had similar probs?

 

[OPJ]

I've not come across this sort of problem with good quality Japanese chisels!! :shock: If you've been doing it for 17 years then I'd say it's safe to trust your judgment. Saying that though, I work with a guy who finished college a decade ago and yet he still insists that the chisel steadies it for the auger to make the cut; meaning the auger should be UP inside the chisel! :roll:

I know this is wrong. Two college courses and numorous articles and features in books, magazines and online also support my theory that you need sufficiant clearence with the auger below the chisel.

I can't imagine your trying to take out more than your chisel can handle? Other than that, perhaps you could try sharpening them first - even if they are brand new? Are the augers bent at all?

Some people also lubricate it just below the chuck with chainsaw oil.

 

[lugo35]

they not bent as far as i know the usual rattle in the chisel.

as for sharpening, i have done in the passed if they are new but never noticed any difference.

i think it is the auger. they are snapping in the same place everytime.

we also have an old hand(well nearly hand, has lost 2 fingers) who likes to hammer the chisel :shock: he hits the wood out!!!!

 

[IanW]

we also have an old hand(well nearly hand, has lost 2 fingers) who likes to hammer the chisel :shock: he hits the wood out!!!!

Do you mean he slams the chisel down with the machine, or just whales into the square chisel, sans auger, with a mallet?

Was wondering about your technique - do you use overlapping strokes, or cut a bunch of full plunges & then go back & take out the bits in between? I don't do this, although the instructions that came with my machine suggest it is a good idea with harder woods. However, I do notice that you have to be careful in hard woods, as the chisel flexes toward the 'hole' as you plunge. By overlapping at least 3/4 of a full cut each time, the flexing is minimised. Could that have anything to do with the snapping chisels??
Cheers,
IW

 

[catface]

re chisel supporting the auger, if you have a long auger (as usual) and no chisel around it, and downfeed hard into hard woods (eg maple), add a poor cutting edge (in need of sharpening) and smaller diameter augers eg quarter inch shaft diameter, will certainly bend. Whether this bend is enough to contact the inside of a mortice chisel when that chisel is in place is a matter of opinion (apparrently). Certainly I've never bent or broken an auger when mounted INSIde the chisel rather than used alone. But we never know the quality of the cheeper stuff were getting from the shops these days.
If you wax the outside of the mortice chisel between passes, (yes I know its slow but its a lot faster than removing jammed or broken chisels), you can usually do that single mortice in hard wood without breaking or binding the chisel. Hope this helps, Catface.

 

[Andy Pullen]

Wouldn't waxing the mortice chisel pollute the mortice and cause glue failure ? I wax things when I don't want glue to stick. How about predrilling the bulk of the waste out with a normal drill bit on a drill press first with a standard HSS drill bit as you might if you were chopping them out by hand ?

 

[catface]

yes waxing the bit could "pollute the mortice". Usually this is not an issue for me as I use the morticer to rough out the hole & clean it up with chisels after. Having said that I've never had a glue failure with mortices done with a waxed chisel & used "straight from the machine", but I guess you're right, I certainly could.
regards, Catface.

 

[lugo35]

i like to take a full cut as the chisels do flex . as for wax on outside of chisel dont see how this will affect the bit?
i think its is bad quality bits that are all snapping about 20mm from bottom.
very strange but we are having probs getting hold of bits?? no local places seem to stock them axminster is out of the jap style gonna try weadon(spelling rubbish)tomorrow.
have ordered the english pattern from axminster hope they last?????

 

[ProShop]

i like to take a full cut as the chisels do flex . as for wax on outside of chisel dont see how this will affect the bit?
i think its is bad quality bits that are all snapping about 20mm from bottom.
very strange but we are having probs getting hold of bits?? no local places seem to stock them axminster is out of the jap style gonna try weadon(spelling rubbish)tomorrow.
have ordered the english pattern from axminster hope they last?????

Have you tried the Draper Profesional range ??. Been using them for a year or so now on hardwods etc, they hold an edge well.