I’m drilling mortises for stretchers into table legs. According to Roland Johnson in issue #185, “How to get more from your mortiser”, the mortises on the ends of the slots should be drilled first to keep them straight, then drill out the connecting wood. However, when I try to remove the hollow chisel from the deep (1 1/2″) end mortise, it binds and the piece has to be hammered down to remove the chisel. I can deal with this by drilling in more shallow stages. But I’m wondering if I should be using a different technique for the deep mortices. Anybody have advice?
Mike
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Replies
Back a long time ago, I used a light duty drill-press with a hollow chisel set-up. When I drilled deep into hardwood, the DP column would flex back a little, which would make the hole slant out as it went down.
When I tried to extract the bit, the column would flex a little the opposite way, which would bind the bit.
I managed to improve the drilling by putting a brace under the table. And when pulling out, I cut a little prop to put between the top of the work and the DP head.
I don't use that tool anymore, and it may not have anything to do with your situation, but might be worth checking out.
I'm using a powermatic tabletop mortiser.
If you have not tested it, there is an easy test. Drill two holes side by side, in the edge of a board, each with opposite sides to the fence, but in line with each other. Then stick a long tight fitting square into each hole. If they are parallel, you are good. If there is a V as they project up, then there may be a problem.
I will do that. Wouldn't it be great if this is all Powermatics' fault?!
Mike, just buy this http://tucson.craigslist.org/tls/890648806.html I'll go with and help you load it. Chris
Chris
There are flies on every wall...
I called. It's sold. But, thanks for the tip.
MikeSawdust & Sunsets
Mike,
What kind of set-up are you using and what is the size of the mortising bit?
-Jerry
I'm using a powermatic tabletop mortiser. I can't detect any flex in the post. The binding does lift the wood being drilled somewhat no matter what I have done to hold it in place.
Mike,
You have already gotten some great tips. I will add one tip that seems to improve the performance of my mortiser: shop vac. I have a PVC nozzle hooked up to my vac system and aimed at the open side of the mortising chisel. Keeping the chisel and mortise free of chips allows the bit to do it's job without clogging and allows me to better see what I am doing.
Best of luck on your table project!
-Jerry
Jerry
those chips are a pain in the wazoo. I use the flipped coin method to yours. I keep my air hose handy and blow them out. Your method would mean I would not have to sweep them up. But the noise of my shop vac is loud, loud. Yes I do have ear protectors so maybe I should try it, but, dang it, there is already so much sawdust on the floor, who cares about another 30 lbs or so.
MikeSawdust & Sunsets
I don't see why you can't use the two layer process. Just proceed on each layer by starting at the ends, then making intermediate cuts spaced slightly, and then clean out the remaining web. Cuts with only one side in the wood and the other in an already cut hold want to flex the chisel. That proceedure gives you either plunges with wood on all four sides, or with two sides equally open and the other equally bound by wood.
Thanks, Steve. This what I have been thinking, too.
You do know that good quality hollow square chisel sets are slightly larger at the bottom end? This is ground into the shape of the chisel to reduce the grabbing effect.
Even so, some woods grab more than others, and going deep makes it worse. I solve that problem by use of a candle to lubricate-this is just parafin wax and goes on a treat when that chisel is warmed up. It will not interfere with the glueing of the joint....
The other thing to note, which is along the lines of what Keith talks of, is to ensure that the work piece is securely clamped, as the slightest movement upwards when withdrawing will cause a jam.
Somehow Roland Johnson's idea does not seem too good to me, as the hollow square chisel machine is supposed to do it all in one shot.
Philip Marcou
Edited 10/26/2008 4:22 am by philip
Phil
I think you missed something on the OP's description of the Roland Johnson method. Sure it's quite possible to chop the full depth, with a well tuned chisel, it's almost never possible to chop the entire mortise at once unless you are making 3/8" square mortises. All that Johnson proposed is that as much as possible do initial chops with wood surrounding on all sides. Since the ends need to be most accurately alighned it's a good idea to start with those. That balanced support keeps the chisel from bending off into an open side. Then the mortise can be cleaned out when the chisel will again be balanced with open space on two sides, avoiding the tendancy to bend the chisel in a different way. It's really the standard method. I'll bet you knew that already.
Steve
I have indeed been thinking that I read too much into Roland's recommendation to push the ends first; that in fact he wasn't insisting that the end mortises be drilled to full depth. BTW the chisel I am using is 3/8". The Staged/multi step approach is the one I have always used but I like to go back into FW to improve my skills. When I read the referenced article I thought I saw a better technique being recommended. However, I'm glad I put this in for discussion because I'm learning about candle wax and other good stuff. Thanks for the follow-up
Mike
Steve, you are right-I did have the wrong end of the stick.Philip Marcou
Interesting. I have been afraid to use any lubricant because of affecting glue adherence but if candlewax solves that problem I'll try it. I'm using Alder so I don't think the wood presents a special problem. As to clamping, I have clamped the leg with reinforcement at the top and side both. I am wondering if the chisel metal expands with the friction of a deep push. This would argue for a phased shallow drilling as SteveShoene suggests.
Mike
Yes, it doesn't require much wax at all-same idea as on a plane sole-it lasts for many mortices-just a dab on each side.
No doubt the chisel expands, but the amount would have no bearing on wood, I would think.
What you need is a compact little machine like Sarge has there....Philip Marcou
Philip
I tried the candle wax. Works fine. Both my technique and satisfaction have improved since starting this thread. I am also now drilling down in a sequence of 1/8" pushes and lifts which allows me to know exactly when the binding starts and to avoid a complete cramp in the wood. Maybe that's a tip for someone else. (not very a very deep tip though :-))
MIKESawdust & Sunsets
Mike,
Now I am interested in why you can only go 1/8" at deep at a time and suspect that your chisel set up is not alright or that the chisel set is blunt or just plain poor quality.
What timber are you working? See my machine-not as hefty as Sarge's , but a 9mm chisel set will plunge 70mm at one go no problem in woods like Iroko or Makore (the Makore imparts a nice mirror polish to any chisel in no time).
My procedure: take one cut at the extreme left of the mortice then move the chisel (mine is fixed table moving head) to the extreme right side then go from right to left advancing about 12 mm each time-that means there will be a "bridge" of about 3mm which I just flatten when completing the mortice by going from left to right. The chisel slot faces me so the chips are not ejected into the mortice, but I keep my air blaster handy so that the table stays clean to recieve the next piece for mortising.
That machine is actually made by Multico, but sold in Germany as Felder, presumably under some marketing scheme of some sort, yah.The brass piece at top of the chisel is a spacer I made so that I could adapt that little 1/4" Delta chisel set-made in USA when they made them good.Philip Marcou
Phillip
I probably actually push in 1/4". And can go deeper except for the binding problem on removal. But no matter, your point is well taken. My hollow chisels are not the most expensive, more like the least expensive. I'm using a Clic ( English) right now. My others are Shop Fox and some Japanese brands. What hollow chisels do you prefer? On the other hand, your Multico is to drool over and certainly must make the process easier than with my machine (see att.). In my defense, I have worked out a have decent procedure for moving the work piece back and forth in spite of not having a moving table like you and Sarge have. One makes do.
see also the photos of the legs I'm working on
Mike
PS-I'm not sure the photos are attached. Let me knowSawdust & Sunsets
>afraid to use any lubricant because of affecting glue adherence That was my first thought after I was going to suggest lube so I kept quiet. I have no experience with power mortisers other than drooling over them until they toss me out of the store. (and a quick flirt with one in high school).However since all this lube/glue thing came up here is my recollection: the Japanese wood workers lube mortising chisels with the camellia oil and claim it does not adversely effect the glue joints. For all I know it may just burn from the heat on the power mortiser chisel.Edited 10/27/2008 12:41 am by roc
Edited 10/27/2008 12:42 am by roc
Spray bottle of vegstabe Oil?
Opps.. this shoud have been posted to Mike. Sorry Will.....
Paraffin.. then take several plunge cuts to allow the waste to clear on the end cuts. Over-lap the middle cuts slightly but making sure the drill bit tip touches nothing but stock. And as mentioned.. clamp it well as the chisel can flex slightly if the stock is very hard and you are not well clamped.
I can start at one end these days and just proceed to the other with my "little" mortiser. I clamp it once and it's clamped. I just turn a "little" wheel and the mortise moves perfectly square from right to left so... doing one end and then another is not really necessary for me. But.. when I had a bench-top I did do one end and then the other and the above methods worked fine.
Good luck...
Sarge..
Edited 10/26/2008 10:58 am ET by SARGEgrinder47
Oh Man!!!
I love your "little" machine. (you are such a tease!) But "mother" wouldn't approve of the expense. I'm just pleased to have my table topper in spite of it's "finickiness". I will try the parrafin/candle wax lube. Thanks for the help.
Mike
Sorry Will.....???
Why? I got some attention! :>) Little?
Damn I thought it was a Milling Machine for making the Gears that drive the props on a Aircraft carrier!
Edited 10/26/2008 3:37 pm by WillGeorge
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