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radkins
07-09-2010, 11:11 AM
Pardon me if this is (probably) one of those classic "dumb" questions but I have never heard this discussed before. I have the chance to pick up some DuMont keyway broachs very cheap (set 10-10A) but all 4 broaches are quite dull however they were correctly used and none have any visible chips. How practical is it to sharpen these things? As I said I have never even heard this discussed and I have no idea whether it is something that is commonly done or not. Any suggestions?

oldtiffie
07-09-2010, 11:14 AM
Its relatively easy if you have a surface grinder.

radkins
07-09-2010, 01:18 PM
No surface grinder, any other way that would be practical?

MuellerNick
07-09-2010, 01:58 PM
any other way that would be practical?

Send them to DuMont? :rolleyes:


Nick

Mcgyver
07-09-2010, 02:11 PM
you need some way of moving an abrasive along or moving the broach along...surface grinder, T&CG are obvious. I suppose you could make a fixture with linear motion that held the stone....would be a bit of work but maybe it could universal enough to make it worthwhile, sort of poor mans tool grinder.

If they'e cheap enough, pick them up and a way to sharpen will present itself; you get a grinder, a buddy gets a grinder, do it at highschool night class...maybe even in a sharpening shop would be reasonably priced.

for dull used cutting tools though i'd think price would have to be very low, so low your worst case is they sit a drawer forever and you dont really care

Highpower
07-09-2010, 02:12 PM
If you intend to sharpen your broaches on your own, we suggest
you send for our free fact sheet, entitled "Broach Sharpening" (info@dumont.com).

http://www.dumont.com/brosharp.html

Black_Moons
07-09-2010, 02:13 PM
Correct me if im wrong.. but a brooch has nice straight teeth, with access to both sides.. no curves or anything.

So whats wrong with sharpening it with a cheap diamond coated file or lap?

Assuming theres no chips in the teeth, it should'nt take much more then a quick touch up. Sure, its gonna take a long ass time to sharpen em. So turn on the tv/radio, sit down with some newspaper or something to collect the dust, and get to it.

Toolguy
07-09-2010, 02:38 PM
As long as the sides aren't worn or galled, they can be sharpened back like new.
Where are you located? Maybe one of the HSM guys in your area could sharpen them for you for a nominal fee.

lakeside53
07-09-2010, 04:05 PM
and if the tips are well rounded with bad sides, grind the sides to the next smaller size (or and "undersize" non-standard" or even "metric" broach").

radkins
07-09-2010, 04:19 PM
OK, I bought them for $75 so I guess I will find out if I can sharpen them or not. This set is on sale right now at Enco for $356 so I am thinking it might be worth it, if not at least I will have the bushings. I was thinking maybe I could use a Granite plate and some wet/dry sand paper with water, make up a jig to hold them straight run them over the paper on the Granite plate? I have sharpened planer blades this way with a home made jig and worked pretty good, still there is a lot of difference between a planer blade and a keyway broach. Worth a try I guess so thanks to everyone for your advice and I will give this a try and see what happens.

MuellerNick
07-09-2010, 04:26 PM
make up a jig to hold them straight run them over the paper on the Granite plate?

A perfect way to finally ruin them!
They do have a relief angle. But with your way that angle will be negative, it will only rubb. You can resharpen it with a stone and a lot of dedication on the chest.

Nick

JCHannum
07-09-2010, 04:31 PM
Broaches are sharpened by grinding on the face. On a T&C grinder, a cup wheel is used at the proper angle. A fixture could be ginned up to stone the teeth manually.

Mcgyver
07-09-2010, 04:32 PM
OK, I bought them for $75 so I guess I will find out if I can sharpen them or not. This set is on sale right now at Enco for $356 so I am thinking it might be worth it, if not at least I will have the bushings. I was thinking maybe I could use a Granite plate and some wet/dry sand paper with water, make up a jig to hold them straight run them over the paper on the Granite plate? I have sharpened planer blades this way with a home made jig and worked pretty good, still there is a lot of difference between a planer blade and a keyway broach. Worth a try I guess so thanks to everyone for your advice and I will give this a try and see what happens.

I think you're going to have to devise a way to sharpen each tooth individually, else as Nick describes you'll have no clearance.

I wonder if with a steady hand and a die grinder and fine stone they couldn't sharpened by taking some off the curved rake surface?

alcova
07-09-2010, 04:48 PM
Also many cutting teeth are stepped so as to take smaller cuts...sort of like a wood saw blade...ie right, left and a cleanup cut and then repeat


Walt

reggie_obe
07-09-2010, 05:51 PM
Before you try and touch them up youself, it may be worth taking them to a precision grind shop/cutting tool sharpening service to get a quote.

Michael Edwards
07-09-2010, 06:32 PM
Before you try and touch them up youself, it may be worth taking them to a precision grind shop/cutting tool sharpening service to get a quote.

That reminds me of that old shop rate sign.... shop rate $40/hr, if you watch $60/hr, if you worked on it first $80/hr. :D

ME

Black_Moons
07-09-2010, 08:32 PM
Yea id get a quote, or sharpen them *manualy* with hand files/laps (diamond coated..)
Each tooth indivualy, probley most of the sharpening done in the relief so as to change the tooth size less..

Yes, tedius. Do you have something more profitable to be doing? If so, Then do that and send em out to be sharpened. Else enjoy the process of sharping teeth untill they are razor sharp. It is a little something to be proud of. Especialy when you first use it and it effortlessly eats whatever you are broching.

MuellerNick
07-10-2010, 02:36 AM
Else enjoy the process of sharping teeth untill they are razor sharp.

Don't make them too sharp! If too sharp, the broach moves away from the back of the bushing into the work and the chip load gets to high. Have a close look at the teeth, the relief should have a tiny flat land.

I made two broaches by myself. I'll never do that again. :(


Nick

Black_Moons
07-10-2010, 04:41 AM
MuellerNick: Now is that sharpness or rake?
Neutral rake I can understand for exactly the reason you provide, but not 'dullness'

MuellerNick
07-10-2010, 05:15 AM
MuellerNick: Now is that sharpness or rake?

It's aggressiveness.
Like you should break in bandsaw blades. They are too sharp in the beginning.

Nick

radkins
07-10-2010, 11:12 AM
OK, scrap the Granite plate and sandpaper idea I see now why that would indeed ruin them (I figured it probably couldn't be that simple! :mad: ). It was just that, an idea so I was asking if it would work and it's good thing I did ask first! That's what this thread is about, I had not a clue if it was practical to sharpen these things or not and I have learned a lot more about broaches than just sharpening them. I understand a lot more now about how the teeth are shaped and how they work.


Thanks guys this is why I really like this place

Paul Alciatore
07-10-2010, 12:47 PM
A perfect way to finally ruin them!
They do have a relief angle. But with your way that angle will be negative, it will only rubb. You can resharpen it with a stone and a lot of dedication on the chest.

Nick

And if you sharpen on the sides you will wind up with a smaller sized broach by whatever amount you take off. Standard sized keys will not fit the keyways they would cut. They MUST be sharpened on the faces ONLY. Even then the clearance angles will cause them to be a bit smaller after sharpening. So you may need to add an additional shim in the bushing when you use them. Remove as little as you can, especially on the last few teeth.

MuellerNick
07-10-2010, 01:39 PM
Even then the clearance angles will cause them to be a bit smaller after sharpening.

The last three or so teeth don't actually cut. They are spares for resharpening.

Nick

lane
07-10-2010, 05:12 PM
Take to a grinding shop to get them done . Like JC said need tool and cutter grinder and a fixture . Do the job right are not at all. Its that simple . Even though you may be a machinist some things have to be done by specialist.

radkins
07-10-2010, 08:25 PM
Take to a grinding shop to get them done . Like JC said need tool and cutter grinder and a fixture . Do the job right are not at all. Its that simple . Even though you may be a machinist some things have to be done by specialist.


For sure I am not going to attempt to sharpen them after what I have learned here, I know now that I simply don't have the proper equipment even if I was willing to try to do it myself.

oldbikerdude37
07-10-2010, 08:37 PM
You can touch each face of the brooch tooth to a vertical belt sander or even a bench grinder. knock off .002"

Its super easy you dont need to be a rocket scientist. Iv made brooches before.

OKChipmaker
07-11-2010, 12:18 AM
I spent 2 years in a grind shop,sharpening broaches 8 hr 5 days a week.

We never ground the face.always sharpened by grinding in the gullet.( the space between the teeth)
This was done(on this type of broach) by placeing the broach on a flat table,clamping it down(no mag.chuck allowed it would mag.the broach making it hold chips)then grind in the gullet on the cutting edge of the tooth with a thin grinding wheel that would go between the teeth.The grinder head is set to give a 7 degree hook to the bottom of the tooth, for steel,for cutting brass or copper it needs about a15 degree hook.(hook is what we called the pos. rake angle).allso leave the bottom of the gullet round to curl the chips.

FWIW each tooth should remove 1 and 1/2 th. of the materal being broached.

lakeside53
07-11-2010, 11:49 AM
A chainsaw chain grinder (overhead type) would do just that! Maybe a small mod - take of the chain holding mechanism.