Critique my patterns, please

[chucketn]

I'm building patterns for 3 tools I need/want. The tools are a follower/traveling rest and steady rest for my 7x lathe, and the body and banjo for the L.H. Sparey Dividing Head.

Please look at my patterns and offer any advise/criticism as appropriate. No draft has been applied yet to any of them. Do I need it? Do they need to be split?

Pic's here: http://s571.photobucket.com/user/chucket...y/patterns

Thanks,

Chuck

[dallen]

when you put your photos in photobucket if you left click where it says IMG in the square that says links to share your photos

will show up here like this



the first thing I would do is the dividing head is split it the same way John did his, your going to need draft on all the sides that aren't round so that when the pattern starts to be lifted it will clear the sand, your going to need some wood filler or bondo the patterns have to be smooth or they will be hard to pull.

look at this pattern I did. draft on this pattern was cut with a tapered endmill that had one degree of taper, the pattern has a slick finish from the paint on it and the sand rams up on it so hard I have a tough time getting it back out of the mold.


if possible use a good hard tight grain wood like maple. also follow the rule that if it gets machined add and eight inch to the measurement for machining nothing worse then doing the pattern making the pour and finding out that the things too short.

use colors that show up better in the photos it will make the patterns easier to look at also the bolt holes will have to be filled in.

also see if you can get that book I mentioned.
DA

[chucketn]

(08-28-2013, 07:39 PM)dallen Wrote: when you put your photos in photobucket if you left click where it says IMG in the square that says links to share your photos

will show up here like this




the first thing I would do is the dividing head is split it the same way John did his, your going to need draft on all the sides that aren't round so that when the pattern starts to be lifted it will clear the sand, your going to need some wood filler or bondo the patterns have to be smooth or they will be hard to pull.

look at this pattern I did. draft on this pattern was cut with a tapered endmill that had one degree of taper, the pattern has a slick finish from the paint on it and the sand rams up on it so hard I have a tough time getting it back out of the mold.


if possible use a good hard tight grain wood like maple. also follow the rule that if it gets machined add and eight inch to the measurement for machining nothing worse then doing the pattern making the pour and finding out that the things too short.

use colors that show up better in the photos it will make the patterns easier to look at also the bolt holes will have to be filled in.

also see if you can get that book I mentioned.
DA

Thanks for an instructive critique, dallen. I will work on adding draft to the patterns. I am aware that it is needed. The steady rest should be split vertically? and the draft should be toward the center, right?
What about the base I added to the DH? That was needed to mount it to my cross slide. I will add another base to mount it on the mill. Still split the DH like Doubleboost did?

Chuck

[dallen]

look at it from the end then put a vertical line thru the middle of the spindle down thru the base thats your parting line, even thing on each side of the line should taper towards inwards as if you were looking at an upside down pyramid if the part is in the drag (bottom half of the mold), the part that is were the spindle loc goes needs a filler of wood putty or bondo which ever is easier for you to work with.

I gotta do some digging I have a pdf of the navy foundry manual somewhere let me see if I can find it or a link to it, it will help you a ton
DA

[dallen]

try this link I think you will find enough to keep you awake late at nights

http://openlibrary.org/search?q=patternm...ltext=true

DA

[chucketn]

(08-28-2013, 09:12 PM)dallen Wrote: try this link I think you will find enough to keep you awake late at nights

http://openlibrary.org/search?q=patternm...ltext=true

DA

Wow! Thanks for the link.
I have a tub of dry wall compound left over from my remodeling days, will that work for fillets and draft?
Chuck

[dallen]

I would use elmers wood filler you can thin it with water so it goes further and doesn't go on so thick, the drywall compound you will just have to try. if it sticks to the wood you should be good to go

you probably figured it out but if you click on the little book icon to the right of the title it will open the thing up online instead of downloading it.

DA

[oldgoaly]

I like clay for the fillets, also good for making up for broken / lost pieces, but no reason to buy something when you already have drywall compound. Does the drywall compound seal with shellac? or some type of wood sealer?

[chucketn]

Haven't tried shellac, or wood sealer. I've just been spray painting over it.

Chuck

[dallen]

If you want to use shellac find some place online that sells it dry and make your own, you just put it in alcohol and you only make up what you need and don't pay 20 bucks a pint for it

I like the preshaped wax fillets but unless your doing a lot they can get expensive, I have some 3/16 that works for most stuff that I do. would like to find some like John had that was in a big block.

Durhams Rock Hard water putty works its that powder that comes in a can you mix with water.

I'm finding that I like the 2.98 a can 10 minute dry time spray paint from waldo world, it dries fast lets you put on a lot in a hurry.

Oh yea one other thing you don't want runs and sags in the paint job as it will cause the pattern to bind up when trying to pull it.

Bet you thought this was going to be easy, didn't you.....

DA