Milling new head for 24" planer

Yesterday, our Powermatic 225 24" planer ate it's own head. One of the bolts that hold the cast iron segmented chipbreaker bar had come out.
This allowed the chipbreakers to rise up in to the head instead of pivot up and around it. Lots of small to not so small pieces of steel and cast iron were dislodged from their proper places.

Head is trashed. Powermatic has decided that since there are thousands of these machines in use after 30-40 years of service, and said machines should be replaced by new ones, that they would cease production of cutterheads.

Searches of Ebay, Woodweb, and my favorite machinery dealers turned up no used heads. I have been advised by several people that the newer insert heads will not hold up to the abuse that this machine tolerates daily.

So, I bought a bar of 4150 HRRS RC-35 to make a new one from.

Questions:

1- If I follow MHB for feeds and speeds for HSS slot milling cutters, is there any practical limit to the depth of cut, other than the power available and the rigidity of the machine?(Southbend-Vernier Model 250 with a 1 1/4" arbor.)

I have coolant on mill.

2- Is it better to cut the outsides of the slot first and then take out the middle? Or vice- versa? I will probably use a 7/16 x 5" stagger tooth cutter (which would get most of it in 2 passes). I do have smaller and larger cutters. There is a step in the slot.

I can't answer exact dimension questions as I'm at home and the head is not.

Thanks, Charlie

Try Ornamental Supply in Cleveland 216-472-0332 ask for Greg or Eric. I have a 20" Powermatic and had the segment style cutter head which was a pain to set and had some stripped adjusting screw holes. Ornamental sold me used standard type one. They have been doing school shop sales for 50 years and have a ton of used parts.
Scott

Thanks, Scott

I'll try them tomorrow.
I quess i could use the bar as a door stop.

Charlie

Charlie
There is another guy you might try. HWF Supply in Willoughby,Ohio 440-951-2949. I just remembered he used to have a used one. I was going to turn it down to use in mine.

Don't mention my name we had a falling out a year age and he hates my guts
Good Luck

If possible, find a replacement. But to answer your question, Most of the cutterheads I've seen were milled with horizontal cutters. That can be done on a vertical machine, of course.

OTOH, I've made a number of short (up to 5" long) 3 or 4 knife cutterheads for my shaper using endmills. Yes, the deeper the cut, the more deflection. Don't ever start "on" your finish line/dimension, leave plenty to creep up on. Use a hog mill (rougher) to remove most of the waste, but leave some material on each side and the bottom for finish cuts. Keep in mind, the (36" long?) blank may move (distort) a bit as it is being cut. Making gradual roughing cuts and going around a few times will help minimize any distortion. Leaving some material for the finish cuts will allow you to remove any developing error from distortion.

If you do it between centers, it can be rough turned, rough milled, removed and checked (inspected), finish turned, and finish milled if necessary.

Another big source of error is if the blank is slipping ever so gradually on the arbor/dog/chuck, whatever your mounting system is and you don't catch it until you get to the last pocket and notice "hey, the space to the first one is different than I thought it would be! (not that that ever happened to me)

I prefer 4 flute mills, think they are a little stiffer for finish cuts, and don't use too small a diameter.

edited: Oops, you are going to use horizontal cutters, good. (My SB mill is a vertical) Consider the notes about possible distortion of the blank. I'll join you in waiting to hear what the horizontal experts say about cutting on the line. Have always wanted to try it that way, but could not quite reconcile cutting to the line on the first go to minimize deflection, against some experience with leaving allowance for distortion. Apologies for the confusion. Will be interesting to hear.

smt

Now would be a good time to decide the angle of the knives in your cutterhead. If you do harder species of hardwood lumber mostly, something like 15 degrees is preferred, but if mostly softwoods, 30 would be better. It may be more like 17 degrees, or something on the hardwood, I've been away from planers for a good while.

Richard

PS: Also, if I'm remembering correctly, the 15 degrees for hardwood would be much quieter than 30 degrees, which is a softwood angle, and meant to shear the shavings away, whereas the 15 degrees "wipes" away the shavings of the shorter-fibered hardwood.

[ 08-09-2007, 02:28 PM: Message edited by: Richard Rogers ]

I have not had good luck trying to skim an edge with a milling cutter. Use a cutter with a width that will allow you to take two full width cuts on the line, then clean up the center. Lots of coolant is a good thing in this case.

Do you have outer and inner supports for your arbor? How do you plan on holding the work?

I got the head turned today, so far, so good.
The groove is a stepped groove approx 1" wide.
My 7/16 cutter is about 1/8" to small- diameter- to reach proper depth. That is, at the hook angle of the original.

Richard,

I hadn't considered changing the hook angle, but, we rarely plane pine. Mostly hardwoods and some cypress. Finish doesn't matter. All we do with it is rough plane prior to ripping and molding.
I think our molder heads are 12Deg. or maybe 15.

As far as workholding, I have a Carroll 10" DH and an 8" Phase II indexer. I don't have room for the DH, and barely enough for the indexer. The length of cut is 24 1/4 and I have 28" of travel.
I will have to rig a tail support as there isn't enough room for a regular tailstock on the table.

I have the outboard support for the mill. I have done very little milling in relatively hard steel with HSS millling cutters. How many passes should I take to reach the 1" depth?

Each knife slot has 3 - .520 holes for the adjusters that are cut in the slot about 1/3 of the diameter, so I figure I'll drill them first.

Scott,

I got into the turning, already having the stock, and forgot to call your contact. If I screw it up, I'll give them a call.


Thanks

Charlie

I'm new here (1st post!. I am in the process of getting a Nichols mill home, which I just picked up on the big auction site on Al Gore's internet.

I would love to see some pics of the cutter head that you're making, but also how you're securing the cutter head as you cut the slots for the blades.

It seems that some cutter heads have the walls of the slot un-parallel if that makes sense, so that the spacer can hold it in securely after it's tightened. Hard for me to explain.

However, I was most pleased to find this recent thread as I didn't know that horizontal mills are good for slotting cutting heads, and I have an old Crescent 8" jointer which pre-dates 1920 and only has a 2 blade cutter head. Seems I could just mill a couple more slots for 2 more blades to have a 4 blade cutter head. I still need to add a pulley and belts to it, it was originally designed to work on flat belt, and was converted to pulleys/v-belts.

Charlie, if you have means to post your Powermatic cutter head, please do, I'd love to see it.

Here's the mill I got, just waiting to see if the freight company will pick it up as it's not on a pallet, but freightquote.com said they think this company will, it's up to the driver's discretion.

(linky pic for visually impaired, like me

I decided to change the hook angle from the stock 36 degrees (how do you get the degree symbol?) to 20 degrees. I got the Autocad drawing of it done today. I will have to bolt a plate on the mill table to bolt the indexer to, in order to get the full travel that is needed to clear the cut.

I was going to take lots of pics but my camera was dead and on charge while turning. I will get some of the milling. I may post some of the setup for expert critique before cutting.

TT, if your jointer is that old and has babbit bearings, it may run at a slower speed than that which 4 knives are needed for. OTOH, if it is a square head, making a round one, even with 2 knives would make it much safer, IMHO. We only use 2 knives in our molder, which runs at 6,000 RPM, but at a feed of 30-50 FPM.

Charlie

Charlie,

My jointer has the round safety head, or what Crescent called the safety head. They were one of the folks to first use it, AFAIK, in replacement of the square head cutter. I have a slightly newer Yates American 6" which I'm using, so haven't been pressed to get the Crescent going.

Good point on the speed, but I need to get a pulley anyway. I have one now which is a triple v-belt pulley at the cutter. I'll need to do the math, which is based on the amount of cutters and revolutions, as well as the motor speed. Several calculators are available online such as this one.

One thing some don't realize is that no matter how many knives are in a head, is that unless the knives are jointed in the head, there WILL be one knife higher than the others. This yeilds what they call a "single knife finish" Having more knives just reduces the chip load on each knife, which can be bad, and does not improve the finish. A low chip load will not carry away the heat. Not a big deal on a jointer, with it's normally intermittent usage.

Charlie

Here is picture of the turned head


Love that Pacemaker!

Charlie

Charlie,

How do you secure the cutter to mill it? Is that the jig/fixture you use? That looks beautiful!

It sounds like I wouldn't be better off adding more cutters, I 'spose I should just leave it as-is.

I'd really like to get at least a 12" jointer, since I have a half decent 12" Parks Planer (also needs a pulley and motor added to it).

Regards,
Alan

Alan,
The head is just setting on a piece of core-box stock we mill. It is just to determine where the head will have to be positioned, so I can figure out how to hold it.
The cutter is just sitting on the shaft for the same reason.

I'm not really trying to tell you that you shouldn't use a 3 or 4 knife head on your jointer, but, I would try the one you have first.
I think it will work fine.

Charlie

Here is a link to a discussion (with nice photographs) on OWWM.org in March of this year about the making of an eight inch jointer cutterhead:

http://www.owwm.org/viewtopic.php?t=23525&postdays=0&postorder=asc&highlight=mcgough&start=0

This might be good reading for those following along here.

Charlie,

I was more wondering how you secure the cutter head to slot it on the horizontal mill.

The pics from owwm are a bit clearer, but not completely to me and I don't have such a rotary table and/or tail stock, nor do I want to incur the cost. I think I could use a couple large v-blocks, one on each side to secure the cutter head while it is slotted. Is that something like you do Charlie? Or is that something like you're planning?

Seems a large v-block secured to a t-slot nut on each side might work. I don't know if the v-blocks would get in the way of the spindle, should be possible to secure them low enough I think.

Regards,
Alan

Here are some pics of my set up. Please feel free to tell me so, if anyone thinks it inadequate.

Gotta go get some sleep.

Charlie

Nice Charlie. That's turning into one nice looking piece of steel...very nice indeed. Very impressive.

Don't waste your time milling the cutterhead with the slots parallel. The knife should be bedded into the cutterhead at an angle. The end result will be very poor performance in the planer. The knife will be scraping the wood away instead of cutting it. I am not sure of the exact angle you need but what you have drawn is definitely wrong. The gibs and gib screws are drawn correclty but the gibs are always tapered on the knife side, to match the cutting angle. I am sure you could get the correct angle from Powermatic. I am a full time furniture maker and an amateur machinist. I made my own cutterhead for my 9" jointer when I was in high school. Surely you could measure the old cutterhead?
I hope you get this information before it is too late.
Sincerely
Michael Moore