chisels

[Reg Mitchell]

I am looking for a quality set of mortising chisels for a PM # 10. I would like them to be able to hold a good edge for a relatively good time or stand up to production demands.
Thoughts, Ideas, Expearances

[Alan Turner]

I'll be interested in any responses. The old P M10. which we have in the teaching studio, required longer bits than most.

[Dev Emch]

O.K. First of all, hollow chisel mortiser bits come in two flavors. Short spur and long spur bits. The short spur bits are not very popular anymore and were actually designed or optimized for hardwood. The long spur bits are best suited for softwood but can be used on hardwood. Where it really matters is that sometimes your excavating a blind mortise and you dont have lots of meat backing you up. If the spur is to long, you can penetrate the back side which would be bad.

Some folks have said that some chisels are better than others. This sometimes has to do with one side of the mortise being scalloped. This scallop effect is more an issue with concentricy in the machine than with the actual bits. The chisel must be concentric to the bit and both have different centering systems so this becomes a problem on cheaper machines.

Most chisel sets sold today are for the new crop of machines. Older professional machines like the oliver 91, the wysong 284 and your powermatic often use bits with a drill bit that much much longer than standard. The chisel is often held in the machine with a machined bushing and the drill shank is four or five inches above this bushing. Also keep in mind that not all chisel mortisers have jacobs chucks. Older machines often had some more primitive attachment method including split bushing collets.

Today, fewer and fewer companies are making these. I know Fische was making these and I believe they still do. But Forrest City makes them and they are available from C. Schmidt in New Jersey. Often the chisel element is the same. What differs is the drill shank length. That you will need to discuss with your vendor.

Bits are nortorious for overheating and turning blue. This is caused by a number of conditions but more often than not this is the result of either the bit being to close in the chisel front or the chip load exceeds what the chisel is designed to remove. Slots in the chisel body are designed to degorge chips during decent. SHould these get covered up or blocked, your chip load will pack the chisel and this is a bad thing.

In any event, do what you can to keep that bit from turning the chisel blue. I got a number of these from a dealer a while back and most were blue and had to be thrown out. The clearance between bit and chisel is important because its through this clearance relationship that the chips leaving the front drill face move upwards and finally are ejected. There is a cone shaped tunnel in which the bits sits and this is the chip path. Placing the bit to close can either cause frictional heating or restrict the path enough to force chips to overheat the bit as well. In either case, your chisel turns blue. The metal is now brittle and will not hold an edge for beans.

[Alan Turner]

I wonder if anyone makes the bits in HSS. These will resist overheating, I would think.

[Dev Emch]

I wonder if anyone makes the bits in HSS. These will resist overheating, I would think.

The chisels are made from HSS appropriate tool steel. But just because Fishe uses HSS to make fostner bits does not mean you can run them at 4000 RPM. They will turn blue also. So it is with these chisel bit combinations. The most frequent reason for them turning blue is the bit is adjusted to high up in the chisel.

[tod evans]

reg, the forest tooling from schmidt will serve you well.....02 tod

[Dev Emch]

reg, the forest tooling from schmidt will serve you well.....02 tod

I concure. The forrest city tooling is also known as stark tooling. Same outfit I believe. Furthermore, schmidt will have a better understanding of which chisels and drlll bit shank lengths your going to need.