Hollow Chisel Mortiser tips etc.

[Victor Robinson]

So I decided to go ahead and bite the bullet (bit of an impulse buy) and get a hollow chisel mortiser. I got the Delta benchtop.

I actually didn't realize what a workout these things can be. Out of the box, the included chisels cut decent enough mortises, but I'm sure the cut quality could be better. Also, the auger bit doesn't do a great job of clearing out debris, and I have to manually scrape out the mortise with a small chisel or a hex key. Is this par for the course?

I know I can hone and sharpen the included chisels, but was probably going to get new chisels from Lee Valley. Would these be a significant/noticeable upgrade over sharpened OEM chisels?

Any other tips for HCMs? Has anyone built their own micro-adjustable fence (the one on the Delta is rack and pinion, actually fairly decent) or added roller guides like the Powermatic has?

[Neil Brooks]

Before *I* spent any extra $$$$ ... I'd surely do the right thing with my OEM chisels.

FWW ARTICLE (http://www.finewoodworking.com/fwnpdf/011185056.pdf)

If you still need better chisels, well ... you'll probably have a more valuable OEM set to sell, if you properly tune them up, first !

Good luck !

[Lee Schierer]

I honed the outside of my OEM chisels to make the surfaces as smooth as possible. It made a major difference on the ease of insertion and extraction from each cut. I make the cuts on each end and then try to overlap each cut about 1/8 of the width of the bit. Your drill bit should clear the bottom of the chisel about the thickness of a dime.

[Matt Winterowd]

I will say that the LV chisels are better than the OEM chisels I've had, but they still need to be honed and tweaked. Just like planes and bench chisels, they just don't sell these tools ready to use. The LVs took less setup, but it still had to be done.

[Kent A Bathurst]

......the auger bit doesn't do a great job of clearing out debris, and I have to manually scrape out the mortise with a small chisel or a hex key.........

I don't know exactly what your mortises look like, or how you are going about it, but I can take a couple of guesses...see if any of this makes sense....It sounds like you aren't letting the chisel/auger do its job:

1] Set it up so the open side of the chisel points to the right. Make your first plunge at the right end of the mortise, then move left. After the first plunge, this lets the chips eject into the open mortise.
2] But - before you get to the left end of the mortise, jump over there, and make a plunge at the left edge, then move back and continue right-to left. The point here: when the chisel is contacting wood on only 3 sides, it will flex to the open side - believe it or not, and I didn't, until I stopped to think through what was causing what I was seeing.
3] When you are done - use a shop vac to suck up all the chips that readily come out.
4] Then, start over and make plunges that are half-width as you move to the other end. You are doing 2 things here - first, you are cleaning up the cheek faces of the mortise, and overlapping the auger holes at the bottom of the mortise, and second - you are picking up and ejecting darn near all of the chips at the bottom that may have gotten jammed in there. You can move very fast on this trip, because there is no resistance from plunging into wood.

These are the techniques I have developed over many mortises and many years, and things work out very well. Others may have different views, but this what works great for me. The other replies about sharpening your chisels are right on target - plus, get one of those inexpensive pairs of sharpening cones from Rockler, or wherever, and use them, as well as honing the outisdes of the chisels flat. Also - I use camellia oil in a small wick-style dispenser to lightly lubricate the sides of the chisel before every mortise.

And - last, but not least - and I can almost hear the howls starting - I used to spent way too much time getting wrapped around the axle on the perfect positioning of the auger with respect to the chisel. Now, I let the auger rest on a small block of hardwood [all those surfaces draw blood] and lift it up to where it is almost-but-not-quite touching the chisel - as close as I can get it, and if it happens to slightly rub against the chisel I don't care. This keeps the bit from "wandering" outside the chisel faces
as it enters the wood - and it wants to to that - and it keeps the bottom of the mortise clean - especially on the fast return trip, because the auger is tight to the chisel, and the chips have to be pulled up - they can't sneak out between the bit and the chisel.

[Neil Brooks]

To Kent's point, about the gap ....

I posted this On Another Forum. I can't remember which publication did the original testing....



According to one test, a gap the thickness of a nickel—roughly 0.072” thick—results in operating temperatures roughly 40 or 50 degrees higher than if you increase that gap to 0.117” (the gap provided by the built-in spacer, on the Powermatic PM701 mortiser, used in their testing.


I have a 0.125” gauge block that I will NOW use to set the gap between bit and chisel.

[Mike Harrison]

Purchase a cone sharpening tool from LV (http://www.leevalley.com/US/wood/page.aspx?p=53252&cat=1,180,42240,53317), no "sharp" tool is ready when you buy it. After a set of sharp chisels, I found an X-Y vise to be the biggest improvement, especially when you have a project with a LOT of mortises.

http://i670.photobucket.com/albums/vv62/mikeinkcmo/Woodworking/Wesleys%20bench/LongMortiseVise.jpg

[Jim Matthews]

Now that's clever.

Where do I send the royalty check, Mike?

[Mike Harrison]

Jim,

There are several write-ups on different WW boards out there, about installing an X-Y vise on bench mortisers. It certainly wasn't my brain child but I did it a bit differently than most (http://s670.photobucket.com/albums/vv62/mikeinkcmo/WW%20tools/Mortise%20Machine/), moving the "X" crank to allow indexing the part with the left hand, and control the chisel with my right. If you follow the link, just click on the pics for larger sizes.

[Jim Matthews]

I just love it when one of the 'jocks solves a problem I couldn't work around.

This would provide all the advantages of mortising by router, with the stability of a drill press.

[Kent A Bathurst]

FWIW - If, at some point, you were to decide that you were going to upgrade your HCM, you would find that the higher-end machines come with, in effect, an X-Y vise built into the base + table - the PM791, for example.

[Brent Ring]

Purchase a cone sharpening tool from LV (http://www.leevalley.com/US/wood/page.aspx?p=53252&cat=1,180,42240,53317), no "sharp" tool is ready when you buy it. After a set of sharp chisels, I found an X-Y vise to be the biggest improvement, especially when you have a project with a LOT of mortises.


I found a HF sliding cross vice to be one of the best investments I have made for my mortiser. I also always make my mortises about 1/16 - 1/32 deeper than required. Saves having to clean the bottoms perfectly. I have loved mine. +1 on the Lee Valley sharpening cones as well.

[Mike Harrison]

Kent,

I think you are refering to the Powermatic 719. Which is at least twice what Victors machine cost.
http://i670.photobucket.com/albums/vv62/mikeinkcmo/WW%20tools/Mortise%20Machine/PowerMatic719.jpg

[Cody Colston]

I have a Delta benchtop HCM. I have replaced the original chisels with ones from Lee Valley. There is no comparing the performance. I also got the cone-shaped diamond hone to keep the chisels sharp. It makes a world of difference.

In operation, I secure the nozzle of my shop vac near the chisel with a thick rubber band. It gets all the chips as I chisel them out. One additional, fast clean-up across the mortise with the chisel and it's good to go.

[Kent A Bathurst]

Kent,

I think you are refering to the Powermatic 719. Which is at least twice what Victors machine cost.

Exactly, Mike - that was my poorly-made point, I guess.

[Max Coller]

Before you invest in new chisels, make sure you really sharpen the OEM set first - they may then do everything you want, and you'll still need that new sharpener even if you do replace your chisels with the Lee Valley set. My Delta chisels arrived with the keen edge that can only come from apparently being sharpened on a sidewalk - it took me several frustrating days of lousy joints and a couple of hours of research here and elsewhere and then a few minutes of sharpening with the cone/polishing the exterior surfaces to make them much, much better.

[Jerome Hanby]

I found a HF sliding cross vice to be one of the best investments I have made for my mortiser. I also always make my mortises about 1/16 - 1/32 deeper than required. Saves having to clean the bottoms perfectly. I have loved mine. +1 on the Lee Valley sharpening cones as well.

+1 on the HF sliding cross vise. One of their great values (IMHO).

[Neil Brooks]

+1 on the HF sliding cross vise. One of their great values (IMHO).

Sort of on-topic for hollow-chisels AND the HF X-Y vise .....

They BOTH need love and attention, out of the box.

I lapped the "gibs" (you tighten screws INTO these "gibs --" the metal bars that -- once you back the screws out -- will slide right out of the tracks) to about 4000 grit, and put a very light coat of grease on them.

This turned a rather jerky inaccurate, "ratchet-action" vise into a very smooth, easy-to-operate, and accurate jig.

It takes all of about an hour. I highly recommend it.

When I get the time, I'll create "sanding blocks" that match the angles of the "dovetailed ways," and lap those, too. Sliding surfaces ... should be nice and smooth, to slide they way they ought to.

But ... my gibs were in sad shape, right out of the box. Something to consider, for those of you that bought the same vise....

[Chris Tsutsui]

So are you supposed to put a mirror finish on the outside of the square chisel and then using cone to hone out the inside?

I have a set of lee valley chisels and they need some sharpening.

They are made in Taiwan btw...

I am wondering if the Harbor Freight hollow chisel is the same... heh

[Kent A Bathurst]

So are you supposed to put a mirror finish on the outside of the square chisel and then using cone to hone out the inside?

Chris - treat the 4 sides of the hollow chisel as you would the backs of 4 regular chisels - they need to be flattened. The cone[s] - usually there is one "coarse" and one "fine" - are used to sharpen the inside of the hollow chisel - after you use them, remove any wire edge from the sides the same way you would with a hand-held chisel.

[Victor Robinson]

Thank you all - some fantastic information in this thread. The cross vise is sheer brilliance, and the fact it's available from HF makes it even sweeter. I will definitely be looking into that the next time I see one of them coupons!

[Larry Edgerton]

I use Clico's and Fische chisels. Even with a better grade of chisel/bit, you will want to take the time to polish the flutes on the bit. This will cure your chip extraction problems. I have a set of english bits for a brace that are perfect, and one of the things that make them so is that the flutes are polished, so I did this to my morticing bits, and no more plugged mortices.

Start your mortice with the open side of the chisel away from the direction that you are moving, and the chips will fall out of the slot into the mortice that is already cut, and there will be a lot less heat. I drilled my bit holder and fit an air line[brake line] blowing on my chisel/mortice with a foot pedal, and it speeded up the process and keeps my chisel/bits cooler. A bit messy, but the mortices stay clean.

Larry

[Paul Canaris]

In addtion to the polishing steps noted above which I agree with; I touch a bar of canning wax to the hot chisel faces every few plunges. This really lubricates the cut and no it does not interfere with the effectivness of joint glue adhesion.

[Brent Ring]

I just keep a small shop vac and run it while mortising...